Method for producing core / shell type semiconductor nanoparticles

Abstract

A method for producing core / shell semiconductor nanoparticles, said method being characterized by having a shell formation step wherein a solution of a VI group element precursor is added to a dispersion of core particles, while adding a solution of a carboxylic acid zinc salt having a branched chain to the dispersion, and the carboxylic acid zinc salt having a branched chain and the VI group element precursor are reacted with each other in the presence of the core particles, thereby forming a shell that contains zinc and a VI group element on the surface of each of the core particles. The present invention is able to provide an easy method for producing semiconductor nanoparticles, said method being capable of producing semiconductor nanoparticles having a core / shell structure and excellent optical characteristics in cases where semiconductor nanoparticles having a core / shell structure are produced using two or more kinds of shell precursors.

Description

Technical Field

[0001] The present invention relates to a method for producing core / shell type semiconductor nanoparticles.

Background Art

[0002] As a wavelength conversion material for displays, semiconductor nanoparticles (quantum dots: QD) with a small particle size are used. Such semiconductor nanoparticles are minute particles that can exhibit a quantum confinement effect, and the width of the bandgap changes depending on the size of the nanoparticles. Then, excitons formed in the semiconductor particles by means such as photoexcitation and charge injection emit photons of energy corresponding to the bandgap by recombination. Therefore, by adjusting the crystal size of the semiconductor nanoparticles, it becomes possible to control the emission wavelength and obtain emission of a desired wavelength.

[0003] Currently, as semiconductor nanoparticles, semiconductor nanoparticles having a core / shell type structure are often used. This is because by adopting a core / shell structure, the effect of filling the dangling bonds on the core surface and reducing surface defects can be obtained.

[0004] As such core / shell type semiconductor nanoparticles, semiconductor nanoparticles composed of a group III-V core and a group II-VI shell are used. However, in a group III-V core and a group II-VI shell, due to the difference in lattice constants, defect levels are easily formed. In semiconductor nanoparticles in which defect levels are formed, non-radiative recombination of excitons via the defect levels occurs, so the optical properties are likely to deteriorate. Therefore, it is important to form a group II-VI shell that suppresses the generation of defect levels on the surface of the group III-V core.

[0005] As a method for forming a shell on the surface of core particles, the SILAR method is known. The SILAR method is a method of forming a shell by alternately adding shell precursors to core particles and reacting the added shell precursors on the particle surface. For example, to core particles, first a Zn precursor is added, then an S precursor is added, then a Zn precursor is added, then an S precursor is added, and so on. In this way, two types of shell precursors that are raw materials for the shell are alternately brought into contact with the core particles to alternately form layers of the two types of shell precursors on the particle surface, and the two types of shell precursors are reacted to form a shell.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[0007] However, in the SILAR method, in the formation of each precursor layer, strict control of the addition amount of the precursor is required. If the addition amount of the precursor is too small, a sufficient shell will not be formed and the optical properties will deteriorate. On the other hand, if the addition amount of the precursor is too large, there is a problem that the particles will be altered and by-products will be generated due to the excess precursor.

[0008] In addition, since two types of shell precursors are brought into contact with the particles separately and alternately a plurality of times, there is also a problem that the manufacturing method of semiconductor nanoparticles becomes complicated.

[0009] Accordingly, an object of the present invention is to provide a method for producing core / shell type semiconductor nanoparticles that is simple and has excellent optical properties when producing core / shell type semiconductor nanoparticles using two or more types of shell precursors.

Means for Solving the Problems

[0010] As a result of intensive studies to solve the above problems, the present inventors used a zinc salt of a carboxylic acid having a branched chain as a Group II element precursor that is added to a dispersion of core particles and reacts with a Group VI element precursor on the surface of the core particles. By doing so, even if the operation of separately and alternately contacting the Group II element precursor and the Group IV element precursor multiple times is not performed, that is, even if the total amounts of the Group II element precursor and the Group VI element precursor are brought into contact with the core particles at once and reacted, it was found that core / shell type semiconductor nanoparticles having excellent optical properties can be obtained, and the present invention has been completed.

[0011] That is, the present invention (1) has a shell formation step of adding a solution of a zinc salt of a carboxylic acid having a branched chain to a dispersion of core particles and adding a solution of a Group VI element precursor, and reacting the zinc salt of the carboxylic acid having a branched chain with the Group VI element precursor in the presence of the core particles to form a shell containing zinc and a Group VI element on the surface of the core particles. A method for producing core / shell type semiconductor nanoparticles is provided.

[0012] Further, the present invention (2) has a shell formation step of adding a solution of a zinc salt of a carboxylic acid having a branched chain and a Group VI element precursor to a dispersion of core particles and reacting the zinc salt of the carboxylic acid having a branched chain with the Group VI element precursor in the presence of the core particles to form a shell containing zinc and a Group VI element on the surface of the core particles. A method for producing core / shell type semiconductor nanoparticles is provided.

[0013] Furthermore, the present invention (3) provides a method for producing the core / shell type semiconductor nanoparticles of (1) or (2), characterized in that the Group VI element contains at least Se.

[0014] Furthermore, the present invention (4) provides a method for producing the core / shell type semiconductor nanoparticles of any one of (1) to (3), characterized in that the Group VI element precursor contains at least trialkylphosphine selenide.

[0015] Furthermore, the present invention (5) provides a method for producing core / shell type semiconductor nanoparticles, which has a shell formation step of adding a solution of a zinc salt of a carboxylic acid having a branched chain to a dispersion of core particles, and then adding a solution of a Group VI element precursor containing at least a Se precursor, and reacting the zinc salt of the carboxylic acid having the branched chain with the Group VI precursor in the presence of the core particles to form a shell containing zinc and a Group VI element on the surface of the core particles.

[0016] Furthermore, the present invention (6) provides a method for producing the core / shell type semiconductor nanoparticles of (5), characterized in that the Se precursor is trialkylphosphine selenide.

[0017] Furthermore, the present invention (7) provides a method for producing the core / shell type semiconductor nanoparticles of any one of (1) to (6), characterized in that the core particles contain In and P.

[0018] Furthermore, the present invention (8) provides a method for producing the core / shell type semiconductor nanoparticles of any one of (1) to (7), characterized in that the zinc salt of the carboxylic acid having a branched chain is one or more selected from the group consisting of zinc 2-ethylhexanoate, zinc 3,5,5-trimethylhexanoate, and zinc 16-methylheptadecanoate.

[0019] Further, the present invention (9) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (1), (3) to (8), characterized in that the solvent of the zinc salt solution of the carboxylic acid having the branched chain is at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit, and liquid paraffin.

[0020] Further, the present invention (10) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (2) to (4), (7), (8), characterized in that the solvent of the solution of the zinc salt of the carboxylic acid having the branched chain and the group VI element precursor is at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit, and liquid paraffin.

[0021] Further, the present invention (11) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (1), (3), (4), (7) to (9), characterized in that the solvent of the solution of the group VI element precursor is at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit, and liquid paraffin.

[0022] Further, the present invention (12) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (5) to (9), characterized in that the solvent of the solution of the group VI element precursor containing at least the Se precursor is at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit, and liquid paraffin.

[0023] Further, the present invention (13) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (1), (3) to (9), (11), (12), characterized in that the solution of the zinc salt of the carboxylic acid having the branched chain is in a solution state at 25°C and 1 atm.

[0024] Further, the present invention (14) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (2)-(4), (7), (8), (10), characterized in that the solution of the zinc salt of the carboxylic acid having the branched chain and the Group VI element precursor is in a solution state at 25°C and 1 atm.

[0025] Further, the present invention (15) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (1)-(14), characterized in that the zinc salt of the carboxylic acid having the branched chain and the Group VI element precursor are reacted at 180-320°C.

[0026] Further, the present invention (16) provides a method for producing core / shell type semiconductor nanoparticles according to (15), characterized in that the zinc salt of the carboxylic acid having the branched chain and the Group VI element precursor are reacted at 250-320°C.

[0027] Further, the present invention (17) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (1)-(16), characterized in that the addition amount of the zinc salt of the carboxylic acid having the branched chain is an addition amount such that the molar ratio of Zn to In in the core particles in the zinc salt of the carboxylic acid having the branched chain (Zn / In) is 7-50.

[0028] Further, the present invention (18) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (1)-(17), characterized in that the addition time of the zinc salt of the carboxylic acid having the branched chain to the dispersion of the core particles is 5-600 minutes.

[0029] Further, the present invention (19) provides a method for producing core / shell type semiconductor nanoparticles according to (18), characterized in that the addition time of the zinc salt of the carboxylic acid having the branched chain to the dispersion of the core particles is 30-180 minutes.

[0030] Further, the present invention (20) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (1) to (19), characterized in that while heating the dispersion of the core particles, a solution of a zinc salt of the carboxylic acid having the branched chain and a solution of the group VI element precursor or a solution of the group VI element precursor containing at least the Se precursor are added to the dispersion of the core particles, or a zinc salt of the carboxylic acid having the branched chain and a solution of the group VI element precursor are added.

[0031] Further, the present invention (21) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (1) to (20), characterized in that the reaction between the zinc salt of the carboxylic acid having the branched chain and the group VI element precursor is carried out in the presence of a dispersant.

[0032] Further, the present invention (22) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (1) to (21), characterized in that the reaction between the zinc salt of the carboxylic acid having the branched chain and the group VI element precursor is carried out in the presence of a halogen element.

[0033] Further, the present invention (23) provides a method for producing core / shell type semiconductor nanoparticles according to (22), characterized in that the halogen element is chlorine or bromine.

[0034] Further, the present invention (24) provides a method for producing core / shell type semiconductor nanoparticles according to any one of (1) to (23), characterized in that the core particles have not undergone a purification process.

[0035] Further, the present invention (25) is a core / shell type semiconductor nanoparticle composite having core / shell type semiconductor nanoparticles and a ligand coordinated on the surface of the core / shell type semiconductor nanoparticles, wherein the shell contains at least Zn and Se, and the ligand contains a carboxylic acid having a branched chain, and provides a core / shell type semiconductor nanoparticle composite characterized thereby.

[0036] Further, in the present invention (26), the molar fraction of the ligand of the carboxylic acid having the branched chain in all the ligands coordinated to the core / shell type semiconductor nanoparticles is 20.0 to 80.0 mol%, which is a characteristic of the core / shell type semiconductor nanoparticle composite (25).

[0037] Also, the present invention (27) provides a core / shell type semiconductor nanoparticle composite (25) or (26), characterized in that the carboxylic acid having the branched chain is one or more selected from the group consisting of 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, and 16-methylheptadecanoic acid.

[0038] Further, the present invention (28) provides a core / shell type semiconductor nanoparticle composite (25) to (27), characterized in that the full width at half maximum (FWHM) of the emission spectrum of the core / shell type semiconductor nanoparticle composite is 35 nm or less.

[0039] Also, the present invention (29) provides a core / shell type semiconductor nanoparticle composite according to any one of (25) to (28), characterized in that the quantum efficiency (QY) of the core / shell type semiconductor nanoparticle composite is 80% or more.

Advantages of the Invention

[0040] According to the present invention, when manufacturing core / shell type semiconductor nanoparticles using two or more types of shell precursors, it is possible to provide a method for manufacturing semiconductor nanoparticles that is simple and can produce core / shell type semiconductor nanoparticles with excellent optical properties.

Embodiments for Carrying Out the Invention

[0041] The method for producing core / shell type semiconductor nanoparticles of the present invention is a method for producing core / shell type semiconductor nanoparticles having any one of the following shell forming steps (1-i), shell forming steps (1-ii), or shell forming steps (1-iii) as a step of forming a shell containing zinc and a Group VI element on the surface of core particles.

[0042] The method for producing core / shell type semiconductor nanoparticles according to the first aspect of the present invention is characterized by having a shell forming step (also referred to as shell forming step (1-i)) of forming a shell containing zinc and a Group VI element on the surface of the core particles by adding a solution of a zinc salt of a carboxylic acid having a branched chain to a dispersion of the core particles while adding a solution of a Group VI element precursor and reacting the zinc salt of the carboxylic acid having a branched chain with the Group VI element precursor in the presence of the core particles.

[0043] Further, the method for producing core / shell type semiconductor nanoparticles according to the second aspect of the present invention is characterized by having a shell forming step (also referred to as shell forming step (1-ii)) of forming a shell containing zinc and a Group VI element on the surface of the core particles by adding a solution of a zinc salt of a carboxylic acid having a branched chain and a solution of a Group VI element precursor to a dispersion of the core particles and reacting the zinc salt of the carboxylic acid having a branched chain with the Group VI element precursor in the presence of the core particles.

