Method for manufacturing nanocrystalline particles

Abstract

The present invention provides a method for producing perovskite luminescent particles with a low FWHM and a PLQY exceeding 85%, even when the emission peak wavelength is 535 nm or higher. [Solution] The process of preparing a solution involves dissolving lead bromide, an organic acid, and an amine in a solvent, and controlling the process temperature T (°C) and process time t (seconds).

Description

Technical Field

[0001] The present invention relates to a method for producing nanocrystalline particles.

Background Art

[0002] Nanocrystalline particles having a perovskite crystal structure are superior in terms of high optical density, high quantum efficiency, high color purity corresponding to a narrow full width at half maximum (FWHM), etc., as compared with non-perovskite nanocrystalline particles not having a perovskite crystal structure such as InP and CdSe. On the other hand, perovskite nanocrystalline particles have a problem that it is difficult to control their stability as compared with non-perovskite nanocrystalline particles. Nanocrystalline particles having a perovskite crystal structure may be referred to as perovskite nanocrystalline particles.

[0003] Perovskite-type photo-responsive nanocrystalline particles are being studied as materials for constituting a photoelectric conversion layer of solar power generation, a color filter, and a backlight source using three-color white light. Further, it is known that perovskite nanocrystalline particles are adopted as materials for constituting a green light emitter and a red light emitter excited by a blue light emitting diode.

[0004] For perovskite nanocrystalline particles, a plurality of synthesis methods such as a hot injection method, a ligand-assisted reprecipitation method, and a flow synthesis method have been studied. Among them, the flow synthesis method is expected to have productivity that can be continuously synthesized by feeding a raw material solution as compared with the batch-type hot injection method.

[0005] Non-patent document 1 discloses a flow synthesis method for synthesizing CsPbBr3 perovskite luminescent particles using a reaction solution prepared by heating at 120°C. The flow synthesis method in patent document 1 further discloses that perovskite luminescent particles with emission peak wavelengths ranging from 462 nm to 520 nm are synthesized in an inline process by controlling the reaction temperature range up to 120°C and the reaction time. The wavelength range of such perovskite luminescent particles corresponds to the emission colors from blue to green in the BT2020 color gamut. In the BT2020 color gamut, the wavelengths corresponding to the chromaticity points of each RGB color on the spectral locus are 630 nm for red, 532 nm for green, and 467 nm for blue.

[0006] On the other hand, Non-Patent Document 2 describes CsPbBr with an emission peak wavelength of 530-535 nm. 3-x I x Since the emission quantum efficiency of perovskite luminescent particles is said to be less than 50%, perovskite luminescent particles of FAPbBr3 are being investigated. FAPbBr3 with an emission peak wavelength of 530 nm, a full width at half maximum (FWHM) of 22 nm, and a photoluminescence quantum yield (PLQY) of 85% has been synthesized by a hot injection method using a reaction solution prepared by heating at 120°C. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Nanoscale 2019, 11 p18790 [Non-Patent Document 2] J.Am.Chem.Soc. 2016, 138 p14202 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, further improvements were needed in terms of the emission color and manufacturing method of nanocrystalline particles containing a perovskite crystal structure composed of formamidine, lead, and bromine. The green emission peak wavelength of nanocrystalline particles containing a perovskite crystal structure may be below 535 nm, which has low luminous sensitivity, and it is expected that a longer wavelength band (536 nm to 545 nm) than 535 nm, which has high luminous sensitivity, will be achieved. In addition, the full width at half maximum (FWHM) of the green emission peak of nanocrystalline particles containing a perovskite crystal structure may be broadened, or the PLQY may be less than 85%, and improvements in color purity and higher PLQY are expected, respectively.

[0009] This invention has been made in view of the above background art, and aims to provide a method for producing nanocrystalline particles containing a perovskite-type crystal structure composed of formamidine, lead, and bromine, which have green luminescence sensitivity and high quantum efficiency and are capable of flow synthesis. [Means for solving the problem]

[0010] To achieve this objective, the method for producing nanocrystalline particles according to the embodiment of the present invention includes a dissolution preparation step of preparing a dissolution by dissolving lead bromide, an organic acid, and an amine in a solvent, The synthesis step includes mixing the aforementioned dissolving solution with a formamidine salt solution to synthesize nanocrystalline particles containing a perovskite-type crystalline structure composed of formamidine, lead, and bromine. When the process temperature for preparing the aforementioned dissolving solution is T (°C) and the process time is t (seconds), The aforementioned dissolving solution preparation step is characterized by being carried out under conditions that satisfy general formulas (1) to (4). General formula (1) 134≦T≦154 General formula (2)t≧600 General formula (3)t≧-66.667×T+10133 General formula (4)t≦-60×T+10740 [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a method for producing nanocrystalline particles containing a perovskite-type crystal structure composed of formamidine, lead, and bromine, which have green luminescence sensitivity and high quantum efficiency and can be synthesized by flow synthesis. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows a schematic diagram of the dissolution preparation step, in which lead bromide, an organic acid, and an amine according to the first embodiment are dissolved in a solvent to prepare a dissolution. [Figure 2] This figure shows the process window of the dissolution preparation step for preparing the dissolution according to the first embodiment. [Figure 3] This figure illustrates the schematic configuration of a flow synthesis apparatus that continuously performs the dissolution preparation step and the synthesis step according to the first embodiment. [Figure 4] This figure illustrates the schematic configuration of an oil bath for checking the liquid supply temperature in the synthesis process according to the first embodiment. [Modes for carrying out the invention]

