Nanoparticle dispersion liquid, method for producing nanoparticle dispersion liquid, nanoparticle film, and light emitting element

Abstract

Provided is a nanoparticle dispersion liquid which has a long life and excellent light durability while maintaining a high photoluminescence quantum yield (PLQY) by adding a light stabilizer that has excellent radical scavenging ability to a metal halide perovskite that forms luminescent nanoparticles.　This nanoparticle dispersion liquid is characterized by containing a metal halide perovskite, a light stabilizer, and a nonpolar organic solvent, and the light stabilizer includes at least one of a hindered amine skeleton represented by general formula (1) and a phenol skeleton represented by general formula (2). (In general formula (1), R1 is at least one selected from the group consisting of a hydrogen atom, an acyclic aliphatic hydrocarbon group, and an oxyl free radical group, R2 to R5 are each independently hydrogen or an acyclic aliphatic hydrocarbon group, and R6 is a hydrogen atom or an organic functional group.) (In general formula (2), R7 to R11 are each independently hydrogen or an organic functional group.)

Description

Nanoparticle dispersion, method for producing nanoparticle dispersion, nanoparticle film, and light-emitting element

[0001] The present invention relates to a luminescent nanoparticle dispersion having excellent dispersion stability and a high photoluminescence quantum yield.

[0002] Luminescent nanoparticles have extremely small diameters and unique optical and electronic properties that follow quantum mechanics different from those of bulk particles, and are therefore expected to be applied to highly functional materials. Due to their quantum confinement effect and particle size dependence, the electrical and optical properties of luminescent nanoparticles can be significantly improved by adjusting the shape and particle size of the quantum dots.

[0003] Among these, luminescent nanoparticles of metal halide perovskite (hereinafter also referred to as "halide perovskite quantum dots" in this section) have physical properties such as quantum confinement effect, as well as chemical properties in which their semiconducting properties change when the halogen in their structure is changed. They are expected to be applied to light-emitting diodes (LEDs), optical amplifiers, single-photon sources, solar cells, and the like.

[0004] Furthermore, halide perovskite quantum dots are excellent phosphors and can be dispersed in water or organic solvents to form inks for use in displays and other applications.

[0005] However, halogenated perovskite quantum dots pose a challenge: their fluorescence intensity decreases when irradiated with excitation light. Some of the free carriers generated by excitation light migrate from the halogenated perovskite quantum dots to the dispersion medium, where they transfer energy to the oxygen and water present in the dispersion, generating radical species and peroxides. These products cause photodegradation of luminescent nanoparticles, leading to the detachment of ligands adsorbed on the particle surface and the formation of defects in the crystal, resulting in a decrease in fluorescence intensity. Therefore, in order to prevent photodegradation in halogenated perovskite quantum dots, which are prone to photodegradation, it was necessary to capture or stabilize the radicals.

[0006] There is a report that the use of 2,6-di-tert-butyl-p-cresol (BHT) as an additive improves the crystallinity and durability of perovskite films, thereby improving the stability, efficiency, and other performance aspects of planar perovskite solar cells (Non-Patent Document 1). Non-Patent Document 1 describes the mechanism by which BHT suppresses the photooxidation of methylammonium lead iodide (MAPbI3) as follows:

[0007]

[0008] Methylammonium lead iodide decomposes and forms various oxidized species in a chain reaction (Equations (1) to (5)). BHT acts to suppress the reaction of Equation (2). In other words, BHT acts as a chain terminator in the initial stage of decomposition of methylammonium lead iodide by removing hydrogen from the phenolic hydroxyl group. The excited species [Pb ＋ . . . I Ｏ ], and methylammonium lead iodide decomposes to form I ２ When released, unstable Pb ＋ The species reacts with oxygen in the air to form O ２－ YaHO ２－ The reactive oxygen species (ROS) further react with iodide to form I ２ and OH － (Equation (2)) OH － However, the ammonium ion is deprotonated, and methylammonium is released to form PbI ２ Forms crystals. ２ reacts with oxygen in the air to form PbO and I ２ is formed (Equation (6)).

[0009] BHT acts as a free radical scavenger to suppress the generation of oxidizing species, thereby suppressing photo-oxidation of the perovskite absorber and stabilizing it. The BHT-doped perovskite absorber described in Non-Patent Document 1 achieved a power conversion efficiency (PCE) of 18%, which is higher than that of the control device (17.1%).

[0010] Non-Patent Document 2 reports that treating luminescent nanoparticles, cadmium selenide quantum dots (CdSe / ZnS QDs), with BHT protects the CdSe / ZnS QDs from air and moisture. The oxidation of BHT, rather than the CdSe QDs, in the solution improves the stability and average lifespan of the solution.

[0011] Hindered amine light stabilizers (HALS) have also been reported as light stabilizers that utilize a mechanism similar to that of BHT-doped perovskite quantum dots as described in Non-Patent Documents 1 and 2. Non-Patent Document 3 reports that HALS is added to methylammonium lead iodide (MAPbI) used in solar cells. ３ It has been reported that it inhibits the photooxidation of

[0012] Sujit Kumar, Yunseong Choi, So-Huei Kang, Nam Khen Oh, Junghyun Lee, Jihyung Seo, Mingyu Jeong, Hyoung Woo Kwon, Sang Il Seok, Changduk Yang and Hyesung Park, ACS Appl. Mater. Interfaces, 2019, 11, 38828-38837JinBeom Kwon, SaeWan Kim, JaeSung Lee, CheolEon Park, OkSik Kim, Binrui Xu, ByoungHo Kang, JinHyuk Bae and ShinWon Kang, Organic Electronics, 2019, 74, 166-171Nevena Marinova, Marius Franckevicius, Leva Matulaitiene, Andrius Devizis, Gediminas Niaura, Vidmantas Gulbinas and Juan Luis Delgado, ChemSusChem, 2017, 10, 3760-3764

[0013] The present invention aims to provide a nanoparticle dispersion that prevents deterioration of perovskite quantum dots while maintaining a high photoluminescence quantum yield (PLQY) by adding a light stabilizer with excellent radical scavenging ability to perovskite quantum dots, thereby providing a long-life, light-resistant nanoparticle dispersion.

[0014] The present invention comprises the following features: [1] A nanoparticle dispersion containing a metal halide perovskite, a light stabilizer, and a non-polar organic solvent, wherein the light stabilizer contains at least one of a hindered amine skeleton represented by general formula (1) and a phenol skeleton represented by general formula (2).

[0015] (In general formula (1), R １ is at least one selected from a hydrogen atom, an acyclic aliphatic hydrocarbon group, and an oxyl free radical group, and R ２ ~R ５ are each independently a hydrogen atom or an acyclic aliphatic hydrocarbon group, and R ６ is a hydrogen atom or an organic functional group.

[0016] (In general formula (2), R ７ ~R １１ are each independently a hydrogen atom or an organic functional group.

[0017] [2] The nanoparticle dispersion according to [1], wherein the amount of the light stabilizer having the hindered amine skeleton is 0.01 to 50 times the amount of the metal halide perovskite.

[0018] [3] The nanoparticle dispersion liquid according to [1], wherein the content of the light stabilizer having a phenol skeleton is 0.01 times or more and 10,000 times or less the amount of substance of the metal halide perovskite.

[0019] [4] The nanoparticle dispersion liquid according to [1], wherein the nonpolar organic solvent includes at least one selected from the group consisting of toluene, hexane, octane, cyclohexane, methylcyclohexane, and decalin.

[0020] [5] A method for producing a nanoparticle dispersion, comprising: a first step of mixing a precursor solution obtained by dissolving a metal halide perovskite precursor in a good solvent with an organic base compound, an organic acid compound, and a poor solvent at 40°C or less to prepare a suspension containing coarse nanoparticles, and recovering the coarse nanoparticles from the suspension by sedimentation; a second step of adding a nonpolar organic solvent to the coarse nanoparticles to redisperse them, removing coarse particles by classification, and aging the mixture for 8 hours or more to obtain a nanoparticle mixed dispersion; and a third step of adding a light stabilizer to the nanoparticle mixed dispersion to obtain a nanoparticle dispersion.

[0021] [6] A nanoparticle film using the nanoparticle dispersion liquid according to any one of [1] to [4].

[0022] [7] A light-emitting device using the nanoparticle film according to [6].

[0023] According to the present invention, it is possible to effectively suppress the deterioration of metal halide perovskite, which is a luminescent nanoparticle, and realize a nanoparticle dispersion liquid that has improved light durability and a longer life while maintaining a high photoluminescence quantum yield (PLQY).

[0024] 1 is a diagram showing an example of a manufacturing process of the nanoparticle dispersion of the present invention using the LARP method. 2 is a graph showing the change in fluorescence intensity under light irradiation of the nanoparticle dispersions of Examples 14 and 15, and Comparative Example 7. 3 is a graph showing the change in fluorescence intensity under light irradiation of the nanoparticle dispersions of Example 16, Comparative Example 8, Comparative Example 9, and Reference Example 1.

[0025] The nanoparticle dispersion, the method for producing the nanoparticle dispersion, the nanoparticle film, and the light-emitting device of the present invention will be described in detail below.

[0026] <Nanoparticle Dispersion> The nanoparticle dispersion of the present invention is a dispersion containing a metal halide perovskite, a light stabilizer, and a non-polar organic solvent.

[0027] The nanoparticle dispersion of the present invention emits light in the visible to near-infrared region (300 to 1000 nm). When light is emitted by photoexcitation, the wavelength of the excitation light is 200 to 800 nm, more preferably 250 to 750 nm. When the nanoparticle dispersion of the present invention is irradiated with ultraviolet light having a wavelength of 370 nm, it emits blue to red fluorescence having a wavelength of 450 to 800 nm.

