Color conversion particles

Abstract

These color conversion particles are equipped with a particle main body which contains chalcogenide perovskite and emits light upon receiving excited light, and a shell which is formed from a semiconductor material for allowing excited light to pass therethrough, and inactivates a surface defect in the particle main body by covering the particle main body. The shell has a band gap which is greater than 2.7eV.

Description

Color conversion particles

[0001] The present invention relates to color conversion particles.

[0002] Color conversion using wavelength conversion (down-conversion), in which excitation light incident on an object from the outside is converted to light with a longer wavelength and then emitted, has been widely used in lighting, display devices, solar cells, etc. In recent years, chalcogenide perovskites, which have superior durability and a high light absorption coefficient compared to other materials, have attracted attention as nanoparticle materials used in this type of color conversion.

[0003] US Patent Application Publication No. 2019 / 0225883 WO 2022 / 113967 WO 2022 / 113984

[0004] However, in conventional chalcogenite perovskite nanoparticles, carriers generated by the nanoparticles absorbing excitation light may be deactivated on the particle surface due to non-radiative recombination, and therefore the luminescence intensity of conventional chalcogenite perovskite nanoparticles is not necessarily sufficient, and further improvement of the luminescence intensity is desired.

[0005] The present invention has been made in view of the above circumstances, and provides color conversion particles that suppress non-radiative recombination of carriers on the particle surface and have higher luminescence intensity than conventional particles.

[0006] A color conversion particle according to one embodiment of the present invention comprises a particle body containing a chalcogenide perovskite and emitting light upon receiving excitation light, and a shell formed of a semiconductor material that transmits the excitation light and covers the particle body to inactivate surface defects of the particle body. The shell has a band gap greater than 2.7 eV.

[0007] According to one aspect of the present invention, it is possible to provide color conversion particles that suppress non-radiative recombination of carriers on the particle surface and have higher luminescence intensity than conventional particles.

[0008] 1 is a schematic diagram showing an example of the configuration of a color conversion particle of this embodiment; 2 is a diagram showing a manufacturing procedure for color conversion particles in an example; 3 is a graph showing the analysis results of an X-ray diffraction device in an example; 4 is a graph showing the emission spectrum of the color conversion particle of an example.

[0009] Hereinafter, embodiments will be described with reference to the drawings. In the embodiments, in order to make the description easier to understand, structures or elements other than the main parts of the present invention will be described in a simplified or omitted manner. Furthermore, in the drawings, the same elements are given the same reference numerals. Note that in the drawings, the shape, dimensions, etc. of each element are shown schematically and do not represent the actual shape, dimensions, etc.

[0010] 1(a) and 1(b) are schematic diagrams showing an example of the configuration of a color conversion particle of this embodiment. The color conversion particle 10 of this embodiment is a particle having an overall shape on the nanometer scale. The color conversion particle 10 performs color conversion by absorbing incident excitation light and re-emitting (emitting) the light as light with a different energy (wavelength).

[0011] The color conversion particle 10 of this embodiment has a particle body 11 that receives excitation light and generates fluorescence of a desired emission wavelength, and a shell 12 that covers the particle body 11.

[0012] (Particle body 11) The particle body 11 absorbs excitation light and causes an inter-electron level transition having an energy corresponding to the desired emission wavelength. As an example, the particle body 11 is a luminescent particle formed entirely of chalcogenite perovskite, as shown in FIG. 1( a). Note that the particle body 11 shown in FIG. 1( a) may contain foreign matter that does not exhibit light absorption or emission, such as an insulator or other composition. By including such foreign matter in the particle body 11, it is possible to improve the luminescence efficiency of the particle body 11 by, for example, scattering light, or to adjust the shape of the particle body 11.

[0013] The chalcogenide perovskite, which is the material of the particle body 11 shown in FIG. 1( a), is a semiconductor consisting of a group of perovskite crystal structures containing chalcogen elements (S, Se, Te) at the X site, and also includes those in which part of the X site is substituted with oxygen (O).

[0014] The perovskites described above represent a group of substances with a cubic crystal structure based on a BX6 octahedron, represented by the chemical formula ABX3. Due to lattice distortion, they can take on tetragonal or orthorhombic crystal structures. Furthermore, several stable crystal structures have been shown computationally for similar ABX3 compositions. These crystal structures range from structures similar to perovskite to structures that are quite different. Furthermore, derivative structures include Ruddlesden-Popper and Dion-Jacobson layered perovskites based on the perovskite structure, as well as double perovskite crystal structures in which different elements are alternately arranged at the B site. In this specification, the above crystal structures are collectively referred to as the "perovskite crystal structure group."

[0015] The perovskite crystal structure group specifically includes substances having the following crystal structures: cubic perovskite, tetragonal perovskite, GdFeO3-type orthorhombic, YScS3-type orthorhombic, NH4CdCl3-type orthorhombic, BaNiO3-type hexagonal, FePS3-type monoclinic, PbPS3-type monoclinic, CeTmS3-type monoclinic, Ruddlesden-Popper-type layered perovskite, Dion-Jacobson-type layered perovskite, and double perovskite. The crystal structure and electronic structure of the perovskite crystal structure group change depending on the composition and synthesis conditions, resulting in changes in the photoelectron properties and chemical characteristics. Therefore, the composition and conditions are selected to obtain a crystal structure suitable for the purpose.

[0016] For example, materials having a cubic perovskite, tetragonal perovskite, GdFeO3-type orthorhombic perovskite, Ruddlesden-Popper-type layered perovskite, or double perovskite structure have excellent optoelectronic and chemical properties. Furthermore, by using a Dion-Jacobson-type layered perovskite structure, chemical stability can be further improved. In particular, materials having a GdFeO3-type orthorhombic perovskite crystal structure represented by ABX3 (A = Group 2, B = Group 4) are known to have excellent optoelectronic properties, including a high optical absorption coefficient.

[0017] The chemical formula of chalcogenide perovskite is ABX3,A'2An-1 B n X 3n+1 , A''A''''B''2X7, A''A2B''3X 10 , A2BB'X6. In the above chemical formula, X represents a chalcogen element (S, Se, Te). A and A' represent Group 2 elements (Ca, Sr, Ba), A'' represents Group 1 elements (Li, Na, K, Rb, Cs), and A''' represents Group 3 elements (rare earth elements) and Bi. B and B' represent Group 4 elements (Ti, Zr, Hf), and B'' represents Group 5 elements (V, Nb, Ta). Furthermore, n is a positive integer. Note that A and A', and B and B' may be the same element. Furthermore, A, A', A'', A''', B, B', B'', and X include mixtures of elements from each group in any ratio.

[0018] As an example, chalcogenite perovskites represented by the chemical formula ABX3 include the following materials: X is selected from the predominant chalcogen elements (S, Se), A is selected from the predominant Group 2 elements (Sr, Ba), and B is selected from the predominant Group 4 elements (Zr, Hf): SrZrS3, SrZrSe3, SrHfS3, SrHfSe3, BaZrS3, BaZrSe3, BaHfS3, BaHfSe3

[0019] As an example, the chemical formula A'2A n-1 B n X 3n+1 Chalcogenite perovskite represented by the formula (1) includes the following substances: X is selected from (S, Se) which is a dominant material among chalcogen elements, A and A' are selected from (Sr, Ba) which is a dominant material among elements in Group 2, and B is selected from (Zr, Hf) which is a dominant material among elements in Group 4. SrBa n-1 Zr n S 3n+1 , SrBa n-1 Zr n Se 3n+1 , Sr n+1 Zr n S 3n+1 , Sr n+1 Zr n Se 3n+1 , BaSrn-1 Zr n S 3n+1 , BaSr n-1 Zr n Se 3n+1 , Ba n+1 Zr n S 3n+1 , Ba n+1 Zr n Se 3n+1 , SrBa n-1 Hf n S 3n+1 , SrBa n-1 Hf n Se 3n+1 , Sr n+1 Hf n S 3n+1 , Sr n+1 Hf n Se 3n+1 , BaSr n-1 Hf n S 3n+1 , BaSr n-1 Hf n Se 3n+1 , Ba n+1 Hf n S 3n+1 , Ba n+1 Hf n Se 3n+1

[0020] These chalcogenide perovskites include (Sr x Ba 1-x ) (Zr y Hf 1-y ) (S z Se 1-z )3 or (Sr x’ Ba 1-x’ )2(Sr x Ba 1-x ) n-1 (Zr y Hf 1-y ) n (S z Se 1-z ) 3n+1 (where x, x', y, and z are values ​​between 0 and 1).

