A method for preparing perovskite quantum dots by using nano transient precipitation

Abstract

The application belongs to the technical field of perovskite quantum dot preparation, and particularly relates to a method for preparing perovskite quantum dots by using nano transient precipitation. The method comprises the following steps: dispersing A-site cation halide, B-site metal ion halide and a ligand of ABX3 type perovskite quantum dots in a polar solvent to obtain a precursor solution; and mixing the precursor solution and a non-polar anti-solvent by jet flow mixing to induce turbulent mixing, and obtaining the perovskite quantum dots after stopping. The preparation method provided by the application can be carried out at normal temperature and pressure, without the need for high-temperature heating and inert atmosphere protection, thereby avoiding the harsh reaction conditions of the hot injection method, and greatly reducing the process complexity and energy consumption cost. The jet flow mixing technology is used to realize efficient mixing in milliseconds, and the mixing time is shortened by 2-3 orders of magnitude compared with the traditional method, so that the transient uniform supersaturation of the precursor is ensured, thereby obtaining perovskite quantum dot products with narrow particle size distribution and excellent optical performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of perovskite quantum dot preparation, and particularly relates to a method for preparing perovskite quantum dots by using nano transient precipitation. BACKGROUND

[0002] As nanoscale semiconductor particles with quantum confinement effect, perovskite quantum dots have unique physical properties such as tunable emission wavelength, high photoluminescence quantum yield, high color purity and low working threshold, which make them have great prospects in various applications such as optoelectronic devices, light-emitting diodes, solar cells, lasers and sensors. Traditional nanoparticle preparation methods include co-precipitation, thermal injection and sol-gel method. The thermal injection method is to inject a Cs source precursor solution into a precursor solution containing a Pb source and a halogen source under high temperature conditions, and to accurately control the size and shape of quantum dots by adjusting the reaction time, although high-quality products can be obtained, but there are problems such as harsh reaction conditions and complex process. It is worth noting that there are essential differences between perovskite quantum dots and ordinary inorganic nanoparticles in preparation. Perovskite has an ABX3 type crystal structure, and A-site, B-site cations and X-site halide anions need to form perovskite phase according to strict stoichiometric ratio and spatial arrangement in the precipitation process. Its nucleation and growth involves a multi-step ion exchange and lattice recombination process, and the nucleation kinetics is much more complex than simple inorganic salts. In addition, the ligand not only plays a stabilizing role in perovskite quantum dots, but also needs to accurately control the crystal face growth rate to achieve quantum confinement effect. Therefore, how to prepare perovskite quantum dots with good environmental stability under mild conditions has become a technical problem to be solved.

[0003] In order to overcome the defects of the hot injection method, researchers have developed various room temperature preparation methods in recent years. The Chinese invention patent with publication number CN119592318A discloses a method for preparing perovskite quantum dots by a room temperature solution reaction method. The first ligand and cation precursor are dissolved in a first solvent, then a second solvent is used to dilute and prepare a cation-ligand solution. The second ligand and lead salt are dissolved in the first solvent and then diluted to obtain a lead salt-ligand solution. The perovskite quantum dots are prepared under room temperature conditions, avoiding the harsh conditions of the hot injection method. The Chinese invention patent with publication number CN119736084A discloses a room temperature preparation method for perovskite quantum dot composite material with ultra-narrow emission spectrum. The method first mixes wide bandgap nanocrystals with high polarity solvent to prepare a wide bandgap nanocrystal solution, then mixes with perovskite quantum dot reaction precursors to prepare a reaction precursor solution. By adding an opposite polarity solvent, a precipitate is formed, and a perovskite quantum dot composite material with ultra-narrow emission spectrum is prepared, with a full width at half maximum of 14.4 nanometers. The Chinese invention patent with publication number CN119025518A discloses a room temperature preparation method for ultra-small size perovskite quantum dots. The perovskite quantum dots are prepared by a room temperature solution reaction method. The ligand and precursor are dissolved and diluted under vigorous stirring conditions, which can overcome the defects of existing synthesis methods that are difficult to realize large-scale and mass production of perovskite quantum dots. Although the above-mentioned room temperature preparation methods have made certain progress in terms of simplicity, there are still problems such as low mixing efficiency, inaccurate control of nucleation process, poor batch consistency of product quality, etc. Although the ligand-assisted precipitation method is simple to operate, it is difficult to separate the nucleation and growth stages due to the fast reaction speed, and it is difficult to accurately control the size and shape of the quantum dots. In addition, a large amount of anti-solvent is usually required, and the local concentration is too high, which will affect the quality of the quantum dots, and the batch reproducibility is poor. These factors limit the promotion of existing methods in industrial applications, and it is urgent to develop a perovskite quantum dot preparation method with high mixing efficiency, controllable reaction process and stable product quality. SUMMARY