[0028] The nanoparticle dispersion of the present invention contains a photostabilizer, so that even when exposed to light, the fluorescence intensity does not decrease and the initial fluorescence intensity is maintained for a long period of time. As shown in Figure 2, the nanoparticle dispersion of the present invention maintains almost 100% of its fluorescence intensity under irradiation with 450 nm excitation light, even after 400 minutes have passed since the light irradiation.

[0029] [Metal Halide Perovskite] Metal halide perovskite is a type of perovskite-type luminescent nanoparticle. Perovskite-type luminescent nanoparticles are semiconductor crystals with sizes ranging from several nanometers to several tens of nanometers. They are usually colloidal quantum dots, and their emission wavelength changes depending on the size of the crystal grains. When exposed to excitation light, they emit light and simultaneously generate radicals. Among luminescent nanoparticles that can control the light absorption and emission region, perovskite-type luminescent nanoparticles are particularly excellent in this property and are suitable in that they can be easily synthesized using a solution process. In the present invention, among the perovskite-type luminescent nanoparticles, luminescent nanoparticles of metal halide perovskite (hereinafter referred to as "perovskite quantum dots") are used.

[0030] In the nanoparticle dispersion of the present invention, luminescent nanoparticles other than metal halide perovskite can be optionally applied. Examples of luminescent nanoparticles other than metal halide perovskite include II-VI compounds, III-V compounds, IV-VI compounds, and combinations thereof. These can be used by mixing one or more types with metal halide perovskite in any ratio.

[0031] Specific examples of the II-VI compounds include CdSe, CdS, ZnS, CdSeS, and CdZnSeS. Specific examples of the III-V compounds include InP, GaN, GaP, AlN, InNP, and GaInNP. Specific examples of the IV-VI compounds include SnS, PbS, PbSe, SnPbS, and SnPbSSe. Specific examples of the IV-VI compounds include Se, Ge, and SiC. In the present invention, the luminescent nanoparticles other than metal halide perovskite may be at least one selected from a mixture of these.

[0032] Luminescent nanoparticles other than perovskite quantum dots generate radicals in the same way as perovskite quantum dots. However, a shell is generally constructed on the surface to improve stability. For example, quantum dots made of luminescent nanoparticles such as CdSe and InP have a ZeS shell. This makes it difficult for radicals to directly contribute to the luminescent nanoparticles. Therefore, radicals generated by excitation light are likely to cause defects on the surface of perovskite quantum dots, which may adversely affect their optical properties.

[0033] Furthermore, since II-VI compounds, III-V compounds, and IV-VI compounds are covalently bonded, perovskite quantum dots, which are ionically bonded, are prone to the formation of surface defects. In perovskite quantum dots, suppressing surface defects is highly important for improving stability.

[0034] Perovskite quantum dots are represented by the general formula A ｐ B ｑ X ｒA represents an organic and / or inorganic monovalent cation occupying the A site, B represents a metal cation occupying the B site, and X represents a monovalent anion occupying the X site. In perovskite quantum dots, B is surrounded by X in an octahedral shape, and the octahedra share X at their vertices, thereby forming a perovskite structure. p represents an integer of 1 or greater and 4 or less, q represents 1 or 2, and r represents an integer of 3 or greater and 9 or less. The integers are selected to satisfy the following formula: p + (2 × q) = r

[0035] The relationship between p, q, and r is preferably positive numbers such that p:q:r is 1:1:3, 4:1:6, and 2:1:4, and particularly preferably p:q:r is 1:1:3.

[0036] The metal halide perovskite used in the nanoparticle dispersion of the present invention has the general formula ABX ３ As described above, among luminescent nanoparticles, perovskite-type luminescent nanoparticles are preferred in that they have excellent optical and electronic properties and can be easily synthesized by a solution process.

[0037] In the metal halide perovskite used in the nanoparticle dispersion of the present invention, examples of the monovalent organic cation occupying the A site include primary to quaternary ammonium ions, formamidinium ion (CH(NH ２ ) ２＋ FA), guanidinium ion ((H ２ N) ２ C=NH ２＋ ;GA), imidazolium ion, 1-methylimidazolium ion, pyridinium ion, 1-methylpyridinium ion, pyrrolidinium ion, and thiouronium ion.

[0038] Examples of primary to quaternary ammonium ions include ammonium ions (NH ４＋ ), methylammonium ion (CH ３ NH ３＋ ;MA), dimethylammonium ion, ethylammonium ion (CH ３ CH ２ NH３＋ ammonium ion, diethylammonium ion, propylammonium ion, isopropylammonium ion, butylammonium ion, isobutylammonium ion, t-butylammonium ion, benzylammonium ion, and phenethylammonium ion. Of these, methylammonium ion is preferred.

[0039] In the metal halide perovskite used in the nanoparticle dispersion of the present invention, examples of monovalent inorganic cations occupying the A site include alkali metal ions, such as cesium ions, rubidium ions, potassium ions, sodium ions, and lithium ions.

[0040] Among these, from the viewpoint of the crystal structure tolerance factor (TF), ABX ３ It is preferred that 60 mol % or more, preferably 70 mol % or more, and more preferably 80 mol % or more of the cations occupying the A sites in the compound be at least one type of cation selected from the group consisting of cesium ion, rubidium ion, methylammonium ion (MA), ethylammonium ion (EA), formamidinium ion (FA), and guanidinium ion (GA). A may be of only one type, or may be of two or more types.

[0041] Examples of metal cations occupying the B site include lead ions, germanium ions, tin ions, antimony ions, bismuth ions, copper ions, nickel ions, cobalt ions, iron ions, manganese ions, chromium ions, cadmium ions, europium ions, ytterbium ions, silver ions, and palladium ions. Among these, lead ions and tin ions are preferred as metal cations occupying the B site. Furthermore, the composition may contain at least one selected from the group consisting of antimony ions, bismuth ions, copper ions, nickel ions, cobalt ions, iron ions, manganese ions, chromium ions, cadmium ions, europium ions, ytterbium ions, and silver ions, with the element ratio of lead ions and tin ions being 5% or less. The metal cations occupying the B site may be of only one type, or may be of two or more types.

[0042] Halide ions occupying the X site include, for example, chloride ions, bromide ions, and iodide ions. ｐ B ｑ Xr may contain one or more types of X. It may also contain monovalent pseudohalide ions such as cyanide, isothiocyanate, oxocyanate, thiocyanate, selenocyanate, sulfide, fulminate ion, azide ion, borohydride ion, and hexafluorophosphate ion, provided that the element ratio of halide ions occupying the X site is 20% or less.

[0043] A, B, and X can be appropriately selected taking into consideration the energy band gap of the luminescent nanoparticles, the sizes of A, B, and X, etc. ｐ B ｑ X ｒ A specific example of ａ１ MA ａ２ EA ａ３ FA ａ４ G.A. ａ５ Na ａ６ Ka ７ Rb(p-a1-a2-a3-a4-a5-a6-a7)Pb ｂ１ Sn ｂ２Ge(q-b1-b2)(Cl(1-y-z)BryIz)r(0≦a1≦p, 0≦a2≦p, 0≦a3≦p, 0≦a4≦p, 0≦a5≦p, 0≦a6≦p, 0≦a7≦p, a1+a2+a3+a4+a5+a6+a7≦p, 0≦b1≦q, 0≦b2≦q, b1+b2≦q, 0≦y≦1, 0≦z≦1, y+z≦1, 1≦p≦4, 1≦q≦2, 3≦r≦9). However, the metal halide perovskite used in the present invention is not limited to these specific examples.

[0044] ABX, a perovskite structure ３ In order for the crystal structure to be stable, the TF must be in the range of 0.70 to 1.10. Examples of such metal halide perovskites include CsPbBr ３ (TF=0.86), FAPbBr ３ (TF=1.01), CsPbI ３ (TF=0.85), CsSnI ３ (TF=0.92) and the like.

[0045] The average particle size of the metal halide perovskite is not particularly limited as long as it is within a range that allows it to function as a light-emitting material. The average particle size, as the particle size of the primary particles, is preferably 1 to 30 nm, more preferably 2 to 20 nm, and particularly preferably 3 to 16 nm.

[0046] When the average particle size of the metal halide perovskite is 1 to 30 nm, the quantum confinement effect is exerted, resulting in a high photoluminescence quantum yield (PLQY).In addition, the sedimentation rate of the metal halide perovskite is sufficiently slow, thereby imparting high dispersibility and dispersion stability.

[0047] If the average particle size of the metal halide perovskite is less than 1 nm, Ostwald ripening and aggregation occur, making it difficult to maintain the crystal structure. Furthermore, the quantum size effect increases the emission wavelength. On the other hand, if the average particle size of the metal halide perovskite is greater than 30 nm, the stability of excitons during excitation decreases, and the photoluminescence quantum yield (PLQY) tends to decrease.

[0048] In this specification, the average particle size is measured using a fluorescence spectrophotometer. ＰＬ The average particle size can be calculated from the maximum wavelength (λ) of photoluminescence (PL) measured by a fluorescence spectrophotometer. ＰＬ The energy band gap of the light-emitting metal halide perovskite changes depending on the particle size, and the maximum wavelength (λ ＰＬ ) changes. For example, CsPbBr ３ The maximum wavelength (λ ＰＬ ) 450 nm, average particle size 6.2 nm, maximum wavelength (λ ＰＬ ) 500 nm, average particle size 15 nm, maximum wavelength (λ ＰＬ Therefore, the maximum wavelength (λ) measured by a fluorescence spectrophotometer is 523 nm. ＰＬ ) the average particle size can be calculated.