[0013] Preferred embodiments of the present invention will be described in detail below with reference to Figures 3 and 4.

[0014] A method for producing nanocrystalline particles containing a perovskite-type crystal structure according to an embodiment of the present invention comprises a solution preparation step of preparing a solution by dissolving lead bromide, an organic acid, and an amine in a solvent. Furthermore, a method for producing nanocrystalline particles containing a perovskite-type crystal structure according to this embodiment comprises a synthesis step of mixing the solution with a formamidine salt solution to synthesize nanocrystalline particles containing a perovskite-type crystal structure composed of formamidine, lead, and bromine. Moreover, when the process temperature T (°C) and process time t (seconds) for preparing the solution are set, the solution preparation step is carried out under conditions that satisfy the following general formulas (1) to (4). General formula (1) 134≦T≦154 General formula (2)t≧600 General formula (3)t≧-66.667×T+10133 General formula (4): t ≤ -60×T + 10740 Hereinafter, each embodiment will be described in more detail.

[0015] <The First Embodiment> FIG. 1 shows an outline of a dissolution solution preparation step of dissolving lead bromide, an organic acid, and an amine according to the first embodiment in a solvent to prepare a dissolution solution, and FIG. 2 shows a process window of a synthesis step of synthesizing nanocrystalline particles including a perovskite crystal structure according to the first embodiment. Table 1 shows experimental results serving as a basis for the process window of the adjustment step of the dissolution solution shown in FIG. 2.

[0016] [Table 1]

[0017] Among the experimental results shown in Table 1, those in which precipitation (dp) of lead compounds, etc., low absolute quantum emission yield LP (PLQY < 0.85), short wavelength shift (LW) of the emission center wavelength, by-products (MC) such as amide compound 4 or oxide 5, etc., were observed were assigned symbols for each process condition. Also, among the experimental results shown in Table 1, events unsuitable for such flow synthesis and events unsuitable for emission characteristics were not observed, and ○ was assigned to the process conditions corresponding to the solution adjustment step for a suitable lead solution.

[0018] The process conditions suitable for flow synthesis read from Table 1 are shown in FIG. 2. The process window can be regarded as the inside surrounded by the boundary lines [1] to [5]. Corresponding to the boundary lines [1], [2], boundary line [3], boundary line [4], boundary line [5], the following general formulas (1) to (4) are derived for the dissolution step temperature T (°C) and the dissolution step time t (seconds). Boundary lines [1], [2]: 134 ≤ T ≤ 154 General formula (1) Boundary line [3]: t ≥ 600 General formula (2) Boundary line [4]: t ≥ -66.667×T + 10133 General formula (3) Boundary line [5]: t ≤ -60×T + 10740 General formula (4) This embodiment includes a solvent preparation step in which lead bromide, an organic acid, and an amine are dissolved in a solvent to prepare a solvent. The organic acid and amine act as dispersion ligands for the perovskite luminescent particles.

[0019] In this embodiment, either saturated or unsaturated fatty acids can be used as organic acids. Examples of saturated fatty acids include lauric acid, caprylic acid, palmitic acid, and stearic acid. Examples of unsaturated fatty acids include oleic acid, palmitoleic acid, linoleic acid, linolenic acid, arachidonic acid, docosahexaenoic acid, eicosapentaenoic acid, and vaccenic acid. These unsaturated fatty acids are suitable organic acids for use in flow synthesis because they are liquid in a temperature range of 5°C to 35°C. Aromatic carboxylic acids such as salicylic acid can also be used. Furthermore, the above organic acids may be used individually or in combination.

[0020] The organic acids applied in this embodiment include fatty acids, and the amines applied in this embodiment include aliphatic amines.

[0021] In this embodiment, either saturated or unsaturated amines can be used. Primary to tertiary amines can also be used.

[0022] Examples of primary saturated amines include octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, nonadecylamine, eicosylamine, henicosylamine, docosylamine, and tricosylamine.

[0023] Examples of primary unsaturated amines include oleylamine, octenamine, nonenamine, decenamine, undecenamine, dodecenamine, tridecenamine, tetradecenamine, pentadecenamine, and hexadeceneamine.

[0024] Examples of secondary amines include dimethyloctylamine, dimethyldecylamine, dimethyldodecylamine, dimethyltetradecylamine, dimethylhexadecylamine, and dimethyloctadecylamine.