[0004] To solve the above problems, the present application provides a method for preparing perovskite quantum dots by nanosecond instantaneous precipitation. This method is based on the limited impact jet mixing technology, which realizes the instantaneous supersaturation precipitation of precursors by accurately controlling the hydrodynamic conditions, thereby preparing high-quality perovskite quantum dots.

[0005] To achieve the above purpose, the present application provides the following technical solutions:

[0006] A method for preparing perovskite quantum dots by nanosecond instantaneous precipitation, comprising the following steps:

[0007] ABX3 type perovskite quantum dots A-site cation halide, B-site metal ion halide and ligand are dispersed in a polar solvent to obtain a precursor solution; the precursor solution and a non-polar antisolvent are mixed by jet flow to induce turbulent mixing, and the perovskite quantum dots are obtained after stopping.

[0008] When jet flow mixing, the precursor substance can reach a supersaturation state in the non-polar antisolvent instantaneously, quickly nucleate to form perovskite quantum dot crystal nuclei, and the ligand molecules quickly coat the surface of the crystal nuclei to prevent further growth of the crystal nuclei, thereby obtaining high-quality perovskite quantum dots.

[0009] Nanometer instantaneous precipitation technology is a nanoparticle preparation technology based on turbulent mixing. When two fluids collide at high speed in a limited space, they can be uniformly mixed at the molecular level in a very short time, creating a transient supersaturation condition. Under this condition, solute molecules quickly nucleate and stop growing under the protection of ligands, forming uniform-sized nanoparticles.

[0010] The present application uses jet flow mixing to achieve efficient preparation through the following mechanisms:

[0011] (1) Fast mixing: opposite high-speed jet flow mixing collision forms strong turbulent mixing, and the mixing time reaches milliseconds;

[0012] (2) Transient supersaturation: the precursor quickly reaches a supersaturation state in the antisolvent;

[0013] (3) Uniform nucleation: uniform nucleation in space and time is achieved under turbulent conditions;

[0014] (4) Ligand protection: ligand molecules timely coat the crystal nuclei to control growth.

[0015] This unique preparation mechanism gives the perovskite quantum dots the following outstanding technical effects:

[0016] (1) Ultra-high luminescent efficiency: by reducing surface defects and non-radiative recombination centers, PLQY can reach 92-94%, close to the theoretical limit;

[0017] (2) Excellent color purity: thanks to uniform particle size distribution and complete crystal structure, the color coordinates are close to international standards;

[0018] (3) Excellent stability: strong bonding of ligands and complete crystal lattice structure make the quantum dots have excellent optical, thermal and chemical stability;

[0019] (4) Precise light emission regulation: full visible spectrum coverage from 408-685nm is achieved through size engineering.

[0020] Preferably, the molar ratio of the A-site cation of the A-site cation halide to the B-site metal ion of the B-site metal ion halide is 1:1-2.

[0021] Preferably, the ligand consists of acid ligand and amine ligand at a molar ratio of 2:1, and the concentration of the acid ligand in the precursor solution is 0.05-0.2 M.

[0022] Optionally, the polar solvent includes but is not limited to N,N-dimethylformamide, dimethyl sulfoxide, isopropanol, 2-pyrrolidone, γ-butyrolactone or γ-valerolactone.

