Method for manufacturing semiconductor nanoparticles, semiconductor nanoparticles, and light-emitting device

Abstract

Provided is a method for efficiently producing semiconductor nanoparticles which luminesce at a band edge and have a high band-edge luminescence purity. The method for producing semiconductor nanoparticles includes heat-treating a mixture comprising a silver (Ag) salt, an indium (In) salt, a compound having a gallium-sulfur (Ga-S) bond, a gallium halide, and an organic solvent to obtain first semiconductor nanoparticles.

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing semiconductor nanoparticles, semiconductor nanoparticles, and light-emitting devices. [Background technology]

[0002] It is known that semiconductor particles exhibit the quantum size effect when their particle size is, for example, 10 nm or less, and such nanoparticles are called quantum dots (also called semiconductor quantum dots). The quantum size effect refers to the phenomenon in which the valence band and conduction band, which are considered continuous in bulk particles, become discrete when the particle size is nanoscale, and the band gap energy changes depending on the particle size.

[0003] Because quantum dots can absorb light and convert its wavelength to light corresponding to its bandgap energy, white light-emitting devices utilizing the emission of quantum dots have been proposed (see, for example, Japanese Patent Publication No. 2012-212862 and Japanese Patent Publication No. 2010-177656). Wavelength conversion films using core-shell structure semiconductor quantum dots that enable band-edge emission and can have a low-toxicity composition have also been proposed (see, for example, Japanese Patent Publication No. 2010-177656). Furthermore, sulfide nanoparticles (see, for example, International Publication Nos. 2018 / 159699, 2019 / 160094, and 2020 / 162622) are being considered as ternary semiconductor nanoparticles that enable band-edge emission and can have a low-toxicity composition. [Overview of the project] [Problems that the invention aims to solve]

[0004] International Publication No. 2018 / 159699 discloses an efficient one-pot synthesis method for obtaining semiconductor nanoparticles exhibiting band-edge emission, but there was room for further improvement in the band-edge emission purity of the obtained semiconductor nanoparticles. Similarly, while International Publication Nos. 2019 / 160094 and 2020 / 162622 disclose semiconductor nanoparticles exhibiting high band-edge emission purity, there was still room for further improvement in terms of efficient manufacturing methods.

[0005] One aspect of this disclosure aims to provide an efficient method for manufacturing semiconductor nanoparticles that exhibit band-edge emission and high band-edge emission purity. [Means for solving the problem]

[0006] The first embodiment is a method for producing semiconductor nanoparticles, comprising first heat treatment of a first mixture containing a silver (Ag) salt, an indium (In) salt, a compound having a gallium (Ga)-sulfur (S) bond, a gallium halide, and an organic solvent to obtain first semiconductor nanoparticles.

[0007] The second embodiment is a semiconductor nanoparticle comprising a first semiconductor containing silver (Ag), indium (In), gallium (Ga), and sulfur (S). A second semiconductor containing Ga and S is disposed on the surface of the semiconductor nanoparticle. The semiconductor nanoparticle exhibits band-edge emission with an emission peak wavelength in the wavelength range of 475 nm to 560 nm when irradiated with light at a wavelength of 365 nm, has a band-edge emission purity of 70% or more, and an internal quantum yield of band-edge emission of 15% or more. In energy-dispersive X-ray analysis, the intensity of characteristic X-rays originating from the Ga of the second semiconductor is greater than the intensity of characteristic X-rays originating from the Ga of the first semiconductor.

[0008] A third embodiment is a light-emitting device comprising a light-converting member containing semiconductor nanoparticles and a semiconductor light-emitting element. [Effects of the Invention]

[0009] According to one aspect of the present disclosure, an efficient method for manufacturing semiconductor nanoparticles that exhibit band-edge emission with high band-edge emission purity can be provided.

Brief Description of Drawings

[0010] [Figure 1] It is a figure which shows an example of the emission spectrum of the semiconductor nanoparticles of Example 1 and Comparative Example 1. [Figure 2] It is a figure which shows an example of the emission spectrum of the semiconductor nanoparticles of Example 2, 3, 4 and 5. [Figure 3] It is a figure which shows an example of the emission spectrum of the semiconductor nanoparticles of Example 6, 7, 8 and 9. [Figure 4A] It is an example of a transmission electron microscope image showing the locus of line analysis of the composition by energy dispersive X-ray analysis for the semiconductor nanoparticles of Example 2. [Figure 4B] It is a figure which shows an example of the line analysis result of the composition by energy dispersive X-ray analysis for the semiconductor nanoparticles of Example 2.

Modes for Carrying Out the Invention

[0011] In this specification, the term "step" includes not only an independent step but also the step in question even if it cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved. Also, the content of each component in the composition means the total amount of the plurality of substances corresponding to each component in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. Furthermore, the upper and lower limits of the numerical ranges described in this specification can be arbitrarily selected and combined with the numerical values exemplified as the numerical ranges. Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below are examples of semiconductor nanoparticles and their manufacturing methods for embodying the technical idea of the present invention, and the present invention is not limited to the semiconductor nanoparticles and their manufacturing methods shown below.

[0012] Method for Manufacturing Semiconductor Nanoparticles A method for producing semiconductor nanoparticles includes a first step of first heat treatment of a first mixture containing a silver (Ag) salt, an indium (In) salt, a compound having a gallium (Ga)-sulfur (S) bond, a gallium halide, and an organic solvent to obtain first semiconductor nanoparticles. The method for producing semiconductor nanoparticles may further include other steps in addition to the first step, as needed.

[0013] 1st step The first step may include a first mixing step of obtaining a first mixture containing an Ag salt, an In salt, a compound having a Ga-S bond, a gallium halide, and an organic solvent, and a first heat treatment step of first heat treatment of the obtained first mixture to obtain first semiconductor nanoparticles.

[0014] By using a compound containing Ga-S bonds as a source of Ga and S in the composition of the first semiconductor nanoparticles, the composition of the manufactured first semiconductor nanoparticles can be easily controlled. Furthermore, by using gallium halides, the particle size of the manufactured first semiconductor nanoparticles can be easily controlled. From the above, it is considered that semiconductor nanoparticles exhibiting band-edge emission and high band-edge emission purity can be efficiently manufactured in a one-pot process.

[0015] In the first mixing step, a first mixture is prepared by mixing an Ag salt, an In salt, a compound having a Ga-S bond, a gallium halide, and an organic solvent. The mixing method in the first mixing step may be appropriately selected from commonly used mixing methods.

[0016] The Ag salt and In salt in the first mixture may be either organic or inorganic salts. Specifically, examples of inorganic salts include nitrates, sulfates, hydrochlorides, and sulfons. Examples of organic salts include formates, acetates, oxalic acid, and acetylacetonates. The Ag salt and In salt may preferably be at least one selected from the group consisting of these salts, and more preferably at least one selected from the group consisting of organic salts such as acetates and acetylacetonates, as these have high solubility in organic solvents and allow the reaction to proceed more uniformly. The first mixture may contain one Ag salt and one In salt each, or two or more of each in combination.

[0017] The Ag salt in the first mixture may include a compound having an Ag-S bond, as this can suppress the by-production of silver sulfide in the first heat treatment step described later. The Ag-S bond may be a covalent bond, an ionic bond, a coordination bond, or any other type. Examples of compounds having an Ag-S bond include Ag salts of sulfur-containing compounds, which may be organic salts of Ag, inorganic salts of Ag, organometallic compounds, etc. Examples of sulfur-containing compounds include thiocarbamic acid, dithiocarbamic acid, thiocarbonates, dithiocarbonates (xanthogenic acid), trithiocarbonates, thiocarboxylic acids, dithiocarboxylic acids, and their derivatives. Among these, at least one selected from the group consisting of xanthogenic acid and its derivatives is preferred because it decomposes at relatively low temperatures. Specific examples of sulfur-containing compounds include, for example, aliphatic thiocarbamic acid, aliphatic dithiocarbamic acid, aliphatic thiocarbonates, aliphatic dithiocarbonates, aliphatic trithiocarbonates, aliphatic thiocarboxylic acids, aliphatic dithiocarboxylic acids, etc. Examples of aliphatic groups in these sulfur-containing compounds include alkyl groups and alkenyl groups having 1 to 12 carbon atoms. Aliphatic thiocarbamic acid may include dialkylthiocarbamic acid, and aliphatic dithiocarbamic acid may include dialkyldithiocarbamic acid. The alkyl group in dialkylthiocarbamic acid and dialkyldithiocarbamic acid may have 1 to 12 carbon atoms, and preferably 1 to 4 carbon atoms. The two alkyl groups in dialkylthiocarbamic acid and dialkyldithiocarbamic acid may be the same or different. Specific examples of compounds having an Ag-S bond include silver dimethyldithiocarbamate, silver diethyldithiocarbamate (Ag(DDTC)), and silver ethylxanthogenicate (Ag(EX)).

[0018] The In salt in the first mixture may contain a compound having an In-S bond. The In-S bond may be a covalent bond, an ionic bond, a coordination bond, or any other type. Examples of compounds having an In-S bond include In salts of sulfur-containing compounds, which may be organic acid salts, inorganic acid salts of In, organometallic compounds, etc. Specific examples of sulfur-containing compounds include thiocarbamic acid, dithiocarbamic acid, thiocarbonate, dithiocarbonate (xanthogenic acid), trithiocarbonate, thiocarboxylic acid, dithiocarboxylic acid, and their derivatives. Among these, at least one selected from the group consisting of xanthogenic acid and its derivatives is preferred because it decomposes at relatively low temperatures. Specific examples of sulfur-containing compounds are the same as above. Specific examples of compounds having an In-S bond include trisdimethyldithiocarbamate indium, trisdiethyldithiocarbamate indium (In(DDTC)3), chlorobisdiethyldithiocarbamate indium, ethylxanthogenic acid indium (In(EX)3), etc.

[0019] The Ga-S bond in the compound having a Ga-S bond in the first mixture may be a covalent bond, an ionic bond, a coordination bond, or any other type. Examples of compounds having a Ga-S bond include Ga salts of sulfur-containing compounds, which may be organic acid salts, inorganic acid salts of Ga, organometallic compounds, etc. Specific examples of sulfur-containing compounds include thiocarbamic acid, dithiocarbamic acid, thiocarbonate, dithiocarbonate (xanthogenic acid), trithiocarbonate, thiocarboxylic acid, dithiocarboxylic acid, and their derivatives. Among these, at least one selected from the group consisting of xanthogenic acid and its derivatives is preferred because it decomposes at relatively low temperatures. Specific examples of sulfur-containing compounds are the same as above. Specific examples of compounds having a Ga-S bond include gallium trisdimethyldithiocarbamate, gallium trisdiethyldithiocarbamate (Ga(DDTC)3), gallium chlorobisdiethyldithiocarbamate, gallium ethylxanthogenic acid (Ga(EX)3), etc. The first mixture may contain one compound having a Ga-S bond, or it may contain two or more compounds in combination.