[0044] Further, the method for producing core / shell type semiconductor nanoparticles according to the third aspect of the present invention is characterized by having a shell forming step (also referred to as shell forming step (1-iii)) of forming a shell containing zinc and a Group VI element on the surface of the core particles by adding a solution of a zinc salt of a carboxylic acid having a branched chain to a dispersion of the core particles and then adding a solution of a Group VI element precursor containing at least a Se precursor and reacting the zinc salt of the carboxylic acid having a branched chain with the Group VI element precursor in the presence of the core particles.

[0045] In the following, regarding the common points among the shell formation step (1-i), the shell formation step (1-ii), and the shell formation step (1-iii), the shell formation step (1-i), the shell formation step (1-ii), and the shell formation step (1-iii) are collectively referred to as the shell formation step (1) and will be described accordingly.

[0046] Note that in the following, the symbol "~" indicating a numerical range indicates a range including the numerical values described before and after the symbol "~" unless otherwise specified. That is, 〇~△ represents 〇 or more and △ or less.

[0047] The shell formation step (1-i) is a step of forming a shell containing zinc and a Group VI element on the surface of core particles by adding a solution of a zinc salt of a carboxylic acid having a branched chain to a dispersion of the core particles while adding a solution of a Group VI element precursor and reacting the zinc salt of the carboxylic acid having a branched chain with the Group VI element precursor in the presence of the core particles.

[0048] Also, the shell formation step (1-ii) is a step of forming a shell containing zinc and a Group VI element on the surface of core particles by adding a solution of a zinc salt of a carboxylic acid having a branched chain and a solution of a Group VI element precursor to a dispersion of the core particles and reacting the zinc salt of the carboxylic acid having a branched chain with the Group VI element precursor in the presence of the core particles.

[0049] Also, the shell formation step (1-iii) is a step of forming a shell containing zinc and a Group VI element on the surface of core particles by adding a solution of a zinc salt of a carboxylic acid having a branched chain to a dispersion of the core particles and then adding a solution of a Group VI element precursor containing at least a Se precursor and reacting the zinc salt of the carboxylic acid having a branched chain with the Group VI element precursor in the presence of the core particles.

[0050] In the shell formation step (1), the zinc precursor added to the dispersion of core particles, that is, the zinc precursor that reacts with the Group VI element precursor, is a zinc salt of a carboxylic acid having a branched chain. The carboxylic acid having a branched chain is a carboxylic acid having a main chain composed of a hydrocarbon and a branched chain branching from the main chain. Examples of the carboxylic acid having a branched chain include 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, 16-methylheptadecanoic acid, and the like. That is, examples of the zinc precursor include zinc salts of 2-ethylhexanoic acid, zinc salts of 3,5,5-trimethylhexanoic acid, zinc salts of 16-methylheptadecanoic acid, and the like. The zinc salt of the carboxylic acid having a branched chain may be a single species or a combination of two or more species. As the zinc precursor, as described later, as long as it is a zinc salt of a carboxylic acid having a branched chain that is in a solution state at 25 ° C and 1 atm when the zinc salt of the carboxylic acid having a branched chain is dissolved in a solvent, it is not limited to zinc salts of 2-ethylhexanoic acid, zinc salts of 3,5,5-trimethylhexanoic acid, and zinc salts of 16-methylheptadecanoic acid.

[0051] In the shell formation step (1-i) or the shell formation step (1-ii), examples of the Group VI element precursor added to the dispersion of core particles, that is, the Group VI element precursor that reacts with the zinc precursor, include a Se precursor, an S precursor, and a Te precursor. The Group VI element precursor may be a single species or a combination of two or more species, and it is preferably included at least a Se precursor. That is, the Group VI element precursor that reacts with the zinc precursor may be a precursor of any one of the Group VI elements, such as only the Se precursor, or, for example, a combination of a Se precursor and an S precursor, a combination of a Se precursor and a Te precursor, a combination of a Se precursor, an S precursor, and a Te precursor, etc., may be a combination of precursors of two or more of the Group VI elements. In the shell formation step (1-i) or the shell formation step (1-ii), when there is only one kind of Se precursor, the effects of the present invention can be more obtained.

[0052] In the shell formation step (1-iii), the Group VI element precursor added to the dispersion of core particles, that is, the Group VI element precursor that reacts with the zinc precursor, is a Group VI element precursor, and at least a part of the Group VI element precursor is a Se precursor. That is, in the shell formation step (1-iii), the "solution of a Group VI element precursor containing at least a Se precursor" added to the dispersion of core particles contains at least a Se precursor as the Group VI element precursor. Further, the "solution of a Group VI element precursor containing at least a Se precursor" may contain a precursor of a Group VI element other than Se, and examples of such a Group VI element precursor include an S precursor and a Te precursor. In the solution of a Group VI element precursor containing at least a Se precursor according to the shell formation step (1-iii), the ratio of the Se precursor to all the Group VI element precursors is preferably 50 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, and particularly preferably 100 mol%.

[0053] In the shell formation step (1), the Se precursor is not particularly limited, and examples thereof include trialkylphosphine selenide and selenol. As the Se precursor, trialkylphosphine selenide is preferred. The Se precursor may be used alone or in combination of two or more.

[0054] In the shell formation step (1), the S precursor is not particularly limited, and examples thereof include trialkylphosphine sulfides such as trioctylphosphine sulfide and tributylphosphine sulfide, thiols, and bis(trimethylsilyl) sulfide. As the S precursor, trioctylphosphine sulfide is preferred. The S precursor may be used alone or in combination of two or more.

[0055] In the shell formation step (1), the Te precursor is not particularly limited, and examples thereof include trioctylphosphine telluride. As the Te precursor, trioctylphosphine telluride is preferred. The Te precursor may be used alone or in combination of two or more.

[0056] In the shell formation step (1), when only a Se precursor is used as the Group VI element precursor, a shell layer containing zinc and Se is formed. When a Se precursor and an S precursor are used in combination, a shell layer containing zinc, Se, and S is formed. When a Se precursor and a Te precursor are used in combination, a shell layer containing zinc, Se, and Te is formed. When a Se precursor, an S precursor, and a Te precursor are used in combination, a shell layer containing zinc, Se, S, and Te is formed.

[0057] In the shell formation step (1), the core particles on which the shell layer is formed are not particularly limited as long as they are used as the core particles of core / shell type semiconductor nanoparticles. Preferably, they are core particles containing In and P, and particularly preferably core particles containing In, P, and a halogen. It is preferable that the core particles contain In and P because semiconductor nanoparticles with a small environmental load and high optical properties can be obtained. Further, it is preferable that the core particles contain a halogen because the optical properties of the core particles and the semiconductor nanoparticles can be enhanced. Examples of the halogen contained in the core particles include F, Cl, Br, and I. Among these, Cl and Br are preferable as the halogen because they have a high effect of narrowing the full width at half maximum and reducing the Stokes shift. Further, the core particles may contain other elements such as Ga, Al, Zn, N, S, Si, and Ge.

[0058] When the core particles contain In and P, in the core particles, the molar ratio of P to In in terms of atoms is 0.20 to 1.20, preferably 0.20 to 0.95, and more preferably 0.40 to 0.95. When the molar ratio of P to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small.

[0059] When the core particles contain a halogen, in the core particles, the molar ratio of the halogen to In in terms of atoms is 0.80 to 15.00, preferably 1.00 to 15.00. When the molar ratio of the halogen to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small. When the core particles contain two or more kinds of halogens, the above-mentioned molar ratio of the halogen to In refers to the value obtained by summing up the molar ratios of each of the two or more kinds of halogens to In.

[0060] The Cd content of the core particles is 100 mass ppm or less, preferably 80 mass ppm or less, and particularly preferably 50 mass ppm or less.

[0061] The average particle size of the core particles is not particularly limited, but is preferably 1.0 nm to 5.0 nm. When the average particle size of the core particles is within the above range, excitation light of 450 nm can be converted into green to red light emission. In the present invention, the average particle size of the core particles is determined by calculating the particle sizes of 10 or more particles as the equivalent diameter of the area circle (Heywood diameter) for the particle images observed by a transmission electron microscope (TEM).

[0062] The method for synthesizing the core particles is not particularly limited and is appropriately selected. In the present invention, the In precursor, P precursor, and halogen precursor are as follows.

[0063] The In precursor is not particularly limited, and examples thereof include indium carboxylates such as indium acetate, indium propionate, indium myristate, indium oleate, indium halides such as indium fluoride, indium bromide, indium iodide, indium thiolate, trialkylindium, and the like.

[0064] The P precursor is not particularly limited, and examples thereof include tris(trimethylsilyl)phosphine, tris(trimethylgermyl)phosphine, tris(dimethylamino)phosphine, tris(diethylamino)phosphine, tris(dioctylamino)phosphine, trialkylphosphine, PH3 Examples include gas and the like. When using tris(trimethylsilyl)phosphine as the P precursor, Si may be incorporated into the semiconductor nanoparticles, but this does not impair the operation of the present invention.

[0065] The halogen precursor is not particularly limited, and examples thereof include carboxylic acid halides such as HF, HCl, HBr, HI, oleyl chloride, oleyl bromide, octanoyl chloride, octynoyl bromide, oleoyl chloride, and metal halides such as zinc chloride, indium chloride, and gallium chloride.

[0066] Examples of the method for synthesizing the core particles containing In and P include the following methods. The method for synthesizing the core particles described below is an example, and the core particles are not limited to those synthesized by the following synthesis methods. The core particles are synthesized, for example, by reacting an In precursor and a P precursor. First, the In precursor and a solvent are mixed, and if necessary, a dispersant and / or an additive are added, and the In precursor solution is mixed under vacuum. After heating at 100 to 300 °C for 6 to 24 hours once, the P precursor is added, and after heating at 200 to 400 °C for several seconds (for example, 2 or 3 seconds) to 60 minutes, and then cooling, a core particle dispersion liquid in which the core particles are dispersed is obtained. Next, a halogen precursor is added to the core particle dispersion liquid, and after heating at 25 to 300 °C for several seconds (for example, 2 or 3 seconds) to 60 minutes and then cooling, a halogen-added core particle dispersion liquid having halogen on a part of the surface of the particles is obtained.

[0067] The dispersant is not particularly limited, and examples thereof include carboxylic acids, amines, thiols, phosphines, phosphine oxides, phosphines, phosphonic acids, etc. The dispersant can also serve as a solvent. The solvent is not particularly limited, and examples thereof include 1-octadecene, hexadecane, squalane, oleylamine, trioctylphosphine, trioctylphosphine oxide, etc. Examples of the additive include the above S precursor, Zn precursor, halogen precursor, etc.

[0068] The dispersion of core particles related to the shell formation step (1) is a dispersion in which the core particles are dispersed in a dispersion medium. The dispersion medium in which the core particles are dispersed is not particularly limited, and examples include 1-octadecene, hexadecane, squalane, squalene, mineral spirit, liquid paraffin, trioctylamine, trioctylphosphine, trioctylphosphine oxide, toluene, hexane, diphenyl ether, etc. These may be used alone or in combination of two or more, and preferably at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit, and liquid paraffin.

[0069] The solution of the zinc salt of the carboxylic acid having a branched chain related to the shell formation step (1-i) or (1-iii) is a solution in which the zinc salt of the carboxylic acid having a branched chain is dissolved in a solvent. The solvent used for the solution of the zinc salt of the carboxylic acid having a branched chain is not particularly limited, and examples include 1-octadecene, hexadecane, squalane, squalene, mineral spirit, liquid paraffin, trioctylamine, trioctylphosphine, trioctylphosphine oxide, toluene, hexane, diphenyl ether, etc. These may be used alone or in combination of two or more, and preferably at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit, and liquid paraffin.

[0070] The zinc salt solution of the carboxylic acid having a branched chain according to the shell formation step (1-i) or (1-iii) is preferably in a solution state at 25 °C and 1 atm. Since the zinc salt solution of the carboxylic acid having a branched chain is in a solution state at 25 °C and 1 atm, even if the addition of the zinc salt solution of the carboxylic acid having a branched chain to the dispersion of the core particles takes time, it is difficult for the zinc salt of the carboxylic acid having a branched chain to precipitate in the supply pipe and cause the problem of clogging the supply pipe. Note that the zinc salt solution of the carboxylic acid having a branched chain being in a solution state at 25 °C and 1 atm means that when the zinc salt solution of the carboxylic acid having a branched chain is held in an environment of 25 °C and 1 atm for 3 hours and then the solution is visually observed, no precipitate is observed in the solution.

[0071] The solution of the Group VI element precursor according to the shell formation step (1-i) is a solution in which the Group VI element precursor is dissolved in a solvent. The solvent used for the solution of the Group VI element precursor is not particularly limited, and examples thereof include 1-octadecene, hexadecane, squalane, squalene, mineral spirit, liquid paraffin, trioctylamine, trioctylphosphine, trioctylphosphine oxide, toluene, hexane, diphenyl ether, etc. Preferably, it is at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit and liquid paraffin.