[0023] Optionally, the acid ligand includes oleic acid or octanoic acid; and the amine ligand includes oleylamine or octylamine.

[0024] Optionally, the non-polar antisolvent includes but is not limited to toluene, n-hexane, chlorobenzene or chloroform.

[0025] Preferably, the preparation temperature of the precursor solution is 20-60°C.

[0026] Preferably, the volume ratio of the precursor solution to the non-polar antisolvent is 1:5-20 when the jet flow is mixed.

[0027] Preferably, the flow rate of the precursor solution is 0.005-0.05 m / s and the flow rate of the non-polar antisolvent is 0.05-1.06 m / s when the jet flow is mixed.

[0028] Preferably, the time of the turbulent flow mixing is 1-10 milliseconds.

[0029] Preferably, the time of the residence is 2-10 seconds.

[0030] Preferably, the residence is further followed by a purification step.

[0031] More preferably, the purification method is centrifugation.

[0032] The present application creatively solves the key technical problems in the preparation of perovskite quantum dots: by optimizing the precursor concentration (the molar ratio of the A-site cation source to the B-site metal source is 1:1-2) and the antisolvent volume ratio (1:5-20), the synchronous supersaturation precipitation of A, B and X ions is realized; by precisely controlling the turbulent flow intensity and the residence time in the mixing chamber (the residence time refers to the effective reaction time of the fluid from the jet flow mixer outlet into the subsequent mixing zone including the PTFE pipeline or other limited reaction channels, and does not include the standing time of the product after flowing out of the mixing zone into the collection container. The present application preferably has a residence time of 2-10 seconds), the effective separation of the nucleation and growth stages is realized; by adjusting the flow rate ratio and the ligand concentration, the quantum dot size is precisely controlled in the range of 5-10 nm, and the continuous adjustable emission from red light to blue light is realized.

[0033] The beneficial technical effects of the present application are as follows:

[0034] The method for preparing perovskite quantum dots by using nano-instantaneous precipitation provided by the present application has significant advantages compared with the prior art. First, the method can be carried out at normal temperature and pressure, without the need for high-temperature heating and inert atmosphere protection, avoiding the harsh reaction conditions of the hot injection method, and greatly reducing the process complexity and energy cost. Second, the millisecond-level efficient mixing is realized by the limited impact jet mixing technology, the mixing time is shortened by 2-3 orders of magnitude compared with the traditional method, ensuring the instantaneous uniform supersaturation of the precursors, so as to obtain perovskite quantum dot products with narrow particle size distribution and excellent optical performance. Third, the method has excellent process controllability, and the size and optical performance of the quantum dots can be accurately controlled by accurately adjusting parameters such as flow rate, concentration, and residence time, with good batch reproducibility and a relative standard deviation of less than 5%. Most importantly, the method is easy to realize continuous and large-scale production, has good industrial application prospects, and can meet the industrialization needs of perovskite quantum dots in the fields of display, lighting, solar cells, etc.

[0035] Taking the preparation of CsPbBr3 quantum dots as an example, through the creative improvement of the nano-instantaneous precipitation technology, the present application first realizes: ultra-narrow half-peak width emission, the FWHM of CsPbBr3 quantum dots is only 15-23 nm, which is much better than the traditional method; excellent batch stability, the PLQY fluctuation is less than 4% for 2 hours of continuous production; deep blue light emission capability, 408 nm deep blue light emission is realized through quantum confinement effect; significant industrialization potential, the yield can reach 6.6 L / 2h, which lays a solid foundation for the large-scale production of perovskite quantum dots. These technical breakthroughs fully embody the significant progress of the present application compared with the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The present application is a schematic diagram of preparing perovskite quantum dots by using instantaneous precipitation method for the present application.

[0037] Figure 2 The TEM image of CsPbBr3 quantum dots prepared in Example 1 of the present application.

[0038] Figure 3 The particle size distribution graph of CsPbBr3 quantum dots prepared in Example 1 of the present application.

[0039] Figure 4 The TEM image of CsPbBr3 quantum dots prepared in Comparative Example 1 of the present application.