[0049] The shape of the metal halide perovskite is not particularly limited. Examples of metal halide perovskite include spherical, cubic, cylindrical, polyhedral, and scaly shapes. Among these, either a spherical or cubic shape, or both, are preferred from the viewpoints of good dispersion stability and little crystal lattice distortion within the particles.

[0050] [Light Stabilizer] The light stabilizer according to the present invention contains at least one of a hindered amine skeleton represented by general formula (1) and a phenol skeleton represented by general formula (2). Light stabilizers having these skeletons are primarily used in polymeric materials such as resins, and act as radical scavengers. It has been reported that the degradation of metal halide perovskites, like polymeric materials, occurs through a mechanism of autoxidation that starts with radical species and progresses in a chain reaction. Therefore, it is believed that the addition of a light stabilizer can improve the lifespan of metal halide perovskites.

[0051] In the present invention, the light stabilizer may be a compound having a hindered amine skeleton represented by general formula (1) or a compound having a phenol skeleton represented by general formula (2), which may be used alone or in combination of two or more. Alternatively, in the present invention, the light stabilizer may be a compound having both a hindered amine skeleton represented by general formula (1) and a phenol skeleton represented by general formula (2), which may be used alone or in combination of two or more. Alternatively, in the present invention, the light stabilizer may be a combination of at least one compound having both a hindered amine skeleton represented by general formula (1) and a phenol skeleton represented by general formula (2), and at least one compound having a hindered amine skeleton represented by general formula (1) or a compound having a phenol skeleton represented by general formula (2).

[0052] Furthermore, the compound having a hindered amine skeleton represented by general formula (1) or the compound having a phenol skeleton represented by general formula (2) may have a plurality of hindered amine skeletons represented by general formula (1) or a plurality of phenol skeletons represented by general formula (2) in the same molecule.

[0053] (Compound having a hindered amine skeleton represented by general formula (1)) The compound having a hindered amine skeleton represented by general formula (1) is an N-R １ N-OR type hindered amine light stabilizers (HALS) or nitroxy radical type piperidine light stabilizers (for example, TEMPO), and are represented by the following structural formula: １ Even if it is a HALS type, １ Depending on the type of N-R １ Although it has the same effect as the N-OR type, in the present invention, １ Compared to the type N-R １ N-R at the point where the polarity of the part is low １ Use a type HALS.

[0054] In general formula (1), R １ is at least one selected from the group consisting of a hydrogen atom, an acyclic aliphatic hydrocarbon group, and an oxyl free radical group, and R ２ ~R５ are each independently a hydrogen atom or an acyclic aliphatic hydrocarbon group, and R ６ is a hydrogen atom or an organic functional group.

[0055] R １ or R ２ ~R ５ Examples of the acyclic aliphatic hydrocarbon group that can be the acyclic aliphatic hydrocarbon group include a linear or branched alkyl group having 1 to 10 carbon atoms. Furthermore, the linear or branched alkyl group having 1 to 10 carbon atoms may contain an oxygen atom, a phosphorus atom, a sulfur atom, a hydroxyl group, an ester bond, or the like, as long as the effects of the present invention are not impaired.

[0056] R ６ The organic functional groups that can be １ or R ２ ~R ５ In addition to the linear or branched alkyl groups that can be R, examples of the alkyl groups include formyl, acetyl, aryl, alkylcarbonyl, alkyloxycarbonyl, hydroxy, amino, ether, and phospho groups. ６ The aryl group that can be the organic functional group of R may contain a substituent such as a linear or branched alkyl group or a hydroxyl group. ６ The organic functional group that can be the hydroxyl group may contain two or more of these types.

[0057] Examples of the light stabilizer having a hindered amine skeleton represented by general formula (1) include 2,2,6,6-tetramethyl-4-piperidyl methacrylate, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl-1-oxyl) sebacate, bis(1,2,2,6,6-pentamethy-4-piperidyl) sebacate, and bis(2,2,6,6-pentamethy-4-piperidyl) sebacate. N,N'-bis(2,2,6,6-tetramethylpiperidin-4-yl)-hexane-1,6-diamine, N1,N3-bis(2,2,6,6-tetramethylpiperidin-4-yl)-isophthalamine, butyl(3,5-di-tert-butyl-4-hydroxybenzyl)malonate bis(1,2,2,6,6-pentamethyl-4-piperidyl), 2,2,6,6-tetramethylpiperidine 1-oxyl free radical (TEMPO), 4-amino-2,2,6,6-tetramethylpiperidinoxy) radical, 4-carboxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-dimethylamino-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-methoxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, and 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl free radical.

[0058] As the compound having a hindered amine skeleton represented by general formula (1), N-R bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate is particularly preferred because it retains its radical capturing effect for a long period of time due to its self-regenerating properties. １ In the present invention, the light stabilizer having a hindered amine skeleton represented by general formula (1) may be used singly or in combination of two or more.

[0059] The light stabilizer having a hindered amine skeleton represented by general formula (1) acts like a catalyst in the mechanism of detoxifying radicals. Because it can permanently capture and detoxify radicals, the light stabilizer having a hindered amine skeleton represented by general formula (1) is a useful light stabilizer.

[0060] Typical HALS are R ２ ~R ５ is a methyl group. １ is a hydrogen atom, R １ is an acyclic aliphatic hydrocarbon group, １ If the polarity of the part is high and a large amount of the hindered amine compound is added, the metal halide perovskite may deteriorate.

[0061] (Compound Having a Phenol Skeleton Represented by General Formula (2)) The compound having a phenol skeleton represented by general formula (2) is a hindered phenol-based, semi-hindered phenol-based, or less-hindered phenol-based antioxidant, and is represented by the following structural formula:

[0062] In general formula (2), R ７ ~R １１ is a hydrogen atom or an organic functional group.

[0063] R ７ ~R １１ Examples of the organic functional group that can be the acyclic aliphatic hydrocarbon group and the organic functional group in general formula (1) include the same.

[0064] Examples of light stabilizers having a phenol skeleton represented by general formula (2) include stearyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 6-tert-butyl-2,4-xylenol, 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butyl-4-ethylphenol, diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 2,6-di-tert-butylphenol, 4,6-di-tert-butylresorcinol, 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, and the like. Hexadecyl hydroxybenzoate, 2-methyl-4,6-bis[(n-octylthio)methyl]phenol, 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), 4,4'-butylidenebis(6-tert-butyl-m-cresol), 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone, 2,5-bis(1,1,3,3-tetramethylbutyl)hydroquinone, 2,2'-methylenebis(6-cyclohexyl-p-cresol) 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], 4,4'-thiobis(6-tert-butyl-m-cresol), 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-N'-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoyl]propanehydrazide, N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], 2,4,8,10-tetraoxaspiro[5,5]undecane-3,9-diylbis( 2-methylpropane-2,1-diyl)bis[3-(3-tert-butyl)-4-hydroxy-5-methylphenylpropanoate], 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene, tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 4,4'-dihydroxy-3,3',5,5'-tetraisopropylbiphenyl, 2,2',6,6'-tetra-tert-butyl-4,4'-dihydroxybiphenyl, 4-[[4,6-bis(n-octylthio)-1,3,5-triazin-2-yl]amino]-2,6-di-tert-butylphenol, 3,5-di-tert-butyl-4-hydroxyanisole, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, 4-(hexyloxy)-2,3,6-trimethylphenol, methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2'-methylene-bis(6-tert-butyl-4-methylphenol)acrylate, bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoic acid][oxalylbis(azanediyl)]bis(ethane-2,1-diyl), N,N'-bis[2-[2 -(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, 3,3',5,5'-tetra-tert-butyl-4,4'-stilbenequinoline, bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylene bis(oxyethylene)], 2,4,6-tris(2,4-dihydroxyphenyl)-1,3,5-triazine, 2,2'-methylene-bis(4-methyl-6-tert-butylphenol), 2,2'-methylene-bis(4-ethyl-6-tert-butylphenol), 2-methyl-4,6-bis[(octylthio)methyl]phenol, 2,4-bis(dodecylthiomethyl)-6-methylphenol, and 2,6-di-tert-butyl-4-methylphenol. In the present invention, the light stabilizer having a phenol skeleton represented by general formula (2) may be used alone or in combination of two or more.

[0065] The light stabilizer having a phenol skeleton represented by general formula (2) is R ７ and R ９ In many cases, a bulky substituent such as a tert-butyl group is introduced into at least one of R ７ and R ９ Compared to R １０can be introduced into a wide range of substituents, from methyl and ethyl groups to bulky groups, and there is a high degree of freedom in the selection of substituents.

[0066] (Composition Ratio) When both the compound having a hindered amine skeleton represented by general formula (1) and the compound having a phenol skeleton represented by general formula (2) are used as light stabilizers, the light stabilizer having a hindered amine skeleton represented by general formula (1) and the light stabilizer having a phenol skeleton represented by general formula (2) may be mixed at any ratio.

[0067] (Compounds Having Multiple Skeletons in the Same Molecule) The light stabilizer may have multiple hindered amine skeletons represented by general formula (1) or multiple phenol skeletons represented by general formula (2) in the same molecule. In light stabilizers having multiple hindered amine skeletons represented by general formula (1) or multiple phenol skeletons represented by general formula (2), each molecular skeleton captures radicals. Therefore, the amount of substance of the light stabilizer is calculated by multiplying the amount of substance by the number of hindered amine skeletons represented by general formula (1) or phenol skeletons represented by general formula (2). For example, 1 mole of a light stabilizer having two phenol skeletons represented by general formula (2) is considered to have a substance amount of 2 moles, and 1 mole of a light stabilizer having four phenol skeletons represented by general formula (2) is considered to have a substance amount of 4 moles. The same applies to compounds having both a hindered amine skeleton represented by general formula (1) and a phenol skeleton represented by general formula (2) in the same molecule.

