Perovskite quantum dot composite material, ink and method for manufacturing perovskite quantum dot composite material

Abstract

A method for manufacturing a perovskite quantum dot composite material that easily forms core-shell particles through a one-stage synthesis step is provided, along with the perovskite quantum dot composite material and an ink containing the perovskite quantum dot composite material. This perovskite quantum dot composite material suppresses surface defects of the perovskite quantum dots by forming an ionic crystal layer comprising halides in the shell layer and exhibits a very high PLQY (Power Level Quality). The perovskite quantum dot composite material comprises core particles and a shell layer surrounding the core particles. The core particles are composed of metal halide perovskites, and the shell layer comprises an organic halide compound with an ionic crystal structure having the same halogen composition as the core particles. The PLQY is greater than 75%, and the change in emission wavelength is less than 5 nm over a period of 10,000 minutes at room temperature.

Description

Technical Field

[0001] This invention relates to a method for manufacturing perovskite quantum dots with high photoluminescence quantum yield, as well as the perovskite quantum dots and inks thereof. Background Technology

[0002] Perovskite quantum dots are particles (dots) with an ion size ranging from 1 nm to tens of nm in diameter, exhibiting unique optical properties that follow quantum mechanics. The emission wavelength emitted upon excitation can be continuously controlled by chemical composition and particle size, and they display luminescence characteristics with very small deviations in the emission wavelength distribution, thus attracting attention in recent years. As wavelength conversion materials based on photoexcitation and self-luminescent materials based on electroexcitation, their practical applications in a wide range of fields such as electronics, medicine, and agriculture are being investigated (Patent Document 1).

[0003] Perovskite quantum dots (PDOs) are susceptible to surface defects due to their large specific surface area. Therefore, surface protection is typically achieved by end-capping with organic ligands such as organic amines and organic acids. However, this method cannot completely protect against defects generated on the particle surface. These surface defects, acting as inactive sites, are a major cause of reduced photoluminescence quantum yield (PLQY). In particular, perovskite PDOs are prone to halogen defects on the particle surface.

[0004] As a reported example related to surface protection of perovskite quantum dots, a method with CsPb(Cl) was described. a Br 1-a- b I b A quantum dot composite material comprising all-inorganic perovskite quantum dots of chemical formula 3 (where 0≤a≤1, 0≤b≤1) and a mutation protective film on the surface of all-inorganic perovskite quantum dots (Patent Document 2). In the quantum dot composite material, the mutation protective film utilizes mesoporous particles, inorganic shell sealing materials, ligand exchangers, microcapsules, polymer sealing materials, silicon-containing sealing materials, oxide or nitride dielectric sealing materials, or combinations thereof.

[0005] There is also an example (Patent Document 3) which describes a method for manufacturing an AMX3 structure as an organometal halide. In one embodiment, the AMX3 structure is described as a crystalline wafer, a nanostructure (e.g., a nanowire), a Q-bit, or an alloy of any of the above, which is a layer in, above, or around a particle (e.g., a layer in a shell-core particle or a part of a quantum dot).

[0006] However, it is known that inorganic oxide coatings such as silica (SiO2) coatings and titanate coatings do not easily cause surface defects after coating formation and do not cause Ostwald ripening, agglomeration, or fusion, thus resulting in very little change in the emission wavelength over time. Non-patent literature 1 reports a technique for coating silica onto the surface of pre-synthesized perovskite quantum dots CsPbBr3 using a multi-stage synthesis process.

[0007] However, even with SiO2 coating on the surface of perovskite quantum dots, surface defects cannot be filled, thus increasing both durability and PLQY (Power Product Quality). Furthermore, the reaction requires two separate stages: perovskite quantum dot fabrication and coating formation, resulting in low efficiency. Moreover, in SiO2 coatings where the insulating layer is present, electricity does not flow through the perovskite quantum dots acting as the core, making it unsuitable for applications requiring electron transmission and reception, such as electro-excited light-emitting devices or solar cells.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent No. 6783296

[0011] Patent Document 2: Japanese Patent No. 6631973

[0012] Patent Document 3: Japanese Patent Publication No. 2018-512364

[0013] Non-patent literature

[0014] Non-patent document 1: Peiyuan Cao, et al, "High stability of silica-wrappedCsPbBr3perovskite quantum dots for light emitting application", CERAM.INT.2020, 46(3), 3882-3888 Summary of the Invention

[0015] The present invention aims to provide a method for manufacturing a perovskite quantum dot composite material that easily forms core-shell particles through a one-stage synthesis step, as well as the perovskite quantum dot composite material and an ink containing the perovskite quantum dot composite material, wherein the perovskite quantum dot composite material suppresses surface defects of the perovskite quantum dots by forming an ionic crystal layer composed of organic halides in the shell layer, and has a very high PLQY.

[0016] This invention comprises the following.

[0017] [1] A perovskite quantum dot composite material, characterized in that it consists of a core particle and a shell layer that covers the core particle, the core particle being composed of a metal halide perovskite, the shell layer being composed of an organic halide compound having an ionic crystal structure having the same halogen composition as the core, a PLQY of 75% or more, and a change in emission wavelength of less than 5 nm during a period up to 10,000 minutes at room temperature.

[0018] [2] A perovskite quantum dot composite material, characterized in that it consists of a core particle and a shell layer that covers the core particle, wherein the core particle material is an inorganic perovskite nanocrystal composed of elements from Group 1, Group 14 and Group 17 of the periodic table, and the shell material is an ionic crystal composed of organic cations and Group 17 elements, with a PLQY of 75% or more.

[0019] [3] According to the perovskite quantum dot composite material of [1] or [2], wherein the solubility of the shell material in an aprotic polar solvent is more than twice the solubility of the core particle material in an aprotic polar solvent.

[0020] [4] The perovskite quantum dot composite material according to any one of [1] to [3], wherein the average particle size of the perovskite quantum dot composite material is 1 to 30 nm.

[0021] [5] An ink, characterized in that it contains a perovskite quantum dot composite material as described in any one of [1] to [4], a polar solvent with a liquid dielectric constant of 20 or more, and a nonpolar solvent with a liquid dielectric constant of 10 or less that is miscible with the polar solvent.