[0025] Examples of tertiary amines include trimethyloctylamine, trimethyldecylamine, trimethyldodecylamine, trimethyltetradecylamine, trimethylhexadecylamine, and trimethyloctadecylamine. These amines may be used individually or in combination.

[0026] In this embodiment, it is preferable to use a solvent with a high boiling point, specifically one with a boiling point of 180°C or higher. Using a high boiling point solvent avoids pulsating currents and boiling in the mixer and supply channel during flow synthesis, enabling stable flow synthesis.

[0027] As solvents used in this embodiment, 1-octadecene, hexadecene, tetradecane, pentadecane, heptadecane, octadecane, tridecene, tridecane, tetradecene, pentadecene, tridecene, dodecene, etc. can be used.

[0028] The process of preparing the solution obtained by dissolving lead bromide, an organic acid, and an amine in a solvent in this embodiment will be explained with reference to Figure 1, Figure 2, and Table 1.

[0029] Lead bromide reacts reversibly with organic acids and amines, as shown in Figure 1. Lead bromide is dissolved by using organic acids and amines in stoichiometric excesses. One of the two bromine atoms in lead bromide is eliminated, forming a monosubstituted salt (1) with the organic acid. The bromine atom eliminated during this process is Br. - and H from organic acids +This forms the amine HBr salt (3). Next, bromine is eliminated from the monosubstituted salt (1) and forms a disubstituted salt (2) with the organic acid, thereby preparing the solution. The nanocrystalline particles composed of formamidine, lead, and bromine in this embodiment are synthesized by mixing the disubstituted salt (2), the amine HBr salt (3), and the formamidine salt solution. Heating is required to form the disubstituted salt (2), but an amide compound (4) is easily produced as a by-product from the organic acid and amine. The amine itself is also oxidized, and an oxide (5) is easily produced as a by-product. These by-products represent an irreversible reaction in the preparation of the solution in this embodiment. Therefore, the concentrations of organic acid and amine in the reaction system decrease during preparation. In particular, when the amine concentration in the reaction system decreases, it becomes difficult to maintain the form of the amine HBr salt (3), and it reversibly becomes an amine, and Br - It then combines with Pb again.

[0030] In this embodiment, the solution obtained by dissolving lead bromide, an organic acid, and an amine in a solvent refers to a solution in which a disubstituted salt (2) and an amine HBr salt (3) are formed from lead bromide. In this embodiment, the solution is considered to be a solution obtained by dissolving lead bromide, an organic acid, and an amine in a solvent if the amount of undissolved lead bromide is 3% or less relative to the number of moles of lead bromide before dissolution began.

[0031] Nanocrystalline particles containing a perovskite-type crystal structure, synthesized from a disubstituted salt (2), an amine HBr salt (3), and a formamidine salt solution, are readily soluble in the presence of amine at high temperatures. Therefore, when preparing a solution by dissolving lead bromide, an organic acid, and an amine in a solvent, the number of moles of amine used is preferably 6 to 9 times, and more preferably 7 to 8.5 times, the number of moles of lead bromide. If the number of moles of amine is less than 6 times the number of moles of lead bromide, lead bromide becomes less soluble. On the other hand, if it is greater than 9 times, the nanocrystalline particles containing the perovskite-type crystal structure synthesized become more readily soluble during synthesis. The number of moles of organic acid is preferably 15 to 18 times, and more preferably 16 to 17 times, the number of moles of lead bromide. If the number of moles of organic acid is less than 15 times the number of moles of lead bromide, lead bromide becomes less soluble. On the other hand, if it is greater than 18 times, the nanocrystalline particles composed of formamidine, lead, and bromine synthesized tend to become coarse particles during synthesis. Furthermore, a large number of nanoplates exhibiting an emission peak at approximately 510 nm tend to be formed as by-products. The number of moles of organic acid is preferably 0.4 to 1.7 times the number of moles of amine, and more preferably 0.45 to 0.6 times. If it is less than 0.45 times, lead bromide becomes less soluble, and if it is greater than 1.7 times, the nanocrystalline particles composed of formamidine, lead, and bromine become more soluble during synthesis.

[0032] In this embodiment, when the process temperature is T (°C) and the process time is t (seconds), the dissolution preparation process is carried out under conditions that satisfy the following general formula (1).