[0068] Examples of light stabilizers having a plurality of hindered amine skeletons represented by general formula (1) or a plurality of phenol skeletons represented by general formula (2) in the same molecule include 1,2,2,6,6-pentamethyl-4-piperidinyl 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzoate, 1,2,2,6,6-pentamethyl-4-piperidinyl 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanoate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)butyl(3,5-di-tert-butyl-4-hydroxybenzyl)malonate, 4,4'-butylidene-bis(6-tert-butyl-m-cresol), 4,4'-thiobis(6-tert-butyl-m-cresol), 2,2'-methylenestyrene-bis(4-methyl-6-tert-butylphenol ... tert-butylphenol), 6,6'-di-tert-butyl-4,4'-butylidene-di-m-cresol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, pentaerythritol tetrakis[3-(3,5-di- tert-butyl-4-hydroxyphenyl)propionate], bis(3,5-di-tert-butyl-4-hydroxybenzyl) sulfide, and 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate.

[0069] [Content of Light Stabilizer in Nanoparticle Dispersion] In the nanoparticle dispersion of the present invention, the lower limit of the amount of substance of the light stabilizer having a hindered amine skeleton represented by general formula (1) relative to the amount of substance of the metal halide perovskite is preferably 0.01, 0.1, or 0.2, and the upper limit is preferably 50, 20, 10, or 6. The range of the amount of substance of the light stabilizer having a hindered amine skeleton represented by general formula (1) is more preferably 0.01 to 50, even more preferably 0.1 to 20, particularly preferably 0.1 to 10, and most preferably 0.2 to 6.

[0070] If the content of the light stabilizer having a hindered amine skeleton represented by general formula (1) is excessive, the metal halide perovskite may deteriorate or aggregate in the nanoparticle dispersion. This tendency is particularly pronounced when the polarity of the light stabilizer is high. When the light stabilizer having a hindered amine skeleton represented by general formula (1) is added in an amount of 0.2 to 6 times the amount of the metal halide perovskite, deterioration due to the light stabilizer is minimized, deterioration of the perovskite quantum dots due to excitation light is suppressed, and sufficiently high fluorescence intensity is obtained.

[0071] In the nanoparticle dispersion of the present invention, the amount of the light stabilizer having a phenol skeleton represented by general formula (2) relative to the amount of the metal halide perovskite is preferably 0.01 times or more, more preferably 0.1 times or more, and even more preferably 0.2 times or more. The amount of the light stabilizer having a phenol skeleton represented by general formula (2) relative to the amount of the metal halide perovskite is not limited as long as it is equal to or less than the saturated solubility (the maximum amount of the light stabilizer that dissolves in the dispersion medium at the reaction temperature), and is preferably 10,000 times or less, and even more preferably 1,000 times or less. The more preferred range of the amount of the light stabilizer having a phenol skeleton represented by general formula (2) is 0.01 times or more and 10,000 times or less, and even more preferably 0.1 times or more and 1,000 times or less.

[0072] When a light stabilizer having a phenol skeleton represented by general formula (2) is added to a metal halide perovskite, the local reactivity is alleviated by the resonance effect of the aromatic ring, so that the metal halide perovskite does not deteriorate or aggregate even if the content of the light stabilizer is excessive.When the light stabilizer having a phenol skeleton represented by general formula (2) is added in an amount 10 times or more relative to the metal halide perovskite, the dispersion can obtain a sufficiently high fluorescence intensity depending on the relative amount of the metal halide perovskite to the light stabilizer.

[0073] When a light stabilizer having multiple hindered amine skeletons represented by general formula (1) or multiple phenol skeletons represented by general formula (2) in the same molecule is used, the amount of the light stabilizer relative to the amount of the metal halide perovskite is preferably 0.01 to 10,000 times, more preferably 0.1 to 1,000 times, and even more preferably 0.2 to 100 times. However, as described above, the amount of the light stabilizer multiplied by the number of hindered amine skeletons represented by general formula (1) or phenol skeletons represented by general formula (2) in the same compound is treated as the amount of the light stabilizer.

[0074] [Non-polar Organic Solvent] The nanoparticle dispersion of the present invention contains a metal halide perovskite, a light stabilizer, and a non-polar organic solvent as a dispersion medium.

[0075] Nonpolar organic solvents affect not only the wettability and dispersibility of nanoparticles, but also the dissociation constant of weak acid or weak base ligands coordinated to the particle surfaces of metal halide perovskite. While the dispersion medium contributes to improving the dispersibility of nanoparticle-mixed dispersions, some dispersion mediums can reduce the photoluminescence quantum yield (PLQY) due to the detachment of ligands. For this reason, nonpolar organic solvents with a liquid dielectric constant of 10.0 μS / cm or less at room temperature (generally 20-25°C) and a measurement frequency of 1 kHz are preferred.

[0076] Examples of such organic solvents include pentane (1.84 μS / cm), hexane (1.88 μS / cm), octane (1.94 μS / cm), cyclohexane (2.02 μS / cm), methylcyclohexane (2.02 μS / cm), decalin (2.43 μS / cm), isooctane (1.94 μS / cm), benzene (2.28 μS / cm), toluene (2.38 μS / cm), xylene (2.58 μS / cm (25 ° C)), mesitylene (2.28 μS / cm), diethyl ether (4.10 μS / cm), dibutyl ether (3.06 μS / cm), cyclopentyl methyl ether (CPME, 4.28 μS / cm), propylene glycol monomethyl ether acetate (PMA, 8.03 μS / cm), etc. These non-polar organic solvents may be used alone or in combination of two or more.

[0077] The organic solvent that serves as the nonpolar organic solvent is preferably at least one selected from toluene, cyclohexane, methylcyclohexane, and decalin, which are alicyclic hydrocarbon compounds having a liquid dielectric constant of 2.0 to 2.5 μS / cm, and more preferably at least one selected from the group consisting of cyclohexane, methylcyclohexane, and decalin, which are saturated alicyclic hydrocarbon compounds having a liquid dielectric constant of 2.0 to 2.5 μS / cm.

[0078] The non-polar organic solvent may contain a non-curable polymer. Examples of the non-curable polymer include olefin polymers, polymethyl methacrylate, polystyrene, polycarbonate, polyvinyl chloride, polyethylene, polyethylene terephthalate, and amorphous fluororesin. These non-curable polymers may be used alone or in combination of two or more.

[0079] The content of the non-curable polymer contained in the non-polar organic solvent is preferably 1% by weight or more, more preferably 5% by weight or more. There is no particular limit to the upper limit of the content of the non-curable polymer as long as the non-curable polymer dissolves in the range, and it is sufficient that the non-polar organic solvent after blending has fluidity. For example, the viscosity of the non-polar organic solvent under room temperature and atmospheric air is preferably 100 Pa s or less, more preferably 10 Pa s or less, and even more preferably 1 Pa s or less.

[0080] [Content in Nonpolar Organic Solvent] The content of the metal halide perovskite in the nonpolar organic solvent is preferably 0.1 mg / mL to 15 mg / mL, more preferably 0.5 mg / mL to 10 mg / mL. If the content of the metal halide perovskite exceeds 15 mg / mL, the metal halide perovskite may aggregate in the nanoparticle dispersion.

[0081] The content of the light stabilizer in the nonpolar organic solvent is preferably 0.05 mmol / L to 10,000 mmol / L, more preferably 0.23 mmol / L to 1,000 mmol / L. The amount of radicals generated increases with the content of metal halide perovskite, so it is advisable to increase the content of the light stabilizer as the content of metal halide perovskite increases.

[0082] <Method for producing nanoparticle dispersion> The method for producing a nanoparticle dispersion of the present invention includes a first step of mixing a precursor solution obtained by dissolving a metal halide perovskite in a good solvent with an organic base compound, an organic acid compound, and a poor solvent at 40°C or less to prepare a suspension containing coarse nanoparticles, and recovering the coarse nanoparticles from the suspension by sedimentation; a second step of adding a non-polar organic solvent to the coarse nanoparticles to re-disperse them, removing coarse particles by classification, and aging the mixture for 8 hours or more to obtain a nanoparticle mixed dispersion; and a third step of adding a light stabilizer to the nanoparticle mixed dispersion to obtain a nanoparticle dispersion.

[0083] The nanoparticle dispersion of the present invention can be produced by a ligand-assisted reprecipitation (LARP) method, a hot injection method, a metathesis synthesis method, a mechanochemical method, an ultrasonic bead mill method, a microflow reactor method, and a forced thin film flow reactor (FTFR) method. In terms of simplicity and high versatility, it is preferable to use one method selected from the group consisting of the LARP method, the metathesis synthesis method, and the FTFR method. In this specification, a production method using the LARP method will be described.

[0084] [Step 1] In Step 1, a metal halide perovskite precursor is first dissolved in a good solvent to prepare a precursor solution. A poor solvent is then prepared, and an organic base compound and an organic acid compound are dissolved in the prepared precursor solution, the poor solvent, or both. The precursor solution is then poured into the poor solvent under stirring at room temperature in the atmosphere, precipitating stable perovskite quantum dots, resulting in a suspension containing coarse nanoparticles. The resulting coarse nanoparticle suspension is then subjected to sedimentation and liquid-phase separation in a centrifuge to obtain the coarse nanoparticles, which are the solid content (top row in Figure 1).