[0072] The solution of the Group VI element precursor according to the shell formation step (1-i) is preferably in a solution state at 25 °C and 1 atm. Since the solution of the Group VI element precursor is in a solution state at 25 °C and 1 atm, even if the addition of the solution of the Group VI element precursor to the dispersion of the core particles takes time, it is difficult for the Group VI element precursor to precipitate in the supply pipe and cause the problem of clogging the supply pipe. Note that the solution of the Group VI element precursor being in a solution state at 25 °C and 1 atm means that when the solution of the Group VI element precursor is held in an environment of 25 °C and 1 atm for 3 hours and then the solution is visually observed, no precipitate is observed in the solution.

[0073] The solution of the Group VI element precursor containing at least a Se element precursor according to the shell formation step (1-iii) is a solution in which the Group VI element precursor is dissolved in a solvent and part or all of the Group VI element precursor is a Se precursor. The solvent used for the solution of the Se precursor is not particularly limited, and examples thereof include 1-octadecene, hexadecane, squalane, squalene, mineral spirit, liquid paraffin, trioctylamine, trioctylphosphine, trioctylphosphine oxide, toluene, hexane, diphenyl ether, etc. Preferably, it is at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit and liquid paraffin.

[0074] The solution of the Group VI element precursor containing at least a Se element precursor according to the shell formation step (1-iii) is preferably in a solution state at 25°C and 1 atm. When the solution of the Group VI element precursor containing at least a Se element precursor is in a solution state at 25°C and 1 atm, even if the addition of the solution of the Group VI element precursor containing at least a Se element precursor to the dispersion of the core particles takes time, it is difficult for the Group VI element precursor to precipitate in the supply pipe and cause a problem of clogging the supply pipe. Note that the solution of the Group VI element precursor containing at least a Se element precursor being in a solution state at 25°C and 1 atm means that when the solution of the Group VI element precursor containing at least a Se element precursor is held in an environment of 25°C and 1 atm for 3 hours and then the solution is visually observed, no precipitate is observed in the solution.

[0075] The solution of the zinc salt of a carboxylic acid having a branched chain and a Group VI element precursor according to the shell formation step (1-ii) is a solution in which both the zinc salt of a carboxylic acid having a branched chain and the Group VI element precursor are dissolved in a solvent. The solvent used for the solution of the zinc salt of a carboxylic acid having a branched chain and the Group VI element precursor is not particularly limited, and examples thereof include 1-octadecene, hexadecane, squalane, squalene, mineral spirit, liquid paraffin, trioctylamine, trioctylphosphine, trioctylphosphine oxide, toluene, hexane, diphenyl ether, etc. These may be used alone or in combination of two or more, and preferably at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit and liquid paraffin.

[0076] The solution of the zinc salt of a carboxylic acid having a branched chain and the Group VI element precursor according to the shell formation step (1-ii) is preferably in a solution state at 25°C and 1 atm. When the solution of the zinc salt of a carboxylic acid having a branched chain and the Group VI element precursor is in a solution state at 25°C and 1 atm, even if it takes time to add the solution of the zinc salt of a carboxylic acid having a branched chain and the Group VI element precursor to the dispersion of the core particles, it is difficult for the zinc salt of a carboxylic acid having a branched chain or the Group VI element precursor to precipitate in the supply pipe and cause the problem of clogging the supply pipe. Note that the fact that the solution of the zinc salt of a carboxylic acid having a branched chain and the Group VI element precursor is in a solution state at 25°C and 1 atm means that when the solution of the zinc salt of a carboxylic acid having a branched chain and the Group VI element precursor is held in an environment of 25°C and 1 atm for 3 hours and then the solution is visually observed, no precipitate is observed in the solution. The solution in which both the zinc salt of a carboxylic acid having a branched chain and the Group VI element precursor are dissolved in a solvent often has a lower viscosity than the case of the solution of the zinc salt of a carboxylic acid having a branched chain alone or the solution of the Group VI element precursor alone, and when added to the dispersion of the core particles, the risk of the above-mentioned problems occurring is further reduced.

[0077] In the shell forming step (1-i), the addition of the solution of the VI group element precursor while adding the solution of the zinc salt of the carboxylic acid having a branched chain to the dispersion of the core particles means that "the solution of the zinc salt of the carboxylic acid having a branched chain is continuously added to the dispersion of the core particles, or added at regular or irregular intervals", and "the solution of the VI group element precursor is continuously added to the dispersion of the core particles, or added at regular or irregular intervals", and "the time period from the start to the end of the addition of the solution of the zinc salt of the carboxylic acid having a branched chain to the dispersion of the core particles and the time period from the start to the end of the addition of the solution of the VI group element precursor to the dispersion of the core particles overlap at least partially, preferably at least 50% overlap, and particularly preferably 80% or more overlap".

[0078] The method of continuously adding the solution of the zinc salt of the carboxylic acid having a branched chain or the solution of the VI group element precursor to the dispersion of the core particles is not particularly limited. For example, the method of positioning the end of the outlet side of the solution supply pipe in the dispersion of the core particles and continuously supplying the solution of the zinc salt of the carboxylic acid having a branched chain or the solution of the VI group element precursor from the solution supply pipe can be mentioned. Further, the method of adding the solution of the zinc salt of the carboxylic acid having a branched chain or the solution of the VI group element precursor to the dispersion of the core particles at regular or irregular intervals is not particularly limited. For example, the method of positioning the end of the outlet side of the solution supply pipe above the liquid level of the dispersion of the core particles and dropping the solution of the zinc salt of the carboxylic acid having a branched chain or the solution of the VI group element precursor at regular or irregular intervals from the solution supply pipe, or the method of injecting a predetermined amount of the solution of the zinc salt of the carboxylic acid having a branched chain or the solution of the VI group element precursor each time at regular or irregular intervals can be mentioned.

[0079] In the shell formation step (1-i), it is preferable to start adding a solution of a zinc salt of a carboxylic acid having a branched chain simultaneously with the start of adding a solution of a Group VI element precursor to the dispersion of core particles, or to start adding a solution of a zinc salt of a carboxylic acid having a branched chain to the dispersion of core particles prior to the solution of the Group VI element precursor. The reason is that when a solution of a Group VI element precursor is added to the core particles in a state where there is no zinc salt of a carboxylic acid having a branched chain around the core particles, first, only the Group VI element precursor easily reacts with the surface of the core particles to form a shell containing the Group VI element and not containing Zn.

[0080] In the shell formation step (1-ii), adding a zinc salt of a carboxylic acid having a branched chain and a solution of a Group VI element precursor to the dispersion of core particles means that first, a solution in which a zinc salt of a carboxylic acid having a branched chain and a Group VI element precursor are dissolved in a solvent is prepared, and then the prepared solution of the zinc salt of a carboxylic acid having a branched chain and the Group VI element precursor is continuously added to the dispersion of core particles, or added at regular or irregular intervals.

[0081] As a method of first preparing a solution of a zinc salt of a carboxylic acid having a branched chain and a Group VI element precursor and then adding the solution to the dispersion of core particles, there are methods such as first mixing a zinc salt of a carboxylic acid having a branched chain and a Group VI element precursor in a solvent to prepare a solution of a zinc salt of a carboxylic acid having a branched chain and a Group VI element precursor, and then adding the prepared solution to the dispersion of core particles; or first adding a solution of a zinc salt of a carboxylic acid having a branched chain and a solution of a Group VI element precursor to a solution preparation container, preparing a solution of a zinc salt of a carboxylic acid having a branched chain and a Group VI element precursor in the solution preparation container, and then adding the solution of a zinc salt of a carboxylic acid having a branched chain and a Group VI element precursor from the solution preparation container to the dispersion of core particles.

[0082] As a method for continuously adding a solution of a zinc salt of a carboxylic acid having a branched chain and a solution of a Group VI element precursor to a dispersion of core particles, there is no particular limitation. For example, a method of positioning the end portion on the outlet side of the solution supply pipe in the dispersion of core particles and continuously supplying the solution of the zinc salt of the carboxylic acid having a branched chain and the solution of the Group VI element precursor from the solution supply pipe can be mentioned. Further, as a method for adding a solution of a zinc salt of a carboxylic acid having a branched chain and a solution of a Group VI element precursor to the dispersion of core particles at regular or irregular intervals, there is no particular limitation. For example, positioning the end portion on the outlet side of the solution supply pipe above the liquid level of the dispersion of core particles and dropping the solution of the zinc salt of the carboxylic acid having a branched chain and the solution of the Group VI element precursor from the solution supply pipe at regular or irregular intervals, or injecting a predetermined amount of the solution of the zinc salt of the carboxylic acid having a branched chain and the solution of the Group VI element precursor each time at regular or irregular intervals, etc. can be mentioned.

[0083] In the shell formation step (1-iii), adding a solution of a Group VI element precursor containing at least a Se element precursor after adding a solution of a zinc salt of a carboxylic acid having a branched chain means continuously adding the total amount of the solution of the zinc salt of the carboxylic acid having a branched chain to the dispersion of core particles, or adding it at regular or irregular intervals, and then continuously adding the total amount of the solution of the Group VI element precursor containing at least a Se element precursor, or adding it at regular or irregular intervals.

[0084] As a method for continuously adding a solution of a zinc salt of a carboxylic acid having a branched chain or a solution of a Group VI element precursor containing at least a Se element precursor to a dispersion of core particles, there is no particular limitation. For example, in the dispersion of core particles, the end portion on the outlet side of the solution supply pipe is positioned, and a solution of a zinc salt of a carboxylic acid having a branched chain or a solution of a Group VI element precursor containing at least a Se element precursor is continuously supplied from the solution supply pipe. Further, as a method for adding a solution of a zinc salt of a carboxylic acid having a branched chain or a solution of a Group VI element precursor containing at least a Se element precursor to the dispersion of core particles at regular or irregular intervals, there is no particular limitation. For example, the end portion on the outlet side of the solution supply pipe is positioned above the liquid level of the dispersion of core particles, and a solution of a zinc salt of a carboxylic acid having a branched chain or a solution of a Group VI element precursor containing at least a Se element precursor is dropped from the solution supply pipe at regular or irregular intervals, or a method of injecting a predetermined amount of a solution of a zinc salt of a carboxylic acid having a branched chain or a solution of a Group VI element precursor containing at least a Se element precursor each time at regular or irregular intervals can be mentioned.

[0085] In the shell formation step (1-iii), it is necessary to add the total amount of the solution of the zinc salt of the carboxylic acid having a branched chain to the dispersion of the core particles and then add the solution of the Group VI element precursor containing at least the Se element precursor. The reason is that if the solution of the Group VI element precursor containing at least the Se element precursor is added to the core particles in a state where the zinc salt of the carboxylic acid having a branched chain does not exist around them, first, only the Group VI element precursor reacts with the surface of the core particles to form a shell containing the Group VI element and not containing Zn.

[0086] In the shell formation step (1), the addition amount of the zinc salt of the carboxylic acid having a branched chain is such that the molar ratio of Zn to In in terms of atoms is preferably 7 to 50, particularly preferably 10 to 35. When the molar ratio of Zn to In is within the above range, the quantum efficiency is high, the half-width is small, and the Stokes shift is small.

[0087] In the shell formation step (1), when only a Se precursor is used as the Group VI element precursor, the addition amount of the Se precursor is such that the molar ratio of Se to In in terms of atoms is preferably 5 to 40, particularly preferably 5 to 25. When the molar ratio of Se to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small.

[0088] In the shell formation step (1), when only an S precursor is used as the Group VI element precursor, the addition amount of the S precursor is such that the molar ratio of S to In in terms of atoms is preferably 5 to 50, particularly preferably 5 to 25. When the molar ratio of S to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small.

[0089] In the shell formation step (1), when both a Se precursor and an S precursor are used as the Group VI element precursors, the total addition amount of the Se precursor and the S precursor is such that the total molar ratio of Se and S to In in terms of atoms is preferably 5 to 40, particularly preferably 5 to 30. When the total molar ratio of Se and S to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small.

[0090] In the shell formation step (1-i) or (1-iii), the solution concentration of the zinc salt of the carboxylic acid having a branched chain in the solution of the zinc salt of the carboxylic acid having a branched chain is preferably 0.01 M to 5.00 M, particularly preferably 0.10 M to 3.00 M, and the concentration of the Group VI element precursor in the solution of the Group VI element precursor is preferably 0.01 M to 10.00 M, particularly preferably 0.10 M to 5.00 M.

[0091] In the shell formation step (1-ii), the solution concentration of the zinc salt of the carboxylic acid having a branched chain in the solution of the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor is preferably 0.01 M to 5.00 M, particularly preferably 0.10 M to 3.00 M, and the concentration of the Group VI element precursor is preferably 0.01 M to 10.00 M, particularly preferably 0.10 M to 5.00 M.