[0033] In this embodiment, the process temperature refers to the actual temperature of the dissolution. For example, when a dissolution is placed in a flask and heated in an oil bath, the process temperature refers to the temperature of the dissolution in the flask, not the temperature of the oil in the oil bath. The process time refers to the time during which the process temperature is acting on the dissolution. If the temperature difference between the oil in the oil bath and the dissolution in the flask is kept below a predetermined temperature difference, the oil temperature in the oil bath may be used as a substitute for the process temperature. General formula (1) 134≦T≦154 General formula (2)t≧600 General formula (3)t≧-66.667×T+10133 General formula (4)t≦-60×T+10740 In the synthesis of nanocrystalline particles composed of formamidine, lead, and bromine in this embodiment, the precipitation of nanocrystalline particles and dissolution by coexisting amines occur competitively. As a result of diligent research by the inventors, it was found that by preparing the dissolution under conditions satisfying general formulas (1) to (4), sufficient disubstituted salts (2) and amine HBr salts (3) are generated, and the by-product formation of amide compounds (4) and oxides (5) is suppressed. Furthermore, it was found that by suppressing the by-product formation of amide compounds (4) and oxides (5), the surface of particles precipitated during synthesis due to the appropriate presence of amines dissolves, and the particle size with an emission peak wavelength of 535 nm or higher is controlled. In addition, the appropriate presence of amines also has the effect of dissolving any nanoplates that are formed as by-products. It was also found that although the dissolution, prepared by dissolving lead bromide, organic acid, and amine in a solvent, is heated, lead bromide precipitation is unlikely to occur even when cooled to room temperature after preparation.

[0034] As mentioned above, heating is required to form the disubstituted salt (2), which also produces amide compounds (4) and oxides (5) as by-products. However, by adopting a process temperature T that satisfies general formula (1), the production of these by-products can be suppressed. If the process temperature T is lower than 134°C, the disubstituted salt (2) is not sufficiently produced, and the perovskite luminescent particles tend to exhibit emission peak wavelengths shorter than 535 nm. If the process temperature T is higher than 154°C, lead bromide is more likely to precipitate from the solution due to the by-product production of amide compounds (4) and oxides (5). Precipitation is particularly pronounced when the solution is cooled to room temperature after preparation.

[0035] In this embodiment, the process time t (seconds) is carried out under conditions that also satisfy the following general formula (2). General formula (2)t≧600 When t is less than 600, the disubstituted salt (2) is not sufficiently formed, and the perovskite luminescent particles tend to exhibit emission peak wavelengths shorter than 535 nm. This is thought to be because insufficient formation of the disubstituted salt (2) leads to a reduction in particle size due to dissolution by the amine.

[0036] In this embodiment, the process temperature T (°C) and process time t (seconds) are carried out under conditions that satisfy the following general equations (3) and (4). General formula (3)t≧-66.667×T+10133 General formula (4)t≦-60×T+10740 Here, by satisfying the conditions of general formulas (3) and (4), the precipitation of lead compounds and the like is suppressed even when the solution is cooled to room temperature after preparation, and it becomes possible to synthesize nanocrystalline particles by flow synthesis using a pump that can deliver liquids at room temperature.

[0037] In this embodiment, the formamidine salt solution is a fatty acid salt solution of formamidine, and is prepared by replacing the fatty acid portion of the fatty acid salt of formamidine with a different fatty acid. When the fatty acid salt of formamidine is difficult to dissolve, a different fatty acid is added to replace the fatty acid portion and make the fatty acid salt of formamidine soluble. As the formamidine salt to be used, it is preferable to use formamidine acetate due to its availability, but since it is difficult to dissolve in the aforementioned solvent, the acetate is replaced with a different fatty acid salt to improve solubility.

[0038] Since fatty acids also act as dispersion ligands for perovskite luminescent particles, they can function as ligands if they are replaced with the desired fatty acids beforehand. In this embodiment, either saturated or unsaturated fatty acids can be used. Examples of saturated fatty acids include lauric acid, caprylic acid, palmitic acid, and stearic acid. Examples of unsaturated fatty acids include oleic acid, palmitoleic acid, linoleic acid, linolenic acid, arachidonic acid, docosahexaenoic acid, eicosapentaenoic acid, and vaccenic acid.

[0039] In this embodiment, in the synthesis step for synthesizing nanocrystalline particles containing a perovskite-type crystal structure, the molar ratio of formamidine to lead (FA / Pb) is preferably 2.5 or higher. If FA / Pb is less than 2.5, nanocrystalline particles containing a perovskite-type crystal structure do not precipitate, or the particle size is small, making it easier to obtain particles that exhibit an emission peak wavelength shorter than 535 nm.

[0040] In this embodiment, nanocrystalline particles containing a perovskite crystal structure are manufactured by flow synthesis. Nanocrystalline particles containing a perovskite crystal structure composed of formamidine, lead, and bromine exhibit different particle sizes and emission peak wavelengths depending on the synthesis temperature. By synthesizing nanocrystalline particles containing a perovskite crystal structure by flow synthesis, nanocrystalline particles can be continuously manufactured at a constant synthesis temperature.

[0041] The flow synthesis method for nanocrystalline particles of this embodiment includes a synthesis step of adjusting a solution containing lead bromide, acid, and amine and a formamidine salt solution to a predetermined temperature in separate liquid delivery pipes. The flow synthesis method for nanocrystalline particles of this embodiment also includes a synthesis step of continuously supplying a heated solution to a mixer at a liquid delivery temperature of x°C, and mixing the solution containing lead bromide, acid, and amine and the formamidine salt solution with the mixer at a liquid mixing temperature of y°C.