[0040] Figure 5 The particle size distribution graph of CsPbBr3 quantum dots prepared in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0041] The following detailed description of various example embodiments of the application should not be considered to be limiting of the application, but rather a description of certain example aspects, features and embodiments of the application. It should be appreciated that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0042] It should be noted that any processes, steps, techniques described herein are merely the most preferred approaches of making and using the present application, and that this application should not be limited to such approaches.

[0043] Further, for numerical ranges such as "between 1 and 10", it is intended that every numeral between the lowest and highest numeral is also expressly stated. For example, "between 1 and 10" is a shorthand for stating each possible numeral between the lowest and highest numeral. Also, it is intended that any range between the lowest and highest value includes any other stated or intervening values. For example, if a range between 1 and 10 is stated, it is intended that any other stated or intervening value (such as 3.14, 4.22, 5.43, 6.75, 8.24, 9.34 etc.) or any other intervening range between 1 and 10 is also expressly stated.

[0044] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described.

[0045] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" or the like are open-ended, i.e., are intended to permit the inclusion of any additional integer, parameter, element or the like beyond those explicitly recited.

[0046] Unless otherwise specified, the room temperature as used herein refers to a temperature of 25±5°C.

[0047] The schematic diagram of preparing perovskite quantum dots by instant precipitation method in the embodiment of the present application is shown in Figure 1 .

[0048] Example 1

[0049] Preparation of CsPbBr3 quantum dots:

[0050] (1) Preparation of precursor solution:

[0051] At 25°C, 3.0 mmol of CsBr (637.5 mg) and 3.6 mmol of PbBr2 (1316.4 mg) were weighed and placed in a 250 mL round-bottom flask, 100 mL of N,N-dimethylformamide (DMF) was added, and the solid was dissolved under magnetic stirring for 30 min. After the solid was completely dissolved, oleic acid (OA, final concentration 0.1 M) and oleylamine (OAm, final concentration 0.05 M) were added as ligands, and the stirring was continued for 15 min until the solution was clear and transparent without any suspended particles, which was the precursor solution.

[0052] (2) Equipment installation and commissioning:

[0053] A 5 mL glass syringe was used to load the precursor solution, and a 30 mL glass syringe was used to load the toluene anti-solvent. The syringes were installed on two high-precision syringe pumps (precision ± 0.5%) respectively. A PTFE tube with an inner diameter of 2.0 mm was used to connect the syringes to the two inlet channels of the confined impinging jet mixer. The mixer uses a head-on design, with a mixing chamber volume of about 2 mL, an inlet channel outlet diameter of 0.5 mm, and an angle between the two channel axes of 180°. A 148.2 cm long PTFE pipeline was connected to the mixer outlet to provide a 5 second residence time. In addition, to achieve long-term continuous liquid supply, the syringe pump can be connected to an external liquid storage bottle, or under laboratory conditions, the same collection volume can be achieved by replacing the syringe multiple times, so the volume of the quantum dot solution collected subsequently can be greater than the nominal volume of a single syringe, without affecting the residence time and mixing conditions.

[0054] (3) Preparation of CsPbBr3 quantum dots

[0055] The precursor solution feed rate was set to 5.0 mL / min (0.026 m / s), and the toluene feed rate was set to 50.0 mL / min (0.265 m / s), ensuring a feed volume ratio of 1:10. At room temperature, start the two syringe pumps and adjust the flow to make the two fluids reach the mixing chamber at the same time. The calculated turbulent mixing time in the mixer is about 3.6 milliseconds. It was observed that the precursor solution and toluene collided at high speed in the mixing chamber, and instantaneous turbulent mixing phenomenon occurred, with the solution color changing from transparent to green fluorescence, indicating the formation of perovskite quantum dots. A 50 mL beaker was used to collect the product at the outlet of the mixer, and a magnetic stirrer was used to stir constantly at 800 rpm to prevent agglomeration. Continuous collection was carried out for 1 min, and about 50 mL of quantum dot ink solution was obtained.