[0092] In the method for producing the core / shell type semiconductor nanoparticles of the present invention, in the shell formation step (1-i), (i) while adding a solution of a zinc salt of a carboxylic acid having a branched chain to a dispersion of core particles, a solution of a Group VI element precursor is added, and in the presence of the core particles, the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor are reacted. Alternatively, in the shell formation step (1-ii), a solution of a zinc salt of a carboxylic acid having a branched chain and a solution of a Group VI element precursor are added to a dispersion of core particles, and in the presence of the core particles, the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor are reacted. Alternatively, in the shell formation step (1-iii), (iii) after adding a solution of a zinc salt of a carboxylic acid having a branched chain to a dispersion of core particles, a solution of a Group VI element precursor containing at least a Se element precursor is added, and in the presence of the core particles, the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor are reacted to form a shell containing zinc and a Group VI element on the surface of the core particles.

[0093] In the shell formation step (1-i), when adding a solution of a zinc salt of a carboxylic acid having a branched chain to the dispersion of core particles and adding a solution of a Group VI element precursor, or in the shell formation step (1-ii), when adding a solution of a zinc salt of a carboxylic acid having a branched chain and a Group VI element precursor to the dispersion of core particles, or in the shell formation step (1-iii), when adding a solution of a zinc salt of a carboxylic acid having a branched chain to the dispersion of core particles and adding a solution of a Group VI element precursor containing at least a Se element precursor, it is preferable to heat the dispersion of core particles to preferably 180 to 320 °C, particularly preferably 250 to 320 °C, to react the zinc salt of the carboxylic acid having a branched chain with the Group VI element precursor. When the temperature of the dispersion of core particles when reacting the zinc salt of the carboxylic acid having a branched chain with the Group VI element precursor is within the above range, the added zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor can form a shell on the core particles where non-radiative recombination of excitons via defect levels hardly occurs, and core / shell type semiconductor nanoparticles having excellent optical properties can be obtained.

[0094] In the shell formation step (1-i), the addition time of the solution of the zinc salt of the carboxylic acid having a branched chain to the dispersion of core particles is preferably 5 to 600 minutes, particularly preferably 30 to 180 minutes. In the shell formation step (1-ii), the addition time of the solution of the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor to the dispersion of core particles is preferably 5 to 600 minutes, particularly preferably 30 to 180 minutes. In the shell formation step (1-iii), the addition time of the solution of the zinc salt of the carboxylic acid having a branched chain to the dispersion of core particles is preferably 5 to 600 minutes, particularly preferably 30 to 180 minutes. When the addition time of the solution of the zinc salt of the carboxylic acid having a branched chain or the solution of the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor to the dispersion of core particles is within the above range, the added shell precursor can efficiently form a shell on the surface of the core particles. In the shell formation step (1-i) or (1-iii), the addition time of the zinc salt solution of the carboxylic acid having a branched chain to the dispersion of core particles refers to the time from when the addition of the zinc salt solution of the carboxylic acid having a branched chain to the dispersion of core particles is started until the addition is completed. In the shell formation step (1-ii), the addition time of the zinc salt solution of the carboxylic acid having a branched chain and the solution of the Group VI element precursor refers to the time from when the addition of the zinc salt solution of the carboxylic acid having a branched chain and the solution of the Group VI element precursor to the dispersion of core particles is started until the addition is completed.

[0095] In the shell formation step (1-i), the addition time of the solution of the Group VI element precursor to the dispersion of core particles is preferably 5 to 600 minutes, particularly preferably 30 to 180 minutes. In the shell formation step (1-iii), the addition time of the solution of the Group VI element precursor containing at least a Se element precursor to the dispersion of core particles is preferably 5 to 600 minutes, particularly preferably 30 to 180 minutes. When the addition time of the solution of the Group VI element precursor or the solution of the Group VI element precursor containing at least a Se element precursor to the dispersion of core particles is within the above range, the added shell precursor can efficiently form a shell on the surface of the core particles. In the shell formation step (1-i), the addition time of the solution of the Group VI element precursor to the dispersion of core particles refers to the time from when the addition of the solution of the Group VI element precursor to the dispersion of core particles is started until the addition is completed. In the shell formation step (1-iii), the addition time of the solution of the Group VI element precursor containing at least a Se element precursor to the dispersion of core particles refers to the time from when the addition of the solution of the Group VI element precursor containing at least a Se element precursor to the dispersion of core particles is started until the addition is completed.

[0096] In the shell formation step (1), the reaction between the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor can be carried out in the presence of a dispersant. That is, in the shell formation step (1-i), when adding the solution of the zinc salt of the carboxylic acid having a branched chain to the dispersion of the core particles and adding the solution of the Group VI element precursor, or in the shell formation step (1-ii), when adding the solution of the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor to the dispersion of the core particles, or in the shell formation step (1-iii), when adding the solution of the zinc salt of the carboxylic acid having a branched chain to the dispersion of the core particles and adding the solution of the Group VI element precursor containing at least the Se element precursor, a dispersant may be present in the dispersion of the core particles. Examples of the dispersant to be present in the dispersion of the core particles include amines such as oleylamine and trioctylamine, carboxylic acids such as oleic acid, and thiols such as dodecanethiol. The amount of the dispersant used is appropriately selected, but preferably 5 to 200 in terms of the molar ratio to In of the core particles, more preferably 10 to 100 in terms of the molar ratio to In of the core particles.

[0097] In the shell formation step (1), the reaction between the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor can be carried out in the presence of a halogen precursor. That is, in the shell formation step (1-i), when adding the solution of the zinc salt of the carboxylic acid having a branched chain to the dispersion of the core particles and adding the solution of the Group VI element precursor, or in the shell formation step (1-ii), when adding the solution of the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor to the dispersion of the core particles, or in the shell formation step (1-iii), when adding the solution of the zinc salt of the carboxylic acid having a branched chain to the dispersion of the core particles and adding the solution of the Group VI element precursor containing at least the Se element precursor, a halogen precursor may be present in the dispersion of the core particles. The halogen precursor is not particularly limited, and examples thereof include carboxylic acid halides such as HF, HCl, HBr, HI, oleyl chloride, oleyl bromide, octanoyl chloride, and octanoyl bromide, and metal halides such as zinc chloride, indium chloride, and gallium chloride. The amount of the halogen used is appropriately selected, but preferably the molar ratio to In of the core particles is 0.3 to 100.0, more preferably the molar ratio to In of the core particles is 0.3 to 30.0. By allowing a halogen precursor to be present in the dispersion of the core particles in the shell formation step (1), core / shell type semiconductor nanoparticles in which halogen is present on the surface of the core particles or in the shell layer can be obtained.

[0098] In the shell formation step (1), in addition to the above, if necessary, carboxylic acids, amines, thiols, phosphines, phosphine oxides, phosphines, phosphonic acids, etc. may be present in the dispersion of the core particles to carry out the reaction between the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor.

[0099] In the method for producing core / shell type semiconductor nanoparticles of the present invention, the core particles generated after the synthesis of the core particles can be used as the core particles used in the shell formation step (1) without purifying the generated core particles. That is, the core particles not subjected to the purification step can be used as the core particles used in the shell formation step (1). In other words, the reaction liquid in which the core particles are dispersed after the synthesis of the core particles can be used as the dispersion liquid of the core particles used in the shell formation step (1). In the shell formation step (1), a zinc salt of a carboxylic acid having a branched chain is used as the zinc precursor for the formation of the shell layer, and the zinc salt of the carboxylic acid having a branched chain and the VI group element precursor are easily reacted on the surface of the core particles, so that the inventors presume that impurities in the dispersion medium are not easily taken into the shell layer during the shell formation, and a shell in which the generation of defect levels is suppressed on the core surface can be formed. Therefore, the core particles not subjected to the purification step can be used as the core particles used in the shell formation step (1).

[0100] In the method for producing core / shell type semiconductor nanoparticles of the present invention, a zinc salt of a branched carboxylic acid is used as the zinc precursor used in the shell formation step (1), so even if it takes time to add a solution of the zinc salt of a branched carboxylic acid or a solution of the zinc salt of a branched carboxylic acid and a Group VI element precursor to the dispersion of core particles, the zinc salt of a branched carboxylic acid is unlikely to precipitate in the supply pipe.

[0101] The method for manufacturing the core / shell type semiconductor nanoparticles of the present invention is simple because, in the shell formation step (1), in order to form the shell layer, it is only necessary to add the total amount of the zinc salt of the carboxylic acid having a branched chain used for forming the shell and the group VI element precursor to the dispersion of the core particles at once. And in the method for manufacturing the core / shell type semiconductor nanoparticles of the present invention, by using the zinc salt of the carboxylic acid having a branched chain as the group II element precursor which is added to the dispersion of the core particles and reacts with the group VI element precursor on the surface of the core particles, even if the operation of separately and alternately contacting the group II element precursor and the group VI element precursor a plurality of times is not performed, that is, even if the total amounts of the group II element precursor and the group VI element precursor are brought into contact with the core particles at once and reacted, core / shell type semiconductor nanoparticles having excellent optical properties can be obtained. In particular, in the method for manufacturing the core / shell type semiconductor nanoparticles of the present invention, in the shell formation step (1), when the group VI element precursor contains at least a Se precursor, that is, when the group VI element precursor is a Se precursor alone or a combination of a Se precursor and another group VI element precursor (for example, an S precursor), even if the total amounts of the group II element precursor and the group VI element precursor are brought into contact with the core particles at once and reacted, the effect that core / shell type semiconductor nanoparticles having excellent optical properties can be obtained becomes higher. In the shell formation step (1), when the group VI element precursor contains at least a Se precursor, the ratio of the Se precursor to the total group VI element precursor in the solution of the group VI element precursor is preferably 50 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, and particularly preferably 100 mol%.

[0102] Further, in the method for producing the core / shell type semiconductor nanoparticles of the present invention, by using the shell formation step (1-i) or (1-ii) as the shell formation step, the effect of narrowing the full width at half maximum of the core / shell type semiconductor nanoparticles is enhanced. In particular, in the method for producing the core / shell type semiconductor nanoparticles of the present invention, by using the shell formation step (1-i) or (1-ii) as the shell formation step, even in the technical field where the full width at half maximum of the core / shell type semiconductor nanoparticles is narrow, it has the effect of narrowing the full width at half maximum. In the technical field where the full width at half maximum of the semiconductor nanoparticles is narrow, since it is difficult to narrow the full width at half maximum, in such a technical field where the full width at half maximum of the semiconductor nanoparticles is narrow, even if the absolute value of the amount of decrease in the full width at half maximum is small, it can be said to be an advantageous effect.

[0103] In addition, in the method for producing core / shell type semiconductor nanoparticles of the present invention, when the shell formation step is the shell formation step (1-iii), the entire amount of the zinc precursor is brought into contact with the core particles first. However, when a zinc salt of a branched carboxylic acid is used as the zinc precursor, even if the zinc salt of a branched carboxylic acid is added to the core particles before the VI group element precursor, the deterioration of the core particles and the generation of by-products can be suppressed, so that an effective shell can be formed even if the VI group element precursor is added after the addition of the zinc salt of a branched carboxylic acid. And, such an effect is high when the Se precursor is used among the VI group element precursors, and the effect is particularly remarkable as the scale of the reaction system becomes larger. In this regard, since the zinc salt of a branched carboxylic acid has low reactivity with the core particles, even if the zinc salt of a branched carboxylic acid is added to the dispersion of the core particles before the addition of the Se precursor, the zinc salt of the branched carboxylic acid is dispersed in the dispersion without reacting with the core particles. It is speculated that when the Se precursor is added thereafter, the reaction between the zinc salt of the branched carboxylic acid, the Se precursor, and the core particles proceeds preferentially, and the surface of the core particles in the core particle dispersion is preferentially covered, and then the formation (growth) of the ZnSe shell begins. The larger the scale of the reaction system, the more likely it is that the precursor will be unevenly distributed during shell formation, so by adding the zinc salt of the branched carboxylic acid first and then adding the Se precursor, the reaction between the zinc salt of the branched carboxylic acid, the Se precursor, and the core particles proceeds preferentially, and then the ZnSe shell grows. This process makes it difficult for the shell formation step (1-iii) to have variations due to uneven distribution of the precursor, which is generally likely to occur when manufacturing at a mass production level. Therefore, by including the shell formation step (1-iii) in the method for producing core / shell type semiconductor nanoparticles of the present invention, core / shell type semiconductor nanoparticles having excellent optical properties can be obtained at a mass production level, as compared to the case where the entire amount of a solution containing only an S precursor as a Group VI element precursor is added after the entire amount of a solution of a zinc salt of a branched carboxylic acid is added to a dispersion liquid of core particles.

[0104] In addition, in the shell formation step (1), when comparing the optical properties of semiconductor nanoparticles obtained using an S precursor, which is a Group VI element, with the optical properties of semiconductor nanoparticles obtained using a Se precursor, it is clear that the Se precursor exhibits higher optical properties. This is presumably because the reactivity among the zinc salt of a carboxylic acid having a branched chain, the Group VI precursor, and the core particles is different between the Se precursor and the S precursor.