[0020] Examples of gallium halides in the first mixture include gallium fluoride, gallium chloride, gallium bromide, and gallium iodide, and may contain at least one selected from this group. Furthermore, the gallium halide may contain at least gallium chloride. The gallium halide may be used alone or in combination of two or more types.

[0021] Examples of organic solvents in the first mixture include amines having a hydrocarbon group with 4 to 20 carbon atoms, such as alkylamines or alkenylamines having 4 to 20 carbon atoms; thiols having a hydrocarbon group with 4 to 20 carbon atoms, such as alkylthiols or alkenylthiols having 4 to 20 carbon atoms; and phosphines having a hydrocarbon group with 4 to 20 carbon atoms, such as alkylphosphines or alkenylphosphines having 4 to 20 carbon atoms. It is preferable to include at least one selected from the group consisting of these. These organic solvents may, for example, ultimately surface-modify the resulting first semiconductor nanoparticles. Two or more organic solvents may be used in combination; for example, a mixed solvent may be used that combines at least one selected from thiols having a hydrocarbon group with 4 to 20 carbon atoms and at least one selected from amines having a hydrocarbon group with 4 to 20 carbon atoms. These organic solvents may also be used in combination with other organic solvents. When the organic solvent contains the thiol and the amine, the volume ratio of thiol to amine (thiol / amine) is, for example, greater than 0 and 1 or less, and preferably 0.007 or more and 0.2 or less.

[0022] The content ratios of Ag, In, Ga, and S in the first mixture may be appropriately selected according to the desired composition. In this case, the content ratios of Ag, In, Ga, and S do not need to be consistent with the stoichiometric ratios. For example, the ratio of the number of moles of Ga to the total number of moles of In and Ga (Ga / (In+Ga)) may be 0.2 to 0.95, 0.4 to 0.9, or 0.6 to 0.9. Also, for example, the ratio of the number of moles of Ag to the total number of moles of Ag, In, and Ga (Ag / (Ag+In+Ga)) may be 0.05 to 0.55. Also, for example, the ratio of the number of moles of S to the total number of moles of Ag, In, and Ga (S / (Ag+In+Ga)) may be 0.6 to 1.6.

[0023] The first mixture may further contain alkali metal salts. a Examples of alkali metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs), with Li being preferred because its ionic radius is close to that of Ag. Examples of alkali metal salts include organic acid salts and inorganic acid salts. Specifically, examples of inorganic acid salts include nitrates, sulfates, hydrochlorides, and sulfonates, while examples of organic acid salts include acetates and acetylacetonates. Among these, organic acid salts are preferred because of their high solubility in organic solvents.

[0024] If the first mixture contains an alkali metal salt, the ratio of the number of atoms of Ag to the total number of alkali metal atoms (M a / (Ag+M a For example, the ratio may be less than 1, preferably 0.8 or less, more preferably 0.4 or less, and even more preferably 0.2 or less. The ratio may also be greater than 0, preferably 0.05 or more, and more preferably 0.1 or more.

[0025] The molar ratio of the gallium halide content to the Ag salt in the first mixture may be, for example, 0.01 or more and 1 or less, and preferably 0.12 or more and 0.45 or less from the viewpoint of internal quantum yield.

[0026] The concentration of the Ag salt in the first mixture may be, for example, 0.01 millimoles / liter or more and 500 millimoles / liter or less, preferably 0.05 millimoles / liter or more and 100 millimoles / liter or less, and more preferably 0.1 millimoles / liter or more and 10 millimoles / liter or less, from the viewpoint of internal quantum yield.

[0027] In the first heat treatment step, the first mixture is subjected to a first heat treatment to obtain first semiconductor nanoparticles. The temperature of the first heat treatment may be, for example, 200°C to 320°C. The first heat treatment step may also include a heating step in which the first mixture is heated to a temperature within the range of 200°C to 320°C, and a synthesis step in which the first mixture is heat-treated at a temperature within the range of 200°C to 320°C for a predetermined time.

[0028] The temperature range for the heating step in the first heat treatment step may be 200°C or more and 320°C or less, preferably 230°C or more and 290°C or less. The heating rate should be adjusted so that the maximum temperature during heating does not exceed the target temperature, for example, 1°C / min or more and 50°C / min or less.

[0029] The temperature of the heat treatment in the synthesis step of the first heat treatment step may be 200°C or more and 320°C or less, preferably 230°C or more and 290°C or less. The time of the heat treatment in the synthesis step may be, for example, 3 seconds or more, preferably 1 minute or more, 10 minutes or more, 30 minutes or more, 60 minutes or more, or 90 minutes or more. The time of the heat treatment may also be, for example, 300 minutes or less, preferably 180 minutes or less, or 150 minutes or less. The time of the heat treatment in the synthesis step is defined as the time when the temperature set within the above temperature range is reached (for example, the time when 250°C is reached if set to 250°C) and the time when the cooling operation is performed is defined as the end time. A dispersion containing the first semiconductor nanoparticles can be obtained by the synthesis step.

[0030] The atmosphere in the first heat treatment step is preferably an inert gas atmosphere, particularly an argon atmosphere or a nitrogen atmosphere. By using an inert gas atmosphere, the formation of oxide by-products and oxidation of the surface of the resulting first semiconductor nanoparticles can be reduced or prevented.

[0031] A method for producing semiconductor nanoparticles may further include a cooling step, following the synthesis step described above, in which the temperature of the dispersion containing the obtained first semiconductor nanoparticles is reduced. The cooling step begins when the operation for reducing the temperature is performed and ends when the temperature has been reduced to 50°C or below.

[0032] The cooling process may include a period in which the cooling rate is 50°C / min or higher, in order to suppress the formation of silver sulfide from unreacted Ag salts. In particular, the cooling rate may be 50°C / min or higher at the start of cooling after the cooling operation has been performed.

[0033] The atmosphere during the cooling process is preferably an inert gas atmosphere, particularly an argon atmosphere or a nitrogen atmosphere. By using an inert gas atmosphere, the formation of oxide by-products and oxidation of the surface of the resulting first semiconductor nanoparticles can be reduced or prevented.

[0034] A method for producing semiconductor nanoparticles may further include a separation step for separating first semiconductor nanoparticles from a dispersion, and may further include a purification step as needed. In the separation step, for example, the dispersion containing the first semiconductor nanoparticles may be subjected to centrifugation to obtain a supernatant containing the first semiconductor nanoparticles. In the purification step, for example, a suitable organic solvent such as alcohol may be added to the supernatant obtained in the separation step and subjected to centrifugation to obtain the first semiconductor nanoparticles as a precipitate. Alternatively, the first semiconductor nanoparticles can also be obtained by volatilizing the organic solvent from the supernatant. The obtained precipitate may be dried, for example, by vacuum degassing, air drying, or a combination of vacuum degassing and air drying. Air drying may be carried out, for example, by leaving it in the air at room temperature and pressure for 20 hours or more, for example, about 30 hours. The obtained precipitate may also be dispersed in a suitable organic solvent.

[0035] In the method for producing semiconductor nanoparticles, the steps of adding an organic solvent such as alcohol and purifying by centrifugation may be performed multiple times as needed. As the alcohol used for purification, lower alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, and n-propyl alcohol, may be used. When dispersing the precipitate in an organic solvent, halogenated solvents such as chloroform, dichloromethane, dichloroethane, trichloroethane, and tetrachloroethane, or hydrocarbon solvents such as toluene, cyclohexane, hexane, pentane, and octane may be used as the organic solvent. From the viewpoint of internal quantum yield, the organic solvent used to disperse the precipitate may be a halogenated solvent.

[0036] The first semiconductor nanoparticles obtained in the above manner may be in the form of a dispersion or a dried powder. The first semiconductor nanoparticles exhibit band-edge emission and can show high band-edge emission purity. The semiconductor nanoparticles obtained by the semiconductor nanoparticle manufacturing method may be the first semiconductor nanoparticles or the second semiconductor nanoparticles obtained after the second step described later.

[0037] A method for producing semiconductor nanoparticles may further include a second step of obtaining second semiconductor nanoparticles by subjecting a second mixture containing first semiconductor nanoparticles and gallium halide to a second heat treatment.

[0038] 2nd process The second step may include a second mixing step of obtaining a second mixture containing the first semiconductor nanoparticles obtained in the first step described above and a gallium halide, and a second heat treatment step of performing a second heat treatment on the obtained second mixture to obtain second semiconductor nanoparticles.

[0039] By subjecting a second mixture containing a first semiconductor nanoparticle and a gallium halide to a second heat treatment, a second semiconductor nanoparticle with improved band-edge emission purity and internal quantum yield can be produced. This can be considered, for example, as follows.

[0040] On the surface of the first semiconductor nanoparticle, a semiconductor containing Ga and S (e.g., GaS x ; x is, for example, 0.8 or more and 1.5 or less), a Ga portion of a gallium halide reacts with a Ga defect (e.g., a portion lacking Ga) to fill the Ga defect, and further reacts with S atoms present in the reaction system, so that the concentrations of Ga and S near the Ga defect increase, and it can be considered that the band-edge emission purity and the internal quantum yield are improved by compensating for the Ga defect. Also, Ga atoms of a gallium halide coordinate with S atoms on the surface of a semiconductor containing Ga and S present on the surface of the first semiconductor nanoparticle, and further, the halogen atoms of the coordinated gallium halide react with the S component present in the reaction system, so that the concentrations of Ga and S near the surface increase, and it can be considered that the band-edge emission purity and the internal quantum yield are improved by reducing the remaining surface defects. Further, when a compound having a Ga-S bond (e.g., gallium ethylxanthate: Ga(EX)3) is used as a raw material for the first semiconductor nanoparticle, xanthic acid remains partially in the obtained first semiconductor nanoparticle, and the gallium halide acts on the partially remaining xanthic acid, so that the conversion to GaS x is promoted, the concentrations of Ga and S near the surface increase, and it can be considered that the band-edge emission purity and the internal quantum yield are improved by reducing the remaining surface defects.