[0085] Metal Halide Perovskite Precursor The metal halide perovskite precursor has the general formula ABX ３ The compound comprises a compound containing an organic and / or inorganic monovalent cation (hereinafter simply referred to as "monovalent cation") occupying the A site, a compound containing a divalent metal cation occupying the B site, and a compound containing a monovalent anion occupying the X site.

[0086] The compound containing a monovalent cation occupying the A site of the metal halide perovskite precursor includes a compound consisting of the monovalent cation and X.

[0087] When the monovalent cation occupying the A site of the metal halide perovskite precursor is an inorganic cation, such as an alkali metal ion, the compound containing the monovalent cation is a salt of the alkali metal ion and X. In this case, X is, for example, a halide ion, a carbonate ion, or an acetate ion, and is preferably a halide ion.

[0088] When the monovalent cation occupying the A site of the metal halide perovskite precursor is an organic cation, the compound containing the monovalent cation is a salt of the organic cation and X. Examples of compounds containing a monovalent cation include ammonium halide salts such as methylammonium bromide, and formamidinium halide salts such as formamidinium bromide.

[0089] Compounds containing divalent metal cations that occupy the B site of the metal halide perovskite precursor include, for example, halide salts, acetate salts, and carbonate salts of germanium ions, tin ions, lead ions, antimony ions, and bismuth ions. The halides are chlorides, bromides, or iodides.

[0090] Examples of compounds containing divalent metal cations that occupy the B site of the metal halide perovskite precursor include lead(II) bromide (PbBr ２ ), lead(II) iodide (PbI ２ ), lead(II) chloride (PbCl ２ ), lead(II) acetate (Pb(C ２ H ３ O ２ ) ２ ), lead(II) carbonate (PbCO ３ ), tin(II) bromide (SnBr ２ ), tin(II) iodide (SnI ２ ), tin(II) chloride (SnCl ２ ), tin(II) acetate (Sn(C ２ H ３ O ２ ) ２ ), tin(II) carbonate (SnCO ３ ), germanium(II) bromide (GeBr ２ ), germanium(II) iodide (GeI ２ ), germanium(II) chloride (GeCl ２ ), germanium(II) acetate (Ge(C ２ H ３ O ２ ) ２ ), and germanium(II) carbonate (GeCO ３These compounds can be used alone or in combination of two or more in any ratio.

[0091] Compounds containing a monovalent anion occupying the X site of the metal halide perovskite precursor include compounds comprising a monovalent anion and the above-mentioned monovalent cation occupying the A site or a divalent metal cation occupying the B site, as well as hydrogen chloride and hydrogen iodide.

[0092] (Organic Base Compound) The organic base compound used in the first step may be any of aliphatic amines, aromatic amines, and quaternary ammonium salts. Examples of the organic base compound include aliphatic amines having 3 to 24 carbon atoms, such as oleylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, hexadecylamine, octadecylamine, 2-hexyldecane-1-amine, 2-decyltetradecane-1-amine, stearylamine, and cyclohexylamine; aniline, benzylamine, phenethylamine, 3-phenyl-2-propene-1-amine, phenylmethylamine, 2,2'-iminodiamine, methyl ... Examples of such compounds include aromatic amines having 6 to 34 carbon atoms, such as benzoic acid, 3-phenylpropylamine, 4-phenylbutylamine, naphthylamine, 4-aminobiphenyl, and 3,4,5-tris(prop-2-en-1-yloxy)benzylamine; and quaternary ammonium salts, such as didecyldimethylammonium salt, benzyltrimethylammonium bromide salt, 3-(N,N-dimethyloctadecylammonio)propanesulfonate salt, and stearyltrimethylammonium salt. These compounds can be used either alone or in combination of two or more in any desired ratio.

[0093] (Organic Acid Compound) Examples of the organic acid compound used in the first step include organic carboxylic acids, organic sulfonic acids, organic sulfinic acids, and phosphorus oxoacid compounds (organic phosphonic acids, organic phosphonates, and organic phosphinic acids). Examples of the organic acid compound include organic carboxylic acids such as oleic acid, stearic acid, palmitic acid, glutaric acid, sebacic acid, benzoic acid, and 3,4,5-tri(2-propenoxy)benzoic acid; organic sulfinic acids such as benzenesulfinic acid; organic phosphonic acids such as octylphosphonic acid, tetradecylphosphonic acid, and tri-n-octylphosphine oxide; and organic phosphinic acids such as di-t-octylphosphinic acid and diisooxylphosphinic acid. These compounds can be used alone or in combination of two or more in any ratio.

[0094] The organic base compound is mainly represented by the general formula A ｐ B ｑ X ｒ The organic base compound is a compound that forms a coordinate bond with X on the particle surface or bonds by replacing A, and the organic acid compound is a compound that mainly forms a coordinate bond with A or B on the particle surface. When producing perovskite-type luminescent nanoparticles, the organic base compound and the organic acid compound act to both uniformize particle size and compensate for surface defects. The addition of both the organic base compound and the organic acid compound can improve both the yield and photoluminescence quantum yield (PLQY) of the nanoparticle dispersion. When the nanoparticle surface is modified with a long chain in the organic base compound or organic acid compound, this site acts to regulate particle growth and uniform particle size.

[0095] (Good Solvent) The good solvent used in the first step may be any solvent that has high solubility for the metal halide perovskite precursor, the organic base compound, and the organic acid compound, and typically, a polar solvent that is miscible with the poor solvent or nonpolar organic solvent described below is used.

[0096] The good solvent is preferably an aprotic organic solvent having a liquid dielectric constant of 30 μS / cm or more at room temperature (generally 20 to 25° C.) and a measurement frequency of 1 kHz, and examples thereof include N,N-dimethylformamide (DMF, 38 μS / cm), N-methylpyrrolidone (NMP, 32 μS / cm), 4-butanolide (GBL, 43 μS / cm), dimethyl sulfoxide (DMSO, 47 μS / cm), propylene carbonate (PC, 64 μS / cm), and acetonitrile (37 μS / cm).

[0097] (Poor Solvent) The poor solvent used in the first step is preferably an organic solvent having a liquid dielectric constant of 10 μS / cm or less at room temperature (generally 20 to 25° C.) and a measurement frequency of 1 kHz. Examples of poor solvents include pentane (1.84 μS / cm), hexane (1.88 μS / cm), cyclohexane (2.02 μS / cm), octane (2.00 μS / cm), decalin (2.43 μS / cm), methylcyclohexane (2.02 μS / cm), xylene (2.58 μS / cm), ethyl methyl carbonate (EMC, 2.92 μS / cm), dimethyl carbonate (DMC, 3.03 μS / cm), diethyl carbonate (DEC, 2.82 μS / cm), and propylene glycol monomethyl ether acetate (PMA, 8.03 μS / cm). Examples include ethyl acetate (6.02 μS / cm), methyl acetate (6.65 μS / cm), chloroform (4.92 μS / cm), chlorobenzene (5.65 μS / cm), toluene (2.38 μS / cm), benzene (2.28 μS / cm (25°C)), dichloromethane (8.90 μS / cm), diethyl ether (4.10 μS / cm), dibutyl ether (3.06 μS / cm)), cyclopentyl methyl ether (CPME, 4.28 μS / cm), and tetrachloromethane (2.24 μS / cm). These may be used alone or in combination of two or more in any ratio, provided that the liquid dielectric constant after mixing is 10 μS / cm or less.

[0098] In the first step, a suspension containing crude nanoparticles is liquid-phase synthesized from a metal halide perovskite precursor, an organic base compound, and an organic acid compound. The organic solvent is then removed from the crude nanoparticle suspension by sedimentation to obtain crude nanoparticles. Sedimentation is typically performed by centrifugation. In the first step, there is loss of unreacted metal halide perovskite precursor and products that do not settle during sedimentation, but the yield is still 85% or higher.

[0099] [Step 2] In Step 2, the coarse nanoparticles recovered in Step 1 are redispersed in a non-polar organic solvent as a dispersion medium, and then coarse particles are removed by classification. The liquid phase is then left to stand in a dark place for 8 hours or more to obtain a nanoparticle-mixed dispersion (middle panel in Figure 1). The aging time is 8 hours or more, preferably 10 hours or more, and more preferably 12 hours or more.

[0100] Immediately after classification, the metal halide perovskite, which is the perovskite quantum dot, in the nanoparticle mixed dispersion exhibits imbalances in ligands and crystallinity. In this state, if radical species or peroxides reach the surface of the perovskite quantum dots, localized degradation occurs. Static aging allows for re-coordination of the ligands and improvement of crystallinity. This results in a nanoparticle mixed dispersion containing metal halide perovskite, which is the perovskite quantum dot, with a uniform surface.

[0101] The aging may be usually carried out between the redispersion in the second step and the third step, preferably after the classification in the second step. If the aging is carried out before the settling and separation in the first step, the number of aggregated particles increases due to the influence of the good solvent contained in the synthesis solvent, which is not preferable.

[0102] The concentration of the crude nanoparticles in the nonpolar organic solvent is preferably 1000 mmol / L or less, more preferably 500 mmol / L or less, and even more preferably 150 mmol / L or less. In the first step, the concentration of the crude nanoparticles in the nonpolar organic solvent can be increased by increasing the amount of precursor solution injected into the poor solvent, but the yield decreases due to the increased solubility of the crude nanoparticles.

[0103] In the second step, the coarse nanoparticles are redispersed in a nonpolar organic solvent, and then coarse particles are removed by classification. There are no particular limitations on the classification method, as long as it can remove coarse particles to leave only particles with a predetermined diameter or less and can improve particle flowability by aligning the particle size distribution. Among these, centrifugation using a centrifugal classifier is preferred because it allows for efficient classification.