[0021] In chalcogenide perovskites, the carrier concentration or crystal structure can be controlled, and other physical and chemical properties can be adjusted, by partially substituting elements of the same or different groups for the constituent elements. For example, elements of Group 1 can be substituted with elements of Groups 1 and 2, elements of Group 2 with elements of Groups 1, 2, and 3, elements of Group 3 with elements of Groups 2, 3, and 4, elements of Group 4 with elements of Groups 3, 4, and 5, and elements of Group 16 with elements of Groups 15, 16, and 17.

[0022] Chalcogenide perovskite has the following characteristics. Chalcogenide perovskite has a large optical absorption coefficient and excellent luminescence performance (luminous efficiency, half-width). Furthermore, the optical absorption coefficient profile of chalcogenide perovskite rises steeply at the band edge. Therefore, chalcogenide perovskite has the characteristic of having high absorbance near the band gap edge. Therefore, the particle body 11 of chalcogenide perovskite has high absorbance and can efficiently absorb excitation light.

[0023] Chalcogenide perovskites are also highly chemically stable and highly resistant to external environments and stimuli such as air, moisture, heat, and light. Furthermore, chalcogenide perovskites are highly safe because they do not contain toxic elements, and they are advantageous in that they do not contain rare metals, resulting in low raw material costs.

[0024] Here, the particle body 11 may be a luminescent particle partially containing chalcogenide perovskite. For example, as shown in Fig. 1(b), the particle body 11 may be a luminescent particle having an inner layer 11a and an outer layer 11b formed of different semiconductor materials, and at least one of the inner layer 11a and the outer layer 11b being chalcogenite perovskite.

[0025] 1(b), the inner layer 11a of the particle body 11 functions as a light-emitting portion, and the outer layer 11b covering the inner layer 11a functions as a light-absorbing portion. When the particle body 11 is exposed to excitation light, it emits light at the inner layer 11a or at the interface between the inner layer 11a and the outer layer 11b.

[0026] The inner layer 11a and the outer layer 11b of the particle body 11 are both formed of a material that absorbs excitation light. The inner layer 11a and the outer layer 11b may have a band alignment that produces a Stokes shift (the energy difference between the absorption spectrum edge and the emission spectrum peak). The particle body 11 may contain multiple granular inner layers 11a.

[0027] 1(b), one or both of the inner layer 11a and the outer layer 11b may contain a foreign substance that does not absorb or emit light, such as an insulator or other composition. By including such a foreign substance in one or both of the inner layer 11a and the outer layer 11b of the particle body 11, it is possible to improve the luminous efficiency of the particle body 11 by scattering light, or to adjust the shape of the particle body 11.

[0028] Here, when the particle body 11 has an inner layer 11a and an outer layer 11b, the material of the inner layer 11a and the material of the outer layer 11b are any of the following combinations (i) to (iii): (i) The material of the inner layer 11a is a chalcogenide perovskite, and the material of the outer layer 11b is a semiconductor material other than chalcogenide perovskite; (ii) The material of the inner layer 11a is a semiconductor material other than chalcogenide perovskite, and the material of the outer layer 11b is a chalcogenide perovskite; or (iii) The material of the inner layer 11a is a chalcogenide perovskite, and the material of the outer layer 11b is a chalcogenide perovskite different from that of the inner layer 11a.

[0029] The chalcogenite perovskite that can be applied to the inner layer 11a in (i), the outer layer 11b in (ii), or the inner layer 11a and outer layer 11b in (iii) is the same as that described in FIG. 1(a), and therefore a duplicated description will be omitted.

[0030] On the other hand, examples of semiconductor materials that can be used for the outer layer 11b of (i) or the inner layer 11a of (ii) include II-VI semiconductors, III-V semiconductors, I-III-VI semiconductors, I-III-IV-VI semiconductors, IV-VI semiconductors, halide perovskite semiconductors, oxide perovskites, organic-inorganic perovskites, Si, carbon materials, and mixed crystal compounds thereof. Furthermore, the semiconductor material that can be used for the inner layer 11a of (ii) may be a substance (so-called activated phosphor) in which an activator that serves as a luminescent center (luminescent ion) is added to a host crystal such as an oxide or nitride.

[0031] In the above structures (i) to (iii), the particle body 11 can be separated into an outer layer 11b as a light-absorbing portion and an inner layer 11a as a light-emitting portion. This allows a large Stokes shift to be achieved, and the outer layer 11b can provide sufficient absorbance without increasing the size of the inner layer 11a. Therefore, the particle body 11 can achieve high absorbance and high luminous efficiency while suppressing reabsorption loss of luminescence in the inner layer 11a.

[0032] Furthermore, when chalcogenide perovskite is used as the material for the inner layer 11a, as in the structures (i) and (iii) above, the light absorption coefficient of the inner layer 11a, which is the light-emitting portion, can be increased, and the durability of the inner layer 11a against heat and other disturbances can be improved.

[0033] Furthermore, when a chalcogenide perovskite is used as the material for the outer layer 11b, as in the structures (ii) and (iii) above, it is possible to improve the durability of the particle body 11 against heat and other disturbances. Furthermore, by transporting photoexcited carriers to the inner layer 11a in the outer layer 11b made of chalcogenide perovskite, which has high absorbance, it is possible to increase the luminous efficiency in the inner layer 11a.

[0034] (Shell 12) The shell 12 has the function of inactivating surface defects of the particle body 11 and suppressing non-radiative recombination of carriers generated in the particle body 11. The material of the shell 12 is formed of a semiconductor material that transmits the excitation light without absorbing it so as not to interfere with the absorption of the excitation light in the particle body 11. Here, the semiconductor material that transmits the excitation light without absorbing it refers to a material that has a band gap larger than that of the excitation light.

[0035] For example, when the excitation light has a wavelength in the visible region, the shell 12 is formed of a material that has a band gap greater than 2.7 eV and transmits blue light (467 nm). The shell 12 may have a band gap greater than 2.7 eV by reducing the thickness of the shell 12 to generate a quantum size effect. When ultraviolet light (400 nm) is transmitted through the shell 12, the shell 12 preferably has a band gap of 3.1 eV or greater. The shell 12 may more preferably have a band gap of 3.6 eV or greater.

[0036] Examples of materials that can be used for the shell 12 include II-VI semiconductors, III-V semiconductors, I-III-VI semiconductors, I-II-IV-VI semiconductors, IV-VI semiconductors, halide perovskite semiconductors, oxide perovskite, organic-inorganic perovskite, Si, carbon materials, and mixed crystal compounds thereof. The material for the shell 12 may also be amorphous.