[0105] In the method for producing core / shell type semiconductor nanoparticles of the present invention, on the surface of the core / shell type semiconductor nanoparticles obtained by performing the shell formation step (1), that is, the shell formation step (1-i), the shell formation step (1-ii), or the shell formation step (1-iii), a carboxylic acid having a branched chain derived from the zinc salt of a carboxylic acid having a branched chain used as a zinc precursor in the shell formation step (1) is coordinated. The carboxylic acid having a branched chain coordinated on the surface of the core / shell type semiconductor nanoparticles functions as a ligand that enhances the dispersibility of the core / shell type semiconductor nanoparticles in the dispersion medium. For example, when a zinc salt of 3,5,5-trimethylhexanoic acid is used as the zinc precursor in the shell formation step (1), 3,5,5-trimethylhexanoic acid is coordinated as a ligand on the surface of the obtained core / shell type semiconductor nanoparticles. Here, the coordination described refers to the fact that the ligand chemically affects the surface of the core / shell type semiconductor nanoparticles. The ligand may be bonded to the surface of the core / shell type semiconductor nanoparticles by a coordination bond or any other optional bonding mode (for example, covalent bond, ionic bond, hydrogen bond, etc.), or when the ligand is present on at least a part of the surface of the core / shell type semiconductor nanoparticles, it does not necessarily have to form a bond.

[0106] In the method for manufacturing the core / shell type semiconductor nanoparticles of the present invention, after performing the shell formation step (1), that is, the shell formation step (1-i), the shell formation step (1-ii), or the shell formation step (1-iii), the generated core / shell type structured particles may be obtained as the core / shell type semiconductor particles as the target product, or alternatively, using the generated core / shell type particles, one or more shell formation steps may be performed to obtain core / shell type semiconductor nanoparticles having two or more layers of shells formed. That is, the method for manufacturing the core / shell type semiconductor nanoparticles of the present invention may have, in addition to the shell formation step (1), one or more shell formation steps for forming a shell on the core / shell type particles containing zinc and group VI elements obtained by performing the shell formation step (1). Further, as the shell formation step to be performed one or more times, the same method as the above shell formation step (1) may be mentioned. That is, except for using core / shell type particles having one or more layers of shells formed on the surface of the core particles instead of the core particles, the shell formation step can be performed in the same manner as the shell formation step (1). Also, as the shell formation step to be performed one or more times, a method other than the same method as the above shell formation step (1) may be used.

[0107] For example, as a method for producing core / shell type semiconductor nanoparticles in which two layers of shells are formed on the surface of core particles, there are a shell formation step (1), and in a dispersion of "particles composed of core particles and one layer of shell formed on the surface of the core particles" obtained by performing the shell formation step (1), (i) while adding a solution of a zinc salt of a carboxylic acid having a branched chain, adding a solution of a Group VI element precursor, (ii) adding a solution of a zinc salt of a carboxylic acid having a branched chain and a Group VI element precursor, or (iii) after adding a solution of a zinc salt of a carboxylic acid having a branched chain, adding a solution of a Group VI element precursor containing at least a Se precursor, and reacting the zinc salt of the carboxylic acid having a branched chain with the Group VI element precursor in the presence of the "particles composed of core particles and one layer of shell formed on the surface of the core particles" to form a shell containing zinc and a Group VI element on the surface of the "particles composed of core particles and one layer of shell formed on the surface of the core particles", and a shell formation step (2). A method for producing core / shell type semiconductor nanoparticles characterized by having the above is mentioned.

[0108] In the method for producing core / shell type semiconductor nanoparticles of the present invention, when the shell formation step (1) is performed once or two or more times, on the surface of the core / shell type semiconductor nanoparticles obtained by performing the method for producing core / shell type semiconductor nanoparticles of the present invention, a carboxylic acid having a branched chain derived from the zinc salt of the carboxylic acid having a branched chain used as a zinc precursor in the shell formation step (1) is coordinated. The carboxylic acid having a branched chain coordinated on the surface of the core / shell type semiconductor nanoparticles functions as a ligand that enhances the dispersibility of the core / shell type semiconductor nanoparticles in the dispersion medium.

[0109] In addition, as a method for producing core / shell type semiconductor nanoparticles in which (n + 1) layers of shells are formed on the surface of core particles, there are a shell formation step (1) and a dispersion of "particles composed of core particles and one or more layers of shells formed on the surface of the core particles" obtained by performing the previous shell formation step. While adding a solution of a zinc salt of a carboxylic acid having a branched chain thereto, add a solution of a Group VI element precursor, (ii) add a solution of a zinc salt of a carboxylic acid having a branched chain and a Group VI element precursor, or (iii) after adding a solution of a zinc salt of a carboxylic acid having a branched chain, add a solution of a Group VI element precursor containing at least a Se precursor, and in the presence of the "particles composed of core particles and one or more layers of shells formed on the surface of the core particles", react the zinc salt of the carboxylic acid having a branched chain with the Group VI element precursor to form a shell containing zinc and a Group VI element on the surface of the "particles composed of core particles and one or more layers of shells formed on the surface of the core particles". And a step of repeating the shell formation step (x) n times. A method for producing core / shell type semiconductor nanoparticles characterized by having is mentioned.

[0110] In the method for producing core / shell type semiconductor nanoparticles of the present invention, when the shell formation step (x) is repeated one or more times after performing the shell formation step (1), on the surface of the core / shell type semiconductor nanoparticles obtained by performing the method for producing core / shell type semiconductor nanoparticles of the present invention, in the shell formation step (1) and the shell formation step (x), a carboxylic acid having a branched chain derived from the zinc salt of the carboxylic acid having a branched chain used as a zinc precursor is coordinated. The carboxylic acid having a branched chain coordinated on the surface of the core / shell type semiconductor nanoparticles functions as a ligand that enhances the dispersibility of the core / shell type semiconductor nanoparticles in the dispersion medium.

[0111] In the method for producing core / shell type semiconductor nanoparticles of the present invention, the core / shell type semiconductor nanoparticles generated by performing the shell formation step can be purified. For example, by adding a polarity-converting solvent such as acetone, the core / shell type semiconductor nanoparticles can be precipitated from the solution. Then, the precipitated core / shell type semiconductor nanoparticles can be recovered by filtration or centrifugation. Further, the filtrate or supernatant containing unreacted starting materials and other impurities can be reused. Next, the recovered semiconductor nanoparticles can be washed with a further solvent and redissolved. This purification operation can be repeated, for example, 2 to 4 times or until the desired purity is reached. Other purification methods include, for example, aggregation, liquid-liquid extraction, distillation, electrodeposition, size exclusion chromatography, ultrafiltration, etc. In purification, these purification methods can be carried out alone or in combination of a plurality.

[0112] Further, by adding a surfactant to the core / shell type semiconductor nanoparticles obtained as described above, stirring, adding an inorganic-containing composition, and stirring again, an oxide layer can be formed on the surface of the core / shell type semiconductor nanoparticles. The surfactant is not particularly limited, and examples thereof include sodium dodecyl sulfate, sodium lauryl sulfate, n-butanol, sodium dioctyl sulfosuccinate, etc. The inorganic-containing composition is not particularly limited, and examples thereof include silane coupling agents, titanate coupling agents, aluminate coupling agents, etc. For example, after purifying the core / shell type semiconductor nanoparticles, an aqueous solution containing a surfactant is added, and the mixture is mixed and stirred to form micelles. The formation of micelles is confirmed by the turbidity of the mixture. The aqueous phase in which micelles are formed is recovered, an inorganic-containing composition is added thereto, and the mixture is stirred at 10 to 30°C for 10 minutes to 6 hours. After removing unreacted substances and purifying again, core / shell type semiconductor nanoparticles having an oxide layer of an oxide are obtained. The method for forming the outermost layer of the oxide is not limited to the above method, and for example, a method of adding an inorganic-containing composition during shell synthesis or other known methods are used.

[0113] Furthermore, the surface of the core / shell type semiconductor nanoparticles obtained as described above may be modified with a ligand. As the method for modification with a ligand, a known method such as a ligand exchange method is used.

[0114] The core / shell type semiconductor nanoparticles obtainable by carrying out the method for producing core / shell type semiconductor nanoparticles of the present invention are particles having a core / shell type structure with at least one shell layer. In the core / shell type semiconductor nanoparticles obtainable by carrying out the method for producing core / shell type semiconductor nanoparticles of the present invention, the shell layer formed on the surface of the core particles, that is, the first shell layer as viewed from the core particle side, is the shell layer formed by carrying out the shell formation step (1). In the core / shell type semiconductor nanoparticles obtainable by carrying out the method for producing core / shell type semiconductor nanoparticles of the present invention, the number of shell layers formed is at least one layer, preferably 1 to 4 layers. When the core / shell type semiconductor nanoparticles obtainable by carrying out the method for producing core / shell type semiconductor nanoparticles of the present invention have two or more shell layers, the method for forming the shell layers after the second layer as viewed from the core particles may be any method, but it is preferably a shell formation method carried out in the same manner as the shell formation step (1) except that the core / shell type particles having one or more shell layers formed by the previous shell layer formation step are used as the object for forming the shell layer instead of the core particles.

[0115] In the core / shell type semiconductor nanoparticles obtainable by carrying out the method for producing core / shell type semiconductor nanoparticles of the present invention, the core preferably contains In and P. In the core / shell type semiconductor nanoparticles obtainable by carrying out the method for producing core / shell type semiconductor nanoparticles of the present invention, in terms of atoms, the molar ratio of P to In is 0.20 to 1.20, preferably 0.20 to 0.95, more preferably 0.40 to 0.95. When the molar ratio of P to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small.

[0116] Among the core / shell type semiconductor nanoparticles obtainable by carrying out the method for producing the core / shell type semiconductor nanoparticles of the present invention, the molar ratio of Zn to In in terms of atoms is preferably from 11.00 to 50.00, particularly preferably from 12.00 to 30.00. When the molar ratio of Zn to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small.

[0117] Among the core / shell type semiconductor nanoparticles obtainable by carrying out the method for producing the core / shell type semiconductor nanoparticles of the present invention, the molar ratio of Se to In in terms of atoms is preferably from 7.00 to 25.00, particularly preferably from 11.00 to 20.00. When the molar ratio of Se to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small.

[0118] Among the core / shell type semiconductor nanoparticles obtainable by carrying out the method for producing the core / shell type semiconductor nanoparticles of the present invention, the molar ratio of S to In in terms of atoms is preferably from 0.00 to 45.00, particularly preferably from 0.00 to 30.00. When the molar ratio of S to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small.

[0119] Among the core / shell type semiconductor nanoparticles obtainable by carrying out the method for producing the core / shell type semiconductor nanoparticles of the present invention, the molar ratio of halogen to In in terms of atoms is preferably from 0.80 to 15.00, particularly preferably from 1.00 to 15.00. When the molar ratio of halogen to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small. When the core / shell type semiconductor nanoparticles obtainable by carrying out the method for producing the core / shell type semiconductor nanoparticles of the present invention contain two or more kinds of halogens, the above-mentioned molar ratio of halogen to In refers to the value obtained by summing up the molar ratios of each of the two or more kinds of halogens to In.

[0120] The average particle size of the core / shell type semiconductor nanoparticles obtained by carrying out the method for producing the core / shell type semiconductor nanoparticles of the present invention is not particularly limited, and is preferably 1.0 to 20.0 nm, particularly preferably 1.0 to 10.0 nm.

[0121] In the core / shell type semiconductor nanoparticles obtained by carrying out the method for producing the core / shell type semiconductor nanoparticles of the present invention, at least a carboxylic acid having a branched chain is coordinated to the core / shell type semiconductor nanoparticles as a ligand. Further, when the core / shell type semiconductor nanoparticles are modified with a ligand, a ligand other than the carboxylic acid having a branched chain may be coordinated to the core / shell type semiconductor nanoparticles. Therefore, the core / shell type semiconductor nanoparticles obtained by carrying out the method for producing the core / shell type semiconductor nanoparticles of the present invention are a core / shell type semiconductor nanoparticle complex having the core / shell type semiconductor nanoparticles and a ligand coordinated on the surface of the core / shell type semiconductor nanoparticles, and contain at least a carboxylic acid having a branched chain as the ligand. Further, the core / shell type semiconductor nanoparticles obtained by carrying out the method for producing the core / shell type semiconductor nanoparticles of the present invention contain at least zinc and selenium in the shell.

[0122] That is, the core / shell type semiconductor nanoparticle complex of the present invention is a core / shell type semiconductor nanoparticle complex having the core / shell type semiconductor nanoparticles and a ligand coordinated on the surface of the core / shell type semiconductor nanoparticles, wherein the shell contains at least zinc and selenium, and the ligand contains a carboxylic acid having a branched chain, and is a core / shell type semiconductor nanoparticle complex characterized by the above.