[0104] Examples of the non-polar organic solvent used in the second step include alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, and decalin, and aromatic hydrocarbons such as toluene.

[0105] The concentration of nanoparticles in the nanoparticle mixed dispersion obtained in the second step is preferably 0.01 to 100 mg / mL, more preferably 0.1 to 50 mg / mL, and even more preferably 0.5 to 20 mg / mL.

[0106] The concentration of nanoparticles in the nanoparticle mixed dispersion is calculated from the dilution ratio at which the absorbance of the nanoparticle mixed dispersion becomes 0.5, using an integrating sphere attached to a fluorescence spectrophotometer FP-8600 (manufactured by JASCO Corporation; excitation wavelength 370 nm).

[0107] [Step 3] In step 3, a nanoparticle dispersion is obtained by adding a light stabilizer to the nanoparticle mixed dispersion obtained in step 2. The method for adding the light stabilizer to the nanoparticle mixed dispersion is not particularly limited, and any known method can be applied.

[0108] <Nanoparticle Film> The nanoparticle film of the present invention is a nanoparticle coating obtained by coating the surface of a substrate such as a flat plate, a film, or particles (powder) with the nanoparticle dispersion of the present invention. By changing the type or composition of the metal halide perovskite, various unique functions of nanoparticles can be expressed on various substrates.

[0109] To coat a flat plate or film with a nanoparticle film, a nanoparticle dispersion in a solvent is applied. The application method is not particularly limited, and can range from simple methods using a brush or bar coater to methods suitable for continuous mass production, such as spray coaters or roll coaters. The nanoparticle film may also be sealed with resin or glass.

[0110] When particles (powder) are coated with a nanoparticle film, the powder may be present during the production process of the nanoparticle dispersion, and the nanoparticles may be precipitated on the powder surface simultaneously with the formation of the nanoparticles.

[0111] Examples of applications of the nanoparticle film include, but are not limited to, photoelectric conversion films, wavelength selective films, transparent conductive films, antistatic films, and hard coats.

[0112] <Light-emitting device> The light-emitting device of the present invention uses the nanoparticle film of the present invention. Since the emitted color can be adjusted by changing the type and composition of halide ions that constitute the metal halide perovskite, the nanoparticle film of the present invention is suitable for use in light-emitting devices such as color films, displays, and lasers.

[0113] If various metal halide perovskites can be synthesized in the future and their ionic composition can be controlled, it is expected that this will lead to further development of solar cells and light-emitting devices, as well as the development of new functional materials and device applications.

[0114] The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples.

[0115] Comparative Example 1 (Preparation of Nanoparticle Dispersion) As a metal halide perovskite precursor, 75 mg (0.6 mmol) of formamidinium bromide (FABr) and lead (II) bromide (PbBr ２A precursor solution was prepared by dissolving 220 mg (0.6 mmol) of propylene glycol monomethyl ether acetate (propylene glycol monomethyl ether acetate) in 1 mL of a screw tube. A poor solvent solution was prepared by adding 1,105 μL (3.5 mmol) of oleic acid and 105 μL (0.32 mmol) of oleylamine to 15 mL of propylene glycol monomethyl ether acetate in a screw tube.

[0116] 900 μL of the precursor solution was added to the stirred poor solvent solution and stirred for 3 minutes to prepare a suspension containing crude nanoparticles. 16.2 mL of the suspension was dispensed into a centrifuge tube using a micropipette, and the precipitate was collected by centrifugation.

[0117] 12 mL of toluene was added to the collected precipitate to re-disperse the precipitate. Centrifugation was again performed, and the supernatant was collected. In this way, a transparent green nanoparticle mixed dispersion liquid was obtained.

[0118] The obtained nanoparticle mixed dispersion was aged for 12 hours in the dark to obtain the perovskite quantum dots FAPbBr. ３ The nanoparticles were then optimized. An appropriate amount of toluene was added to the optimized nanoparticle mixed dispersion to adjust the weight concentration of the nanoparticle mixed dispersion to 0.5 mg / mL (1.02 μmol / mL). ３ A nanoparticle dispersion was obtained. The following photostability test was carried out using 5 mL of the obtained nanoparticle dispersion (5.1 μmol of perovskite quantum dots).

[0119] (Photostability Test) A nanoparticle dispersion, which is a perovskite quantum dot dispersion, placed in a transparent screw-top vial was irradiated from the outside of the vial with a wavelength of 450 nm and an irradiation intensity of 67 mW / cm at room temperature and in the atmosphere. ２ The continuous irradiation times were 180 minutes, 300 minutes, 450 minutes, and 630 minutes.

[0120] An integrating sphere was attached to a fluorescence spectrophotometer FP-8600 (manufactured by JASCO Corporation; excitation wavelength 370 nm) to measure the photoluminescence quantum yield (PLQY) of the PeQD dispersion. The PLQY after irradiation relative to the PLQY before irradiation was defined as the relative PLQY. A relative PLQY of 0.8 or more was judged as pass, and a relative PLQY of less than 0.8 was judged as fail. The results of the photostability evaluation are shown in Table 1.

[0121] (Fluorescence spectrum measurement) FAPbBr ３ The nanoparticle dispersion was subjected to fluorescence spectrum measurement using a fluorescence spectrophotometer FP-8600 (manufactured by JASCO Corporation; excitation wavelength: 370 nm). ＰＬ ) was 517 nm. Therefore, the metal halide perovskite FAPbBr ３ The average particle size was 6.5 nm.

[0122] [Example 1] (Preparation of nanoparticle dispersion) As in Comparative Example 1, 0.5 mg / mL of FAPbBr ３ A nanoparticle mixed dispersion was prepared. To 5 mL of the prepared nanoparticle mixed dispersion, 0.25 mg (1.14 μmol, having a phenol skeleton represented by general formula (2)) of 2,6-di-tert-butyl-p-cresol (BHT) was added as a light stabilizer to prepare FAPbBr. ３ A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (FAPbBr ３ The molar amount of the compound was 0.22 times that of the compound (II).

[0123] (Photostability test) Prepared FAPbBr ３ The nanoparticle dispersion was used to evaluate the light stability in the same manner as in Comparative Example 1. The results of the light stability evaluation are shown in Table 1.

[0124] [Example 2] (Preparation of nanoparticle dispersion) As in Comparative Example 1, 0.5 mg / mL of FAPbBr ３ A nanoparticle mixed dispersion was prepared. 2.5 mg (11.35 μmol) of BHT was added as a light stabilizer to 5 mL of the prepared nanoparticle mixed dispersion to prepare FAPbBr. ３A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (FAPbBr ３ The molar amount was 2.2 times that of the compound (II).

[0125] (Photostability test) Prepared FAPbBr ３ The nanoparticle dispersion was used to evaluate the light stability in the same manner as in Comparative Example 1. The results of the light stability evaluation are shown in Table 1.

[0126] [Example 3] (Preparation of nanoparticle dispersion) As in Comparative Example 1, 0.5 mg / mL of FAPbBr ３ A nanoparticle mixed dispersion was prepared. 25 mg (113.5 μmol) of BHT was added as a light stabilizer to 5 mL of the prepared nanoparticle mixed dispersion to prepare FAPbBr. ３ A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (FAPbBr ３ ) was 22 times the molar amount of

[0127] (Photostability test) Prepared FAPbBr ３ The nanoparticle dispersion was used to evaluate the light stability in the same manner as in Comparative Example 1. The results of the light stability evaluation are shown in Table 1.

[0128] [Example 4] (Preparation of nanoparticle dispersion) As in Comparative Example 1, 0.5 mg / mL of FAPbBr ３ A nanoparticle mixed dispersion was prepared. 250 mg (1135 μmol) of BHT was added as a light stabilizer to 5 mL of the prepared nanoparticle mixed dispersion to prepare FAPbBr. ３ A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (FAPbBr ３ The molar amount was 220 times that of the compound (III).

[0129] (Photostability test) Prepared FAPbBr ３ The nanoparticle dispersion was used to evaluate the light stability in the same manner as in Comparative Example 1. The results of the light stability evaluation are shown in Table 1.

[0130] [Example 5] (Preparation of nanoparticle dispersion) A 0.5 mg / mL FAPbBr dispersion was prepared in the same manner as in Comparative Example 1, except that the aging time was changed to 10 hours. ３ A nanoparticle mixed dispersion was prepared. To 5 mL of the prepared nanoparticle mixed dispersion, 26.7 mg (22.7 μmol, having a phenol skeleton represented by general formula (2)) of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (PTP) was added as a light stabilizer, to prepare FAPbBr. ３ A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (FAPbBr ３ ) was 18 times the molar amount of

[0131] (Photostability test) Prepared FAPbBr ３ The nanoparticle dispersion was used to evaluate the light stability in the same manner as in Comparative Example 1. The results of the light stability evaluation are shown in Table 1.

[0132] Comparative Example 2 (Preparation of Nanoparticle Dispersion) A nanoparticle dispersion of 0.5 mg / mL FAPbBr was prepared in the same manner as in Comparative Example 1, except that the dispersion medium was changed from toluene to cyclohexane and the aging time was changed to 10 hours. ３ A nanoparticle mixed dispersion was prepared.

[0133] (Photostability test) Prepared FAPbBr ３ The nanoparticle mixed dispersion was used to evaluate the light stability in the same manner as in Comparative Example 1. The results of the light stability evaluation are shown in Table 1.