[0037] Furthermore, chalcogenide perovskite can also be used as the material for the shell 12. When the entire particle body 11 or the outer layer 11b is formed of chalcogenite perovskite, forming the shell 12 of chalcogenide perovskite reduces defects at the interface between the particle body 11 and the shell 12, thereby reducing non-radiative recombination, from the viewpoints of affinity with the constituent elements of the particle body 11 and matching of the crystal structure and lattice constant. As a result, the color conversion particle 10 of this embodiment can be expected to have a higher luminous efficiency of the particle body 11. Furthermore, when the entire particle body 11 or the outer layer 11b is formed of chalcogenite perovskite, forming a solid solution between the particle body 11 and the shell 12 can further reduce defects at the interface.

[0038] For example, when chalcogenide perovskite is used as the material for the shell 12, one of the following substances can be selected that is different from the material for the particle body 11 and has a band gap larger than 2.7 eV: SrZrS3, SrZrSe3, SrHfS3, SrHfSe3, BaZrS3, BaZrSe3, BaHfS3, BaHfSe3, Sr2Ba n-1 Zr n S 3n+1 , SrBa n-1 Zr n Se 3n+1 , Sr n+1 Zr n S 3n+1 , Sr n+1 Zr n Se 3n+1 , BaSr n-1 Zr n S 3n+1 , BaSr n-1 Zr n Se 3n+1 , Ba n+1 Zr n S 3n+1 , Ba n+1 Zr n Se 3n+1 , SrBa n-1 Hf n S 3n+1 , SrBa n-1 Hf n Se 3n+1 , Srn+1 Hf n S 3n+1 , Sr n+1 Hf n Se 3n+1 , BaSr n-1 Hf n S 3n+1 , BaSr n-1 Hf n Se 3n+1 , Ba n+1 Hf n S 3n+1 , Ba n+1 Hf n Se 3n+1

[0039] Furthermore, the band alignment between the particle body 11 and the shell 12 is preferably Type-I band alignment. That is, it is preferable that the condition be satisfied in which the energy of the lower end of the conduction band of the shell 12 is greater than the energy of the lower end of the conduction band of the particle body 11, and the energy of the upper end of the valence band of the shell 12 is less than the energy of the upper end of the valence band of the particle body 11. In this case, electrons and holes are confined in the particle body 11, which makes it easier for light emission to occur due to recombination of electrons and holes within the particle body 11, and the luminous efficiency of the particle body 11 can be further improved.

[0040] (Size of Color Conversion Particles 10) Although there are no particular limitations, the particle size at which color conversion particles 10 can exist stably is preferably 1 nm or greater.

[0041] Furthermore, if the particle size of the color conversion particles 10 becomes too large, when a large number of color conversion particles 10 are incorporated into a film, coating, resin, etc., the gaps between the particles become larger, resulting in a decrease in the density of the color conversion particles 10. In this case, the absorbance of the wavelength conversion material using the color conversion particles 10 decreases. Furthermore, when applying an ink in which the color conversion particles 10 are dispersed in a solvent using, for example, an inkjet method, if the particle size of the color conversion particles 10 is too large, it can cause nozzle clogging. Even in other application methods, large particle sizes of the color conversion particles 10 can pose process issues. From the above perspectives, the particle size of the color conversion particles 10 is preferably 500 nm or less, more preferably 100 nm or less, and even more preferably 20 nm or less.

[0042] (Thickness of Shell 12) The upper limit of the thickness of the shell 12 may be less than the upper limit of the size of the particle body 11. That is, the thickness of the shell 12 may be in the range of 1 to 250 nm. Furthermore, when a desired band gap is to be expressed in the color conversion particle 10 by the quantum size effect, the thickness of the shell 12 is preferably less than 15 nm, although this cannot be generally limited because it varies depending on the physical properties of the material used.

[0043] (Method for manufacturing color conversion particles 10) Next, a description will be given of a method for manufacturing color conversion particles 10. Color conversion particles 10 are manufactured by carrying out a first synthesis step for synthesizing particle bodies 11, followed by a second synthesis step for synthesizing shells 12.

[0044] (First Synthesis Step) In the first synthesis step for synthesizing the particle body 11, the particle body 11, which is a nano-luminescent particle, is produced from a chalcogenide perovskite. The chalcogenide perovskite involved in the first synthesis step of this embodiment can be synthesized, for example, by reacting a complex having a first metal atom and a complex having a second metal atom, both of which have ligands that do not contain oxygen atoms (O) or halogen atoms as coordinating atoms, in a liquid phase, setting the temperature of the liquid phase to 120°C to 450°C, and setting the reaction time to 0 seconds or longer. Note that 0 seconds refers to the start of the reaction between the complex having the first metal atom and the complex having the second metal atom. For example, in the hot injection method, this refers to the time when the complex having the first metal atom, the complex having the second metal atom, and the complex having the first metal atom are all present in the liquid phase, and in the heat-up method, this refers to the time when the liquid phase reaches a predetermined temperature. The present inventors have found that when synthesizing chalcogenide perovskite in the liquid phase, the presence of components containing halogen atoms, such as halides, or components containing oxygen atoms (O), such as acetates, during liquid-phase synthesis can inhibit the reaction and affect the purity and crystal structure of the target chalcogenide perovskite. Examples of halogen atoms include fluorine atoms (F), chlorine atoms (Cl), bromine atoms (Br), and iodine atoms (I).

[0045] In the first synthesis step of this embodiment, a complex having a first metal atom and a complex having a second metal atom, both of which have ligands that do not contain oxygen atoms or halogen atoms as coordinating atoms, are reacted in the liquid phase. This allows the liquid-phase synthesis reaction to proceed without the presence of components containing oxygen atoms, such as metal acetates, or components containing halogen atoms, such as metal halides, in the liquid phase. This suppresses reactions between the constituent elements of the chalcogenide perovskite and oxygen atoms and halogen atoms in the liquid phase. As a result, a crystal structure similar to that obtained by solid-phase synthesis can be obtained.

[0046] Hereinafter, methods for synthesizing the starting materials, ie, the complex having a first metal atom, the complex having a second metal atom, and the chalcogenide perovskite will be described.

[0047] [Complex Having a First Metal Atom and Complex Having a Second Metal Atom] The ligands of the complex having a first metal atom and the complex having a second metal atom used in the first synthesis step of this embodiment are not particularly limited, as long as they do not contain an oxygen atom or a halogen atom as a coordinating atom. Examples include ligands coordinated by an atom selected from the group consisting of a nitrogen atom (N), a sulfur atom (S), a selenium atom (Se), a tellurium atom (Te), a carbon atom (C), and a phosphorus atom (P).

[0048] The ligands that coordinate with nitrogen atoms include alkylamines (NR amines) such as amine, dimethylamine, diethylamine, and methylethylamine. ２ arylamines (NHAr) such as phenylamine; trialkylsilylamines (N(SiR) such as silylamine and trimethylsilylamine) ３ ) ２ ), nitrogen-containing aromatic rings such as pyrazole, etc.

[0049] The ligands that coordinate with sulfur atoms include dithiocarbamate (S ２ CNR ２ ), xanthate (S ２ COR), trithiocarbamate (S ２ CSR), dithioester (S ２Examples of the ligand that coordinates with a selenium atom or a tellurium atom include compounds in which some or all of the sulfur atoms of the above-mentioned ligand that coordinates with a sulfur atom are substituted with selenium atoms or tellurium atoms.

[0050] The complex having the first metal atom and the complex having the second metal atom may be a single compound (multinuclear complex). Preferably, the first metal atom and the second metal atom may be bonded via a ligand coordinated by a sulfur atom, a selenium atom, or a tellurium atom. Examples of multinuclear complexes in which the ligand is coordinated by a sulfur atom include heterobimetallic thiolates and heterobimetallic sulfides. Examples of multinuclear complexes in which the ligand is coordinated by a selenium atom or a tellurium atom include those in which some or all of the sulfur atoms in a multinuclear complex in which the ligand is coordinated by a sulfur atom are replaced with selenium atoms or tellurium atoms.