[0041] In the second mixing step, the first semiconductor nanoparticle and a gallium halide are mixed to obtain a second mixture. The second mixture may further contain an organic solvent. The organic solvent contained in the second mixture is the same as the organic solvents exemplified in the first step described above. When the second mixture contains an organic solvent, the concentration of the first semiconductor nanoparticle is, for example, 5.0×10 -7 mol / liter or more and 5.0×10 -5 mol / liter or less, particularly 1.0×10 -6 mol / liter or more and 1.0×10 -5The second mixture may be prepared so that the concentration is less than or equal to moles / liter. Here, the concentration of the first semiconductor nanoparticles is set based on the amount of substance as particles. The amount of substance as particles is the amount of moles when one particle is considered as a large molecule, and the number of nanoparticles contained in the dispersion is Avogadro's number (NA = 6.022 × 10⁻¹⁰). 23 It is equal to the value obtained by dividing by ).

[0042] Examples of gallium halides in the second mixture include gallium fluoride, gallium chloride, gallium bromide, and gallium iodide, and may contain at least one selected from this group. Furthermore, the gallium halide may contain at least gallium chloride. The gallium halide may be used alone or in combination of two or more types.

[0043] The molar ratio of the gallium halide content to the amount of substance of the first semiconductor nanoparticles in the second mixture may be, for example, 0.01 to 50, and preferably 0.1 to 10.

[0044] In the second heat treatment step, the second mixture is subjected to a second heat treatment to obtain second semiconductor nanoparticles. The temperature of the second heat treatment may be, for example, 200°C to 320°C. The second heat treatment step may include a heating step of raising the temperature of the second mixture to a temperature in the range of 200°C to 320°C, and a modification step of heat-treating the second mixture at a temperature in the range of 200°C to 320°C for a predetermined time.

[0045] Furthermore, the second heat treatment step may further include a preheat treatment step in which the second mixture is heat-treated at a temperature of 60°C to 100°C before the heating step. The heat treatment temperature in the preheat treatment step may be, for example, 70°C to 90°C. The heat treatment time in the preheat treatment step may be, for example, 1 minute to 30 minutes, and preferably 5 minutes to 20 minutes.

[0046] The temperature range for heating in the heating step of the second heat treatment step may be 200°C or more and 320°C or less, preferably 230°C or more and 290°C or less. The heating rate should be adjusted so that the maximum temperature during heating does not exceed the target temperature, for example, 1°C / min or more and 50°C / min or less.

[0047] The heat treatment temperature in the modification step of the second heat treatment step may be 200°C or more and 320°C or less, preferably 230°C or more and 290°C or less. The heat treatment time in the modification step may be, for example, 3 seconds or more, preferably 1 minute or more, 10 minutes or more, 30 minutes or more, 60 minutes or more, or 90 minutes or more. The heat treatment time may also be, for example, 300 minutes or less, preferably 180 minutes or less, or 150 minutes or less. The heat treatment time in the modification step starts when the temperature set within the above temperature range is reached (for example, when set to 250°C, the time when 250°C is reached) and ends when the cooling operation is performed.

[0048] The atmosphere for the second heat treatment step is preferably an inert gas atmosphere, particularly an argon atmosphere or a nitrogen atmosphere. By using an inert gas atmosphere, the formation of oxide by-products and oxidation of the surface of the resulting second semiconductor nanoparticles can be reduced or prevented.

[0049] The method for producing semiconductor nanoparticles may further include a cooling step, following the modification step described above, in which the temperature of the dispersion containing the obtained second semiconductor nanoparticles is reduced. The cooling step begins when the operation for reducing the temperature is performed and ends when the temperature has been reduced to 50°C or below.

[0050] The cooling process may include a period during which the cooling rate is 50°C / min or higher. In particular, the cooling rate may be 50°C / min or higher at the start of cooling after the cooling operation has been performed.

[0051] The atmosphere during the cooling process is preferably an inert gas atmosphere, particularly an argon atmosphere or a nitrogen atmosphere. By using an inert gas atmosphere, the formation of oxide by-products and oxidation of the surface of the resulting second semiconductor nanoparticles can be reduced or prevented.

[0052] The method for producing semiconductor nanoparticles may further include a separation step for separating the second semiconductor nanoparticles from the dispersion, and may further include a purification step as needed. The separation step and purification step have been previously explained in relation to the first semiconductor nanoparticles, so a detailed explanation therein will be omitted.

[0053] The method for producing semiconductor nanoparticles may further include a surface modification step. The surface modification step may include contacting the resulting second semiconductor nanoparticles with a surface modifier.

[0054] In the surface modification step, for example, the second semiconductor nanoparticles may be brought into contact with the surface modifier by mixing the second semiconductor nanoparticles with the surface modifier. The ratio of the surface modifier to the second semiconductor nanoparticles in the surface modification step is, for example, 1 × 10⁻⁶ of the second semiconductor nanoparticles. -8 For moles, 1 × 10 -8 Any number of moles or more is acceptable, preferably 2 × 10⁻⁶ -8 More than 5 x 10⁻⁶ moles -8 The amount is less than or equal to a mole. The contact temperature may be, for example, 0°C to 300°C, preferably 10°C to 300°C. The contact time may be, for example, 10 seconds to 10 days, preferably 1 minute to 1 day. The contact atmosphere may be an inert gas atmosphere, with an argon atmosphere or a nitrogen atmosphere being particularly preferred.

[0055] Specific examples of surface modifiers used in the surface modification process include amino alcohols having 2 to 20 carbon atoms, ionic surface modifiers, nonionic surface modifiers, nitrogen-containing compounds having 4 to 20 hydrocarbon groups, sulfur-containing compounds having 4 to 20 hydrocarbon groups, oxygen-containing compounds having 4 to 20 hydrocarbon groups, phosphorus-containing compounds having 4 to 20 hydrocarbon groups, halides of Group 2, Group 12, or Group 13 elements, etc. Surface modifiers may be used individually or in combination of two or more different types.

[0056] The amino alcohol used as a surface modifier may be any compound having an amino group and an alcoholic hydroxyl group, and containing a hydrocarbon group with 2 to 20 carbon atoms. The number of carbon atoms in the amino alcohol is preferably 10 or less, more preferably 6 or less. The hydrocarbon group constituting the amino alcohol may be derived from hydrocarbons such as linear, branched, or cyclic alkanes, alkenes, and alkynes. Derived from hydrocarbons means that it is composed by removing at least two hydrogen atoms from a hydrocarbon. Specific examples of amino alcohols include aminoethanol, aminopropanol, aminobutanol, aminopentanol, aminohexanol, and aminooctanol. The amino group of the amino alcohol binds to the surface of the semiconductor nanoparticle, and the hydroxyl group is exposed on the opposite, outermost surface of the particle, causing a change in the polarity of the semiconductor nanoparticle, which improves its dispersibility in alcohol-based solvents (e.g., methanol, ethanol, propanol, butanol, etc.).

[0057] Examples of ionic surface modifiers used as surface modifiers include nitrogen-containing compounds, sulfur-containing compounds, and oxygen-containing compounds that have ionic functional groups in their molecules. The ionic functional group may be cationic or anionic, but it is preferable that it has at least a cationic group. For specific examples of surface modifiers and methods of surface modification, refer to, for example, Chemistry Letters, Vol. 45, pp. 898-900, 2016.

[0058] The ionic surface modifier may be, for example, a sulfur-containing compound having a tertiary or quaternary alkylamino group. The number of carbon atoms in the alkylamino group may be, for example, 1 to 4. The sulfur-containing compound may also be an alkyl or alkenylthiol with 2 to 20 carbon atoms. Specific examples of ionic surface modifiers include hydrogen halides of dimethylaminoethanethiol, halogenated salts of trimethylammoniumethanethiol, hydrogen halides of dimethylaminobutanethiol, and halogenated salts of trimethylammoniumbutanethiol.

[0059] Examples of nonionic surface modifiers used as surface modifiers include nitrogen-containing compounds, sulfur-containing compounds, and oxygen-containing compounds having nonionic functional groups, such as alkylene glycol units and alkylene glycol monoalkyl ether units. The number of carbon atoms in the alkylene group of the alkylene glycol unit may be, for example, 2 to 8, preferably 2 to 4. The number of repeating alkylene glycol units may be, for example, 1 to 20, preferably 2 to 10. Nitrogen-containing compounds constituting the nonionic surface modifier may have an amino group, sulfur-containing compounds may have a thiol group, and oxygen-containing compounds may have a hydroxyl group. Specific examples of nonionic surface modifiers include methoxytriethyleneoxyethanethiol and methoxyhexaethyleneoxyethanethiol.

[0060] Examples of nitrogen-containing compounds having hydrocarbon groups with 4 to 20 carbon atoms include amines and amides. Examples of sulfur-containing compounds having hydrocarbon groups with 4 to 20 carbon atoms include thiols. Examples of oxygen-containing compounds having hydrocarbon groups with 4 to 20 carbon atoms include carboxylic acids, alcohols, ethers, aldehydes, and ketones. Examples of phosphorus-containing compounds having hydrocarbon groups with 4 to 20 carbon atoms include trialkylphosphines, triarylphosphines, trialkylphosphine oxides, and triarylphosphine oxides.

[0061] Examples of halides of Group 2, Group 12, or Group 13 elements include magnesium chloride, calcium chloride, zinc chloride, cadmium chloride, aluminum chloride, and gallium chloride.

[0062] Semiconductor nanoparticles The semiconductor nanoparticles may be composed of a first semiconductor containing silver (Ag), indium (In), gallium (Ga), and sulfur (S), with a second semiconductor containing Ga and S arranged on its surface. When irradiated with light at a wavelength of 365 nm, the semiconductor nanoparticles exhibit band-edge emission with an emission peak wavelength in the wavelength range of 475 nm to 560 nm, have a band-edge emission purity of 70% or more, and have an internal quantum yield of 15% or more. In energy-dispersive X-ray analysis, the intensity of characteristic X-rays originating from the Ga of the second semiconductor may be greater than the intensity of characteristic X-rays originating from the Ga of the first semiconductor.