[0134] [Example 6] (Preparation of nanoparticle dispersion) As in Comparative Example 2, 0.5 mg / mL of FAPbBr ３ A nanoparticle mixed dispersion was prepared. 50 mg (226.7 μmol) of BHT was added as a light stabilizer to 5 mL of the prepared nanoparticle mixed dispersion to prepare FAPbBr. ３ A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (FAPbBr ３ ) was 45 times the molar amount of

[0135] (Photostability test) Prepared FAPbBr ３ The nanoparticle dispersion was used to evaluate the light stability in the same manner as in Comparative Example 1. The results of the light stability evaluation are shown in Table 1.

[0136] Comparative Example 3 (Preparation of Nanoparticle Dispersion) As a metal halide perovskite precursor, 136.2 mg (0.64 mmol) of cesium bromide (CsBr) and 136.2 mg (0.64 mmol) of lead (II) bromide (PbBr ２ 234.9 mg (0.64 mmol) of dimethylammonium bromide was dissolved in 16 mL of DMF. 4.1 mL (13 mmol) of oleic acid and 101.3 μL (0.87 mmol) of amylamine were added to this solution to prepare a precursor solution. 463.2 mg (1.0 mmol) of dilauryldimethylammonium bromide was dissolved in 2 mL of DMF to prepare a ligand solution.

[0137] Next, 8.2 mL of the precursor solution was added to 28 mL of ethyl acetate stirred in a screw cap, followed by 840 μL of the ligand solution after 10 seconds. Stirring was continued for another 3 minutes to produce a suspension containing crude nanoparticles. The suspension containing crude nanoparticles was transferred to a centrifuge tube and centrifuged to recover the precipitate.

[0138] To the collected precipitate, 18 mL of toluene was added to re-disperse the precipitate. Centrifugation was again performed, and the supernatant was collected. In this way, a transparent green nanoparticle mixed dispersion liquid was obtained.

[0139] The obtained nanoparticle mixed dispersion was aged for 12 hours in the dark to obtain perovskite quantum dots, CsPbBr ３ The nanoparticles were then made suitable. An appropriate amount of toluene was added to the suitable nanoparticle mixed dispersion to adjust the weight concentration of the nanoparticle mixed dispersion to 1.0 mg / mL (1.72 μmol / mL).

[0140] (Photostability test) Obtained CsPbBr ３ Using 5 mL of the nanoparticle dispersion (8.6 μmol of perovskite quantum dots), photostability was evaluated in the same manner as in Comparative Example 1. The results of the photostability evaluation are shown in Table 1.

[0141] (Fluorescence spectrum measurement) CsPbBr３ The nanoparticle dispersion was subjected to fluorescence spectrum measurement using a fluorescence spectrophotometer FP-8600 (manufactured by JASCO Corporation; excitation wavelength: 370 nm). ＰＬ ) was 511 nm. Therefore, the metal halide perovskite CsPbBr ３ The average particle size was 9.2 nm.

[0142] [Example 7] (Preparation of nanoparticle dispersion) As in Comparative Example 3, 1.0 mg / mL of CsPbBr ３ A nanoparticle mixed dispersion was prepared. 1.16 μL (2.27 μmol) of HALS-C was added as a light stabilizer to 5 mL of the prepared nanoparticle mixed dispersion. ３ A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (CsPbBr ３ The molar amount of the compound was 0.53 times that of the compound (II).

[0143] (Photostability test) Prepared CsPbBr ３ The nanoparticle dispersion was used to evaluate the light stability in the same manner as in Comparative Example 1. The results of the light stability evaluation are shown in Table 1.

[0144] [Example 8] (Preparation of nanoparticle dispersion) As in Comparative Example 3, 1.0 mg / mL of CsPbBr ３ A nanoparticle mixed dispersion was prepared. 11.63 μL (22.7 μmol) of HALS-C was added as a light stabilizer to 5 mL of the prepared nanoparticle mixed dispersion. ３ A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (CsPbBr ３ The molar amount was 5.3 times that of the compound (II).

[0145] (Photostability test) Prepared CsPbBr ３ The nanoparticle dispersion was used to evaluate the light stability in the same manner as in Comparative Example 1. The results of the light stability evaluation are shown in Table 1.

[0146] [Example 9] (Preparation of nanoparticle dispersion) As in Comparative Example 3, 1.0 mg / mL of CsPbBr ３ A nanoparticle mixed dispersion was prepared. 50 mg (226.7 μmol) of BHT was added as a light stabilizer to 5 mL of the prepared nanoparticle mixed dispersion, and CsPbBr ３ A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (CsPbBr ３ ) was 26 times the molar amount of

[0147] (Photostability test) Prepared CsPbBr ３ The nanoparticle dispersion was used to evaluate the light stability in the same manner as in Comparative Example 1. The results of the light stability evaluation are shown in Table 1.

[0148] [Example 10] (Preparation of nanoparticle dispersion) As in Comparative Example 1, 0.5 mg / mL of FAPbBr ３ A nanoparticle mixed dispersion was prepared. 1.8 mg (11.35 μmol) of 2,2,6,6-tetramethylpiperidine 1-oxyl free radical (TEMPO) was added as a light stabilizer to 5 mL of the prepared nanoparticle mixed dispersion to prepare FAPbBr ３ A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (FAPbBr ３ The molar amount was 2.2 times that of the compound (II).

[0149] (Photostability test) Prepared FAPbBr ３ Using 5 mL of the nanoparticle dispersion, the photostability was evaluated in the same manner as in Comparative Example 1. The results of the photostability evaluation are shown in Table 1.

[0150] Example 11 Preparation of Nanoparticle Dispersion A nanoparticle dispersion of 0.5 mg / mL FAPbBr was prepared in the same manner as in Example 10, except that the dispersion medium was changed from toluene to a polymer solution (a 20 wt % solution of a cyclic olefin polymer (a norbornene-based polymer, manufactured by Zeon Corporation, trade name: ZEONOR (registered trademark), COP) dissolved in toluene). ３ A nanoparticle dispersion was prepared.

[0151] (Photostability test) Prepared FAPbBr ３ Using 5 mL of the nanoparticle dispersion, the photostability was evaluated in the same manner as in Comparative Example 1. The results of the photostability evaluation are shown in Table 1.

[0152] Comparative Example 4 (Preparation of Nanoparticle Dispersion) A nanoparticle dispersion of 0.5 mg / mL FAPbBr was prepared in the same manner as in Comparative Example 1, except that the dispersion medium was changed from toluene to a polymer solution (a 20 wt % solution of a cyclic olefin polymer (a norbornene-based polymer, manufactured by Zeon Corporation, trade name: ZEONOR (registered trademark), COP) dissolved in toluene). ３ A nanoparticle dispersion was prepared.

[0153] (Photostability test) Prepared FAPbBr ３ Using 5 mL of the nanoparticle dispersion, the photostability was evaluated in the same manner as in Comparative Example 1. The results of the photostability evaluation are shown in Table 1.

[0154] Comparative Example 5 (Preparation of Nanoparticle Dispersion) Precursor solution 1 was prepared by dissolving 82 mg (0.9 mmol) of methylammonium acetate in 1.0 mL (3.17 mmol) of oleic acid. Precursor solution 2 was prepared by dissolving 172.8 mg (0.9 mmol) of cesium acetate in 1.0 mL (3.17 mmol) of oleic acid. Precursor solution 3 was prepared by mixing 115.3 mg (0.25 mmol) of lead(II) iodide, 117.5 mg (0.38 mmol) of dodecylamine hydroiodide, 1250 μL of ethyl acetate, 155 μL (0.49 mmol) of oleic acid, and 180 μL (0.55 mmol) of oleylamine and dissolving the mixture by ultrasonic waves.

[0155] A poor solvent solution was prepared by taking 504 μL of precursor solution 3 and mixing it with 250 μL of ethyl acetate in a 9 mL screw tube. A mixed solution of 40 μL of precursor solution 1 and 40 μL of oleic acid was injected into the stirred poor solvent solution using a syringe and stirred for 10 minutes. Next, 40 μL of precursor solution 2 was injected using a syringe and stirred for an additional 10 minutes. Next, 40 μL of tri-n-octylphosphine was injected and stirred for an additional 3 minutes to obtain a suspension containing crude nanoparticles. Of the resulting suspension, 860 μL was transferred to a centrifuge tube using a micropipette, and the precipitate was collected by centrifugation.

[0156] To the collected precipitate, 8 mL of toluene was added to redisperse the precipitate, and the mixture was centrifuged again to collect the supernatant, thereby obtaining a transparent red nanoparticle mixed dispersion.

[0157] The obtained nanoparticle mixed dispersion was aged for 8 hours in the dark to obtain CsPbI perovskite quantum dots. ３ The nanoparticles were optimized. An appropriate amount of toluene was added to the optimized nanoparticle mixed dispersion to adjust the weight concentration of the nanoparticle mixed dispersion to 0.5 mg / mL (0.694 μmol / mL). 5 mL of this dispersion (3.47 μmol of perovskite quantum dots) was used to conduct the following photostability test.

[0158] (Photostability Test) A perovskite quantum dot dispersion, CsPbI, was placed in a transparent screw-top bottle. ３ The nanoparticle dispersion was irradiated from the outside of the bottle at room temperature and in the atmosphere with a wavelength of 450 nm and an irradiation intensity of 44 mW / cm ２ The continuous irradiation time was set to 30 minutes and 90 minutes.

[0159] An integrating sphere was attached to a fluorescence spectrophotometer FP-8600 (manufactured by JASCO Corporation; excitation wavelength 400 nm) to measure the photoluminescence quantum yield (PLQY) of the PeQD dispersion. The PLQY after irradiation was defined as the relative PLQY, with a relative PLQY of 0.8 or more being considered pass, and a relative PLQY of less than 0.8 being considered fail. The results of the photostability evaluation are shown in Table 2.