[0042] By performing the synthesis process such that the liquid delivery temperature x and liquid mixing temperature y satisfy general formulas (5) to (7), perovskite luminescent particles with a narrow FWHM and a PLQY of 85% or more can be produced, even if the emission peak wavelength is 535 nm or higher. General formula (5) 130≦x≦360 General formula (6) 130≦y≦160 General formula (7)yx≦3 When x and y exceed 160°C, excessive dissolution of the precipitated particle surface by amine occurs, and the emission peak wavelength tends to become smaller than 535 nm. On the other hand, when x and y are lower than 130°C, the formation of nanoplates as a by-product becomes significant. Furthermore, the difference between the liquid mixing temperature y (°C) and the liquid delivery temperature x (°C) is preferably 3°C or less, and preferably 1°C or less.

[0043] The nanocrystalline particles containing the perovskite crystal structure in this embodiment are produced by flow synthesis from a solution of lead bromide, acid, and amine, and a formamidine salt solution. Flow synthesis in this embodiment refers to the continuous synthesis of compounds while the reaction solution flows through a channel or the space of a mixer. As shown in Figure 3, multiple reaction solutions are continuously supplied to the mixer 2 by the pump 1, and nanocrystalline particles containing the perovskite crystal structure are continuously produced. The supply pipe that delivers the liquid between the pump 1 and the mixer 2 is designated as the forward channel 3, and the supply pipe that discharges the liquid from the mixer is designated as the backward channel 4. The mixer 2 and a portion of the backward channel 4 are heated to a high temperature of y°C by the heating means 5. In the backward channel, the perovskite luminescent particles are recovered from the heating means 5 via an ice bath 6 to the recovery unit 7. The solution of lead bromide, acid, and amine, and the formamidine salt solution are supplied from the reaction tank 8 to the pump 1, respectively. When multiple reaction solutions are supplied and heated to x°C in the forward channel 3, and then continuously supplied to the mixer 2, the multiple reaction solutions are mixed while their temperature rises from x°C to y°C. The mixer 2 that can be used in this embodiment is not particularly limited and commercially available microreactors can be used. For example, T-shaped reactors from YMC Corporation, 3-way joints from From, DH-type mixers and α-type mixers from Nakamura Superhard Co., Ltd., K2-24-M and K1-24M from Noritake Corporation, and SMCR from Kobe Steel, Ltd. can be used. The liquid supply pipes used in the forward channel 3 and the backward channel 4 are not particularly limited and can be made of synthetic resin, ceramic, glass, metal, etc., but stainless steel and nickel alloys are preferred from the viewpoint of heat resistance and corrosion resistance. Examples of such stainless steels include austenitic stainless steels such as SUS304 and SUS316, and nickel alloys such as Hastelloy (registered trademark). The heating means 5 is not particularly limited, but can be an oil bath, Peltier element, ribbon heater, rubber heater, hot plate, etc. Among these methods, the oil bath allows the mixer and the liquid delivery pipe to be heated in the same tank, and also makes it easier to bring the temperature of the reaction solution and the mixing temperature closer together. Furthermore, by combining the heating means 5 into a single tank, the heated reaction solution can be delivered to the mixer without lowering its temperature.If the heating means 5 for the mixer 2 and the forward flow path 3 are separated (using separate heating means), there is a possibility that the temperature of the heated reaction liquid will decrease between the heating means. Examples of pumps 1 that can be used in this embodiment include diaphragm pumps, turbine pumps, piston pumps, screw pumps, plunger pumps, gear pumps, centrifugal pumps, and propeller pumps. Among these, plunger pumps suppress pulsation, and the effect of suppressing pulsation is further enhanced by using a multi-plunger pump. When pulsation occurs severely, variations in the mixing ratio of the reaction liquids tend to occur.

[0044] In this embodiment, when the process temperature T (°C) and process time t (seconds) for preparing the dissolving solution are given, the conditions 150 ≤ T ≤ 154 and 1200 ≤ t ≤ 1500 are satisfied. Furthermore, when the temperature at which the liquid is continuously supplied to the mixer is x°C, and the temperature at which the solutions are mixed in the mixer is y°C, the supply temperature x (°C) and the liquid mixing temperature y (°C) are set to satisfy the condition of being between 155°C and 160°C.

[0045] The inventors have found that under the above conditions, nanocrystalline particles containing a perovskite-type crystal structure composed of formamidine, lead, and bromine with a PLQY of over 90% can be synthesized even when the emission peak wavelength is 540 nm or higher. This is thought to be because sufficient disubstituted salts (2) and amine HBr salts (3) are formed, suppressing the by-product formation of amide compounds (4) and oxides (5), and the presence of an appropriate amount of amine, along with a suitable synthesis temperature, results in optimal solubility on the surface of the precipitated particles during synthesis.