[0063] When irradiated with light at a wavelength of 365 nm, the semiconductor nanoparticles exhibit band-edge emission with an emission peak wavelength in the wavelength range of 475 nm to 560 nm, as well as high band-edge emission purity and high internal quantum yield of band-edge emission. This can be attributed, for example, to the fact that the crystal structure of the first semiconductor located in the center of the semiconductor nanoparticle is substantially tetragonal (chalcopyrite structure), and the second semiconductor arranged on the surface of the semiconductor nanoparticle has a crystal structure with few Ga defects (e.g., areas where Ga is deficient). The second semiconductor may be a semiconductor with a higher Ga composition ratio than the first semiconductor, or a semiconductor with a lower Ag composition ratio than the first semiconductor, and may be a semiconductor substantially composed of Ga and S. Furthermore, in the semiconductor nanoparticles, an adsorbent containing the second semiconductor may be arranged on the surface of the particle containing the first semiconductor, or the particle containing the first semiconductor may be covered with an adsorbent containing the second semiconductor. In addition, the semiconductor nanoparticles may have a core-shell structure in which, for example, a particle containing the first semiconductor serves as the core, an adsorbent containing the second semiconductor serves as the shell, and the shell is arranged on the surface of the core.

[0064] The first semiconductor constituting semiconductor nanoparticles contains Ag, In, Ga, and S. Generally, semiconductors containing Ag, In, and S, and having a tetragonal, hexagonal, or orthorhombic crystal structure, are described in literature and other sources as having the compositional formula AgInS2. However, in reality, the composition is not stoichiometric as represented by the above general formula, and in particular, the ratio of the number of Ag atoms to the number of In and Ga atoms (Ag / In+Ga) may be less than 1, or conversely, greater than 1. Also, the sum of the number of Ag atoms and the number of In and Ga atoms may not be equal to the number of S atoms. Therefore, in this specification, when it is not necessary to know whether a semiconductor containing a specific element has a stoichiometric composition, the semiconductor composition will be represented by an expression such as Ag-In-Ga-S, where the constituent elements are connected by "-". Therefore, the semiconductor composition of the semiconductor nanoparticles according to this embodiment can be considered as Ag-In-Ga-S and Ag-Ga-S, for example, by replacing Ag-In-S and part or all of the group 13 element In with Ga, which is also a group 13 element.

[0065] Furthermore, the first semiconductor containing the aforementioned elements and having a hexagonal crystal structure is of the wurtzite type, while the semiconductor having a tetragonal crystal structure is of the chalcopyrite type. The crystal structure is identified, for example, by measuring the XRD pattern obtained by X-ray diffraction (XRD) analysis. Specifically, the XRD pattern obtained from the first semiconductor is compared with a known XRD pattern of semiconductor nanoparticles represented by the AgInS2 composition, or an XRD pattern obtained by simulation from crystal structure parameters. If there is a pattern among the known patterns and simulation patterns that matches the pattern of the first semiconductor, then the crystal structure of the semiconductor nanoparticle can be said to be the crystal structure of the matching known or simulation pattern.

[0066] In an aggregate of semiconductor nanoparticles, semiconductor nanoparticles containing a first semiconductor with different crystal structures may be mixed. In that case, peaks originating from multiple crystal structures will be observed in the XRD pattern. In one embodiment of semiconductor nanoparticles, the first semiconductor may be substantially tetragonal, and peaks corresponding to the tetragonal structure may be observed, while peaks originating from other crystal structures may not be substantially observed.

[0067] The total content of Ag in the composition of the first semiconductor may be, for example, 10 mol% to 30 mol%, preferably 15 mol% to 25 mol%. The total content of In and Ga in the composition of the first semiconductor may be, for example, 15 mol% to 35 mol%, preferably 20 mol% to 30 mol%. The total content of S in the composition of the first semiconductor may be, for example, 35 mol% to 55 mol%, preferably 40 mol% to 55 mol%.

[0068] The first semiconductor may contain at least Ag, and a portion of it may be substituted to further contain a Group 1 or Group 11 element which is at least one of Cu, Au, and an alkali metal, and the Group 1 and Group 11 elements contained in the first semiconductor may be substantially composed of Ag. Here, "substantially" means that the ratio of the number of atoms of elements other than Ag to the total number of atoms of Ag and other Group 1 and Group 11 elements is, for example, 10% or less, preferably 5% or less, and more preferably 1% or less. Furthermore, the first semiconductor may be substantially composed of Ag and alkali metals (hereinafter, M aAlkali metals (sometimes written as ) may be used as constituent elements. Here, "substantially" means that the ratio of the number of atoms of Group 1 and Group 11 elements other than Ag and alkali metals to the total number of atoms of Group 1 and Group 11 elements other than Ag and alkali metals is, for example, 10% or less, preferably 5% or less, and more preferably 1% or less. Alkali metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). Since alkali metals can become monovalent cations like Ag, they can substitute for a portion of Ag in the composition of the first semiconductor. Li, in particular, has an ionic radius similar to that of Ag and is therefore preferably used. By substituting a portion of Ag in the composition of the first semiconductor, for example, the band gap widens and the emission peak wavelength shifts to the shorter wavelength side. In addition, although the details are unclear, it is thought that lattice defects in the first semiconductor are reduced and the internal quantum yield of band edge emission is improved. If the first semiconductor contains alkali metals, it may contain at least Li.

[0069] The first semiconductor is Ag and alkali metal (M a If it contains ), the alkali metal content in the composition of the first semiconductor is, for example, greater than 0 mol% and less than 30 mol%, preferably 1 mol% or more and 25 mol% or less. Also, the number of Ag atoms and alkali metal (M) in the composition of the first semiconductor. a Alkali metals (M) relative to the total number of atoms of ) a The ratio of the number of atoms (M a / (Ag+M a For example, the ratio is less than 1, preferably 0.8 or less, more preferably 0.4 or less, and even more preferably 0.2 or less. The ratio is also greater than 0, preferably 0.05 or more, and more preferably 0.1 or more.

[0070] The first semiconductor contains In and Ga, and may further contain at least one of Al and Tl, a group 13 element, by substitution of a portion thereof, and the group 13 elements contained in the first semiconductor may be substantially composed of In and Ga. Here, "substantially" means that the ratio of the number of atoms of group 13 elements other than In and Ga to the total number of atoms of In and Ga and other group 13 elements is, for example, 10% or less, preferably 5% or less, and more preferably 1% or less.

[0071] The ratio of the number of In atoms to the total number of In and Ga atoms in the first semiconductor (In / (In+Ga)) may be, for example, 0.01 or more and less than 1, preferably 0.1 or more and 0.99 or less. When the ratio of the number of In atoms to the total number of In and Ga atoms is within a predetermined range, a short-wavelength emission peak wavelength (for example, 545 nm or less) can be obtained. The ratio of the number of Ag atoms to the total number of In and Ga atoms (Ag / (In+Ga)) may be, for example, 0.3 or more and 1.2 or less, preferably 0.5 or more and 1.1 or less. The ratio of the number of S atoms to the total number of Ag, In and Ga atoms (S / (Ag+In+Ga)) may be, for example, 0.8 or more and 1.5 or less, preferably 0.9 or more and 1.2 or less.

[0072] The first semiconductor contains S, and may further contain at least one of the Group 16 elements Se and Te by substitution of a portion thereof, and the Group 16 elements contained in the first semiconductor may be substantially composed of S. Here, "substantially" means that the ratio of the number of atoms of Group 16 elements other than S to the total number of atoms of Group 16 elements other than S is, for example, 10% or less, preferably 5% or less, and more preferably 1% or less.

[0073] The first semiconductor may consist substantially of Ag, In, Ga, S, and elements that partially substitute for them. Here, the term "substantially" is used considering that other elements other than Ag, In, Ga, S, and elements that partially substitute for them may inevitably be present due to the inclusion of impurities, etc.

[0074] The first semiconductor may have a composition represented by, for example, the following formula (1). (Ag p M a (1-p) ) q In r Ga (1-r) S (q+3) / 2 (1) Here, p, q, and r satisfy 0 < p ≤ 1, 0.20 < q ≤ 1.2, and 0 < r < 1. M a represents an alkali metal.

[0075] In the semiconductor nanoparticles, a second semiconductor may be disposed on the surface. The second semiconductor may include a semiconductor having a larger bandgap energy than the first semiconductor. The composition of the second semiconductor may be a composition having a larger molar content of Ga than the composition of the first semiconductor. The ratio of the molar content of Ga in the composition of the second semiconductor to the molar content of Ga in the composition of the first semiconductor may be, for example, greater than 1 and less than or equal to 5, preferably 1.1 or more, and also preferably 3 or less.

[0076] Also, the composition of the second semiconductor may have a composition with a smaller molar content of Ag than the composition of the first semiconductor. The ratio of the molar content of Ag in the composition of the second semiconductor to the molar content of Ag in the composition of the first semiconductor may be, for example, 0.1 or more and 0.7 or less, preferably 0.2 or more, and also preferably 0.5 or less. The ratio of the molar content of Ag in the composition of the second semiconductor may be, for example, 0.5 or less, preferably 0.2 or less, or 0.1 or less, and may be substantially 0. Here, "substantially" means that when the total number of atoms of all elements contained in the second semiconductor is 100%, the ratio of the number of Ag atoms is, for example, 10% or less, preferably 5% or less, more preferably 1% or less.

[0077] In the semiconductor nanoparticles, the second semiconductor disposed on the surface may include a semiconductor containing Ga and S. The semiconductor containing Ga and S may be a semiconductor having a larger bandgap energy than the first semiconductor.

[0078] In the composition of the semiconductor containing Ga and S included in the second semiconductor, a portion of Ga may be substituted with at least one Group 13 element selected from the group consisting of boron (B), aluminum (Al), indium (In), and thallium (Tl). Also, a portion of S may be substituted with at least one Group 16 element selected from the group consisting of oxygen (O), selenium (Se), tellurium (Te), and polonium (Po).

[0079] A semiconductor containing Ga and S may be a semiconductor consisting substantially of Ga and S. Here, "substantially" means that when the total number of atoms of all elements contained in the semiconductor containing Ga and S is taken as 100%, the proportion of atoms of elements other than Ga and S is, for example, 10% or less, preferably 5% or less, and more preferably 1% or less.

[0080] The semiconductor containing Ga and S may be constructed by selecting its composition and other properties according to the bandgap energy of the first semiconductor described above. Alternatively, if the composition and other properties of the semiconductor containing Ga and S have been determined in advance, the first semiconductor may be designed so that its bandgap energy is smaller than that of the semiconductor containing Ga and S. Generally, a semiconductor made of Ag-In-S has a bandgap energy of 1.8 eV to 1.9 eV.