[0160] (Fluorescence spectrum measurement) CsPbI ３ The nanoparticle dispersion was subjected to fluorescence spectrum measurement using a fluorescence spectrophotometer FP-8600 (manufactured by JASCO Corporation; excitation wavelength: 370 nm). ＰＬ ) was 608 nm. Therefore, the metal halide perovskite CsPbI ３ The average particle size was 3.0 nm.

[0161] [Example 12] (Preparation of nanoparticle dispersion) As in Comparative Example 5, 0.5 mg / mL of CsPbI ３ A nanoparticle mixed dispersion was prepared. 50 mg (226.7 μmol) of BHT was added as a light stabilizer to 5 mL of the prepared nanoparticle mixed dispersion to obtain CsPbI ３ A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (CsPbI ３ ) was 65 times the molar amount of

[0162] (Photostability test) Prepared CsPbI ３ The nanoparticle dispersion was used to evaluate the light stability in the same manner as in Comparative Example 5. The results of the light stability evaluation are shown in Table 2.

[0163] [Example 13] (Preparation of nanoparticle dispersion) As in Comparative Example 5, 0.5 mg / mL of CsPbI ３ A nanoparticle mixed dispersion was prepared. 500 mg (2267 μmol) of BHT was added to 5 mL of the prepared nanoparticle mixed dispersion, and CsPbI ３ A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (CsPbI ３ The molar amount of the compound was 650 times that of the compound (III).

[0164] (Photostability test) Prepared CsPbI ３ The nanoparticle dispersion was used to evaluate the light stability in the same manner as in Comparative Example 5. The results of the light stability evaluation are shown in Table 2.

[0165]

[0166]

[0167] [Comparison of changes over time due to light irradiation] [Example 14] In the same manner as in Example 9, CsPbBr containing BHT was ３ A nanoparticle dispersion was prepared.

[0168] (Photostability test) A CsPbBr perovskite quantum dot dispersion in a transparent screw-top bottle was ３ The nanoparticle dispersion was irradiated from the outside of the bottle at room temperature and in the atmosphere with a wavelength of 450 nm and an irradiation intensity of 67 mW / cm ２ The continuous irradiation time was set to 180 minutes, 300 minutes, 450 minutes, and 630 minutes.

[0169] An integrating sphere was set on a fluorescence spectrophotometer FP-8600 (manufactured by JASCO Corporation; excitation wavelength 370 nm) and the photoluminescence quantum yield (PLQY) was measured before irradiation and for each irradiation time. As in Comparative Example 1, the relative PLQY, which is the PLQY after irradiation relative to the PLQY before irradiation, was calculated. The results of the change in relative PLQY with respect to the light irradiation time are shown in Figure 2.

[0170] Example 15: In the same manner as in Example 7, CsPbBr containing HALS-C was ３ A nanoparticle dispersion was prepared.

[0171] (Photostability test) A CsPbBr perovskite quantum dot dispersion in a transparent screw-top bottle was ３ The nanoparticle dispersion was irradiated from the outside of the bottle at room temperature and in the atmosphere with a wavelength of 450 nm and an irradiation intensity of 67 mW / cm ２ The continuous irradiation time was set to 180 minutes, 300 minutes, 450 minutes, and 630 minutes.

[0172] The PLQY was measured before irradiation and for each irradiation time, and the relative PLQY was calculated in the same manner as in Example 14. The results of the change in relative PLQY during light irradiation are shown in Figure 2.

[0173] Comparative Example 6: In the same manner as in Comparative Example 3, CsPbBr ３ A nanoparticle dispersion was prepared.

[0174] (Photostability test) A CsPbBr perovskite quantum dot dispersion in a transparent screw-top bottle was ３ The nanoparticle dispersion was irradiated from the outside of the bottle at room temperature and in the atmosphere with a wavelength of 450 nm and an irradiation intensity of 67 mW / cm ２ The continuous irradiation time was set to 180 minutes, 300 minutes, 450 minutes, and 630 minutes.

[0175] The PLQY was measured before irradiation and for each irradiation time, and the relative PLQY was calculated in the same manner as in Example 14. The results of the change in relative PLQY during light irradiation are shown in Figure 2.

[0176] (Discussion) In Examples 14 and 15, the relative PLQY remained at 80% or higher even after 450 minutes of irradiation. On the other hand, in Comparative Example 6, in which no light stabilizer was added, after 300 minutes of irradiation, the relative PLQY decreased to 80% or lower compared to immediately after light irradiation, and after 630 minutes of irradiation, the relative PLQY decreased to approximately 50% compared to immediately after light irradiation. The fluorescence properties of luminescent nanoparticles rapidly deteriorate when irradiated with light energy above a certain level. The addition of a light stabilizer suppressed the decrease in PLQY.

[0177] [Comparison of changes over time depending on aging time] [Example 16] As in Comparative Example 1, 0.5 mg / mL FAPbBr ３ A nanoparticle mixed dispersion was prepared. 50 mg (226.7 μmol) of BHT was added as a light stabilizer to 5 mL of the prepared nanoparticle mixed dispersion to prepare FAPbBr. ３ A nanoparticle dispersion was prepared. The molar amount of the light stabilizer was 1000 ppm. The perovskite quantum dots were metal halide perovskite (FAPbBr ３ ) was 45 times the molar amount of

[0178] (Photostability test) Prepared FAPbBr ３ The nanoparticle dispersion was placed in a transparent screw-top vial, and the vial was irradiated with light from the outside at room temperature and in the atmosphere at a wavelength of 450 nm and an irradiation intensity of 67 mW / cm. ２ The continuous irradiation time was set to 180 minutes, 300 minutes, 450 minutes, and 630 minutes.

[0179] The PLQY was measured before irradiation and for each irradiation time, and the relative PLQY was calculated in the same manner as in Example 14. The results of the change in relative PLQY during light irradiation are shown in Figure 3.

[0180] Comparative Example 7 FAPbBr was prepared in the same manner as in Comparative Example 1, except that the aging time was changed to 36 hours. ３ A nanoparticle dispersion was prepared.

[0181] (Photostability Test) PLQY was measured before irradiation and for each irradiation time, and relative PLQY was calculated in the same manner as in Example 16. The results of the change in relative PLQY upon light irradiation are shown in Figure 3.

[0182] Comparative Example 8: FAPbBr was prepared in the same manner as in Comparative Example 1, except that aging was not performed. ３ A nanoparticle dispersion was prepared.

[0183] (Photostability Test) PLQY was measured before irradiation and for each irradiation time, and relative PLQY was calculated in the same manner as in Example 16. The results of the change in relative PLQY upon light irradiation are shown in Figure 3.

[0184] Reference Example 1 FAPbBr was prepared in the same manner as in Example 16, except that aging was not performed. ３ A nanoparticle dispersion was prepared.

[0185] (Photostability Test) PLQY was measured before irradiation and for each irradiation time, and relative PLQY was calculated in the same manner as in Example 16. The results of the change in relative PLQY upon light irradiation are shown in Figure 3.

[0186] (Discussion) Comparing Comparative Example 7 and Comparative Example 8, the deterioration of PLQY after an irradiation time of 450 minutes was significantly greater in Comparative Example 7. Aging optimized the perovskite quantum dots, delaying the time it took for the relative PLQY to fall below 0.8. There was no difference in the amount of radicals generated between Comparative Example 7 and Comparative Example 8. In other words, it is believed that optimizing the perovskite quantum dots through aging suppressed the formation of defects on the perovskite quantum dot surface due to radical species and peroxides. By combining this with radical scavenging by a light stabilizer, deterioration due to light irradiation could be significantly suppressed.

Claims

1. A nanoparticle dispersion containing a metal halide perovskite, a light stabilizer, and a non-polar organic solvent, characterized in that the light stabilizer contains at least one of a hindered amine skeleton represented by general formula (1) and a phenol skeleton represented by general formula (2). (In general formula (1), R １ is at least one selected from a hydrogen atom, an acyclic aliphatic hydrocarbon group, and an oxyl free radical group, and R ２ ~R ５ are each independently a hydrogen atom or an acyclic aliphatic hydrocarbon group, and R ６ is a hydrogen atom or an organic functional group. (In general formula (2), R ７ ~R １１ are each independently a hydrogen atom or an organic functional group.

2. The nanoparticle dispersion according to claim 1, wherein the amount of the light stabilizer having a hindered amine skeleton is 0.01 to 50 times the amount of the metal halide perovskite.

3. The nanoparticle dispersion according to claim 1, wherein the amount of the light stabilizer having a phenol skeleton is 0.01 to 10,000 times the amount of the metal halide perovskite.

4. The nanoparticle dispersion according to claim 1, wherein the non-polar organic solvent comprises at least one selected from the group consisting of toluene, hexane, octane, cyclohexane, methylcyclohexane, and decalin.

5. A method for producing a nanoparticle dispersion, comprising: a first step of mixing a precursor solution obtained by dissolving a metal halide perovskite precursor in a good solvent with an organic base compound, an organic acid compound, and a poor solvent at 40°C or less to prepare a suspension containing coarse nanoparticles, and recovering the coarse nanoparticles from the suspension by sedimentation; a second step of adding a non-polar organic solvent to the coarse nanoparticles to re-disperse them, removing coarse particles by classification, and aging the mixture for 8 hours or more to obtain a nanoparticle mixed dispersion; and a third step of adding a light stabilizer to the nanoparticle mixed dispersion to obtain a nanoparticle dispersion.

6. A nanoparticle film using the nanoparticle dispersion liquid according to any one of claims 1 to 4.

7. A light-emitting device using the nanoparticle film according to claim 6.

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