[0022] [6] A method for manufacturing a perovskite quantum dot composite material, characterized in that it comprises: step 1, mixing a polar solvent with a liquid dielectric constant of 20 or higher, an alkali metal halide, a metal halide, and an organic halogen compound to prepare a precursor solution; and step 2, injecting the precursor solution into a nonpolar solvent with a liquid dielectric constant of 10 or lower.

[0023] [7] According to the method for manufacturing perovskite quantum dot composite material described in [6], wherein step 1 is a step of preparing a precursor solution by mixing a core particle material composed of alkali halide metals and metal halide and a shell material composed of organic halogen compounds, wherein the ratio of the molar amount of the shell material added to the minimum necessary amount of the shell material covering the surface of the core particle (added amount / necessary amount) is 1.00 to 2.40.

[0024] [8] The method for manufacturing perovskite quantum dot composite materials according to [6] or [7] is characterized in that, in step 2, the temperature of the precursor solution and the nonpolar solvent is below 40°C.

[0025] [9] A method for manufacturing perovskite quantum dot composite materials according to any one of [6] to [8], wherein, in step 2, the nonpolar solvent further comprises at least one selected from the group consisting of organic acids and organic amine compounds.

[0026] According to the present invention, a method for manufacturing perovskite quantum dot composite materials capable of easily forming core-shell particles through a single-stage synthesis step is provided. In this manufacturing method, an ionic crystal layer is formed on the surface of the core particle during shell formation. Therefore, surface defects in the perovskite quantum dots are suppressed, resulting in a perovskite quantum dot composite material with very high PLQY. Attached Figure Description

[0027] Figure 1 This diagram illustrates the process of injecting a precursor solution containing a core particle material and a shell material into a solution containing a nonpolar solvent, an organic acid, and an organic amine compound with a dielectric constant of less than 10, to form a perovskite quantum dot composite material.

[0028] Figure 2 This is a graph showing the relationship between x and y in perovskite quantum dot composite materials, where the average particle size (nm) of the nucleus particles acting as luminescent bodies is set as the x-axis (horizontal axis) and the molar amount of shell material actually added to coat the surface of the nucleus particles is set as the y-axis (vertical axis).

[0029] Figure 3 This is a graph plotted for the perovskite quantum dot composite materials of Examples 1-6 and Comparative Examples 1-7, with the ratio of the actual amount of added shell material to the amount of shell material required for coating the surface of the nucleus particles set as the horizontal axis and the PLQY of the perovskite quantum dot composite material set as the vertical axis. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings.

[0031] [Perovskite quantum dot composite materials]

[0032] The perovskite quantum dot composite material of the present invention consists of a core particle and a shell layer that covers the core particle. The core particle is composed of a metal halide perovskite, and the shell layer is composed of an organic halide compound having an ionic crystal structure with the same halogen composition as the core particle. The change in emission wavelength is less than 5 nm and the change rate of PLQY is less than 5% during a period of 10,000 minutes at room temperature.

[0033] Nuclear particle materials are inorganic materials with a perovskite-type crystal structure represented by the general formula AMX3. Specifically, they are inorganic perovskite nanocrystals composed of elements from Groups 1, 14, and 17 of the periodic table.

[0034] A represents alkali metals such as cesium, rubidium, potassium, sodium, and lithium. Cesium is preferred. By using alkali metals that become inorganic cations, unlike typical organic cations, perovskite quantum dot composite materials with low solubility in nonpolar solvents can be fabricated.

[0035] M represents lead, germanium, tin, and silicon, among others. Lead and tin are preferred. In addition, antimony, bismuth, copper, nickel, cobalt, iron, manganese, chromium, cadmium, europium, ytterbium, and silver may also be included within a range of less than 5% of the elemental percentage of M.

[0036] X represents halogens such as chlorine, bromine, and iodine.

[0037] Specific examples of AMX3 include: CsPb(Cl a Br 1-a-b I b )3(0≤a≤1, 0≤b≤1, a+b≤1), CsSn(Cl a Br 1-a-b I b )3(0≤a≤1, 0≤b≤1, a+b≤1), CsGe(Cl a Br 1-a-b I b )3(0≤a≤1, 0≤b≤1, a+b≤1), CsSn y Pb (1-y) (Cl a Br 1-a-b I b )3(0≤a≤1, 0≤b≤1, a+b≤1, 0<y<1), CsGe z Pb (1-z) (Cl a Br 1-a- b I b )3(0≤a≤1, 0≤b≤1, a+b≤1, 0<z<1), CsGe z Sn (1-z) (Cl a Br 1-a-b I b )3(0≤a≤1, 0≤b≤1, a+b≤1, 0<z<1) and CsPb (1-y-z) Sn y Ge z (Cl a Br 1-a-b I b)3 (0≤a≤1, 0≤b≤1, a+b≤1, 0<y<1, 0<z<1, y+z<1), etc.

[0038] The shell material forming the shell is represented by the general formula BX, specifically, it is an organic halide compound composed of an organic cation and a group 17 element. In the general formula BX, X represents a halogen, and B represents an organic acid that forms a halide with X.

[0039] Examples of BX include formamidine hydrohalic acid (FAX), methylamine hydrohalic acid (MAX), guanidine hydrohalic acid (GAX), and ethylamine hydrohalic acid (EAX). They typically exist as salts. For instance, formamidine hydrohalic acid (FAX) exists as formamidine hydrobromide, formamidine hydrochloride, and formamidine hydroiodide; methylamine hydrohalic acid (MAX) exists as methylamine hydrobromide, methylamine hydrochloride, and methylamine hydroiodide; guanidine hydrohalic acid (GAX) exists as guanidine hydrobromide, guanidine hydrochloride, and guanidine hydroiodide; and ethylamine hydrohalic acid (EAX) exists as ethylamine hydrobromide, ethylamine hydrochloride, and ethylamine hydroiodic acid.

[0040] For BX to become a shell material, it needs to have the same halogen composition as the nucleus particle AMX3. If the halogen composition is different, halogen exchange occurs between BX and AMX3, sometimes resulting in reversible changes in hue.