[0123] The core / shell type semiconductor nanoparticle composite of the present invention contains, as a ligand, a carboxylic acid having at least a branched chain. Further, the core / shell type semiconductor nanoparticle composite of the present invention can contain, if necessary, ligands other than the carboxylic acid having a branched chain. In the core / shell type semiconductor nanoparticle composite of the present invention, the molar fraction of the ligand of the carboxylic acid having a branched chain in all the ligands coordinated to the core / shell type semiconductor nanoparticles is preferably 20.0 to 80.0 mol%, particularly preferably 20.0 to 60.0 mol%.

[0124] In the core / shell type semiconductor nanoparticle composite of the present invention, examples of the carboxylic acid having a branched chain that coordinates to the core / shell type semiconductor nanoparticles include carboxylic acids having a main chain composed of a hydrocarbon and a branched chain branching from the main chain, and preferably 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, and 16-methylheptadecanoic acid.

[0125] In the core / shell type semiconductor nanoparticle composite of the present invention, in the shell formation step, since the shell precursor easily reacts on the surface of the core particles, a shell that suppresses the generation of defect energy levels on the core surface is formed. Therefore, the full width at half maximum (FWHM) of the emission spectrum of the core / shell type semiconductor nanoparticle composite of the present invention is preferably 35 nm or less, particularly preferably 33 nm or less. Further, the quantum efficiency (QY) of the core / shell type semiconductor nanoparticle composite of the present invention is preferably 80% or more, particularly preferably 83% or more.

[0126] The core / shell semiconductor nanoparticle complex of the present invention, namely, the core / shell semiconductor nanoparticle with ligands coordinated thereto, is a particle having a core / shell structure with at least one shell layer. In the core / shell semiconductor nanoparticle according to the core / shell semiconductor nanoparticle complex of the present invention, the shell layer formed on the surface of the core particle, that is, the first shell layer when viewed from the core particle side, contains at least Zn and Se. In the core / shell semiconductor nanoparticle according to the core / shell semiconductor nanoparticle complex of the present invention, the number of shell layers formed is at least one layer, preferably 1 to 4 layers. When the core / shell semiconductor nanoparticle according to the core / shell semiconductor nanoparticle complex of the present invention has two or more shell layers, the shell layers after the second layer when viewed from the core particle preferably contain Zn and a Group VI element, particularly preferably Zn and Se or S.

[0127] In the core / shell semiconductor nanoparticle according to the core / shell semiconductor nanoparticle complex of the present invention, the core preferably contains In and P. In the core / shell semiconductor nanoparticle according to the core / shell semiconductor nanoparticle complex of the present invention, in terms of atoms, the molar ratio of P to In is 0.20 to 1.20, preferably 0.20 to 0.95, more preferably 0.40 to 0.95. When the molar ratio of P to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small.

[0128] In the core / shell semiconductor nanoparticle according to the core / shell semiconductor nanoparticle complex of the present invention, in terms of atoms, the molar ratio of Zn to In is preferably 11.00 to 50.00, particularly preferably 12.00 to 30.00. When the molar ratio of Zn to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small.

[0129] In the core / shell type semiconductor nanoparticle composite of the present invention, in the core / shell type semiconductor nanoparticles, the molar ratio of Se to In in terms of atoms is preferably 7.00 to 25.00, particularly preferably 11.00 to 20.00. When the molar ratio of Se to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small.

[0130] In the core / shell type semiconductor nanoparticle composite of the present invention, in the core / shell type semiconductor nanoparticles, the molar ratio of S to In in terms of atoms is preferably 0.00 to 45.00, particularly preferably 0.00 to 30.00. When the molar ratio of S to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small.

[0131] In the core / shell type semiconductor nanoparticle composite of the present invention, in the core / shell type semiconductor nanoparticles, the molar ratio of halogen to In in terms of atoms is preferably 0.80 to 15.00, particularly preferably 1.00 to 15.00. When the molar ratio of halogen to In is within the above range, the quantum efficiency is high, the full width at half maximum is small, and the Stokes shift is small. When the core / shell type semiconductor nanoparticles of the core / shell type semiconductor nanoparticle composite of the present invention contain two or more kinds of halogens, the above-mentioned molar ratio of halogen to In refers to the value obtained by summing up the molar ratios of each of the two or more kinds of halogens to In.

[0132] <Measurement> For the elemental analysis of semiconductor nanoparticles, elemental analysis can be performed using a high-frequency inductively coupled plasma optical emission spectrometer (ICP) or a wavelength dispersive X-ray fluorescence spectrometer (XRF). In ICP measurement, the purified semiconductor nanoparticles are dissolved in nitric acid, heated, diluted with water, and then measured by the calibration curve method using an ICP optical emission spectrometer (ICPS-8100, manufactured by Shimadzu Corporation). In XRF measurement, a sample impregnated with the dispersion liquid on a filter paper is placed in a sampling holder, and quantitative analysis is performed using a wavelength dispersive X-ray fluorescence spectrometer (ZSX100e, manufactured by Rigaku Corporation).

[0133] Regarding the optical identification of semiconductor nanoparticles, measurements can be carried out using a fluorescence quantum efficiency measurement system (manufactured by Otsuka Electronics Co., Ltd., QE-2100) and a visible ultraviolet spectrophotometer (manufactured by JASCO Corporation, V670). An excitation light is applied to a dispersion obtained by dispersing semiconductor nanoparticles in a dispersion medium to obtain an emission spectrum. From the emission spectrum obtained here, after removing the re-excitation fluorescence emission spectrum of the portion that is re-excited and emits fluorescence, the peak wavelength (λ max ), fluorescence quantum efficiency (QY), and full width at half maximum (FWHM) are calculated. Examples of the dispersion medium include normal hexane, octadecene, toluene, acetone, and PGMEA. The excitation light used for the measurement is single light with a wavelength of 450 nm, and as the dispersion, one with the concentration of semiconductor nanoparticles adjusted so that the absorption rate is 20 to 30% is used. On the other hand, regarding the absorption spectrum, it can be measured by applying ultraviolet to visible light to a dispersion obtained by dispersing semiconductor nanoparticles in a dispersion medium.

[0134] Regarding the ligands coordinated to core / shell type semiconductor nanoparticles, gas chromatography can be used to identify the types and calculate the molar fractions. Core / shell type semiconductor nanoparticles are introduced into a sample vaporization chamber, heated at 350 °C or higher, passed through a column together with a carrier gas, and then the types and amounts of each ligand are identified from the retention time and peak area of the signal obtained by the detector. From the types and amounts of each ligand obtained, the existing types and existing ratios of the ligands coordinated to the core / shell type semiconductor nanoparticles can be calculated.

[0135] Note that the configurations, methods, procedures, processes, etc. described in this specification are examples and do not limit the present invention. A number of modified forms are applicable within the scope of the present invention.

[0136] Hereinafter, the present invention will be described based on specific experimental examples, but the present invention is not limited thereto.

Example

[0137] Semiconductor nanoparticles were prepared according to the following method, and the composition and optical properties of the obtained semiconductor nanoparticles were measured.

[0138] <Synthesis of core particles> Indium acetate (0.5 mmol), myristic acid (1.5 mmol), zinc myristate (0.2 mmol), and octadecene (10 mL) were charged into a two-necked flask. The inside of the flask was evacuated and heated to 120 °C under vacuum (<10 Pa). After maintaining for 30 minutes from the time when the vacuum degree dropped below 10 Pa, nitrogen was introduced into the flask and cooled to room temperature (25 °C) to obtain an In precursor. Also, in a glove box under a nitrogen atmosphere, tris(trimethylsilyl)phosphine was mixed with tri-n-octylphosphine so that the molar concentration became 0.2 M to obtain a P precursor. Next, 2 mL of the P precursor was injected into the In precursor at room temperature (25 °C) under a nitrogen atmosphere, and the temperature was raised to 280 °C at 30 °C / min. After holding at 280 °C for 2 minutes, the reaction solution was cooled to room temperature to obtain the reaction solution as a dispersion of InP core particles.

[0139] <Solution of zinc precursor> Zinc carboxylate and octadecene described in Table 1 were mixed so that the molar concentration of zinc became 0.3 M, evacuated at 100 °C for 1 hour, then purged with nitrogen and cooled to room temperature (25 °C) to obtain a solution of each zinc precursor in Table 1.

[0140] <Solution of Se precursor> 100 mmol of powdered selenium and 50 mL of tri-n-octylphosphine were mixed under a nitrogen atmosphere and stirred until the selenium powder completely dissolved to obtain a solution of the Se precursor.

[0141] <Solution of S precursor> 100 mmol of powdered sulfur and 50 mL of tri-n-octylphosphine were mixed under a nitrogen atmosphere and stirred until the sulfur powder completely dissolved to obtain a solution of the S precursor.

[0142] <Manufacture of core / shell semiconductor nanoparticles> (Example 1) 5 mL of trioctylamine was added to 10 mL of a dispersion of InP core particles (In: 0.4 mmol), and the temperature of the dispersion of InP core particles was raised to 230°C. Next, when the temperature of the dispersion of InP core particles reached 230°C, 20 mL of the zinc precursor solution and 2.0 mL of the Se precursor solution shown in Table 1 were added within 1 minute, and the temperature of the dispersion of InP core particles was raised to 280°C at a rate of 1°C / min. Then, 60 minutes after the temperature of the dispersion of InP core particles reached 280°C, heating was terminated, and it was cooled to room temperature (25°C) to obtain a dispersion of core / shell semiconductor nanoparticles (reaction solution). Next, acetone was added to the obtained dispersion of core / shell semiconductor nanoparticles to aggregate the semiconductor nanoparticles. Then, after centrifugation (4000 rpm, 10 minutes), the supernatant was removed, and the core / shell semiconductor nanoparticles were redispersed in hexane. This was repeated to obtain purified core / shell semiconductor nanoparticles. The optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2. In the measurement of the optical properties of the semiconductor nanoparticles, the excitation wavelength was a single wavelength of 450 nm. The same applies to the measurement of the optical properties of the following semiconductor nanoparticles.

[0143] (Example 2) 5 mL of trioctylamine was added to 10 mL of a dispersion of InP core particles (In: 0.4 mmol), and the temperature of the dispersion of InP core particles was raised to 230°C. Next, when the temperature of the dispersion of InP core particles reached 230°C, the addition of the zinc precursor solution shown in Table 1 at a rate of 0.4 mL / min and the addition of the Se precursor solution at a rate of 0.04 mL / min were simultaneously started. 50 minutes after the start of the addition of the zinc precursor solution and the Se precursor solution, the addition of both was simultaneously terminated (addition time: 50 minutes). At this time, simultaneously with the start of the addition of the zinc precursor solution and the Se precursor solution, the temperature of the dispersion of InP core particles was started to be raised to 280°C at a rate of 1°C / min. Then, 60 minutes after the temperature of the dispersion of InP core particles reached 280°C, heating was terminated, and it was cooled to room temperature (25°C) to obtain a dispersion of core / shell semiconductor nanoparticles (reaction solution). Next, purification was carried out in the same manner as in Example 1 to obtain purified core / shell semiconductor nanoparticles. The optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0144] (Example 3) A solution of the zinc precursor and a solution of the Se precursor shown in Table 1 were mixed at a volume ratio of 10:1 to prepare a solution of the zinc precursor and the Se precursor. 5 mL of trioctylamine was added to 10 mL of a dispersion of InP core particles (In: 0.4 mmol), and the temperature of the dispersion of InP core particles was raised to 230°C. Then, when the dispersion of InP core particles reached 230°C, the addition of the solution of the zinc precursor and the Se precursor was started at a rate of 0.44 mL / min. The addition of the solution of the zinc precursor and the Se precursor was completed 50 minutes after the start of the addition (addition time: 50 minutes). At this time, simultaneously with the start of the addition of the solution of the zinc precursor and the Se precursor, the temperature of the dispersion of InP core particles was raised at a rate of 1°C / min to 280°C. Then, 60 minutes after the dispersion of InP core particles reached 280°C, the heating was terminated, and it was cooled to room temperature (25°C) to obtain a dispersion (reaction solution) of core / shell semiconductor nanoparticles. Next, purification was carried out in the same manner as in Example 1 to obtain purified core / shell semiconductor nanoparticles. The optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0145] (Example 4) A solution of the zinc precursor and a solution of the Se precursor shown in Table 1 were mixed at a volume ratio of 10:1 to prepare a solution of the zinc precursor and the Se precursor. 5 mL of trioctylamine was added to 10 mL of the dispersion of InP core particles (In: 0.4 mmol), and the temperature of the dispersion of InP core particles was raised to 230 °C. Subsequently, 0.2 mmol of oleoyl chloride was added to the dispersion of InP core particles and held at 230 °C for 30 minutes. Next, the addition of the solution of the zinc precursor and the Se precursor to the dispersion of InP core particles was started at a rate of 0.44 mL / min. The addition of the solution of the zinc precursor and the Se precursor was completed 50 minutes after the start of the addition (addition time: 50 minutes). At this time, simultaneously with the start of the addition of the solution of the zinc precursor and the Se precursor, the temperature of the dispersion of InP core particles was started to be raised to 280 °C at 1 °C / min. Then, 60 minutes after the dispersion of InP core particles reached 280 °C, the heating was terminated and cooled to room temperature (25 °C) to obtain a dispersion of core / shell semiconductor nanoparticles (reaction solution). Subsequently, purification was carried out in the same manner as in Example 1 to obtain purified core / shell semiconductor nanoparticles. The types of ligands coordinated to the obtained core / shell semiconductor nanoparticles and the molar fraction of each ligand were measured by gas chromatography. As a result, it was confirmed that 43.6 mol% of the total ligands coordinated to the obtained core / shell semiconductor nanoparticles was 3,5,5-trimethylhexanoic acid. In addition, the optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0146] (Example 5) The procedure of Example 4 was repeated except that the zinc precursor shown in Table 1 was used as the zinc precursor. The types of ligands coordinated to the obtained core / shell semiconductor nanoparticles and the molar fraction of each ligand were measured by gas chromatography. As a result, it was confirmed that 41.7 mol% of the total ligands coordinated to the obtained core / shell semiconductor nanoparticles was 2-ethylhexanoic acid. In addition, the optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0147] (Example 6) Except for using the zinc precursor shown in Table 1 as the zinc precursor, the procedure was the same as in Example 4. The results are shown in Table 2.