[0081] Specifically, the semiconductor containing Ga and S may have a band gap energy of, for example, 2.0 eV to 5.0 eV, and more particularly 2.5 eV to 5.0 eV. Furthermore, the band gap energy of the semiconductor containing Ga and S may be larger than the band gap energy of the first semiconductor by, for example, about 0.1 eV to 3.0 eV, more particularly about 0.3 eV to 3.0 eV, and more particularly about 0.5 eV to 1.0 eV. When the difference between the band gap energy of the semiconductor containing Ga and S and the band gap energy of the first semiconductor is greater than or equal to the aforementioned lower limit, the proportion of emission other than band edge emission from the semiconductor nanoparticles tends to decrease, and the proportion of band edge emission tends to increase.

[0082] The second semiconductor may contain oxygen (O) atoms. Semiconductors containing oxygen atoms tend to have a larger bandgap energy than the first semiconductor described above. The form of the oxygen-containing semiconductor in the second semiconductor is not clearly defined, but it may be, for example, Ga-OS, Ga2O3, etc.

[0083] The second semiconductor is made of alkali metal (M) in addition to Ga and S. a ) may further contain. The alkali metal contained in the second semiconductor may contain at least lithium. If the second semiconductor contains an alkali metal, the ratio of the number of alkali metal atoms to the sum of the number of alkali metal atoms and the number of Ga atoms may be, for example, 0.01 or more and less than 1, or 0.1 or more and 0.9 or less. Also, the ratio of the number of S atoms to the sum of the number of alkali metal atoms and the number of Ga atoms may be, for example, 0.25 or more and 0.75 or less.

[0084] The second semiconductor may have a crystal system familiar to that of the first semiconductor, and its lattice constant may be the same as or close to that of the first semiconductor. A second semiconductor that is familiar to the crystal system and has a close lattice constant (here, a second semiconductor whose lattice constant is a multiple of that of the first semiconductor is also considered to have a close lattice constant) may provide good coverage around the first semiconductor. For example, the first semiconductor described above is generally tetragonal, and familiar crystal systems for it include tetragonal and orthorhombic. If Ag-In-S is tetragonal, its lattice constants are 0.5828 nm, 0.5828 nm, and 1.119 nm, and it is preferable that the second semiconductor covering it is tetragonal or orthorhombic, and that its lattice constant or a multiple thereof is close to that of Ag-In-S. Alternatively, the second semiconductor may be amorphous (non-crystalline).

[0085] Whether the second semiconductor is amorphous (non-crystalline) can be confirmed by observing the semiconductor nanoparticles with HAADF-STEM. Specifically, if the second semiconductor is amorphous (non-crystalline), a portion with a regular pattern, such as stripes or dots, will be observed in the center, while a portion surrounding it that does not exhibit a regular pattern will be observed in HAADF-STEM. According to HAADF-STEM, materials with a regular structure, such as crystalline materials, will be observed as images with a regular pattern, while materials without a regular structure, such as amorphous materials, will not be observed as images with a regular pattern. Therefore, if the second semiconductor is amorphous, it can be observed as a clearly different portion from the first semiconductor (which may have a crystalline structure such as a tetragonal system) that is observed as an image with a regular pattern.

[0086] Furthermore, when the second semiconductor consists of Ga-S, Ga is a lighter element than Ag and In, which are present in the first semiconductor. Therefore, in images obtained by HAADF-STEM, the second semiconductor tends to appear darker than the first semiconductor.

[0087] Whether the second semiconductor is amorphous can also be confirmed by observing the semiconductor nanoparticles of this embodiment with a high-resolution transmission electron microscope (HRTEM). In the image obtained with HRTEM, the first semiconductor portion is observed as a crystal lattice image (an image with a regular pattern), while the amorphous second semiconductor portion is not observed as a crystal lattice image. Although black and white contrast is observed, the regular pattern is not visible.

[0088] On the other hand, it is preferable that the second semiconductor does not form a solid solution with the first semiconductor. If the second semiconductor forms a solid solution with the first semiconductor, the two become one, and the mechanism of this embodiment, in which band-edge emission is obtained by placing the second semiconductor on the surface of the semiconductor nanoparticle, cannot be obtained. For example, it has been confirmed that even if zinc sulfide (Zn-S) in a stoichiometric or non-stoichiometric composition is placed on the surface of semiconductor nanoparticles containing the first semiconductor composed of Ag-In-S, band-edge emission cannot be obtained from the semiconductor nanoparticles. In relation to Ag-In-S, Zn-S satisfies the above conditions with respect to the band gap energy and gives type-I band alignment. Nevertheless, it is presumed that the reason why band-edge emission could not be obtained from the particular semiconductor was that the first semiconductor and ZnS formed a solid solution.

[0089] The particle size of the semiconductor nanoparticles may have an average particle size of, for example, 50 nm or less. From the viewpoint of ease of manufacturing and internal quantum yield of band edge emission, the average particle size is preferably in the range of 1 nm to 20 nm, more preferably 1.6 nm to 8 nm, and particularly preferably 2 nm to 7.5 nm.

[0090] The average particle size of semiconductor nanoparticles can be determined, for example, from TEM images taken using a transmission electron microscope (TEM). Specifically, the particle size of an individual particle is defined as the longest line segment within the particle, formed by connecting any two points on the outer circumference of the particle observed in the TEM image.

[0091] However, if the particle has a rod shape, the length of the minor axis is considered to be the particle size. Here, a rod-shaped particle is one that has a minor axis and a major axis perpendicular to the minor axis in the TEM image, and the ratio of the length of the major axis to the length of the minor axis is greater than 1.2. Rod-shaped particles are observed in the TEM image as, for example, a quadrilateral shape including a rectangle, an ellipse, or a polygon. The shape of the cross-section, which is the plane perpendicular to the major axis of the rod shape, may be, for example, a circle, an ellipse, or a polygon. Specifically, for a rod-shaped particle, the length of the major axis refers to the length of the longest line segment connecting any two points on the outer circumference of the particle in the case of an ellipse, and the length of the longest line segment that is parallel to the longest side that defines the outer circumference and connects any two points on the outer circumference of the particle in the case of a rectangle or polygon. The length of the minor axis refers to the length of the longest line segment that connects any two points on the outer circumference and is perpendicular to the line segment that defines the length of the major axis.

[0092] The average particle size of semiconductor nanoparticles is determined by measuring the particle size of all measurable particles observed in TEM images at magnifications between 50,000x and 150,000x, and taking the arithmetic mean of these particle sizes. Here, "measurable" particles are those whose entire contour can be observed in the TEM image. Therefore, particles whose contour is partially cut off in the TEM image are not considered measurable. If a single TEM image contains 100 or more measurable particles, the average particle size is determined using that TEM image. On the other hand, if a single TEM image contains fewer than 100 measurable particles, the imaging location is changed, additional TEM images are acquired, and the particle size of 100 or more measurable particles contained in two or more TEM images is measured to determine the average particle size.

[0093] In semiconductor nanoparticles, the portion consisting of the first semiconductor may be particulate, and may have an average particle size of, for example, 10 nm or less, particularly 8 nm or less, or less than 7.5 nm. The average particle size of the first semiconductor may be in the range of, for example, 1.5 nm or more and 10 nm or less, preferably 1.5 nm or more and less than 8 nm, or 1.5 nm or more and less than 7.5 nm. When the average particle size of the first semiconductor is below the above upper limit, the quantum size effect is easily obtained.

[0094] The thickness of the portion of the semiconductor nanoparticle consisting of the second semiconductor may be in the range of 0.1 nm to 50 nm, 0.1 nm to 10 nm, and especially in the range of 0.3 nm to 3 nm. When the thickness of the second semiconductor is greater than or equal to the lower limit, the effects of the arrangement of the second semiconductor in the semiconductor nanoparticle are sufficiently obtained, and band-edge emission is easily obtained.

[0095] The average particle size of the first semiconductor and the thickness of the second semiconductor may be determined by observing the semiconductor nanoparticles, for example, using HAADF-STEM. In particular, if the second semiconductor is amorphous, the thickness of the second semiconductor portion, which is easily observed as a separate part from the first semiconductor, can be easily determined by HAADF-STEM. In that case, the particle size of the first semiconductor can be determined according to the method described above for semiconductor nanoparticles. If the thickness of the second semiconductor is not constant, the smallest thickness is taken as the thickness of the second semiconductor in the semiconductor nanoparticle.

[0096] Semiconductor nanoparticles are preferably substantially tetragonal in their crystal structure. The crystal structure is identified by measuring the XRD pattern obtained by X-ray diffraction (XRD) analysis, as described above. Substantially tetragonal means that the ratio of the height of the main peak around 26°, which indicates tetragonality, to the height of the peaks around 48°, which indicate hexagonal and orthorhombic structures, is, for example, 10% or less, or 5% or less.

[0097] The semiconductor nanoparticles may exhibit band-edge emission with an emission peak wavelength in the wavelength range of 475 nm to 560 nm when irradiated with light of a wavelength of 365 nm, preferably in the range of 510 nm to 550 nm, and more preferably in the range of 515 nm to 545 nm. Furthermore, the full width at half maximum (FWHM) of the emission spectrum of the semiconductor nanoparticles may be, for example, 45 nm or less, preferably 40 nm or less, or 35 nm or less. The lower limit of the FWHM may be, for example, 15 nm or more. In addition, it is preferable that the emission lifetime of the main component (band-edge emission) is 200 ns or less.

[0098] Here, "emission lifetime" refers to the lifetime of emission measured using a device called a fluorescence lifetime measuring device. Specifically, the "emission lifetime of the main component" is determined by the following procedure. First, semiconductor nanoparticles are irradiated with excitation light to cause emission, and the change in attenuation (afterglow) over time is measured for light with wavelengths near the peak of the emission spectrum, for example, within a range of ±50 nm of the peak wavelength. The change over time is measured from the point when the irradiation of excitation light is stopped. The resulting attenuation curve is generally the sum of multiple attenuation curves derived from relaxation processes such as emission and heat. Therefore, in this embodiment, assuming that there are three components (i.e., three attenuation curves), parameter fitting is performed so that the attenuation curve can be expressed by the following equation when the emission intensity is I(t). Parameter fitting is performed using dedicated software. I(t) = A1exp(-t / τ1) + A2exp(-t / τ2) + A3exp(-t / τ3)

[0099] In the above equation, τ1, τ2, and τ3 for each component represent the time required for the luminescence intensity to decay to the initial 1 / e (36.8%), and these correspond to the luminescence lifetime of each component. τ1, τ2, and τ3 are listed in order of increasing luminescence lifetime. A1, A2, and A3 are the contribution rates of each component. For example, A x exp(-t / τ xWhen the integral value of the curve represented by ) is largest is taken as the principal component, the emission lifetime τ of the principal component is 200 ns or less. Such emission is presumed to be band edge emission. Note that when identifying the principal component, A x exp(-t / τ x A is obtained by integrating the value of t from 0 to infinity. x ×τ x We compare these values ​​and select the one with the largest value as the principal component.