[0046] The perovskite crystal structure composed of formamidine, lead, and bromine in this embodiment is not particularly limited and may be a compound having any of three-dimensional, two-dimensional, or pseudo-two-dimensional structures. In the case of a three-dimensional structure, the perovskite compound is represented as ABX3, and in the case of a two-dimensional structure, it is represented as A2BX4. The three-dimensional perovskite compound represented as ABX3 is FAPbBr3. The two-dimensional perovskite compound represented as A2BX4 is FA2PbBr4. Furthermore, perovskite compounds doped with Eu, Gd, Yb, Mn, Ce, Bi, Sm, Ho, or Tb may also be used. [Examples]

[0047] In this embodiment, a specific example of a method for producing perovskite luminescent particles according to the embodiment will be described using the embodiment.

[0048] A solution of lead bromide, acid, and amine was prepared with the following composition.

[0049] Lead bromide and 1-octadecene were placed in a flask with a stirring bar and immersed in an oil bath heated to 160°C. Next, oleic acid was added and the stirring bar was rotated with a magnetic stirrer to disperse the lead bromide. After 25 minutes, the liquid temperature in the flask stabilized at 154°C (process temperature T). Oleylamine heated to 154°C was then added, and the dissolution of lead bromide was started while degassing with a diaphragm pump. After 20 minutes (process time t: 1200 seconds), the flask was removed from the oil bath and cooled in a water bath, but no lead bromide precipitated, and a solution of dissolved lead bromide, acid, and amine was prepared. Lead bromide 1.242 g (3.375 mmol as lead) Oleic acid 18 ml Oleylamine 9 ml 1-Octadecene 63 ml The formamidine salt solution was prepared with the following composition.

[0050] Formamidine acetate, oleic acid, and 1-octadecene were placed in a flask, a stirring bar was added, and the flask was immersed in an oil bath heated to 120°C. While degassing with a diaphragm pump, the stirring bar was rotated with a magnetic stirrer to replace the formamidine acetate with the oleate. After 30 minutes, the flask was removed from the oil bath and cooled in a water bath, but no precipitation of formamidine acetate or oleate occurred, and a formamidine salt solution was prepared. Formamidine acetate 1.054 g (10.125 mmol as FA) Oleic acid 27.2 ml 1-Octadecene 62.8 (ml) An oil bath heated to 160°C was used as the heating means 5. A GL Sciences PU-916 plunger pump was used as pump 1, and a Noritake K2-24-M mixer was used as mixer 2. A SUS314 tube with an outer diameter of 1 / 8 inch and an inner diameter of 2.17 mm was used for the forward flow path 3 connecting pump 1 and mixer 2. The same SUS314 tube was also used for the rear flow path 4 at the discharge point from the mixer. The rear flow path 4, from the connection point with mixer 2 for a length of 0.18 m, was immersed in the oil bath together with mixer 2, and the rest was connected to the recovery unit 7 via the atmosphere and an ice water bath 6.

[0051] As shown in Figure 3, a solution containing lead bromide, acid, and amine dissolved at room temperature was pumped at a rate of 20 ml / min into a forward channel 3 immersed in an oil bath of a heating means 5, which was temperature-controlled to 160°C. Next, the temperature of the reaction solution B discharged from the end point 10 of the forward channel 3 was measured using a thermocouple 9 placed at the end point 10 of the forward channel 3. As shown in Figures 4(a) to 4(c), the length of the forward channel immersed in the oil bath was increased, and it was confirmed that the temperature rose to 158.8°C when it was immersed for 1.2 m. When a formamidine salt solution at room temperature was pumped at a rate of 20 ml / min, the forward channel reached 158.8°C when it was immersed for 1.2 m, similar to the solution containing lead bromide, acid, and amine. Both the forward channel 3 of the lead bromide, acid, and amine solution and the formamidine salt solution were immersed in the same oil bath as the mixer 2 for a length of 1.2 m and connected to the mixer 2. As a result, the reaction solutions, heated to 184.8°C and 185°C, are continuously supplied to mixer 2. The solution containing lead bromide, acid, and amine is supplied at a rate of 20 ml / min, and the formamidine salt solution is supplied at a rate of 20 ml / min, resulting in a formamidine-to-lead molar ratio of FA / Pb = 3.0, which is then supplied to mixer 2. Since mixer 2 is immersed in an oil bath heated to 160°C, the reaction solutions are mixed at 160°C in the mixer, and perovskite luminescent particles (FAPbBr3) are synthesized. The synthesized solution containing the perovskite luminescent particles is cooled in an ice bath 6 and discharged into recovery unit 7 at a rate of 40 ml / min.