[0056] (4) Separation and purification:

[0057] The collected product was transferred to a centrifuge tube, first centrifuged at 3000 rcf for 3 min to remove unreacted large particle impurities. The supernatant was taken, and three times the volume of methyl acetate was added as a precipitant. After mixing well, centrifugation was carried out at 8000 rcf for 10 min. The supernatant was discarded, and the green precipitate at the bottom was redispersed with a small amount of n-hexane and centrifuged again for purification. Finally, the purified CsPbBr3 quantum dots were dispersed in 10 mL of anhydrous n-hexane and stored at 5°C in the dark.

[0058] Example 2

[0059] Preparation of CsPbI3 quantum dots:

[0060] (1) Preparation of precursor solution:

[0061] CsI (778.8 mg) and PbI2(1662.0 mg) were weighed in a 250 mL round bottom flask at 30 °C and dissolved in 100 mL of dimethyl sulfoxide (DMSO). Since the iodides dissolved slowly in DMSO, stirring was required for 45 min and moderate heating to 40 °C. After complete dissolution, the solution was cooled to room temperature, and oleic acid (final concentration 0.12 M) and oleylamine (final concentration 0.06 M) were added, and stirring was continued for 20 min. The solution was dark yellow, transparent and free of precipitates, which was the precursor solution.

[0062] (2) Equipment installation and commissioning:

[0063] A 5 mL glass syringe was used to load the precursor solution, and a 30 mL glass syringe was used to load the toluene anti-solvent. The syringes were installed on two high-precision syringe pumps (precision ± 0.5%) respectively. A PTFE pipe with an inner diameter of 2.0 mm was used to connect the syringes to the two inlet channels of the confined impinging jet mixer. The mixer used a head-on design, with a mixing chamber volume of about 2 mL, an inlet channel outlet diameter of 0.5 mm, and a two-channel axis angle of 180°. In addition, to achieve continuous liquid supply for a long time, the syringe pump can be connected to an external liquid storage bottle, or under laboratory conditions, the same collection volume can be achieved by replacing the syringe multiple times, so the volume of the quantum dot solution collected subsequently can be greater than the nominal volume of a single syringe, without affecting the residence time and mixing conditions.

[0064] (3) Preparation of CsPbI3 quantum dots:

[0065] The precursor feeding speed was 4.0 mL / min (0.0212 m / s), and the toluene feeding speed was 48.0 mL / min (0.254 m / s) (feeding volume ratio 1:12), the residence time was 6 seconds (pipe length 165 cm), the turbulent mixing time in the mixer was about 3.8 milliseconds, the collection temperature was room temperature, and the operation was carried out in the dark during the collection process. During the preparation process, it was observed that the color of the solution changed rapidly from transparent to red-brown, and under the irradiation of a 365 nm ultraviolet lamp, it showed bright red fluorescence. The collection time was 12 min, and about 624 mL of product was obtained.

[0066] (4) Separation and purification:

[0067] The collected product was transferred to a centrifuge tube, first centrifuged at 3000 rcf for 3 min to remove unreacted large particle impurities. The supernatant was taken, and three times the volume of methyl acetate was added as a precipitant, mixed thoroughly, and then centrifuged at 8000 rcf for 10 min. The supernatant was discarded, and the green precipitate at the bottom was redispersed with a small amount of n-hexane and centrifuged again for purification. The purified CsPbI3 quantum dots were dispersed in 10 mL of anhydrous n-hexane, and stored in the dark at 5 °C.

[0068] Example 3

[0069] Preparation of CsPbCl3 quantum dots:

[0070] (1) Preparation of precursor solution:

[0071] Dissolve 3.0 mmol CsCl (506.1 mg) and 3.6 mmol PbCl2 (999.6 mg) in 120 mL DMF at room temperature. Due to the low solubility of chlorides, stirring for 60 min and slight heating to 50 °C are required to promote dissolution. Add oleic acid (final concentration 0.08 M) and oleylamine (final concentration 0.04 M), and the solution is colorless and transparent, which is the precursor solution.