[0100] Furthermore, the difference between the decay curves drawn by equations obtained by parameter fitting assuming that the luminescence decay curve contains three, four, or five components, and the actual decay curve, is not significant. Therefore, in this embodiment, when determining the luminescence lifetime of the main component, we assume that the number of components included in the luminescence decay curve is three, thereby avoiding the complexity of parameter fitting.

[0101] The emission of semiconductor nanoparticles may include defect emission (e.g., donor-acceptor emission) in addition to band-edge emission, but it is preferable that it be substantially band-edge emission only. Defect emission generally has a long emission lifetime and a broad spectrum, and its peak is at a longer wavelength than that of band-edge emission. Here, substantially band-edge emission only means that the purity of the band-edge emission component in the emission spectrum (hereinafter also referred to as "band-edge emission purity") is 40% or more, preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and particularly preferably 95% or more. The upper limit of the purity of the band-edge emission component may be, for example, 100% or less, less than 100%, or 99% or less. "Purity of the band-edge emission component" is expressed by the following formula when the emission spectrum is separated into two peaks, a1 and a2, by parameter fitting assuming that the shapes of the band-edge emission peak and the defect emission peak are normally distributed, and their areas are a1 and a2, respectively. Purity of band-edge emission component (%) = a1 / (a1+a2)×100 If the emission spectrum contains no band-edge emission at all, i.e., only defect emission, the value is 0%. If the peak areas of band-edge emission and defect emission are the same, the value is 50%. If it contains only band-edge emission, the value is 100%.

[0102] The internal quantum yield of band-edge emission is defined as the value obtained by multiplying the internal quantum yield calculated using a quantum yield measuring device at a temperature of 25°C under the conditions of an excitation light wavelength of 450 nm and an emission wavelength range of 470 nm to 900 nm, or under the conditions of an excitation light wavelength of 365 nm and an emission wavelength range of 450 nm to 950 nm, or under the conditions of an excitation light wavelength of 450 nm and an emission wavelength range of 500 nm to 950 nm, by the purity of the band-edge emission component and dividing by 100. The internal quantum yield of band-edge emission of semiconductor nanoparticles is, for example, 15% or more, preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, and particularly preferably 80% or more.

[0103] The band-edge emission emitted by semiconductor nanoparticles can be altered by changing the particle size of the semiconductor nanoparticles. For example, reducing the particle size of semiconductor nanoparticles tends to shift the peak wavelength of the band-edge emission to shorter wavelengths. Furthermore, reducing the particle size of semiconductor nanoparticles tends to reduce the full width at half maximum (FWHM) of the band-edge emission spectrum.

[0104] When semiconductor nanoparticles exhibit defect emission in addition to band-edge emission, the intensity ratio of the band-edge emission may be, for example, 0.75 or higher, preferably 0.85 or higher, more preferably 0.9 or higher, and particularly preferably 0.93 or higher. The upper limit may be, for example, 1 or less, less than 1, or 0.99 or less. The intensity ratio of the band-edge emission is expressed by the following formula when the emission spectrum is separated into two peaks, the band-edge emission peak and the defect emission peak, by parameter fitting assuming that the shapes of the band-edge emission peak and the defect emission peak are both normally distributed, and their maximum peak intensities are denoted as b1 and b2, respectively. Band edge emission intensity ratio = b1 / (b1+b2) The intensity ratio of band edge emission is 0 if the emission spectrum contains no band edge emission at all, i.e., only defect emission; 0.5 if the maximum peak intensity of band edge emission and defect emission are the same; and 1 if it contains only band edge emission.

[0105] It is preferable that the absorption spectrum or excitation spectrum (also called the fluorescence excitation spectrum) of the semiconductor nanoparticles exhibits an exciton peak. The exciton peak is a peak obtained by exciton generation, and its appearance in the absorption spectrum or excitation spectrum means that the particles have a small particle size distribution and few crystal defects, making them suitable for band-edge emission. The steeper the exciton peak, the more particles with uniform particle size and few crystal defects are contained in the aggregate of semiconductor nanoparticles. Therefore, the full width at half maximum of the emission is expected to be narrower, and the luminescence efficiency is expected to improve. In the absorption spectrum or excitation spectrum of the semiconductor nanoparticles of this embodiment, the exciton peak is observed, for example, in the range of 400 nm to 550 nm, preferably 430 nm to 500 nm. The excitation spectrum for checking the presence or absence of the exciton peak may be measured by setting the observation wavelength to near the peak wavelength.

[0106] Semiconductor nanoparticles may have their surfaces modified with surface modifiers. Specific examples of surface modifiers include amino alcohols having 2 to 20 carbon atoms, ionic surface modifiers, nonionic surface modifiers, nitrogen-containing compounds having 4 to 20 hydrocarbon groups, sulfur-containing compounds having 4 to 20 hydrocarbon groups, oxygen-containing compounds having 4 to 20 hydrocarbon groups, phosphorus-containing compounds having 4 to 20 hydrocarbon groups, halides of group 2, group 12, or group 13 elements, etc. Surface modifiers may be used individually or in combination of two or more different types. Further details of the surface modifiers exemplified here are as described above.

[0107] The surface of the semiconductor nanoparticles may be modified with a gallium halide. Surface modification of the semiconductor nanoparticles with a gallium halide improves the internal quantum yield of band-edge emission. Specific examples of gallium halides include gallium chloride, gallium fluoride, gallium bromide, and gallium iodide.

[0108] The second semiconductor in semiconductor nanoparticles may have its surface modified with a gallium halide. Surface modification of the second semiconductor in semiconductor nanoparticles with a gallium halide improves the internal quantum yield of band-edge emission.

[0109] The luminescence of semiconductor nanoparticles surface-modified with gallium halide may include defect luminescence (donor-acceptor luminescence) in addition to band-edge luminescence, but it is preferable that it be substantially band-edge luminescence only. Substantially band-edge luminescence is as described above for semiconductor nanoparticles, and the purity of the band-edge luminescence component is preferably 70% or higher, more preferably 80% or higher, even more preferably 90% or higher, and particularly preferably 95% or higher.

[0110] The measurement of the internal quantum yield of band-edge emission of semiconductor nanoparticles surface-modified with gallium halide is as described above for semiconductor nanoparticles, and the internal quantum yield of band-edge emission is, for example, 15% or more, preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, and particularly preferably 80% or more.

[0111] A semiconductor nanoparticle containing a first semiconductor may have a second semiconductor disposed on its surface. If the composition of the second semiconductor has a larger molar content of Ga than the composition of the first semiconductor, the intensity of characteristic X-rays originating from Ga, as measured by energy-dispersive X-ray spectroscopy (EDX), will be greater for the second semiconductor than for the first semiconductor. Here, the intensity of characteristic X-rays is measured as a net count of characteristic X-rays. Note that "the intensity of the second semiconductor is greater than the intensity of the first semiconductor" may mean that the maximum intensity of characteristic X-rays originating from Ga in the second semiconductor is greater than the minimum intensity of characteristic X-rays originating from Ga in the first semiconductor. Alternatively, it may mean that the average intensity of characteristic X-rays originating from Ga in the second semiconductor is greater than the average intensity of characteristic X-rays originating from Ga in the first semiconductor.

[0112] For example, if the particle shape of semiconductor nanoparticles is observed using a scanning transmission electron microscope (STEM) and line analysis of the composition in the diametrical direction of the semiconductor nanoparticles is performed using EDX, the intensity of characteristic X-rays originating from Ga detected in the first region near the surface of the semiconductor nanoparticle corresponding to the second semiconductor will be greater than the intensity of characteristic X-rays originating from Ga detected in the second region near the center of the semiconductor nanoparticle corresponding to the first semiconductor. The first region may be, for example, a region having a thickness of 2 nm or less, preferably 1 nm or less, in the direction from the surface of the semiconductor nanoparticle toward the center. The second region may be, for example, a region within the range of 2 nm to 8 nm, preferably 1 nm to 9 nm, in the direction from the surface of the semiconductor nanoparticle toward the center.

[0113] Furthermore, the ratio of the maximum intensity of characteristic X-rays originating from the Ga of the second semiconductor to the minimum intensity of characteristic X-rays originating from the Ga of the first semiconductor is, for example, greater than 1, preferably between 1.1 and 3, more preferably between 1.2 and 1.5, and also between 2.5 and 1.6. The intensity of characteristic X-rays originating from Ga by EDX is measured, for example, using a multifunctional electron microscope equipped with an XDS detector (e.g., JEOL JEM-F200) under the conditions of acceleration voltage of 80kV, resolution: 256×256, frame time: 5 seconds, and number of frames: 500.

[0114] Light-emitting devices The light-emitting device comprises a light-converting member containing the aforementioned semiconductor nanoparticles and a semiconductor light-emitting element. With this light-emitting device, for example, a portion of the light emitted from the semiconductor light-emitting element is absorbed by the semiconductor nanoparticles, resulting in the emission of longer wavelength light. The light from the semiconductor nanoparticles and the remainder of the light emitted from the semiconductor light-emitting element are then mixed, and this mixed light can be used as the light emitted by the light-emitting device.

[0115] Specifically, a light-emitting device that emits white light can be obtained by using a semiconductor light-emitting element that emits blue-violet or blue light with a peak wavelength of approximately 400 nm to 490 nm, and semiconductor nanoparticles that absorb blue light and emit yellow light. Alternatively, a white light-emitting device can also be obtained by using two types of semiconductor nanoparticles: one that absorbs blue light and emits green light, and another that absorbs blue light and emits red light.

[0116] Alternatively, a white light-emitting device can be obtained by using a semiconductor light-emitting element that emits ultraviolet light with a peak wavelength of 400 nm or less, and by using three types of semiconductor nanoparticles that absorb ultraviolet light and emit blue, green, and red light, respectively. In this case, it is desirable to have all the light from the light-emitting element absorbed and converted by the semiconductor nanoparticles so that the ultraviolet light emitted from the light-emitting element does not leak to the outside.

[0117] Alternatively, by using a material that emits blue-green light with a peak wavelength of approximately 490 nm to 510 nm, and using semiconductor nanoparticles that absorb the above blue-green light and emit red light, a device that emits white light can be obtained.

[0118] Alternatively, by using a semiconductor light-emitting element that emits visible light, for example, red light with a wavelength of 700 nm to 780 nm, and semiconductor nanoparticles that absorb visible light and emit near-infrared light, a light-emitting device that emits near-infrared light can also be obtained.