[0051] Examples of the ligand coordinated at a carbon atom include alkanes such as methyl and ethyl; unsaturated hydrocarbon rings such as cyclopentadiene, cyclooctadiene, and indene, or benzyl groups and other groups derived from the above-mentioned unsaturated hydrocarbon rings; and cyanide (CN).

[0052] Examples of the ligands that coordinate with phosphorus atoms include trialkylphosphines (PRs) such as trioctylphosphine and tricyclohexylphosphine. ３ triarylphosphines (PAr) such as triphenylphosphine and tri(o-tolyl)phosphine; ３ ); diphosphine (R ２ P-(CH ２ ) ｍ -PR ２ ) etc.

[0053] The ligand may be a derivative of the above-mentioned ligand.

[0054] In each of the general formulas above, R is a hydrogen atom, a saturated hydrocarbon group having 1 to 20 carbon atoms, or an unsaturated hydrocarbon. When one ligand contains two or more R, the R may be the same or different from each other. Ar is an aryl group having 6 to 20 carbon atoms, such as a phenyl group, a naphthyl group, or an anthracenyl group, which may have a substituent. Examples of the substituent include alkyl groups having 1 to 10 carbon atoms. When one ligand contains two or more Ar, the Ar may be the same or different from each other. m is an integer from 1 to 10.

[0055] Among the above-mentioned ligands, ligands coordinated by nitrogen atoms or ligands coordinated by sulfur atoms are preferred. Also preferred are ligands having a structure selected from the group consisting of the following formulas (1) to (7): ２ CNR ａ ２ (1) S ２ COR (2) S ２ CSR ａ (3) S ２ CR ａ (4) SR ａ (5) NR ａ ２ (6) N(SiR ａ ３ ) ２ (7) (wherein, R ａ is a hydrogen atom, a saturated hydrocarbon group having 1 to 20 carbon atoms, or an unsaturated hydrocarbon group having 1 to 20 carbon atoms. ａ When the ａ may be the same or different.)

[0056] Examples of the saturated hydrocarbon group and unsaturated hydrocarbon include an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, a cycloalkenyl group having 3 to 20 carbon atoms, a cycloalkynyl group having 3 to 20 carbon atoms, a cycloalkadienyl group having 3 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms. The saturated hydrocarbon group and the unsaturated hydrocarbon may have a substituent. An example of the substituent is an alkyl group having 1 to 10 carbon atoms.

[0057] In one embodiment, the ligand is preferably a compound represented by the above formula (1). ａ is preferably an alkyl group having 1 to 10 carbon atoms, and more preferably an alkyl group having 2 to 6 carbon atoms.

[0058] The ligand used in the first synthesis step of this embodiment can be synthesized by a conventional method, or a commercially available compound may be used.

[0059] In one embodiment, the metal atom of the complex having the first metal atom is a metal atom selected from alkaline earth metal elements, and the metal atom of the complex having the second metal atom is a metal atom selected from transition metal elements. In one embodiment, the metal atom of the complex having the first metal atom is at least one of Mg, Ca, Sr, and Ba, and the metal atom of the complex having the second metal atom is at least one of Ti, Zr, and Hf.

[0060] The complex having the first metal atom and the complex having the second metal atom can be synthesized by selecting raw material components according to the type of metal atom and ligand possessed by each of them and by a known method. Alternatively, a commercially available metal complex may be used. Hereinafter, as an example of a method for synthesizing a complex having the first metal atom and a complex having the second metal atom, a method for synthesizing a complex having a ligand (S ２ CNR ２ Metal complexes (M(S ２ CNR ２ ) Ｘ ) synthesis will be described.

[0061] First, at least one metal source (M) serving as a source of metal atoms for the metal complex, such as at least one selected from Ba, Sr, Ca, Mg, Ti, Zr, and Hf, or a salt thereof, is dissolved in a solvent such as water. The solvent is not particularly limited as long as it is capable of dissolving the metal source (M), and may be, for example, an organic solvent. Next, ammonia or an amine compound is added to the solution containing the dissolved metal source as a source of nitrogen (N) contained in the complex ligand to be synthesized, and the mixture is stirred. As the amine compound, primary amines or secondary amines can be used without any particular limitation, and the type of substituted hydrocarbon group, etc., in these amine compounds is also not particularly limited.

[0062] Next, a source of sulfur (S) contained in the complex ligand to be synthesized is added to the solution containing the nitrogen (N) source and stirred. ２ However, other compounds can be used depending on the composition of the complex ligand to be synthesized. When Se or Te is contained instead of sulfur (S), CSe ２ , CTe ２ Next, the solid produced by stirring or the precipitate deposited in the solution can be isolated by a known method to obtain the target metal complex.

[0063] [Method for synthesizing chalcogenide perovskite] In this embodiment, the chalcogenide perovskite is synthesized by reacting the above-described complex having the first metal atom and complex having the second metal atom in a solvent. The solvent is selected based on the solubility of the complex having the first metal atom and complex having the second metal atom, and the H ２The solvent can be appropriately selected from the viewpoint of S generation efficiency, etc. Examples of the solvent include saturated aliphatic hydrocarbons, unsaturated aliphatic hydrocarbons, aromatic hydrocarbons, nitrogen-containing heterocyclic compounds, alcohols, aldehydes, carboxylic acids, primary amines, secondary amines, tertiary amines, phosphine compounds, and thiols. As the solvent, it is preferable to use one with a higher boiling point, taking into consideration that the liquid phase may be heated to a high temperature of, for example, 300°C or higher in the liquid-phase synthesis stage described below. For example, alkenes having 10 to 30 carbon atoms, such as octadecene, have a high boiling point and can be suitably used as the solvent.

[0064] In one embodiment, in addition to the complex having a first metal atom and the complex having a second metal atom, a chalcogen compound can be added to the liquid phase. For example, when neither the ligands of the complex having a first metal atom nor the complex having a second metal atom contain a chalcogen element such as sulfur (S), or when the chalcogen elements contained in the ligands are insufficient, the composition of the target chalcogenide perovskite can be adjusted by adding a chalcogen compound to the liquid phase. As the chalcogen compound, one that does not contain oxygen atoms (O) and halogen atoms is preferably used. For example, sulfur or carbon disulfide (CS) ２ ), hydrogen sulfide (H ２ S), sulfides such as selenium or selenides, tellurium or tellurides, hexanethiol, octanethiol, decanethiol, dodecanethiol (n-dodecanethiol, t-dodecanethiol), hexadecanethiol, mercaptopropylsilane, thiourea compounds (S═C(NR ２ ) ２ ), sulfur-trioctylphosphine (trioctylphosphine sulfide; S-TOP), sulfur-tributylphosphine (S-TBP), sulfur-triphenylphosphine (S-TPP), sulfur-trioctylamine (S-TOA), bis(trimethylsilyl) sulfide, ammonium sulfide, sodium sulfide, selenium-trioctylphosphine (Se-TOP), selenium-tributylphosphine (Se-TBP), and selenium-triphenylphosphine. Among these, thiourea compounds (S═C(NR２ ) is, for example, carbon disulfide (CS ２ ) and therefore can be suitably used as a chalcogen compound.