[0041] In addition, when BX is replaced by an ammonium halide instead of an ammonium halide, BX is also in a solid state at room temperature, which is preferred.

[0042] The shell material is soluble in polar solvents but poorly soluble in nonpolar solvents.

[0043] The solubility of the shell material in a polar solvent is preferably more than twice that of the solubility of the core material in a polar solvent. By selecting the structures of the shell material and the core material to achieve such solubility, the core particles precipitate first during synthesis, thus avoiding the formation of a mixed crystal structure (i.e., a crystal structure that is uniformly mixed with the shell material to a certain extent) and instead creating a core-shell structure.

[0044] In this specification, a polar solvent refers to an aprotic solvent with a liquid dielectric constant of 20 or higher and which is miscible with the nonpolar solvents described below. Examples of polar solvents include N-methylpyrrolidone (NMP; liquid dielectric constant 32.2), N,N-dimethylformamide (DMF; liquid dielectric constant 36.7), and acetonitrile (liquid dielectric constant 35.9), but are not limited thereto.

[0045] On the other hand, nonpolar solvents refer to solvents with a liquid dielectric constant of 10 or less. Examples of nonpolar solvents include toluene (liquid dielectric constant 2.4), hexane (liquid dielectric constant 1.9), octadecene, ethyl acetate (liquid dielectric constant 6.4), chlorobenzene (liquid dielectric constant 5.6), and chloroform (liquid dielectric constant 4.8), but are not limited to these.

[0046] The perovskite quantum dot composite material of the present invention is an inorganic perovskite nanocrystal with a core composed of metal halide, and a shell composed of an organic halide compound forming an ionic crystal structure with the same halogen composition as the core. The perovskite quantum dot composite material can exist stably for a long time, with a change in emission wavelength of less than 5 nm over a period of 10,000 minutes at room temperature.

[0047] The average particle size of the perovskite quantum dot composite material is typically 1–30 nm, preferably 2–20 nm, and more preferably 4–16 nm. By setting the average particle size of the perovskite quantum dot composite material to within this range, inks containing perovskite quantum dot composite materials with high solvent dispersibility can be prepared.

[0048] As described, the perovskite quantum dot composite material consists of a core particle and a shell layer surrounding the core particle. For the shell layer to function, it needs to be formed on the surface of the core particle with a certain thickness. In the perovskite quantum dot composite material of the present invention, if the molar amount of shell material required to coat the surface of the core particle is y, and the average particle size of the core particle is x, then y = 15x. -1 The relationship holds true. 15 is a value calculated based on experimental values. Figure 2 This is a graph showing the relationship between x and y in perovskite quantum dot composites, where the average particle size (nm) of the nucleus particles that act as luminescent bodies is set as the x-axis and the molar amount of shell material actually added to coat the surface of the nucleus particles is set as the y-axis.

[0049] The amount of necessary shell material depends on the total surface area of ​​the nuclei. Even with the same molar mass of nuclei, if the particle size is large, the total surface area decreases, and the amount of necessary shell material decreases. Conversely, if the particle size is small, the surface area of ​​each ion decreases, but due to the increased number of nuclei, the total surface area increases, and the amount of necessary shell material increases. In other words, the molar mass of the necessary shell material can be determined from the molar mass and particle size of the nuclei.

[0050] The ratio of the molar amount of shell material added to the minimum necessary amount of shell material required to cover the surface of the nucleus particle (added amount / necessary amount) is typically 1.00 to 2.40, preferably 1.05 to 2.00, and more preferably 1.05 to 1.60. Coating the surface of the nucleus particle with a shell material significantly improves PLQY. Figure 3 This is a graph showing the ratio of the actual amount of shell material added to the amount of shell material required to coat the surface of the core particles for the perovskite quantum dot composite materials of Examples 1-6 and Comparative Examples 1-5, plotted with the ratio of the molar amount of shell material actually added to the molar amount of shell material required to coat the surface of the core particles as the horizontal axis and the PLQY of the perovskite quantum dot composite material as the vertical axis.

[0051] The average particle size of the nuclei in perovskite quantum dot composite materials, which serve as luminescent agents, is typically 1–25 nm, preferably 1–18 nm, and more preferably 3–15 nm. If the nuclei become extremely small, the variation in emission wavelength due to quantum confinement effects increases, or the crystal structure cannot be well maintained, resulting in a larger deviation in emission wavelength. If the nuclei become extremely large, the stability of excitons during excitation decreases, thereby reducing PLQY. From the viewpoint of luminescence properties, the average particle size of the nuclei is preferably within a specified range. On the other hand, the thickness of the shell also depends on the size of the nuclei, and is approximately 0.5–5 nm. If the shell is too thin, halogen defects, Ostwald ripening, or agglomeration and fusion occur from the insufficiently coated areas, reducing PLQY.

[0052] The average particle size of the perovskite quantum dot composite material of the present invention can be determined by dynamic light scattering spectrophotometer (DLS) or transmission electron microscope (TEM). For example, it can be determined by the average value along the long axis measured by observing 50 to 100 perovskite quantum dot composite materials using TEM.

[0053] The average particle size of nuclear particles can be determined by the maximum wavelength (λ) of photoluminescence (PL) based on fluorescence spectrophotometers, etc. PL The band gap of the nuclear particle, which acts as the luminescent body, varies with its particle size, and the maximum wavelength (λ) of photoluminescence (PL) is determined. PL ) variation. For example, in perovskite quantum dots CsPbBr3, the maximum wavelength (λ) is observed at an average particle size of 2.6 nm. PL The wavelength is 450 nm, and the maximum wavelength (λ) is at an average particle size of 6.2 nm. PL The wavelength is 500 nm, and the maximum wavelength (λ) is at an average particle size of 15 nm. PL The wavelength is 523nm.

[0054] The thickness of the shell can be calculated by dividing the difference between the average particle size of the perovskite quantum dot composite and the average particle size of the nucleus by 2.

[0055] The perovskite quantum dot composite material of the present invention is capable of emitting light in the visible to near-infrared wavelength region. Preferably, it exhibits the property of emitting light through excitation, and even more preferably, it emits light through excitation based on excitation light and excitation based on electricity.