[0052] When the emission was evaluated using blue light-emitting diode light with a maximum peak wavelength of 445 nm, the PLQY was 90.3%, the emission peak wavelength was 540 nm, and the full width at half maximum of the emission peak was 22 nm. [Examples]

[0053] In this example, the solvent used in Example 1 was changed from 1-octadecene to dodecane, and the formamidine salt solution was prepared with the following composition, so that the molar ratio of formamidine to lead was FA / Pb = 3.4, and the solution was delivered to mixer 2. The procedure was the same as in Example 1. Formamidine acetate 1.1981 g (10.125 mmol as FA) Oleic acid 30.9 ml Dodecane 59.1 ml Emission evaluation revealed a PLQY of 88.1%, an emission peak wavelength of 542 nm, and a full width at half maximum of 21 nm. [Examples]

[0054] In this example, the process was carried out in the same manner as in Example 1, except that the process temperature T was set to 134°C and the process time t was set to 2400 seconds. When the emission evaluation was performed, the PLQY was 91%, the emission peak wavelength was 536 nm, and the full width at half maximum of the emission peak was 22 nm. [Examples]

[0055] In this example, the process was carried out in the same manner as in Example 3, except that the process temperature T was set to 134°C and the process time t was set to 1200 seconds. When the emission evaluation was performed, the PLQY was 91%, the emission peak wavelength was 537 nm, and the full width at half maximum of the emission peak was 22.5 nm. [Examples]

[0056] In this example, the process was carried out in the same manner as in Example 1, except that the process time t was set to 1500 seconds. When the emission evaluation was performed, the PLQY was 88%, the emission peak wavelength was 538 nm, and the full width at half maximum of the emission peak was 22 nm. [Examples]

[0057] In this example, the solvent used in Example 1 was changed from 1-octadecene to dodecane, and the formamidine salt solution was prepared with the following composition, so that the molar ratio of formamidine to lead was FA / Pb = 4, and the solution was delivered to mixer 2. The procedure was the same as in Example 1, except that the solution was delivered to mixer 2. Formamidine acetate 1.409 g (11.912 mmol as FA) Oleic acid 26.3 ml Dodecane 63.7 ml Emission evaluation revealed a PLQY of 88%, an emission peak wavelength of 540 nm, and a full width at half maximum of 21 nm. [Examples]

[0058] In this example, the solvent used in Example 1 was changed from 1-octadecene to dodecane, and the formamidine salt solution was prepared with the following composition, so that the molar ratio of formamidine to lead was FA / Pb = 2.5, and the solution was delivered to mixer 2. The procedure was the same as in Example 1. Formamidine acetate 0.8806 g (7.445 mmol as FA) Oleic acid 17.1 ml Dodecane 72.9 ml Emission evaluation revealed a PLQY of 87%, an emission peak wavelength of 536 nm, and a full width at half maximum (FMAX) of 23 nm. [Examples]

[0059] In this example, the procedure was the same as in Example 2, except that the formamidine to lead was prepared with the following composition, resulting in a molar ratio of FA / Pb = 3.5, and the mixture was delivered to mixer 2 at 130°C using a heating means 5 that was temperature-controlled to 130°C. Formamidine acetate 1.398 g (11.813 mmol as FA) Oleic acid 35.7 ml Dodecane 54.3 ml Emission evaluation revealed a PLQY of 90%, an emission peak wavelength of 536 nm, and a full width at half maximum (FMAX) of 22 nm. [Examples]

[0060] In this example, the procedure was the same as in Example 1, except that the formamidine salt solution prepared with the following composition in Example 1 was used and perovskite luminescent particles were synthesized by the hot injection method. Formamidine acetate 1.054 g (10.125 mmol as FA) Oleic acid 27.2 ml 1-Octadecene 22.8 (ml) Lead bromide and 1-octadecene were placed in a flask, a stirring bar was added, and the flask was immersed in an oil bath heated to 160°C. Next, oleic acid was added, and the stirring bar was rotated with a magnetic stirrer to disperse the lead bromide. After 25 minutes, the liquid temperature in the flask stabilized at 154°C (process temperature T). Oleylamine heated to 154°C was then added, and the dissolution of lead bromide was started while degassing with a diaphragm pump. After 20 minutes (process time t: 1200 seconds), degassing was stopped, and a formamidine salt solution heated to 154°C was added to the flask. After 5 seconds, the flask was removed from the oil bath and cooled in an ice bath. Emission evaluation showed a PLQY of 88.3%, an emission peak wavelength of 538 nm, and a full width at half maximum of 22 nm.

[0061] [Comparative Example 1] In this comparative example, a solution was prepared by dissolving lead bromide, acid, and amine with the same composition as in Example 1. Unlike Example 1, the process temperature T was set to 163°C. Precipitation of initially dissolved lead bromide was observed around 600 seconds into the process. When the flask was removed from the oil bath and cooled in a water bath at 1200 seconds into the process, further precipitation of lead bromide increased, making it difficult to pump the solution with pump 1.