[0148] (Example 7) A solution of the zinc precursor, a solution of the Se precursor, and a solution of the S precursor shown in Table 1 were mixed at a volume ratio of 10:0.5:0.5 to prepare a solution of the zinc precursor, the Se precursor, and the S precursor. 5 mL of trioctylamine was added to 10 mL of a dispersion of InP core particles (In: 0.4 mmol), and the temperature of the dispersion of InP core particles was raised to 200 °C. Next, 0.2 mmol of oleoyl chloride was added to the dispersion of InP core particles and held at 230 °C for 30 minutes. Next, the addition of the solution of the zinc precursor, the Se precursor, and the S precursor to the dispersion of InP core particles was started at a rate of 0.44 mL / min. The addition of the solution of the zinc precursor, the Se precursor, and the S precursor was completed 50 minutes after the start of the addition (addition time: 50 minutes). At this time, simultaneously with the start of the addition of the solution of the zinc precursor, the Se precursor, and the S precursor, the temperature of the dispersion of InP core particles was started to be raised at 1 °C / min to 280 °C. Next, 60 minutes after the dispersion of InP core particles reached 280 °C, the heating was terminated and cooled to room temperature (25 °C) to obtain a dispersion of core / shell semiconductor nanoparticles (reaction solution). Next, purification was performed in the same manner as in Example 1 to obtain purified core / shell semiconductor nanoparticles. The optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0149] (Example 8) A solution of the zinc precursor, a solution of the Se precursor, and a solution of the S precursor shown in Table 1 were mixed at a volume ratio of 10:1.0:1.0 to prepare a solution of the zinc precursor, the Se precursor, and the S precursor, and except that the addition rate of the solution of the zinc precursor, the Se precursor, and the S precursor was 0.48 mL / min, the procedure was the same as in Example 7. The addition time was 50 minutes at this time. The results are shown in Table 2.

[0150] (Example 9) The procedure of Example 7 was repeated, except that the addition rates of the solutions of the zinc precursor, Se precursor, and S precursor were set to 0.84 mL / min. The addition time was 50 minutes at this time. The results are shown in Table 2.

[0151] (Example 10) The solutions of the zinc precursor and Se precursor shown in Table 1 were mixed at a volume ratio of 10:1 to prepare a solution of the zinc precursor and Se precursor. 5 mL of trioctylamine was added to 10 mL of a dispersion of InP core particles (In: 0.4 mmol), and the temperature of the dispersion of InP core particles was raised to 230°C. Next, 0.2 mmol of oleoyl chloride was added to the dispersion of InP core particles and held at 230°C for 30 minutes. Next, the addition of the solution of the zinc precursor and Se precursor to the dispersion of InP core particles was started at a rate of 0.22 mL / min, and the addition of the solution of the zinc precursor and Se precursor was completed 100 minutes after the start of the addition (addition time: 100 minutes). At this time, simultaneously with the start of the addition of the solution of the zinc precursor and Se precursor, the temperature of the dispersion of InP core particles was started to be raised at 0.5°C / min to 250°C, and after reaching 250°C, the temperature of the dispersion of InP core particles was raised to 280°C at 1°C / min. Next, 60 minutes after the dispersion of InP core particles reached 280°C, heating was terminated, and it was cooled to room temperature (25°C) to obtain a dispersion of core / shell semiconductor nanoparticles (reaction solution). Next, purification was carried out in the same manner as in Example 1 to obtain purified core / shell semiconductor nanoparticles. The optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0152] (Example 11) The solutions of the zinc precursor and Se precursor shown in Table 1 were mixed at a volume ratio of 10:1 to prepare a solution of the zinc precursor and Se precursor. 5 mL of trioctylamine was added to 10 mL of the dispersion of InP core particles (In: 0.4 mmol), and the temperature of the dispersion of InP core particles was raised to 230 °C. Next, 0.2 mmol of oleoyl chloride was added to the dispersion of InP core particles and held at 230 °C for 30 minutes. Next, the addition of the solution of the zinc precursor and the Se precursor to the dispersion of InP core particles was started at a rate of 0.055 mL / min. The addition of the solution of the zinc precursor and the Se precursor was completed 400 minutes after the start of the addition (addition time: 400 minutes). At this time, simultaneously with the start of the addition of the solution of the zinc precursor and the Se precursor, the temperature of the dispersion of InP core particles was started to be raised at 0.125 °C / min to 250 °C, and after reaching 250 °C, the temperature of the dispersion of InP core particles was raised to 280 °C at 1 °C / min. Next, 60 minutes after the dispersion of InP core particles reached 280 °C, the heating was terminated and cooled to room temperature (25 °C) to obtain a dispersion of core / shell semiconductor nanoparticles (reaction solution). Next, purification was carried out in the same manner as in Example 1 to obtain purified core / shell semiconductor nanoparticles. The optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0153] (Example 12) The procedure of Example 4 was repeated except that the solvent of the solution of the zinc precursor was changed to squalene instead of octadecene. The addition time was 50 minutes at this time. The results are shown in Table 2.

[0154] (Comparative Example 1) The procedure of Example 1 was repeated except that the zinc precursor was changed to zinc carboxylate described in Table 1. The results are shown in Table 2.

[0155] (Comparative Example 2) The procedure of Example 2 was repeated except that the zinc precursor was changed to zinc carboxylate described in Table 1. In Comparative Example 2, clogging of the supply pipe of the solution of the zinc precursor occurred multiple times during the addition of the solution of the zinc precursor, and each time, after eliminating the clogging, the addition of the solution of the zinc precursor and the addition of the solution of the Se precursor were restarted. The results are shown in Table 2.

[0156] (Comparative Example 3) The zinc precursor was the zinc carboxylate described in Table 1, and the procedure was the same as in Example 4 except for this. In Comparative Example 4, clogging of the supply pipe occurred multiple times during the addition of the solutions of the zinc precursor and the Se precursor. Each time, after eliminating the clogging, the addition of the solution of the zinc precursor and the solution of the Se precursor was resumed. The results are shown in Table 2.

[0157] (Production of Core / Shell / Shell Semiconductor Nanoparticles) (Examples 1 to 12, Comparative Examples 1 to 3) The procedure was the same as in each of the above Examples or Comparative Examples to obtain a dispersion (reaction solution) of core / shell semiconductor nanoparticles. Next, the obtained dispersion (reaction solution) of core / shell semiconductor nanoparticles was heated to 280°C. After reaching 280°C, a solution of the zinc precursor shown in Table 1 was simultaneously added to the dispersion (reaction solution) of core / shell semiconductor nanoparticles at a rate of 0.2 mL / min, and a solution of the S precursor was added at a rate of 0.03 mL / min. 100 minutes after starting the addition of the solution of the zinc precursor and the solution of the S precursor, the addition of both was simultaneously terminated (addition time: 100 minutes). Then, 60 minutes after the addition was completed, the heating was terminated, and it was cooled to room temperature (25°C) to obtain core / shell / shell semiconductor nanoparticles. A dispersion (reaction solution) was obtained. Next, acetone was added to the obtained dispersion of core / shell / shell semiconductor nanoparticles to aggregate the semiconductor nanoparticles. Then, after centrifugation (4000 rpm, 10 minutes), the supernatant was removed, and the core / shell / shell semiconductor nanoparticles were redispersed in hexane. This was repeated to obtain purified core / shell / shell semiconductor nanoparticles. The optical properties of the obtained core / shell / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0158] (Production of Core / Shell Semiconductor Nanoparticles on a Large Scale) (Example 13) (Preparation of Dispersion of InP Core Particles) Indium acetate (50 mmol), myristic acid (150 mmol), zinc myristate (20 mmol), and octadecene (1000 mL) were charged into a two-necked flask. The inside of the flask was evacuated and heated to 120 °C under vacuum (<10 Pa). After maintaining for 60 minutes from the time when the vacuum degree dropped below 10 Pa, nitrogen was introduced into the flask and cooled to room temperature (25 °C) to obtain an In precursor. Also, in a glove box under a nitrogen atmosphere, tris(trimethylsilyl)phosphine was mixed with tri-n-octylphosphine so that the molar concentration became 0.2 M to obtain a P precursor. Next, at room temperature (25 °C) under a nitrogen atmosphere, 200 mL of the P precursor was injected into the In precursor, and the temperature was raised to 280 °C at 10 °C / min. After holding at 280 °C for 2 minutes, the reaction solution was cooled to room temperature to obtain the reaction solution as a dispersion of InP core particles. (Production of core / shell semiconductor nanoparticles) Next, the solution of the zinc precursor and the solution of the Se precursor shown in Table 1 were mixed at a volume ratio of 10:1 to prepare a solution of the zinc precursor and the Se precursor. Next, 50 mL of trioctylamine was added to 1000 mL of the dispersion of InP core particles (In: 40 mmol), and the dispersion of InP core particles was heated to 230 °C. Then, 20 mmol of oleoyl chloride was added to the dispersion of InP core particles and held at 230 °C for 30 minutes. Then, the addition of the solution of the zinc precursor and the Se precursor was started to the dispersion of InP core particles at a rate of 44 mL / min. The addition of the solution of the zinc precursor and the Se precursor was completed 50 minutes after the start of the addition (addition time: 50 minutes). At this time, simultaneously with the start of the addition of the solution of the zinc precursor and the Se precursor, the temperature of the dispersion of InP core particles was started to be raised to 280 °C at 0.5 °C / min. Then, 60 minutes after the dispersion of InP core particles reached 280 °C, the heating was terminated and cooled to room temperature (25 °C) to obtain a dispersion of core / shell semiconductor nanoparticles (reaction solution). Next, purification was performed in the same manner as in Example 1 to obtain purified core / shell semiconductor nanoparticles. The optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0159] (Example 14) (Preparation of dispersion of InP core particles) A dispersion of InP core particles was obtained in the same manner as in Example 13. (Production of core / shell semiconductor nanoparticles) Next, 50 mL of trioctylamine was added to 1000 mL of the dispersion of InP core particles (In: 40 mmol), and the temperature of the dispersion of InP core particles was raised to 230°C. Then, 20 mmol of oleoyl chloride was added to the dispersion of InP core particles and held at 230°C for 30 minutes. Then, the addition of the solution of the zinc precursor shown in Table 1 and the solution of the Se precursor were simultaneously started at a rate of 40 mL / min and 4 mL / min, respectively, to the dispersion of InP core particles. 50 minutes after the start of the addition of the solution of the zinc precursor and the solution of the Se precursor, the addition of the solution of the zinc precursor and the solution of the Se precursor was completed (addition time: 50 minutes). At this time, simultaneously with the start of the addition of the solution of the zinc precursor and the solution of the Se precursor, the temperature of the dispersion of InP core particles was started to be raised at 0.5°C / min to 280°C. Then, 60 minutes after the dispersion of InP core particles reached 280°C, the heating was terminated and cooled to room temperature (25°C) to obtain a dispersion of core / shell semiconductor nanoparticles (reaction solution). Next, purification was carried out in the same manner as in Example 1 to obtain purified core / shell semiconductor nanoparticles. The optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0160] (Example 15) (Preparation of dispersion of InP core particles) A dispersion of InP core particles was obtained in the same manner as in Example 13. (Production of core / shell semiconductor nanoparticles) Next, 50 mL of trioctylamine was added to 1000 mL of the InP core particle dispersion (In: 40 mmol), and the temperature of the InP core particle dispersion was raised to 230°C. Next, 20 mmol of oleoyl chloride was added to the InP core particle dispersion and held at 230°C for 30 minutes. Next, the addition of the zinc precursor solution shown in Table 1 to the InP core particle dispersion was started at a rate of 40 mL / min, and 50 minutes after the start of the addition of the zinc precursor solution, the addition of the zinc precursor solution was completed (addition time: 50 minutes). Next, the addition of the Se precursor solution to the InP core particle dispersion in which the total amount of the zinc precursor solution had been added was started at a rate of 4 mL / min, and 50 minutes after the start of the addition of the Se precursor solution, the addition of the Se precursor solution was completed (addition time: 50 minutes). At this time, simultaneously with the start of the addition of the zinc precursor solution, the temperature of the InP core particle dispersion was started to be raised to 280°C at a rate of 0.5°C / min. Next, 60 minutes after the InP core particle dispersion reached 280°C, heating was terminated and cooled to room temperature (25°C) to obtain a dispersion of core / shell semiconductor nanoparticles (reaction solution). Next, purification was performed in the same manner as in Example 1 to obtain purified core / shell semiconductor nanoparticles. The optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0161] (Example 16) (Preparation of InP Core Particle Dispersion) A dispersion of InP core particles was obtained in the same manner as in Example 13. (Production of Core / Shell Semiconductor Nanoparticles) Next, 50 mL of trioctylamine was added to 1000 mL of the InP core particle dispersion (In: 40 mmol), and the temperature of the InP core particle dispersion was raised to 230°C. Next, 20 mmol of oleoyl chloride was added to the InP core particle dispersion and held at 230°C for 30 minutes. Next, the addition of the zinc precursor solution shown in Table 1 to the InP core particle dispersion was started at a rate of 667 mL / min, and the addition of the zinc precursor solution was completed 3 minutes after the start of the addition of the zinc precursor solution (addition time: 3 minutes). Next, the addition of the Se precursor solution to the InP core particle dispersion in which the total amount of the zinc precursor solution had been added was started at a rate of 4 mL / min, and the addition of the Se precursor solution was completed 50 minutes after the start of the addition of the Se precursor solution (addition time: 50 minutes). At this time, simultaneously with the start of the addition of the zinc precursor solution, the temperature of the InP core particle dispersion was started to be raised to 280°C at 0.5°C / min. Next, 60 minutes after the InP core particle dispersion reached 280°C, heating was terminated and cooled to room temperature (25°C) to obtain a dispersion of core / shell semiconductor nanoparticles (reaction solution). Next, purification was carried out in the same manner as in Example 1 to obtain purified core / shell semiconductor nanoparticles. The optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0162] (Comparative Example 4) (Preparation of InP Core Particle Dispersion) A dispersion of InP core particles was obtained in the same manner as in Example 13. (Production of Core / Shell Semiconductor Nanoparticles) The procedure of Example 15 was repeated except that the S precursor solution was added to the InP core particle dispersion in which the total amount of the zinc precursor solution had been added at a rate of 4 mL / min. The results are shown in Table 2.