[0065] In one embodiment, in addition to the above-described complex having a first metal atom and complex having a second metal atom, an amine compound can be further added to the liquid phase. The amine compound functions as a reaction initiator. The amine compound may also be used as the above-described solvent. The amine compound is preferably one that does not contain oxygen atoms (O) or halogen atoms. Examples include alkylamines having one alkyl group, such as oleylamine, hexadecylamine, and octadecylamine, dialkylamines having two alkyl groups having 1 to 30 carbon atoms, and trialkylamines (e.g., trioctylamine) having three alkyl groups having 1 to 30 carbon atoms. From the viewpoint of fully exhibiting its function as a reaction initiator between the ligand and the metal component, the amine compound is preferably added in an amount equal to or greater than the total amount of the ligands contained in the complex having a first metal atom and the complex having a second metal atom added to the liquid phase. Furthermore, from the viewpoint of exhibiting the function as a surfactant that adheres to the surfaces of the chalcogenide perovskite particles that are finally obtained, the amine compound may be added to the liquid phase in an amount in excess of the aforementioned amount (equivalent to the total number of ligands).

[0066] In the first synthesis step of this embodiment, the above-described complex having a first metal atom and complex having a second metal atom are reacted in a liquid phase with a chalcogen compound and an amine compound as needed, and the procedure is not particularly limited. The synthesis of this embodiment can be performed by known methods such as a hot injection method, a heat-up method, or a flow synthesis method. The compounding ratio of the complex having a first metal atom and the complex having a second metal atom can be adjusted according to the composition of the target chalcogenide perovskite.

[0067] In a first synthesis step according to one embodiment, when raw material components include a complex having at least a first metal atom, a complex having a second metal atom, and a solvent, a first raw material containing at least the solvent is prepared, and a second raw material containing at least the remaining raw material components not included in the first raw material is prepared. The second raw material is then added to the first raw material, causing a reaction. In this embodiment, it is preferable to preheat at least one of the first raw material and the second raw material, and then add the second raw material to the first raw material. Alternatively, the second raw material may be added to the first raw material and then heated to cause a reaction.

[0068] The first synthesis step of this embodiment will be described below using an example in which the hot injection method is used. First, the first raw material is preheated. The temperature rise rate is not particularly limited, but is, for example, 1 to 30°C / min, typically 1 to 10°C / min. The temperature of the first raw material after heating is not particularly limited, but may be, for example, room temperature to 450°C, or 120 to 360°C.

[0069] Next, the second raw material is added to the first raw material to cause a reaction between the complex having the first metal atom and the complex having the second metal atom. The second raw material may also be preheated, as with the first raw material. The addition rate of the second raw material is not particularly limited, but is preferably adjusted taking into account the decrease in liquid phase temperature due to the addition of the second raw material. The liquid phase temperature after mixing is 120 to 450°C, preferably 120 to 400°C, and more preferably 220 to 360°C.

[0070] For example, either the complex having the first metal atom or the complex having the second metal atom may contain a ligand represented by the above formula (1) (dithiocarbamate (S ２ CNR ２)), if the liquid phase temperature is 120°C or higher, the metal complex having the ligand can initiate a reaction with an amine compound, and the reaction between the complex having the first metal atom and the complex having the second metal atom proceeds smoothly. Note that the reaction can also be initiated without using an amine compound, but in this case, it is preferable to set the liquid phase temperature higher than 120°C. Furthermore, by setting the liquid phase temperature to 360°C or lower, evaporation of a commonly used solvent is suppressed, allowing for stable liquid phase synthesis.

[0071] In this embodiment, by adding the second raw material to the first raw material in a preheated state, once all of the components contributing to the synthesis of the chalcogenide perovskite (the solvent, the complex having the first metal atom, and the complex having the second metal atom) are in a liquid phase, all of these components are suddenly brought to a high temperature state, so that the reaction of the complex having the first metal atom and the reaction of the complex having the second metal atom can start at approximately the same time. As a result, the reaction of the complex having the first metal atom and the reaction of the complex having the second metal atom proceed in a well-balanced manner, allowing the synthesis of a high-purity chalcogenide perovskite.

[0072] When the above-mentioned amine-based compound is added to the liquid phase as a reaction initiator, the raw material components include a solvent, a complex having a first metal atom, a complex having a second metal atom, and an amine-based compound. The combination of the first raw material component and the second raw material component is not particularly limited. For example, the first raw material may be a solvent alone, and the second raw material may be a mixture of a complex having a first metal atom, a complex having a second metal atom, and an amine-based compound. Alternatively, the first raw material may be a mixture of a solvent and an amine-based compound, and the second raw material may be a mixture of a complex having a first metal atom and a complex having a second metal atom. Alternatively, the first raw material may be a mixture of either a complex having a first metal atom or a complex having a second metal atom and a solvent, and the second raw material may be a mixture of the other of a complex having a first metal atom or a complex having a second metal atom and an amine-based compound.

[0073] Furthermore, when the chalcogen compound is added to the liquid phase, the raw material components include a solvent, a complex having a first metal atom, a complex having a second metal atom, and a chalcogen compound. In this case, the combination of the first raw material component and the second raw material component is not particularly limited. For example, the first raw material may be a solvent alone, and the second raw material may be a mixture of a complex having a first metal atom, a complex having a second metal atom, and a chalcogen compound. Alternatively, the first raw material may be a mixture of a solvent and a chalcogen compound, and the second raw material may be a mixture of a complex having a first metal atom and a complex having a second metal atom. Alternatively, the first raw material may be a mixture of either a complex having a first metal atom or a complex having a second metal atom and a solvent, and the second raw material may be a mixture of the other of a complex having a first metal atom or a complex having a second metal atom and a chalcogen compound.

[0074] The liquid phase obtained by adding the second raw material to the first raw material is heated and stirred for 0 seconds or longer, preferably 10 hours or longer and 24 hours or shorter, while maintaining the temperature at 120 to 450° C., preferably 120 to 400° C., and more preferably 220 to 360° C. After stirring is completed, the precipitate deposited in the liquid phase is isolated by a known method, thereby obtaining the target chalcogenide perovskite particles.

[0075] The above-mentioned series of liquid phase syntheses are preferably carried out in a state where components such as water and oxygen are removed as much as possible so that they are not present in the synthesis atmosphere. For example, the above-mentioned series of liquid phase syntheses are preferably carried out in an inert atmosphere filled with nitrogen or argon.

[0076] The first synthesis step of this embodiment may be performed, for example, by a flow synthesis method described below. First, a complex having a first metal atom, a complex having a second metal atom, and at least one of a chalcogen compound and an amine compound are dissolved in a solvent and circulated separately as three or four raw material flows. Next, the raw material flows are merged simultaneously or stepwise to initiate the reaction. At this time, it is preferable to preheat at least one of the raw material flows before merging. The raw material flow to be preheated is preferably the flow with the highest flow rate. Furthermore, since the reaction field in flow synthesis is small, the temperature can be instantly raised even if the raw material flows are heated immediately after merging, and the reaction of the complex having the first metal atom and the reaction of the complex having the second metal atom can start approximately simultaneously. The heating rate during heating and the temperature of the components after heating are the same as those in the hot injection method. The following steps are the same as those in the hot injection method.

[0077] According to flow synthesis, the components contributing to the synthesis of chalcogenide perovskite can be heated in a short time after joining, allowing the reaction of the complex containing the first metal atom and the complex containing the second metal atom to start at approximately the same time. Furthermore, because the reaction field is small in flow synthesis, the collision probability between the raw materials, i.e., reaction efficiency, is high. Therefore, the reaction of the complex containing the first metal atom and the reaction of the complex containing the second metal atom proceed in a well-balanced manner, allowing the synthesis of chalcogenide perovskite with high purity. Furthermore, the yield of chalcogenide perovskite is increased, reducing energy costs. Furthermore, the amount of waste impurities contained in the final synthesis product can be reduced, thereby reducing environmental impact. Furthermore, accidents such as explosions on the production line caused by impurities can be prevented, thereby improving production safety.