[0056] The wavelength of the excitation light can be, for example, 200nm to 800nm, 250nm to 750nm, or 300nm to 600nm.

[0057] [Ink]

[0058] The ink of the present invention contains the perovskite quantum dot composite material, a polar solvent with a liquid dielectric constant of 20 or higher, and a nonpolar solvent with a liquid dielectric constant of 10 or lower that is miscible with the polar solvent.

[0059] With the aforementioned configuration, the ink possesses a stable structure in which the surface of perovskite quantum dots is covered by a shell composed of the general formula BX. If the core-shell state of the perovskite quantum dot composite material in the ink is observed using transmission electron microscopy (TEM) or electron diffraction (ED), it can be seen that the surface of the core particles is coated with a shell material.

[0060] If the ink is irradiated with excitation light, such as ultraviolet light with a wavelength of 370 nm, it emits blue to red fluorescence (wavelength 450 to 800 nm).

[0061] The volume ratio of nonpolar solvent to polar solvent is typically 7 times or more, preferably 10 times or more, and more preferably 15 times or more. From the viewpoint of improving the redissolution inhibition and reaction yield of the precipitated perovskite quantum dot composite material, it is preferable to have less polar solvent than nonpolar solvent.

[0062] Polar solvents can also be partially removed after the synthesis of perovskite quantum dot composites. Alternatively, nonpolar solvents can be added after synthesis.

[0063] [Manufacturing Method of Perovskite Quantum Dot Composite Materials]

[0064] The method for manufacturing the perovskite quantum dot composite material of the present invention comprises: step 1, mixing a polar solvent with a liquid dielectric constant of 20 or higher, an alkali metal halide, a metal halide, and an organic halogen compound to prepare a precursor solution; and step 2, injecting the precursor solution into a nonpolar solvent with a liquid dielectric constant of 10 or lower.

[0065] In step 1, a precursor solution is prepared by mixing a polar solvent with a liquid dielectric constant of 20 or higher, an alkali metal halide, a metal halide, and an organic halogen compound.

[0066] Alkali metal halides include, for example, cesium bromide (CsBr), cesium iodide (CsI), cesium chloride (CsCl), rubidium bromide (RbBr), rubidium iodide (RbI), rubidium chloride (RbCl), potassium bromide (KBr), potassium iodide (KI), potassium chloride (KCl), sodium bromide (NaBr), sodium iodide (NaI), and sodium chloride (NaCl). These compounds can be used alone or in mixtures of two or more in any ratio.

[0067] Metal halides, such as lead(II) bromide (PbBr2), lead(II) iodide (PbI2), lead(II) chloride (PbCl2), tin(II) bromide (SnBr2), tin(II) iodide (SnI2), tin(II) chloride (SnCl2), germanium(II) bromide (GeBr2), germanium(II) iodide (GeI2), and germanium(II) chloride (GeCl2), are used. These compounds can be used alone or in mixtures of two or more in any ratio.

[0068] Organohalogen compounds include methylamine hydrobromide (CH5N·HBr), methylamine hydroiodide (CH5N·HI), methylamine hydrochloride (CH5N·HCl), formamidinium hydrobromide (CH4N2·HBr), formamidinium hydroiodide (CH4N2·HI), formamidinium hydrochloride (CH4N2·HCl), guanidinium hydrobromide (CH5N3·HBr), guanidinium hydroiodide (CH5N3·HI), guanidinium hydrochloride (CH5N3·HCl), ethylamine hydrobromide (C2H7N·HBr), ethylamine hydrochloride (C2H7N·HCl), and ethylamine hydroiodide (C2H7N·HI). These compounds can be used alone or in mixtures of two or more in any ratio.

[0069] The mixing ratio of alkali halide metals to halide metals is typically 1:10 to 10:1, preferably 1:3 to 3:1, and more preferably 1:1.5 to 1.5:1. As the difference in mixing ratio increases, the metal element at the M site of the nucleus acquires a perovskite crystal structure with different valences, and PLQY tends to decrease.

[0070] The mixing ratio of the alkali halide metal halide and the metal halide with the organohalogen compound, which are nuclear particle materials, is usually 1:0.6 to 1:10, preferably 1:0.8 to 1:7, and more preferably 1:1 to 1:5.

[0071] The concentration of the alkali metal halide and the metal halide in the precursor solution is 0.01–0.30 mol / L, preferably 0.02–0.10 mol / L, and the concentration of the organic halogen compound is 0.01–1.0 mol / L, preferably 0.02–0.60 mol / L.

[0072] In step 2, as follows Figure 1 The precursor solution prepared in step 1 is injected into a nonpolar solvent with a liquid dielectric constant of less than 10.

[0073] Here, the invention is characterized by injecting a precursor solution containing both core particle material and shell material into a nonpolar solvent with a dielectric constant of 10 or less; that is, simultaneously injecting the core particle material and shell material into the nonpolar solvent. By performing this method, a large number of core particles precipitate at the reaction interface between the precursor solution and the nonpolar solvent, forming a high-concentration suspended particle field. The shell then precipitates in this suspended particle field. If the surface area of ​​the core particles at the reaction interface is sufficiently large, the crystal growth based on the shell material becomes energy-advantageous, and the shell material can be easily coated onto the surface of the core particles.

[0074] On the other hand, when a precursor solution containing only core particles is initially injected into a nonpolar solvent with a dielectric constant of less than 10, followed by the injection of the shell material, the core particles precipitate and disperse in the nonpolar solvent before the shell material is injected. In this nonpolar solvent, the core particles are completely dispersed at a low density; therefore, if the shell material is injected, the number of core particles present at the reaction interface is also small, making it difficult to coat the surface of the core particles with the shell material. Consequently, most of the shell material precipitates separately. As a result, the coating on the surface of the core particles is insufficient and uneven, the core particles contain surface defects, and the PLQY of the resulting perovskite quantum dot composite material is not adequately improved.

[0075] In step 2, the nonpolar solvent with a liquid dielectric constant of 10 or less preferably also contains at least one selected from the group consisting of organic acids and organic amine compounds.