[0163] (Comparative Example 5) (Preparation of InP Core Particle Dispersion) A dispersion of InP core particles was obtained in the same manner as in Example 13. (Production of Core / Shell Semiconductor Nanoparticles) The dispersion of InP core particles after adding the total amount of the zinc precursor solution was treated in the same manner as in Example 16, except that the solution of the S precursor was added at a rate of 4 mL / min. The results are shown in Table 2.

[0164] (Comparative Example 6) (Preparation of Dispersion of InP Core Particles) A dispersion of InP core particles was obtained in the same manner as in Example 13. (Production of Core / Shell Semiconductor Nanoparticles) Next, 50 mL of trioctylamine was added to 1000 mL of the dispersion of InP core particles (In: 40 mmol), and the temperature of the dispersion of InP core particles was raised to 230 °C. Then, after reaching 230 °C, the addition of the zinc precursor solution shown in Table 1 to the dispersion of InP core particles at a rate of 667 mL / min and the addition of the Se precursor solution at a rate of 66.7 mL / min were simultaneously started. Three minutes after starting the addition of the zinc precursor solution and the Se precursor solution, the addition of the zinc precursor and Se precursor solutions was terminated (addition time: 3 minutes). At this time, simultaneously with the start of the addition of the zinc precursor solution and the Se precursor solution, the temperature of the dispersion of InP core particles was started to be raised at 0.5 °C / min to 280 °C. Then, 60 minutes after the dispersion of InP core particles reached 280 °C, the heating was terminated, and it was cooled to room temperature (25 °C) to obtain a dispersion (reaction solution) of core / shell semiconductor nanoparticles. Next, purification was performed in the same manner as in Example 1 to obtain purified core / shell semiconductor nanoparticles. The optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 2.

[0165] (Comparative Example 7) The procedure of Example 14 was repeated, except that the zinc precursor was zinc carboxylate described in Table 1. The results are shown in Table 2.

[0166] (Comparative Example 8) Although an attempt was made to carry out the procedure in the same manner as in Example 13, except that the zinc precursor was changed to the zinc carboxylate shown in Table 1, clogging occurred in the piping multiple times during the addition. Even though the addition was carried out while resolving the clogging, aggregation occurred in the obtained particles, and the optical properties could not be measured.

[0167]

Table 1

[0168]

Table 2

[0169] In Example 4, in the shell formation step, by using the zinc salt of 3,5,5-trimethylhexanoic acid as the zinc precursor, it was confirmed that 3,5,5-trimethylhexanoic acid derived from the zinc precursor coordinates as a ligand to the obtained core / shell type semiconductor nanoparticles. Also, in Example 5, in the shell formation step, by using the zinc salt of 2-ethylhexanoic acid as the zinc precursor, it was confirmed that 2-ethylhexanoic acid derived from the zinc precursor coordinates as a ligand to the obtained core / shell type semiconductor nanoparticles. Further, in Examples 1 to 3 and Examples 6 to 12 as well, since the zinc salt of a carboxylic acid having a branched chain was used as the zinc precursor in the shell formation step in the same manner as in Examples 4 and 5, it is presumed that, similar to Examples 4 and 5, a carboxylic acid having a branched chain derived from the zinc precursor coordinates as a ligand to the obtained core / shell type semiconductor nanoparticles.

Claims

1. While adding a solution of a zinc salt of a carboxylic acid having a branched chain to a dispersion of core particles, a solution of a Group VI element precursor is added, and in the presence of the core particles, the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor are reacted to form a shell containing zinc and a Group VI element on the surface of the core particles. A method for producing core / shell type semiconductor nanoparticles, characterized by having a shell forming step.

2. A solution of a zinc salt of a carboxylic acid having a branched chain and a solution of a Group VI element precursor are added to a dispersion of core particles, and in the presence of the core particles, the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor are reacted to form a shell containing zinc and a Group VI element on the surface of the core particles. A method for producing core / shell type semiconductor nanoparticles, characterized by having a shell forming step.

3. The method for producing core / shell type semiconductor nanoparticles according to claim 1 or 2, wherein the Group VI element contains at least Se.

4. After adding a solution of a zinc salt of a carboxylic acid having a branched chain to a dispersion of core particles, a solution of a Group VI element precursor containing at least a Se precursor is added, and in the presence of the core particles, the zinc salt of the carboxylic acid having a branched chain and the Group VI element precursor are reacted to form a shell containing zinc and a Group VI element on the surface of the core particles. A method for producing core / shell type semiconductor nanoparticles, characterized by having a shell forming step.

5. The method for producing core / shell type semiconductor nanoparticles according to any one of claims 1 to 4, wherein the core particles contain In and P.

6. The zinc salt of the carboxylic acid having a branched chain is one or more selected from the group consisting of zinc 2-ethylhexanoate, zinc 3,5,5-trimethylhexanoate, and zinc 16-methylheptadecanoate. The method for producing core / shell type semiconductor nanoparticles according to any one of claims 1 to 5.

7. The solvent of the solution of the zinc salt of the carboxylic acid having a branched chain is at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit, and liquid paraffin. The method for producing core / shell type semiconductor nanoparticles according to any one of claims 1, 3 to 6.

8. The solvent of the solution of the zinc salt of the carboxylic acid having the branched chain and the Group VI element precursor is at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit, and liquid paraffin. The method for producing core / shell type semiconductor nanoparticles according to any one of claims 2, 3, 5, and 6.

9. The solvent of the solution of the Group VI element precursor is at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit, and liquid paraffin. The method for producing core / shell type semiconductor nanoparticles according to any one of claims 1, 3, 5 to 7.

10. The solvent of the solution of the Group VI element precursor containing at least the Se precursor is at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirit, and liquid paraffin. The method for producing core / shell type semiconductor nanoparticles according to any one of claims 4 to 7.

11. The solution of the zinc salt of the carboxylic acid having the branched chain is in a solution state at 25 ° C. and 1 atm. The method for producing core / shell type semiconductor nanoparticles according to any one of claims 1, 3 to 7, 9, and 10.

12. The solution of the zinc salt of the carboxylic acid having the branched chain and the Group VI element precursor is in a solution state at 25 ° C. and 1 atm. The method for producing core / shell type semiconductor nanoparticles according to any one of claims 2, 3, 5, 6, and 8.

13. The zinc salt of the carboxylic acid having the branched chain and the Group VI element precursor are reacted at 180 to 320 ° C. The method for producing core / shell type semiconductor nanoparticles according to any one of claims 1 to 12.

14. The zinc salt of the carboxylic acid having the branched chain and the Group VI element precursor are reacted at 250 to 320 ° C. The method for producing core / shell type semiconductor nanoparticles according to claim 13.

15. The addition amount of the zinc salt of the carboxylic acid having the branched chain is an addition amount such that the molar ratio of Zn to In in the core particles in the zinc salt of the carboxylic acid having the branched chain (Zn / In) is 7 to 50. The method for producing core / shell type semiconductor nanoparticles according to any one of claims 1 to 14.

16. The manufacturing method of the core / shell type semiconductor nanoparticles according to any one of claims 1 to 15, wherein the addition time of the zinc salt of the carboxylic acid having the branched chain to the dispersion of the core particles is 5 to 600 minutes.

17. The manufacturing method of the core / shell type semiconductor nanoparticles according to claim 16, wherein the addition time of the zinc salt of the carboxylic acid having the branched chain to the dispersion of the core particles is 30 to 180 minutes.

18. While heating the dispersion of the core particles, a solution of the zinc salt of the carboxylic acid having the branched chain and a solution of the group VI element precursor or a solution of the group VI element precursor containing at least the Se precursor are added to the dispersion of the core particles, or a zinc salt of the carboxylic acid having the branched chain and a solution of the group VI element precursor are added. The manufacturing method of the core / shell type semiconductor nanoparticles according to any one of claims 1 to 17.

19. The manufacturing method of the core / shell type semiconductor nanoparticles according to any one of claims 1 to 18, wherein the reaction between the zinc salt of the carboxylic acid having the branched chain and the group VI element precursor is carried out in the presence of a dispersant.

20. The manufacturing method of the core / shell type semiconductor nanoparticles according to any one of claims 1 to 19, wherein the reaction between the zinc salt of the carboxylic acid having the branched chain and the group VI element precursor is carried out in the presence of a halogen element.

21. The manufacturing method of the core / shell type semiconductor nanoparticles according to claim 20, wherein the halogen element is chlorine or bromine.

22. The manufacturing method of the core / shell type semiconductor nanoparticles according to any one of claims 1 to 21, wherein the core particles have not undergone a purification process.

23. A core / shell type semiconductor nanoparticle composite having core / shell type semiconductor nanoparticles and a ligand coordinated on the surface of the core / shell type semiconductor nanoparticles, wherein the shell contains at least zinc and selenium, and the ligand contains a carboxylic acid having a branched chain. A core / shell type semiconductor nanoparticle composite characterized by the above.

24. The core / shell type semiconductor nanoparticle composite according to claim 23, wherein the molar fraction of the ligand of the carboxylic acid having the branched chain in all the ligands coordinated to the core / shell type semiconductor nanoparticles is 20.0 to 80.0 mol%.

25. The core / shell type semiconductor nanoparticle composite according to claim 23 or 24, wherein the carboxylic acid having the branched chain is one or more selected from the group consisting of 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, and 16-methylheptadecanoic acid.

26. The core / shell type semiconductor nanoparticle composite according to claims 23 to 25, wherein the full width at half maximum (FWHM) of the emission spectrum of the core / shell type semiconductor nanoparticle composite is 35 nm or less.

27. The core / shell type semiconductor nanoparticle composite according to any one of claims 23 to 26, wherein the quantum efficiency (QY) of the core / shell type semiconductor nanoparticle composite is 80% or more.

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