[0078] In the first synthesis step of this embodiment described above, chalcogenide perovskite particles can be obtained without a calcination step. Generally, when a calcination step is performed, nano-sized primary particles aggregate to form secondary particles. However, by not performing a calcination step, the formation of such secondary particles is suppressed. Therefore, fine chalcogenide perovskite nanoparticles can be obtained.

[0079] The first synthesis step of this embodiment described above is based on a liquid-phase synthesis method, which makes it less likely for impurities to be mixed into the particles during the synthesis process than solid-phase synthesis. Furthermore, liquid-phase synthesis is characterized by uniform nucleation and particle growth from the liquid phase, making it possible to obtain fine nanoparticles with a narrow particle size distribution by preventing aggregation of the nuclei generated in the liquid phase (see, for example, "Kanie, S. et al., 'Liquid-Phase Synthesis of Size- and Shape-Controlled Functional Inorganic Nanoparticles and Their Application to Hybrid Materials through Surface Precise Organic Modification,' Journal of the Japanese Society for Crystal Growth, 2017, Vol. 44, No. 2, pp. 66-73"). Therefore, according to the first synthesis step of this embodiment, chalcogenide perovskite nanoparticles with low impurity content and a narrow, uniform particle size distribution can be obtained.

[0080] Furthermore, in the first synthesis step, the particle body 11 having an inner layer 11a and an outer layer 11b may be produced by the following method. First, the inner layer 11a is produced by the above-described nanoparticle production method. However, in this case, the inner layer 11a does not necessarily have to be a chalcogenide perovskite nanoparticle. Then, the outer layer 11b may be synthesized on the outside of the inner layer 11a by the following method.

[0081] As an example of the synthesis process for the outer layer 11b, a case where the hot injection method is applied will be described. In the hot injection method, a solution containing nanoparticles forming the inner layer 11a, a precursor compound containing a metal element, and a solvent is reacted with a precursor compound containing an anion element or a solution containing a precursor compound containing an anion and a solvent in a reaction vessel at a temperature ranging from 50°C to 350°C for 0 to 100 hours. This allows the synthesis of the target particle body 11 having the inner layer 11a and the outer layer 11b. After completion of the reaction, the target particle body 11 is recovered after washing with an organic solvent or water.

[0082] Precursor compounds containing the above metal elements include metal powders, alkylated metal compounds, metal alkoxides, metal carboxylates, metal nitrates, metal perchlorates, metal sulfates, metal acetylacetonates, metal halides, metal cyanides, metal hydroxides, metal sulfides, metal halides, and combinations thereof.

[0083] The precursor compound containing the anion element may be a simple anion element or a compound containing an anion element. For example, when the anion element is chalcogen, examples of the precursor compound include metal sulfides, carbon disulfide, hydrogen sulfide, hydrogen selenide, hydrogen telluride, thiol compounds, phosphine compounds, sulfur, selenium, tellurium, or dispersions of these compounds in amine or acid solvents, and combinations thereof.

[0084] Examples of the solvent include commonly used organic solvents including primary amines having a hydrocarbon group, secondary amines having a hydrocarbon group, tertiary amines having a hydrocarbon group, aromatic hydrocarbons, nitrogen-containing heterocyclic compounds, sulfur-containing heterocyclic compounds, aliphatic hydrocarbons, phosphine compounds having a hydrocarbon group, phosphine oxide compounds having a hydrocarbon group, and carboxylic acid compounds having a hydrocarbon group, or water (or a combination of these solvents).

[0085] In synthesizing the outer layer 11b, the target particle body 11 can be obtained through a nucleation growth process in which the outer layer 11b grows on the nanoparticles of the inner layer 11a used in the reaction. The above reaction includes synthesizing the target product in a continuous flow process using a micro reaction vessel. The above reaction also includes synthesizing the target product in an inert atmosphere or in an air atmosphere. The above reaction also includes synthesizing nanoparticles that will become the inner layer 11a and then continuously synthesizing the outer layer 11b. The above reaction also includes synthesizing nanoparticles that will become the inner layer 11a and then adding a precursor of the outer layer 11b to the reaction vessel to synthesize the particle body 11.

[0086] (Second synthesis step) In the second synthesis step for synthesizing the shell 12, the shell 12 is synthesized on the surface of the chalcogenide perovskite particle body 11 obtained in the first synthesis step. For example, the color conversion particles 10 may be synthesized by depositing the shell material on the surface of the particle body 11 by a vapor phase growth method such as ALD or CVD.

[0087] Furthermore, a one-pot synthesis method or a hot injection method may be applied to synthesize the shell 12. In this case, nano-luminescent particles that will become the particle body 11 and a precursor of the shell material are mixed in a solvent. This results in the synthesis of color conversion particles 10 in which the surface of the particle body 11 is coated with the shell material. The one-pot synthesis method and the hot injection method can also be applied to the formation of the chalcogenide perovskite shell 12.

[0088] Alternatively, in the second synthesis step, the shell 12 may be synthesized using a hot injection method in a manner similar to that used to form the outer layer 11b. For example, when the hot injection method is used as an example of the second synthesis step, a solution containing the particle body 11, a precursor compound containing a metal element, and a solvent is reacted with a precursor compound containing an anion element or a solution containing a precursor compound containing an anion and a solvent in a reaction vessel at a temperature ranging from 50°C to 350°C for 0 to 100 hours. This allows the synthesis of the target color-converting particles 10 having the particle body 11 and the shell 12. After the reaction is complete, the target color-converting particles 10 are recovered after washing with an organic solvent or water. Examples of the precursor compound containing a metal element, the precursor compound containing an anion element, and the solvent are the same as those used for the outer layer 11b.

[0089] In the second synthesis step, the target color conversion particles 10 can be obtained through a nucleus growth process in which the shell 12 grows on the nanoparticles of the particle body 11 used in the reaction. The above reaction includes synthesizing the target product in a continuous flow process using a micro reaction vessel. The above reaction also includes synthesis in an inert atmosphere or in an air atmosphere. The above reaction also includes synthesizing nanoparticles that will become the particle body 11 and continuously synthesizing the shell 12. The above reaction also includes synthesizing nanoparticles that will become the particle body 11 and adding a precursor of the shell 12 to the reaction vessel to synthesize the color conversion particles 10.

[0090] The effects of the color conversion particle 10 of this embodiment will be described below. The color conversion particle 10 of this embodiment comprises a particle body 11 that contains chalcogenide perovskite and emits light upon receiving excitation light, and a shell 12 that is formed of a semiconductor material that transmits the excitation light and that covers the particle body 11 to inactivate surface defects of the particle body 11. The shell 12 has a band gap greater than 2.7 eV.

[0091] In this embodiment, since the particle body 11 contains chalcogenide perovskite, the particle body 10 has higher light absorption performance and higher durability against heat and light than particles made of other materials.

[0092] For example, when the color conversion particles 10 of this embodiment are applied to various devices such as display devices and lighting devices, their high light absorption performance makes it easier to convert colors without transmitting blue excitation light. Furthermore, when the color conversion particles 10 of this embodiment are applied to various devices such as display devices and lighting devices, it is possible to thin the color conversion layer of the device, which is advantageous in terms of cost and manufacturing of the device. Furthermore, because the color conversion particles 10 of this embodiment have high durability against heat and light, they are also suitable for use in high-temperature, light-irradiated environments, such as during the operation of microLEDs.