[0076] If organic acids and organic amine compounds are added, the shell or core particles are partially modified by alkyl chains. With such modification sites, the crystal growth of the core particles can be adjusted and their particle size controlled during the synthesis of perovskite quantum dot complexes. As a result, the maximum wavelength can be shifted towards a specified emission wavelength, and the emission wavelength distribution deviation can be reduced.

[0077] Preferably, at least one of organic acids and organic amine compounds is added.

[0078] Examples of organic acids include carboxylic acids such as oleic acid, stearic acid, palmitic acid, glutaric acid, sebacic acid, and benzoic acid; oxyphosphonic acid compounds of phosphorus such as octylphosphonic acid, tetradecylphosphonic acid, and di-tert-octylphosphonic acid; and sulfinic acids such as benzenesulfinic acid.

[0079] Organic amine compounds can be any of aliphatic amine compounds, aromatic amine compounds, and quaternary ammonium salts. Examples include aliphatic amine compounds with 3 to 16 carbon atoms, such as oleylamine, propylamine, butylamine, pentylamine, octylamine, hexadecylamine, and octadecylamine; aromatic amine compounds with 6 to 34 carbon atoms, such as aniline, benzylamine, phenethylamine, 3-phenyl-2-propen-1-amine, phenylmethylamine, 2,2'-iminodibenzoic acid, 3-phenylpropylamine, 4-phenylbutylamine, naphthylamine, 4-aminobiphenyl, and 3,4,5-tris(prop-2-en-1-yloxy)benzylamine; and aliphatic quaternary ammonium salts such as diecryldimethylammonium salt, benzyltrimethylammonium bromide, 3-(N,N-dimethyloctadecylammonium)propane sulfonate, and stearyltrimethylammonium salt.

[0080] It can also be a compound containing an acid or an amino group, such as γ-aminobutyric acid and 3-[(3-methacrylamidopropyl)dimethylamino]propane-1-sulfonic acid.

[0081] The concentration of organic acids and organic amine compounds added only needs to be below the concentration dissolved in the precursor solution and nonpolar solvent of step 2. Generally, it is preferable that the total weight of the added alkali metal halide and metal halide is 1% by mass or more.

[0082] Organic acids and organic amine compounds can also be removed after the synthesis of perovskite quantum dot composites. Furthermore, to impart higher dispersion stability to the perovskite quantum dot composites, other organic acids and organic amine compounds can be added after removal. Alternatively, other organic acids and organic amine compounds can be added without removal.

[0083] In step 2, considering the simplicity of the process and the stability of the shell material, it is preferable to keep the temperature of the precursor solution and the non-polar solvent below 40°C. For example, some organic halogen compounds dissociate and vaporize through chemical equilibrium in polar solvents. If the temperature is increased, the amount of shell material in the precursor solution will decrease, resulting in insufficient coating.

[0084] As described above, the perovskite quantum dot composite material of the present invention exhibits a very high PLQY, specifically 75% or more, preferably 80% or more, and more preferably 90% or more. Furthermore, the shell layer has an ionic crystal layer as an organohalogen compound, providing a stable structure that suppresses surface defects. Therefore, even after 10,000 minutes at room temperature, the change in emission wavelength is less than 5 nm, and the PLQY is stably maintained. This can be attributed to the fact that the shell material forms a BMX3 ionic crystal with the crystalline ends of the nucleus particle surface, and the PLQY is improved through robust halogen retention based on the crystalline layer.

[0085] The perovskite quantum dot composite material of the present invention can be used as a wavelength conversion material as a composition comprising a perovskite quantum dot composite material and a curing material. The curing material can also be any one of thermoplastic resin, thermosetting resin, glass, and ceramic.

[0086] Furthermore, by coating a substrate with an ink containing the perovskite quantum dot composite material of the present invention, it can be used as a light-emitting material upon electro-excitation. Examples of substrates include glass plates, resin plates, and semiconductor plates.

[0087] Example

[0088] The present invention will now be described in more detail based on embodiments, but the present invention is not limited to the following embodiments.

[0089] [Example 1]

[0090] As a precursor solution, the actual amount of shell material added (mol / mol) relative to the molar amount (mol / mol) of the shell material required for coating the nucleus particle surface (hereinafter referred to as "added amount / required amount") was 1.05. That is, 1.41 mg of cesium bromide (CsBr), 2.42 mg of lead(II) bromide (PbBr2), and 3.34 mg of methylaminohydrobromic acid (CH5N·HBr) were dissolved in 0.2 ml of N,N-dimethylformamide (DMF).

[0091] A nonpolar solvent was prepared by adding 4.5 ml of ethyl acetate, 16.7 μl of oleic acid, and 13.3 μl of oleylamine to a 9 ml screw-cap tube. The precursor solution was injected while stirring at room temperature and atmospheric pressure.

[0092] The mixture was centrifuged at 16,500 rpm in a benchtop centrifuge AS165W (manufactured by AS ONE Co., Ltd.) for 2 minutes. After removing a portion of the supernatant, the precipitate was redispersed with toluene. Then, the supernatant was recovered after centrifugation at 16,500 rpm for 3 minutes to obtain an ink containing a perovskite quantum dot composite material.

[0093] An integrating sphere was set on a fluorescence spectrophotometer FP-8600 (manufactured by Nippon Spectrophotometer Co., Ltd.; excitation wavelength 350 nm) to measure PLQY. PLQY was 95%, and the maximum wavelength (λ) of photoluminescence (PL) was... PL The wavelength is 461nm.

[0094] According to λ PL Determine the particle size of the core of the perovskite quantum dot composite material that serves as the luminescent agent. The particle size of the core is 3.5 nm.

[0095] Table 1 shows the method of adding shell material, the molar amount of shell material required for coating the surface of the nucleus particles (hereinafter referred to as "required amount"), the actual molar amount of shell material added (hereinafter referred to as "added amount"), the added amount / required amount, and the maximum wavelength (λ) of photoluminescence (PL) of the perovskite quantum dot composite material. PL ) and particle size and PLQY.