[0062] [Comparative Example 2] In this example, the procedure was the same as in Example 1, except that a formamidine salt solution prepared with the following composition was used. Formamidine acetate 0.705 g (5.956 mmol as FA) Oleic acid 13.2 ml Dodecane 76.8 ml When the emission evaluation was performed, the PLQY was 68%, the emission peak wavelength was 531 nm, and the full width at half maximum of the emission peak was 34 nm, indicating a decrease in emission characteristics compared to Example 1.

[0063] [Comparative Example 3] In this comparative example, the procedure was the same as in Example 5, except that the process time t was set to 3600 seconds. When the solution containing lead bromide, acid, and amine was cooled in a water bath, a small precipitate of lead bromide was observed at the bottom of the flask. After removing the precipitated lead bromide, the solution containing lead bromide, acid, and amine was used. When the emission was evaluated, the PLQY was 79%, the emission peak wavelength was 538 nm, and the full width at half maximum of the emission peak was 21 nm, resulting in a lower PLQY than in Example 5.

[0064] [Comparative Example 4] In this comparative example, the procedure was the same as in Example 5, except that the process temperature T was set to 124°C. When the emission evaluation was performed, the PLQY was 89%, the emission peak wavelength was 534 nm, and the full width at half maximum of the emission peak was 23 nm, so the emission peak wavelength fell slightly short of 535 nm.

[0065] [Comparative Example 5] In this comparative example, the procedure was the same as in Example 1, except that a heating means 5, which was temperature-controlled to 130°C, was used and the mixture was mixed in a mixer at 130°C. When the emission was evaluated, the main emission peak wavelength was 532 nm with a PLQY of 85%, and the full width at half maximum of the emission peak was 24 nm, but an emission peak originating from the nanoplate was also confirmed at 508 nm. [Explanation of Symbols]

[0066] 1 pump 2 Mixer 3. Forward channel 4. Rear channel 5 Heating means 6. Ice bath 7. Recovery unit 8. Reaction vessel 9 Thermocouples 10 End of the forward channel

Claims

1. A solvent preparation step involves dissolving lead bromide, an organic acid, and an amine in a solvent to prepare a solvent, The synthesis step includes mixing the aforementioned dissolving solution with a formamidine salt solution to synthesize nanocrystalline particles containing a perovskite-type crystalline structure composed of formamidine, lead, and bromine, When the process temperature for preparing the aforementioned dissolving solution is T (°C) and the process time is t (seconds), A method for producing nanocrystalline particles, characterized in that the aforementioned dissolution preparation step is carried out under conditions that satisfy general formulas (1) to (4). General formula (1) 134≦T≦154 General formula (2) t≧600 General formula (3) t≧-66.667×T+10133 General formula (4) t≦-60×T+10740

2. The aforementioned synthesis step is A step of adjusting the temperature of a first solution containing the lead bromide, the acid, and the amine, and a second solution containing a formamidine salt, to a predetermined liquid temperature in separate liquid delivery pipes. A step of supplying the first solution and the second solution, whose liquid temperatures have been adjusted, to a mixer at a supply temperature of x°C, The process includes the step of mixing the first solution and the second solution with the mixer at a liquid mixing temperature y°C, The method for producing nanocrystalline particles according to claim 1, wherein the liquid delivery temperature x (°C) and the liquid mixing temperature y (°C) satisfy general formulas (5) to (7). General formula (5) 130≦x≦360 General formula (6) 130≦y≦160 General formula (7) y−x≦3

3. The aforementioned perovskite-type crystal structure is FAPbBr ３ A method for producing nanocrystalline particles according to claim 1 or 2, characterized in that it is the same.

4. A method for producing nanocrystalline particles according to claim 1 or 2, characterized in that the acid is a fatty acid and the amine is an aliphatic amine.

5. A method for producing nanocrystalline particles according to claim 1 or 2, characterized in that the molar ratio of formamidine to lead is 2.5 or more in the synthesis step for synthesizing nanocrystalline particles containing the perovskite-type crystal structure.

6. The method for producing nanocrystalline particles according to claim 1 or 2, characterized in that the formamidine salt solution is a fatty acid salt solution of formamidine, and is prepared by replacing the fatty acid portion of the fatty acid salt of formamidine with a different fatty acid.

7. When the process temperature for preparing the aforementioned dissolving solution is T (°C) and the process time is t (seconds), The process temperature T and process time t (seconds) satisfy general formulas (8) and (9). In the synthesis step, when the liquid is continuously supplied to the mixer at a supply temperature of x°C, and the first solution and the second solution are mixed by the mixer at a liquid mixing temperature of y°C, The synthesis step is a method for producing nanocrystalline particles according to claim 1 or 2, satisfying general formulas (10) to (12). General formula (8) 150≦T≦154 General formula (9) 1200≦t≦1500 General formula (10) 150≦x≦360 General formula (11) 150≦y≦160 General formula (12) y−x≦3

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