[0093] Furthermore, the color conversion particles 10 of this embodiment have a shell 12 that covers the particle body 11 and inactivates surface defects of the particle body 11. Therefore, according to this embodiment, the shell 12 suppresses non-radiative recombination of carriers on the particle surface, thereby improving the luminescence intensity of the particle body 11 compared to when the shell 12 is not present. Furthermore, the shell 12 is formed of a semiconductor material that transmits excitation light and has a band gap greater than 2.7 eV. Therefore, excitation light in the visible region is not absorbed by the shell 12, and therefore the luminescence intensity of the color conversion particles 10 is not suppressed by the formation of the shell 12.

[0094] <Product Forms and Application Examples of Color-Converting Particles 10> Next, product forms and application examples of the color-converting particles 10 will be described. Product forms of the color-converting particles 10 include powder, solution, thin film, and sheet. Furthermore, application examples of the color-converting particles 10 include application to various devices.

[0095] (Powder) The powder is color conversion particles 10 in an aggregated state. Hereinafter, color conversion particles 10 will be referred to as primary particles, and color conversion particles 10 in an aggregated state will be referred to as secondary particles. There are no particular restrictions on the size of the primary particles and secondary particles, but primary particles are preferably in the range of 5 nm to 1000 nm. Ligands may also be attached to the surfaces of the primary particles and secondary particles. In order to improve properties such as luminescence characteristics, dispersibility of the color conversion particles, and film-forming properties, other materials may be added as additives to the powder of color conversion particles 10.

[0096] Furthermore, there are no particular limitations on the uses of the powder of color conversion particles 10. For example, they may be dispersed in a solvent to prepare a solution, dispersed in a resin or solid medium to prepare a composite, sintered to be used as a sputtering target, or used as a powder directly as a source for evaporation or the like.

[0097] (Solution) A solution is a state in which the color conversion particles 10 are dispersed in a solvent. There are no particular restrictions on the sizes of the primary particles and secondary particles, but the primary particles are preferably in the range of 5 nm to 1000 nm. Furthermore, "dispersed" refers to a state in which the color conversion particles 10 are floating or suspended in the solvent, although some may have settled. Furthermore, ligands may be attached to the surfaces of the primary particles and secondary particles.

[0098] The solution may contain one or more solvents, including, but not limited to, the following: Water, esters such as methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, and pentyl acetate; ketones such as γ-butyrolactone, acetone, dimethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone; ethers such as diethyl ether, methyl tert-butyl ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, 4-methyldioxolane, tetrahydrofuran, methyltetrahydrofuran, anisole, and phenetole; methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol, methoxypropanol, diacetone alcohol, cyclohexanol, 2-fluoroethanol, 2,2,2-trifluoroethanol, and 2,2,2-trifluoroethanol. alcohols such as ethanol and 2,2,3,3-tetrafluoro-1-propanol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate and triethylene glycol dimethyl ether; organic solvents having an amide group such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, acetamide and N,N-dimethylacetamide; organic solvents having a nitrile group such as acetonitrile, isobutyronitrile, propionitrile and methoxyacetonitrile; organic solvents having a carbonate group such as ethylene carbonate and propylene carbonate; organic solvents having a halogenated hydrocarbon group such as methylene chloride and chloroform; organic solvents having a hydrocarbon group such as n-pentane, cyclohexane, n-hexane, benzene, toluene and xylene; dimethyl sulfoxide, etc.

[0099] Furthermore, in order to improve the light-emitting properties, dispersibility of the color conversion particles 10, film-forming properties, and other properties, an additive such as an acid, a base, or a binder material may be added to the above solution. Furthermore, the use of the above solution is not particularly limited. For example, the solution may be used for film formation by a coating method, a spray method, a doctor blade method (or other solution film-forming method), for preparing a composite by combining with a solid dispersion medium, or for preparing a device using these.

[0100] (Thin Film) A thin film is a state in which the color conversion particles 10 are aggregated in a planar form. There are no particular restrictions on the sizes of the primary particles and secondary particles, but the primary particles are preferably in the range of 5 nm to 1000 nm. Ligands may be attached to the surfaces of the primary particles and secondary particles. Other materials may be added to the thin film as additives to improve properties such as the luminescence characteristics and dispersibility of the color conversion particles 10.

[0101] The method for producing the thin film is not particularly limited. For example, the thin film may be produced by a coating method, a spray method, a doctor blade method, an inkjet method, or other solution film production methods, or by a vacuum process such as a sputtering method or a vacuum deposition method. Furthermore, the color-converting particles 10 may be formed into a film by coating or other methods, and then may be baked or otherwise treated so that the particle shape is no longer maintained.

[0102] (Sheet) A sheet is a planar dispersion medium in which color conversion particles 10 are dispersed. There are no particular restrictions on the sizes of the primary particles and secondary particles, but the primary particles are preferably in the range of 5 nm to 1000 nm. Ligands may be attached to the surfaces of the primary particles and secondary particles.

[0103] The material used as the sheet dispersion medium can be any polymer known to those skilled in the art for this purpose. In a suitable embodiment, this type of polymer is substantially translucent or substantially transparent. For example, polymers suitable for the sheet dispersion medium include, but are not limited to, polyvinyl butyral, polyvinyl acetate, silicone, and silicone derivatives. Silicone derivatives include, but are not limited to, polyphenylmethylsiloxane, polyphenylalkylsiloxane, polydiphenylsiloxane, polydialkylsiloxane, fluorinated silicones, vinyl- and hydride-substituted silicones, ionomers, polyethylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polypropylene, polyester, polycarbonate, polystyrene, polyacrylonitrile, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-methacrylic acid copolymer film, nylon, and the like.

[0104] To improve properties such as the light-emitting properties and the dispersibility of the color conversion particles 10, the sheet may contain additives such as silica fine particles or the solvent described above for the solution. The method for producing the sheet is not particularly limited. For example, the sheet may be produced by kneading and stretching a powder and a dispersion medium, or by mixing and applying an ink containing the color conversion particles 10 with a dispersion medium or a precursor thereof.

[0105] (Devices) The color conversion particles 10, or the above-mentioned powders, solutions, films, and sheets, are expected to be used for down-conversion of ultraviolet light, blue light, etc. in various devices. Examples of the types of devices include light-emitting devices such as LEDs and organic ELs, display devices including such light-emitting devices, lighting devices including such light-emitting devices, image sensors, photoelectric conversion devices, and bioluminescent tags.

[0106] <Examples> Examples of color conversion particles of the present invention will be described below. The color conversion particles of the examples have a particle body made of BaZrS3 and a shell made of ZnS. The band gap of ZnS is 3.6 eV. Figure 2 is a diagram showing the manufacturing procedure for color conversion particles in the examples. In the examples, color conversion particles were produced by liquid phase synthesis using the following procedure.

[0107] First, Ba diisobutyldithiocarbamate (527.94 mg) and Zr diisobutyldithiocarbamate (908.76 mg) were weighed into a 50 ml three-neck flask, and 1-octadecene (ODE: 5 ml) was added and stirred. Next, the three-neck flask was moved into a draft while maintaining the internal atmosphere at a N2 atmosphere, and the temperature was raised to 310 °C at a rate of 5 °C / min. Then, room temperature oleylamine (OLA: 3200 mg) was injected into the three-neck flask using a Luer-lock syringe.

[0108] The solution in the three-necked flask was then stirred for 18 hours while being maintained at 310°C, and then cooled to room temperature. The solution in the three-necked flask was then divided into two. One of the solutions was added with butanol to cause precipitation, which was then recovered by centrifugation to give a powder of the synthesized product (BaZrS ３ To the other solution, toluene and ethanol were added to cause precipitation, followed by centrifugation. The supernatant was discarded, and the residue was dispersed in toluene to obtain a dispersion of the synthesized product (BaZrS ３ A dispersion was obtained.