[0096] Ink containing dispersed perovskite quantum dot composite material was added to a screw-top tube, the cap was closed, and the tube was left to stand at room temperature for 10,000 minutes. The maximum wavelength (λ) of photoluminescence (PL) before and after the standing period was compared. PL ) and PLQY, maximum wavelength (λ) PL The change in ) is 2nm, and the change rate of PLQY is -3%.

[0097] [Example 2]

[0098] As a precursor solution, a solution was prepared with an addition / necessary amount of 1.26. That is, in Example 1, the perovskite quantum dot composite ink was prepared in the same manner as in Example 1, except that the amount of methylamine hydrobromide (CH5N·HBr) was changed from 3.34 mg to 4.00 mg.

[0099] The maximum wavelength (λ) of PLQY and photoluminescence (PL) was determined in the same manner as in Example 1. PL The particle size of the core of the perovskite quantum dot composite material. PLQY is 97%, and the maximum wavelength (λ) of photoluminescence (PL) is... PL The diameter of the core is 461 nm, and the particle size of the core is 3.5 nm.

[0100] The results are shown in Table 1 and... Figure 2 As shown.

[0101] [Example 3]

[0102] As a precursor solution, the solution was prepared with an addition / necessary amount of 1.60. That is, 4.26 mg of cesium bromide (CsBr), 7.34 mg of lead(II) bromide (PbBr2) and 4.48 mg of methylaminohydrobromic acid (CH5N·HBr) were dissolved in 0.6 ml of N,N-dimethylformamide (DMF).

[0103] A nonpolar solvent was prepared by adding 4.5 ml of ethyl acetate, 120 μl of oleic acid, and 6.0 μl of oleylamine to a 9 ml screw-cap tube. The precursor solution was injected while stirring at room temperature and atmospheric pressure.

[0104] The mixture was centrifuged at 16,500 rpm in a benchtop centrifuge AS165W (manufactured by AS ONE Co., Ltd.) for 3 minutes. After removing a portion of the supernatant, the precipitate was redispersed with toluene. Then, the supernatant was recovered after centrifugation at 16,500 rpm for 3 minutes to obtain an ink containing a perovskite quantum dot composite material.

[0105] An integrating sphere was set up on a fluorescence spectrophotometer FP-8600 (manufactured by Nippon Spectrophotometer Co., Ltd.; excitation wavelength 400 nm) to measure PLQY. The maximum wavelength (λ) of PLQY and photoluminescence (PL) was determined. PL The particle size of the core of the perovskite quantum dot composite material. PLQY is 96%, and the maximum wavelength (λ) of photoluminescence (PL) is... PL The diameter of the core is 515 nm, and the particle size of the core is 12 nm.

[0106] The results are shown in Table 1 and... Figure 2 As shown.

[0107] [Example 4]

[0108] As a precursor solution, a solution was prepared with an addition / necessary amount of 2.40. That is, in Example 3, the perovskite quantum dot composite ink was prepared in the same manner as in Example 3, except that the amount of methylamine hydrobromic acid (CH5N·HBr) was changed from 4.48 mg to 6.72 mg.

[0109] The maximum wavelength (λ) of PLQY and photoluminescence (PL) was determined in the same manner as in Example 3. PL The particle size of the core of the perovskite quantum dot composite material. PLQY is 95%, and the maximum wavelength (λ) of photoluminescence (PL) is... PL The diameter of the core is 516 nm, and the particle size of the core is 12 nm.

[0110] The results are shown in Table 1 and... Figure 2 As shown.

[0111] [Example 5]

[0112] As a precursor solution, the solution was prepared with an addition / necessary amount ratio of 1.26. That is, 169.2 mg of cesium bromide (CsBr), 290.4 mg of lead(II) bromide (PbBr2), and 480 mg of methylaminohydrobromic acid (CH5N·HBr) were dissolved in 24.0 ml of N,N-dimethylformamide (DMF).

[0113] A nonpolar solvent was prepared by mixing 600 ml of ethyl acetate, 2220 μl of oleic acid, and 1780 μl of oleylamine.

[0114] Using a forced-film microreactor ULREA SS-11-75 (manufactured by M Technique Co., Ltd.), the precursor solution was injected into the device at a rate of 4 ml per minute and the non-polar solvent was injected at a rate of 90 ml per minute while stirring at room temperature and atmospheric conditions. After 3 minutes from the start of injection, the mixed solution discharged from the device was collected after 1 minute.

[0115] The resulting mixture was used to recover the ink from the perovskite quantum dot composite material in the same manner as in Example 1.

[0116] The maximum wavelength (λ) of PLQY and photoluminescence (PL) was determined in the same manner as in Example 1. PL The particle size of the core of the perovskite quantum dot composite material. PLQY is 99%, and the maximum wavelength (λ) of photoluminescence (PL) is... PL The diameter of the core is 460nm, and the particle size of the core is 3.5nm.

[0117] The results are shown in Table 1 and... Figure 2 As shown.

[0118] [Example 6]

[0119] As a precursor solution, the solution was prepared with an addition / necessary amount of 1.00. That is, 4.26 mg of cesium bromide (CsBr), 7.34 mg of lead(II) bromide (PbBr2) and 3.76 mg of formamidinium hydrobromic acid (CH4N2·HBr) were dissolved in 0.6 ml of N,N-dimethylformamide (DMF).

[0120] To prepare a nonpolar solvent, 4.5 ml of ethyl acetate, 60.0 μl of oleic acid, and 3.0 μl of oleylamine were added to a 9 ml screw-cap tube. The precursor solution was injected while stirring at room temperature and atmospheric pressure.

[0121] The resulting mixture was used to recover the ink from the perovskite quantum dot composite material in the same manner as in Example 3.

[0122] The maximum wavelength (λ) of PLQY and photoluminescence (PL) was determined in the same manner as in Example 3. PL The particle size of the core of the perovskite quantum dot composite material. PLQY is 91%, and the maximum wavelength (λ) of photoluminescence (PL) is... PL The diameter of the core is 512 nm, and the particle size of the core is 10 nm.

[0123] The results are shown in Table 1 and... Figure 2 As shown.

[0124] like Figure 2 As shown, in Examples 1 to 6, where the addition amount / necessary amount was 1.00 to 2.40, surface defects of perovskite quantum dots were suppressed, and the PLQY was very high at 91 to 99%.