[0119] Semiconductor nanoparticles may be used in combination with other semiconductor quantum dots, or with other non-quantum dot phosphors (e.g., organic or inorganic phosphors). Other semiconductor quantum dots are, for example, binary semiconductor quantum dots. As non-quantum dot phosphors, for example, garnet-based phosphors such as aluminum garnet can be used. Examples of garnet-based phosphors include cerium-activated yttrium-aluminum-garnet phosphors and cerium-activated lutetium-aluminum-garnet phosphors. Other examples include nitrogen-containing calcium aluminosilicate phosphors activated with europium and / or chromium, silicate phosphors activated with europium, β-SiAlON phosphors, nitride phosphors such as CASN or SCASN, and LnSi3N 11 Rare earth nitride phosphors such as the LnSiAlON system, BaSi2O2N2:Eu system, or Ba3Si6O 12 N2:Eu-based oxynitride phosphors, CaS-based, SrGa2S4-based, ZnS-based sulfide phosphors, chlorosilicate phosphors, SrLiAl3N4:Eu phosphors, SrMg3SiN4:Eu phosphors, K2SiF6:Mn phosphors and K2(Si,Al)F6:Mn phosphors as manganese-activated fluoride complex phosphors (e.g., K2Si 0.99 Al 0.01 F 5.99 Elements such as Mn can be used. In this specification, in formulas representing the composition of a phosphor, multiple elements separated by commas (,) mean that at least one of these elements is included in the composition. Also, in formulas representing the composition of a phosphor, the element before the colon (:) represents the matrix crystal, and the element after the colon (:) represents the activating element.

[0120] In a light-emitting device, the photo-converting member containing semiconductor nanoparticles may be, for example, a sheet or plate-shaped member, or a member having a three-dimensional shape. An example of a member having a three-dimensional shape is a sealing member formed by filling a recess with resin to seal a semiconductor light-emitting element when the semiconductor light-emitting element is placed on the bottom surface of a recess formed in a package of a surface-mount type light-emitting diode.

[0121] Alternatively, another example of a light conversion member is a resin member formed to surround the top and side surfaces of a semiconductor light-emitting element with a substantially uniform thickness, in the case where a semiconductor light-emitting element is arranged on a planar substrate. Or, yet another example of a light conversion member is a resin member formed in a flat plate shape with a predetermined thickness on top of the semiconductor light-emitting element and the resin member containing the reflective material, in the case where a resin member containing a reflective material is filled around the semiconductor light-emitting element such that its upper end is in the same plane as the semiconductor light-emitting element.

[0122] The light conversion member may be in contact with the semiconductor light-emitting element, or it may be provided away from the semiconductor light-emitting element. Specifically, the light conversion member may be a pellet-shaped member, a sheet-shaped member, a plate-shaped member, or a rod-shaped member provided away from the semiconductor light-emitting element, or it may be a member provided in contact with the semiconductor light-emitting element, for example, a sealing member, a coating member (a member that covers the light-emitting element and is provided separately from the molded member), or a molded member (for example, a member having a lens shape).

[0123] Furthermore, in a light-emitting device, if two or more types of semiconductor nanoparticles exhibiting different wavelengths of emission are used, the two or more types of semiconductor nanoparticles may be mixed within a single light-converting member, or two or more light-converting members containing only one type of semiconductor nanoparticle may be used in combination. In this case, the two or more types of light-converting members may form a laminated structure, or they may be arranged on a plane as a dot-like or stripe-like pattern.

[0124] An example of a semiconductor light-emitting element is an LED chip. An LED chip may have a semiconductor layer made of one or more materials selected from the group consisting of GaN, GaAs, InGaN, AlInGaP, GaP, SiC, and ZnO. A semiconductor light-emitting element that emits blue-violet light, blue light, or ultraviolet light may have a composition such as In X Al Y Ga 1-X-Y This device incorporates a GaN-based compound represented by N(0≦X, 0≦Y, X+Y<1) as a semiconductor layer.

[0125] The light-emitting device of this embodiment is preferably incorporated into a liquid crystal display device as a light source. Since band-edge emission by semiconductor nanoparticles has a short emission lifetime, the light-emitting device using them is suitable as a light source for liquid crystal display devices that require a relatively fast response speed. Furthermore, the semiconductor nanoparticles of this embodiment can exhibit emission peaks with a small half-width as band-edge emission. Therefore, in a light-emitting device: blue light with a peak wavelength in the range of 420 nm to 490 nm is obtained by a blue semiconductor light-emitting element, and green light with a peak wavelength in the range of 510 nm to 550 nm, preferably 530 nm to 540 nm, and red light with a peak wavelength in the range of 600 nm to 680 nm, preferably 630 nm to 650 nm, is obtained by semiconductor nanoparticles; or in a light-emitting device, ultraviolet light with a peak wavelength of 400 nm or less is obtained by a semiconductor light-emitting element, and blue light with a peak wavelength in the range of 430 nm to 470 nm, preferably 440 nm to 460 nm, green light with a peak wavelength in the range of 510 nm to 550 nm, preferably 530 nm to 540 nm, and red light with a peak wavelength in the range of 600 nm to 680 nm, preferably 630 nm to 650 nm, is obtained by semiconductor nanoparticles, thereby obtaining a liquid crystal display device with good color reproduction without using a dark color filter. Light-emitting devices are used, for example, as direct-lit backlights or edge-lit backlights.

[0126] Alternatively, a sheet, plate-shaped member, or rod made of resin or glass containing semiconductor nanoparticles may be incorporated into the liquid crystal display device as a light conversion member independent of the light-emitting device. [Examples]

[0127] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0128] (Example 1) 1st step 0.1 mmol of silver ethylxanthogenic acid (Ag(EX)), 0.12 mmol of indium acetate (In(OAc)3), 0.2 mmol of gallium ethylxanthogenic acid (Ga(EX)3), and 0.020 mmol of gallium chloride were mixed with 20 mL of oleylamine (OLA) to obtain the first mixture. The first mixture was heat-treated at 260°C for 120 minutes under a nitrogen atmosphere with stirring. After the resulting suspension was allowed to cool, it was subjected to centrifugation (radius 146 mm, 3800 rpm, 5 minutes) to remove the precipitate and obtain a dispersion of the first semiconductor nanoparticles.

[0129] Measurement of emission spectrum The emission spectra of the first semiconductor nanoparticles obtained above were measured, and the band-edge emission peak wavelength, full width at half maximum, band-edge emission purity, and internal quantum yield of band-edge emission were calculated. The emission spectra were measured using a quantum efficiency measurement system (Otsuka Electronics, product name QE-2100) at room temperature (25°C) with an excitation light wavelength of 365 nm, in the wavelength range of 300 nm to 950 nm. The internal quantum yield was calculated from the wavelength range of 450 nm to 950 nm. The results are shown in Table 1 and Figure 1.

[0130] (Comparative Example 1) Synthesis of semiconductor nanoparticles 0.4 mmol of silver acetate (AgOAc), 0.16 mmol of indium acetylacetonate (In(acac)3), 0.24 mmol of gallium acetylacetonate (Ga(acac)3), 8 mL of anhydrous oleylamine (OLA), and 1.25 mmol, 0.3 mL of dodecanethiol (DDT) were measured out into a reaction vessel. The reaction vessel was degassed and replaced with a nitrogen atmosphere, then heated to approximately 50°C. The lid was opened, and 0.8 mmol, 60.8 mg of thiourea crystals were added to obtain the mixture. Subsequently, degassing was performed for a very short time, and the temperature was raised at a rate of 10°C / min until it reached 150°C. After reaching 150°C by measurement, the heat treatment was continued for 60 seconds. The reaction vessel was then immersed in 50°C water to rapidly cool and stop the synthesis reaction. In the initial stages of rapid cooling, the temperature was cooled at an average rate of approximately 40°C / min. After removing coarse particles by centrifugation, 9 mL of methanol was added to the supernatant to precipitate the semiconductor nanoparticles, which were then recovered by centrifugation. The recovered solid was dispersed in 5 mL of hexane.

[0131] 3.3 mL of the hexane dispersion of the semiconductor nanoparticles synthesized above was measured out into the reaction vessel as the semiconductor nanoparticle dispersion, and 0.2 mmol of gallium acetylacetonate (Ga(acac)3), 0.3 mmol of 1,3-dimethylthiourea, and 36.5 mmol of tetradecylamine were added to obtain a mixture. The obtained mixture was degassed under vacuum and heated to 50°C while removing the hexane by volatilization, melting the tetradecylamine. Next, the atmosphere was changed to nitrogen and the temperature was raised to 270°C (heating rate 10°C / min), and held for 1 hour after reaching 270°C. Subsequently, it was allowed to cool to about 100°C, and the reaction vessel was degassed under vacuum to remove volatile sulfur compounds and other by-products while continuing to cool to about 60°C. After adding 3 mL of hexane to the obtained reaction solution, coarse particles were removed by centrifugation. Next, 8 mL of methanol was added and centrifuged to precipitate and remove larger particles. Then, 12 mL of methanol was added to the supernatant to precipitate the semiconductor nanoparticles, which were recovered by centrifugation. After washing with 10 mL of methanol, the obtained semiconductor nanoparticles were dispersed in 3 mL of hexane. Table 1 shows the emission spectrum measurements of the obtained semiconductor nanoparticles, performed in the same manner as in Example 1. Figure 1 shows the emission spectrum of the relative emission intensity normalized by the maximum emission intensity of the semiconductor nanoparticles from Example 1.

[0132] (Example 2) 1st step 0.1 mmol of silver ethylxanthogenic acid (Ag(EX)), 0.12 mmol of indium acetate (In(OAc)3), 0.2 mmol of gallium ethylxanthogenic acid (Ga(EX)3), and 0.010 mmol of gallium chloride were mixed with 20 mL of oleylamine to obtain the first mixture. The first mixture was heat-treated at 260°C for 120 minutes under a nitrogen atmosphere with stirring. After the resulting suspension was allowed to cool, it was subjected to centrifugation (radius 146 mm, 3800 rpm, 5 minutes) to remove the precipitate and obtain a dispersion of the first semiconductor nanoparticles.