[0109] Also, BaZrS ３ The dispersion (0.5 ml) was added to dodecanethiol (DDT: 5.0 ml), and after 30 minutes of vacuuming at 80°C, the temperature was increased to 240°C at a rate of 5°C / min. Once the temperature was stabilized, BaZrS was added to the dodecanethiol. ３ To the solution containing the dispersion, a Zn solution prepared in a separate three-neck flask was added at a rate of 1 ml / min, and the mixture was heated and stirred for 1 hour. The Zn solution was prepared by adding Zn(OSt) (2529 mg) to dodecanethiol (0.96 ml) and octadecene (4.0 ml), and then maintaining the mixture at 190°C for 30 minutes.

[0110] The solution after the reaction was allowed to cool to room temperature. Excess methanol was added to the resulting solution, and the aggregates were centrifuged. After the supernatant was removed, toluene was added to disperse the aggregates. This procedure was repeated several times to obtain a powder of the color-changing particles of this example (synthetic product: BaZrS ３ This powder was dispersed in toluene to obtain a dispersion of color-changing particles (BaZrS ３ / ZnS dispersion) was obtained.

[0111] 3 is a graph showing the results of analysis by an X-ray diffractometer (XRD) in the examples. ３ The powder has an X-ray diffraction intensity profile of BaZrS ３ Therefore, in the process of the example, the particle body, BaZrS ３ It can be confirmed that the above has been synthesized.

[0112] In addition, the above BaZrS obtained in the examples ３ The X-ray diffraction intensity profile of the ZnS powder closely matches the characteristics of the JCPDS data for ZnS. This confirms that a ZnS shell is formed on the surface of the particle body in the process of the example.

[0113] 4 is a graph showing the emission spectrum of a toluene dispersion of the color conversion particles of the example. The horizontal axis of FIG. 4 represents the emission wavelength, and the vertical axis of FIG. 4 represents the normalized emission intensity. In FIG. 4, the color conversion particles of the example (BaZrS ３ 4 shows the emission spectrum of color conversion particles (BaZrS / ZnS dispersion) as a comparative example, in which a shell is not formed on the particle body of BaZrS. ３ The emission spectrum of the dispersion is shown by the dashed line.

[0114] As shown in Figure 4, the wavelength at the peak of the emission spectrum is almost unchanged between the Examples and Comparative Examples. On the other hand, it was confirmed that in the Examples, the formation of a shell suppresses non-radiative recombination of carriers on the particle surface, and therefore the emission intensity at the peak of the emission spectrum is significantly higher in the Examples than in the Comparative Examples. Furthermore, by forming a solid solution at the interface between the shell and the core, the core particle size is reduced, resulting in a size effect, which allows the emission wavelength to be changed.

[0115] Although the embodiments of the present invention have been described above, they are presented as examples and are not intended to limit the scope of the present invention. The embodiments can be implemented in various forms other than those described above, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the present invention. The embodiments and their modifications are included within the scope and spirit of the present invention, and the inventions described in the claims and their equivalents are also included within the scope and spirit of the present invention.

[0116] This application claims priority based on Japanese Patent Application No. 2022-203590, filed on December 20, 2022, the entire contents of which are incorporated herein by reference.

[0117] 10... Color conversion particle 11... Particle body 11a... Inner layer 11b... Outer layer 12... Shell

Claims

1. a particle body that contains a chalcogenide perovskite and emits light upon receiving excitation light; a shell formed of a semiconductor material that transmits the excitation light, the shell covering the particle body and inactivating surface defects of the particle body; The shell has a bandgap greater than 2.7 eV Color transformation particles.

2. The chalcogenide perovskite may be a cubic perovskite, a tetragonal perovskite, or GdFeO 3 The perovskite has one of the following crystal structures: orthorhombic perovskite, Ruddlesden-Popper layered perovskite, Dion-Jacobson layered perovskite, or double perovskite. The color conversion particle according to claim 1 .

3. The chemical formula of the chalcogenide perovskite is ABX 3 or A' 2 A n-1 B n X 3n+1 (A and A' are elements of Group 2, B is an element of Group 4, and X is a chalcogen element, where n is an integer of 1 or more) The color conversion particle according to claim 2 .

4. The A, A', B, and X each include a mixture of elements from each group in any ratio. The color conversion particle according to claim 3 .

5. The chalcogenide perovskite is SrZrS 3 , SrZrSe 3 , SrHfS 3 , SrHfSe 3 , BaZrS 3 , BaZrSe 3 , BaHfS 3 , BaHfSe 3 , Sr 2 Ba n-1 Zr n S 3n+1 , Sr 2 Ba n-1 Zr n Se 3n+1 , Sr n+1 Zr n S 3n+1 , Sr n+1 Zr n Se 3n+1 , Ba 2 Sr n-1 Zr n S 3n+1 , Ba 2 Sr n-1 Zr n Se 3n+1 , Ba n+1 Zr n S 3n+1 , Ba n+1 Zr n Se 3n+1 , Sr 2 Ba n-1 Hf n S 3n+1 , Sr 2 Ba n-1 Hf n Se 3n+1 , Sr n+1 Hf n S 3n+1 , Sr n+1 Hf n Se 3n+1 , Ba 2 Sr n-1 Hf n S 3n+1 , Ba 2 Sr n-1 Hf n Se 3n+1 , Ba n+1 Hf n S 3n+1 , Ba n+1 Hf n Se 3n+1 (where n is an integer of 1 or more), The color conversion particle according to claim 1 .

6. The chalcogenide perovskite is (Sr x Ba 1-x ) (Zr y Hf 1-y ) (S z Se 1-z ) 3 or (Sr x’ Ba 1-x’ ) 2 (Sr x Ba 1-x ) n-1 (Zr y Hf 1-y ) n (S z Se 1-z ) 3n+1 (where x, x', y, and z are values ​​between 0 and 1) The color conversion particle according to claim 1 .

7. The shell has a band gap of 3.1 eV or more. The color conversion particle according to claim 1 .

8. The shell has a band gap of 3.6 eV or more. The color conversion particle according to claim 7 .

9. The particle body is entirely formed of the chalcogenide perovskite. The color conversion particle according to claim 1 .

10. The particle body is The inner layer serves as a light-emitting part, an outer layer that encompasses the inner layer and absorbs the excitation light; The inner layer is formed of the chalcogenide perovskite. The color conversion particle according to claim 1 .

11. The particle body is The inner layer serves as a light-emitting part, an outer layer that encompasses the inner layer and absorbs the excitation light; The outer layer is formed of the chalcogenide perovskite. The color conversion particle according to claim 1 .

12. The inner layer is formed of a chalcogenide perovskite different from that of the outer layer. The color conversion particle according to claim 11 .

13. The shell is formed of the chalcogenide perovskite different from the particle body. The color conversion particle according to claim 1 .

14. The energy of the bottom of the conduction band of the shell is greater than the energy of the bottom of the conduction band of the particle body, and the energy of the top of the valence band of the shell is less than the energy of the top of the valence band of the particle body. The color conversion particle according to claim 1 .

15. The particle body is BaZrS 3 and The shell is ZnS The color conversion particle according to claim 9 .

16. A powder comprising the color conversion particles according to any one of claims 1 to 15.

17. A solution comprising the color conversion particles according to claim 1 .

18. A thin film comprising the color conversion particles according to any one of claims 1 to 15.

19. A sheet comprising the color conversion particles according to any one of claims 1 to 15.

20. A device comprising color conversion particles according to any one of claims 1 to 15.