[0125] [Comparative Example 1]

[0126] A precursor solution was prepared by dissolving 1.41 mg of cesium bromide (CsBr) and 2.42 mg of lead(II) bromide (PbBr2) in 0.2 ml of N,N-dimethylformamide (DMF).

[0127] Add 4.5 ml of ethyl acetate, 16.7 μl of oleic acid and 13.3 μl of oleylamine to a 9 ml screw tube, and inject the precursor solution while stirring at room temperature and atmospheric conditions.

[0128] The resulting mixture was used to recover the ink from the perovskite quantum dot composite material in the same manner as in Example 1.

[0129] The maximum wavelength (λ) of PLQY and photoluminescence (PL) was determined in the same manner as in Example 1. PL The particle size of the core of perovskite quantum dot composites. The maximum wavelength (λ) of photoluminescence (PL). PL The particle size is 507 nm, and the core particle size is 7.0 nm. In the perovskite quantum dot composite material of Comparative Example 1 without a shell, the PLQY is as low as 15%.

[0130] The results are shown in Table 1 and... Figure 2 As shown.

[0131] Ink containing dispersed perovskite quantum dot composite material was added to a screw-cap tube and left to stand at room temperature for 30 minutes with the cap closed. The maximum wavelength (λ) of photoluminescence (PL) before and after the standing period was compared. PL ) and PLQY, maximum wavelength (λ) PL The change in ) was 16 nm, and the change rate of PLQY was -52%. Furthermore, it became inactive and stopped emitting light after 10,000 minutes.

[0132] [Comparative Example 2]

[0133] As a precursor solution, the solution was prepared with an addition / necessary amount of 0.63. That is, 1.41 mg of cesium bromide (CsBr), 2.42 mg of lead(II) bromide (PbBr2), and 2.00 mg of methylaminohydrobromic acid (CH5N·HBr) were dissolved in 0.2 ml of N,N-dimethylformamide (DMF).

[0134] Add 4.5 ml of ethyl acetate, 16.7 μl of oleic acid and 13.3 μl of oleylamine to a 9 ml screw tube, and inject the precursor solution while stirring at room temperature and atmospheric conditions.

[0135] The resulting mixture was used to recover the ink from the perovskite quantum dot composite material in the same manner as in Example 1.

[0136] The maximum wavelength (λ) of PLQY and photoluminescence (PL) was determined in the same manner as in Example 1. PL The particle size of the core of perovskite quantum dot composites. The maximum wavelength (λ) of photoluminescence (PL). PL The particle size is 461 nm, and the core particle size is 3.5 nm. The amount added / necessary is small, therefore the surface protection of the perovskite quantum dots becomes less than ideal, with a PLQY of 13%.

[0137] The results are shown in Table 1 and... Figure 2 As shown.

[0138] [Comparative Example 3]

[0139] As a precursor solution, a solution was prepared with an addition / necessary amount of 0.84. That is, in Comparative Example 2, the perovskite quantum dot composite material was prepared in the same manner as in Comparative Example 2, except that the amount of methylamine hydrobromic acid (CH5N·HBr) was changed from 2.00 mg to 2.67 mg.

[0140] The maximum wavelength (λ) of PLQY and photoluminescence (PL) was determined in the same manner as in Example 1. PL The particle size of the core of perovskite quantum dot composites. The maximum wavelength (λ) of photoluminescence (PL). PL The particle size was 461 nm, and the core particle size was 3.5 nm. The PLQY was 28%. Although the amount added / necessary was greater than that of Comparative Example 2, it was as small as 0.84, and the PLQY was not very high.

[0141] The results are shown in Table 1 and... Figure 2 As shown.

[0142] [Comparative Example 4]

[0143] A precursor solution was prepared by dissolving 4.26 mg of cesium bromide (CsBr) and 7.34 mg of lead(II) bromide (PbBr2) in 0.6 ml of N,N-dimethylformamide (DMF).

[0144] Add 4.5 ml of ethyl acetate, 120 μl of oleic acid and 6.0 μl of oleylamine to a 9 ml screw tube, and inject the precursor solution while stirring at room temperature and atmospheric conditions.

[0145] The resulting mixture was used to recover the ink from the perovskite quantum dot composite material in the same manner as in Example 3.

[0146] The maximum wavelength (λ) of PLQY and photoluminescence (PL) was determined in the same manner as in Example 3. PL The particle size of the core of perovskite quantum dot composites. The maximum wavelength (λ) of photoluminescence (PL). PL The particle size is 518 nm, and the core particle size is 12 nm. PLQY is 50%.

[0147] Similar to Comparative Example 1, since Comparative Example 4 does not have a shell, although the PLQY is not very high, the particle size of the nucleus particles that are luminescent is large, so the PLQY is higher than that of Comparative Example 1.

[0148] The results are shown in Table 1 and... Figure 2 As shown.

[0149] [Comparative Example 5]

[0150] As a precursor solution, the solution was prepared with an addition / necessary amount of 0.80. That is, 4.26 mg of cesium bromide (CsBr), 7.34 mg of lead(II) bromide (PbBr2) and 2.24 mg of methylaminohydrobromic acid (CH5N·HBr) were dissolved in 0.6 ml of N,N-dimethylformamide (DMF).

[0151] Add 4.5 ml of ethyl acetate, 120 μl of oleic acid and 6.0 μl of oleylamine to a 9 ml screw tube, and inject the precursor solution while stirring at room temperature and atmospheric conditions.

[0152] The resulting mixture was used to recover the ink from the perovskite quantum dot composite material in the same manner as in Example 3.

[0153] The maximum wavelength (λ) of PLQY and photoluminescence (PL) was determined in the same manner as in Example 3. PL The particle size of the core of perovskite quantum dot composites. The maximum wavelength (λ) of photoluminescence (PL). PL The particle size is 516 nm, and the core diameter is 12 nm. The PLQY is 22%.

[0154] The results are shown in Table 1 and... Figure 2 As shown.