[0133] 2nd process A dispersion containing 0.02 mmol of the 10 mL of the first semiconductor nanoparticles obtained above was mixed with 0.07 mmol of gallium chloride (GaCl3) to obtain a second mixture. The second mixture was heated under reduced pressure while stirring, raised to 80°C, and then heat-treated at 80°C for 10 minutes under reduced pressure. Subsequently, the temperature was raised to 260°C under a nitrogen atmosphere and heat-treated for 120 minutes. After the heat treatment, the obtained suspension was allowed to cool to obtain a dispersion of the second semiconductor nanoparticles. The emission spectrum measurements of the obtained second semiconductor nanoparticles, performed in the same manner as in Example 1, are shown in Table 1 and Figure 2.

[0134] (Example 3) The procedure was carried out in the same manner as in Example 2, except that the amount of gallium chloride in the first mixture in the first step was changed to 0.020 mmol, to obtain a dispersion of second semiconductor nanoparticles. The emission spectrum measurements of the obtained second semiconductor nanoparticles, performed in the same manner as in Example 1, are shown in Table 1. Figure 2 shows the emission spectrum of the relative emission intensity normalized by the maximum emission intensity of the semiconductor nanoparticles of Example 2.

[0135] (Example 4) Except for changing the amount of gallium chloride in the first mixture in the first step to 0.015 mmol, the procedure was carried out in the same manner as in Example 2 to obtain a dispersion of second semiconductor nanoparticles. The emission spectrum measurements of the obtained second semiconductor nanoparticles, performed in the same manner as in Example 1, are shown in Table 1. Figure 2 shows the emission spectrum of the relative emission intensity normalized by the maximum emission intensity of the semiconductor nanoparticles of Example 2.

[0136] (Example 5) The procedure was carried out in the same manner as in Example 2, except that the amount of gallium chloride in the first mixture in the first step was changed to 0.050 mmol, to obtain a dispersion of second semiconductor nanoparticles. The emission spectrum measurements of the obtained second semiconductor nanoparticles, taken in the same manner as in Example 1, are shown in Table 1. Figure 2 shows the emission spectrum of the relative emission intensity normalized by the maximum emission intensity of the semiconductor nanoparticles of Example 2.

[0137] (Example 6) In the first step, 0.04 mmol of silver ethylxanthogenic acid (Ag(EX)), 0.048 mmol of indium acetate (In(OAc)3), 0.08 mmol of gallium ethylxanthogenic acid (Ga(EX)3), and 0.008 mmol of gallium chloride were mixed with 20 mL of oleylamine to obtain the first mixture. The procedure was carried out in the same manner as in Example 2 to obtain a dispersion of second semiconductor nanoparticles. The emission spectrum measurements of the obtained second semiconductor nanoparticles were performed in the same manner as in Example 1 and the results are shown in Table 1 and Figure 3.

[0138] (Example 7) Except for changing the amount of gallium chloride in the first mixture in the first step to 0.016 mmol, the procedure was carried out in the same manner as in Example 6 to obtain a dispersion of second semiconductor nanoparticles. The emission spectrum measurements of the obtained second semiconductor nanoparticles, performed in the same manner as in Example 1, are shown in Table 1. Figure 3 shows the emission spectrum of the relative emission intensity normalized by the maximum emission intensity of the semiconductor nanoparticles of Example 6.

[0139] (Example 8) In the first step, 0.06 mmol of silver ethylxanthogenic acid (Ag(EX)), 0.072 mmol of indium acetate (In(OAc)3), 0.12 mmol of gallium ethylxanthogenic acid (Ga(EX)3), and 0.012 mmol of gallium chloride were mixed with 20 mL of oleylamine to obtain the first mixture. The procedure was carried out in the same manner as in Example 2 to obtain a dispersion of second semiconductor nanoparticles. The emission spectrum measurements of the obtained second semiconductor nanoparticles, taken in the same manner as in Example 1, are shown in Table 1. Figure 3 shows the emission spectrum of the relative emission intensity normalized by the maximum emission intensity of the semiconductor nanoparticles of Example 6.

[0140] (Example 9) In the first step, 0.14 mmol of silver ethylxanthogenic acid (Ag(EX)), 0.168 mmol of indium acetate (In(OAc)3), 0.28 mmol of gallium ethylxanthogenic acid (Ga(EX)3), and 0.028 mmol of gallium chloride were mixed with 20 mL of oleylamine to obtain the first mixture. The procedure was carried out in the same manner as in Example 2 to obtain a dispersion of second semiconductor nanoparticles. The emission spectrum measurements of the obtained second semiconductor nanoparticles, taken in the same manner as in Example 1, are shown in Table 1. Figure 3 shows the emission spectrum of the relative emission intensity normalized by the maximum emission intensity of the semiconductor nanoparticles of Example 6.

[0141] [Table 1]

[0142] Table 1 shows that in Example 1, semiconductor nanoparticles exhibiting band-edge emission with emission peak wavelengths in the range of 480 nm to 560 nm and high band-edge emission purity were obtained by one-pot synthesis, confirming that this is a more efficient manufacturing method compared to Comparative Example 1.

[0143] As shown in Table 1, in Examples 2 to 9, semiconductor nanoparticles exhibiting higher band-edge emission purity and internal quantum yield were obtained compared to Example 1.

[0144] Scanning transmission electron microscopy (STEM) - Energy-dispersive X-ray analysis (XDS) The semiconductor nanoparticles obtained in Example 2 were subjected to line analysis of their composition along the diameter direction of the semiconductor nanoparticles using a multifunctional electron microscope (JEOL; JEM-F200) equipped with a dry SD detector under the following conditions. The trajectory of the line analysis is shown in Figure 4A, and the results of the composition analysis are shown in Figure 4B. In Figure 4B, the intensity of characteristic X-rays originating from Ga in a predetermined region of the second semiconductor is shown as X1, and the intensity of characteristic X-rays originating from Ga in a predetermined region of the first semiconductor is shown as X2.

[0145] Measurement conditions STEM…Acceleration voltage: 80kV, EDX…Acceleration voltage: 80kV, Resolution: 256×256, Frame time: 5sec, Number of frames: 500

[0146] As shown in Figure 4B, the intensity of characteristic X-rays originating from Ga near the surface of the semiconductor nanoparticle is greater than the intensity of characteristic X-rays originating from Ga near the center of the semiconductor nanoparticle.

[0147] The disclosure of Japanese Patent Application No. 2021-036717 (filing date: March 8, 2021) is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. The method involves first heat treatment of a first mixture containing a silver (Ag) salt, an indium (In) salt, a compound having a gallium (Ga)-sulfur (S) bond, a gallium halide, and an organic solvent to obtain first semiconductor nanoparticles. The aforementioned Ag salt includes dithiocarbonate (xanthogenic acid) Ag salt or a derivative thereof. The In salt is an organic acid salt and comprises at least one of an acetate salt and an acetylacetonate salt. The compound having the Ga-S bond includes a dithiocarbonate (xanthogenic acid) Ga salt or a derivative thereof. The gallium halide contains gallium chloride, The organic solvent comprises at least one selected from the group consisting of amines having a hydrocarbon group having 4 to 20 carbon atoms, thiols having a hydrocarbon group having 4 to 20 carbon atoms, and phosphines having a hydrocarbon group having 4 to 20 carbon atoms. The first heat treatment is a method for producing semiconductor nanoparticles, performed at a temperature of 200°C to 320°C.

2. The method for producing semiconductor nanoparticles according to claim 1, wherein the molar ratio of the gallium halide content to the Ag salt in the first mixture is 0.01 or more and 1 or less.

3. A method for producing semiconductor nanoparticles according to claim 1 or 2, wherein the concentration of the Ag salt in the first mixture is 0.01 mmol / liter or more and 500 mmol / liter or less.

4. The method for producing semiconductor nanoparticles according to any one of claims 1 to 3, wherein the first heat treatment is performed at a temperature of 200°C to 290°C for 30 minutes to 180 minutes.

5. The method for producing semiconductor nanoparticles according to any one of claims 1 to 4, wherein the compound having a Ga-S bond comprises a dithiocarbonate (xanthogenic acid) Ga salt having an alkyl group having 1 to 4 carbon atoms.

6. The method for producing semiconductor nanoparticles according to any one of claims 1 to 5, wherein the Ag salt comprises a dithiocarbonate (xanthogenic acid) Ag salt having an alkyl group having 1 to 4 carbon atoms.

7. A method for producing semiconductor nanoparticles according to any one of claims 1 to 6, further comprising second heat treatment of a second mixture containing the first semiconductor nanoparticle and a gallium halide to obtain second semiconductor nanoparticles.

8. The method for producing semiconductor nanoparticles according to claim 7, wherein the molar ratio of gallium halide to first semiconductor nanoparticles in the second mixture is 0.1 or more and 10 or less.

9. The method for producing semiconductor nanoparticles according to claim 7 or 8, wherein the gallium halide in the second mixture is gallium chloride.

10. The method for producing semiconductor nanoparticles according to any one of claims 7 to 9, wherein the second heat treatment is performed at a temperature of 200°C or higher and 320°C or lower.

11. A semiconductor nanoparticle comprising a first semiconductor containing silver (Ag), indium (In), gallium (Ga), and sulfur (S), A second semiconductor containing Ga and S is disposed on the surface of the aforementioned semiconductor nanoparticles. When irradiated with light at a wavelength of 365 nm, it exhibits band-edge emission with an emission peak wavelength in the wavelength range of 475 nm to 560 nm. The band edge emission purity is 70% or higher. The internal quantum yield of band-edge emission is 15% or more. In energy-dispersive X-ray analysis, the intensity of characteristic X-rays originating from the Ga of the second semiconductor is greater than the intensity of characteristic X-rays originating from the Ga of the first semiconductor. Semiconductor nanoparticles in which the ratio of the molar content of Ag in the composition of the second semiconductor to the molar content of Ag in the composition of the first semiconductor is 0.1 or more and 0.7 or less.

12. The semiconductor nanoparticle according to claim 11, wherein the ratio of the maximum value of the characteristic X-ray intensity derived from the Ga of the second semiconductor to the minimum value of the characteristic X-ray intensity derived from the Ga of the first semiconductor is 1.1 or more and 3 or less.

13. The semiconductor nanoparticle according to claim 11 or 12, wherein the full width at half maximum in the emission spectrum of the semiconductor nanoparticle is 45 nm or less.

14. The semiconductor nanoparticle according to any one of claims 11 to 13, wherein the surface of the semiconductor nanoparticle is surface-modified with a gallium halide.

15. A light-emitting device comprising a light-converting member containing semiconductor nanoparticles according to any one of claims 11 to 14, and a semiconductor light-emitting element.

16. The light-emitting device according to claim 15, wherein the semiconductor light-emitting element is an LED chip.

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