[0155] [Comparative Example 6]

[0156] A precursor solution was prepared by dissolving 1.41 mg of cesium bromide (CsBr) and 2.42 mg of lead(II) bromide (PbBr2) in 0.2 ml of N,N-dimethylformamide (DMF).

[0157] 4.5 ml of ethyl acetate, 16.7 μl of oleic acid, and 13.3 μl of oleylamine were added to a 9 ml screw-top tube. The precursor solution was then injected while stirring at room temperature and atmospheric pressure, resulting in the precipitation of perovskite quantum dots, which became completely dispersed.

[0158] Furthermore, a solution containing 3.71 mg of methylamine hydrobromic acid (CH5N·HBr) dissolved in 18.5 μl of DMF was added to the dispersion. The ratio of the amount of shell material added to the required amount of nucleus particle material was 1.17.

[0159] The resulting mixture was used to recover the ink from the perovskite quantum dot composite material in the same manner as in Example 1.

[0160] The maximum wavelength (λ) of PLQY and photoluminescence (PL) was determined in the same manner as in Example 1. PL The particle size of the core of perovskite quantum dot composites. The maximum wavelength (λ) of photoluminescence (PL). PL The particle size is 461 nm, and the core diameter is 3.5 nm. The PLQY is 68%.

[0161] Although the addition / necessary amount is 1.17, which is greater than 1, the perovskite quantum dots contain surface defects and the PLQY is not very high after the addition of shell material.

[0162] The results are shown in Table 1 and... Figure 2 As shown.

[0163] [Comparative Example 7]

[0164] A precursor solution was prepared by dissolving 4.26 mg of cesium bromide (CsBr) and 7.34 mg of lead(II) bromide (PbBr2) in 0.6 ml of N,N-dimethylformamide (DMF).

[0165] 4.5 ml of ethyl acetate, 120 μl of oleic acid, and 6.0 μl of oleylamine were added to a 9 ml screw-top tube. The precursor solution was then injected while stirring at room temperature and atmospheric pressure, resulting in the precipitation of perovskite quantum dots, which became completely dispersed.

[0166] Furthermore, a solution containing 4.48 mg of methylamine hydrobromic acid (CH5N·HBr) dissolved in 22.3 μl of DMF was added to the dispersion. The ratio of the amount of shell material added to the amount of nucleus material required was 1.60.

[0167] The resulting mixture was used to recover the ink from the perovskite quantum dot composite material in the same manner as in Example 3.

[0168] The maximum wavelength (λ) of PLQY and photoluminescence (PL) was determined in the same manner as in Example 3. PL The particle size of the core of perovskite quantum dot composites. The maximum wavelength (λ) of photoluminescence (PL). PL The particle size is 518 nm, and the core diameter is 12 nm. PLQY is 70%.

[0169] In Comparative Example 7, where a shell material was subsequently added and the amount added was 1.60, PLQY was higher than that of Comparative Example 4, where no shell material was added at all, but not sufficiently.

[0170] The results are shown in Table 1 and... Figure 2 As shown.

[0171] [Table 1]

[0172]

[0173] In Examples 1 to 6, where a specified amount or more of coating material was added simultaneously, a very high PLQY was observed. Even with subsequent additions, a slight increase in PLQY was observed, but the coating was not uniform; therefore, the results indicate that simultaneous addition is excellent.

[0174] As described above, the perovskite quantum dot composite material of the present invention exhibits excellent stability of emission wavelength and high PLQY.

[0175] It is envisioned that by using the perovskite quantum dot composite material of the present invention, wavelength conversion materials and self-luminescent materials with excellent luminescence properties and stability can be produced.

Claims

1. A perovskite quantum dot composite material, It consists of a nuclear particle and a single-layered shell that surrounds the nuclear particle. The nuclear particles are composed of metal halide perovskites. The shell is composed of an organic halide compound with an ionic crystal structure having the same halogen composition as the nucleus particles. The perovskite quantum dot composite material is characterized in that... The halide metal perovskite is a compound represented by the general formula AMX3, wherein, A is cesium, M is lead, X is bromine, and the organohalogen compound is formamidinium hydrobromide or methylamine hydrobromide. The perovskite quantum dot composite material has a particle size of 3.5–12 nm, an emission maximum wavelength of 460 nm or more and 516 nm or less, a PLQY of 91% or more, and a change in the emission maximum wavelength of 2 nm or less over a period of 10,000 minutes at room temperature.

2. An ink, characterized in that, The mixture contains the perovskite quantum dot composite material as described in claim 1, a non-proton polar solvent with a liquid dielectric constant of 20 or higher, and a non-polar solvent with a liquid dielectric constant of 10 or lower that is miscible with the polar solvent.

3. A method for manufacturing the perovskite quantum dot composite material according to claim 1, characterized in that, have: Based on the predetermined average particle size x of the nuclear particles, using y = 15x -1 The steps to calculate the necessary minimum molar amount y of the shell material covering the surface of the nucleus particle; Step 1 involves using a non-protic polar solvent with a dielectric constant of 20 or higher. Nuclear particle materials composed of alkali metal halides and metal halides, wherein the alkali metal halide is cesium bromide, the metal halide is lead bromide, and... Shell material composed of formamidinium hydrobromide or methylamine hydrobromide. In the process of forming a shell material on the surface of nuclear particle materials, a precursor solution is prepared by mixing materials in a manner where the ratio of the added molar amount of the shell material to the necessary minimum molar amount y, i.e., the added amount / necessary amount is 1.00 to 2.40; and Step 2 involves injecting the precursor solution at a temperature below 40°C into a solution composed of a nonpolar solvent with a liquid dielectric constant below 10 and at least one compound selected from the group consisting of organic acids and organic amines, to prepare a perovskite quantum dot composite material with a single-layer shell. The perovskite quantum dot composite material has a particle size of 3.5–12 nm, an emission maximum wavelength of 460 nm or more and 516 nm or less, a PLQY of 91% or more, and a change in the emission maximum wavelength of 2 nm or less over a period of 10,000 minutes at room temperature.

4. The method for manufacturing the perovskite quantum dot composite material according to claim 3, wherein, The solubility of the shell material in aprotic polar solvents is more than twice that of the solubility of the nuclear particle material in aprotic polar solvents.

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