[0072] (2) Installation and commissioning of equipment:

[0073] Load the precursor solution into a 5 mL glass syringe and the toluene anti-solvent into a 30 mL glass syringe. Install the syringes on two high-precision syringe pumps (precision ± 0.5%). Connect the syringes to the two inlet channels of the confined impinging jet mixer using PTFE tubing with an inner diameter of 2.0 mm. The mixer uses a head-on design, with a mixing chamber volume of about 2 mL, an inlet channel outlet diameter of 0.5 mm, and an angle between the two channel axes of 180°. In addition, to achieve continuous liquid supply for a long time, the syringe pumps can be connected to external liquid storage bottles, or under laboratory conditions, the same collection volume can be achieved by replacing the syringe multiple times, so the volume of the quantum dot solution collected subsequently can be greater than the nominal volume of a single syringe, without affecting the residence time and mixing conditions.

[0074] (3) Preparation of CsPbCl3 quantum dots:

[0075] The precursor feeding speed is 3.5 mL / min (0.0186 m / s), the toluene feeding speed is 42.0 mL / min (0.0223 m / s) (feeding volume ratio 1:12), the residence time is 4 seconds (line length 97 cm), the turbulent mixing time in the mixer is about 4.4 milliseconds, and the preparation temperature is 25 °C. During the preparation process, it is observed that the solution becomes colorless and transparent, and presents blue fluorescence under ultraviolet lamp irradiation. The collection time is 10 min, and about 455 mL of product is obtained.

[0076] (4) Separation and purification:

[0077] Transfer the collected product to a centrifuge tube, first centrifuge at 3000 rcf for 3 min to remove unreacted large particle impurities. Take the supernatant, add three times the volume of methyl acetate as a precipitant, mix thoroughly, and centrifuge at 8000 rcf for 10 min. Discard the supernatant, and redisperse the green precipitate at the bottom with a small amount of n-hexane, and centrifuge again for purification. The purified CsPbCl3 quantum dots are dispersed in 10 mL of anhydrous n-hexane, and stored at 5 °C in the dark

[0078] Example 4

[0079] Preparation of FAPbBr3 quantum dots:

[0080] (1) Preparation of precursor solution:

[0081] Dissolve 3.0 mmol of lead formamidinate bromide (FABr, 378.0 mg) and 3.6 mmol of PbBr2(1316.4 mg) in 100 mL of DMF at room temperature. Since the FA-based perovskite is more thermally stable, the ligand concentration can be appropriately increased, and oleic acid (final concentration 0.11 M) and oleylamine (final concentration 0.055 M) are added. Stir for 40 min until completely clear, which is the precursor solution.

[0082] (2) Installation and commissioning of equipment:

[0083] Load the precursor solution using a 5 mL glass syringe and load the toluene anti-solvent using a 30 mL glass syringe. Install the syringes on two high-precision syringe pumps (precision ± 0.5%) respectively. Connect the syringes to the two inlet channels of the confined impinging jet mixer using PTFE tubing with an inner diameter of 2.0 mm. The mixer uses a head-on design, with a mixing chamber volume of about 2 mL, an inlet channel outlet diameter of 0.5 mm, and a two-channel axis angle of 180°. In addition, to achieve continuous liquid supply for a long time, the syringe pump can be connected to an external liquid storage bottle, or under laboratory conditions, the same collection volume can be achieved by replacing the syringe multiple times, so the volume of the quantum dot solution collected subsequently can be greater than the nominal volume of a single syringe, without affecting the residence time and mixing conditions.

[0084] (3) Preparation of FAPbBr3 quantum dots:

[0085] The precursor feeding speed is 4.5 mL / min (0.0239 m / s), the toluene feeding speed is 49.5 mL / min (0.262 m / s) (feeding volume ratio 1:11), the residence time is 5 seconds (line length 143 cm), the turbulent mixing time in the mixer is about 3.7 milliseconds, and the preparation temperature is 28°C. During the preparation process, it is observed that the solution exhibits green fluorescence. The collection time is 15 min, and about 810 mL of product is obtained.

[0086] (4) Separation and purification:

[0087] The collected product was transferred to a centrifuge tube, first centrifuged at 3000rcf for 3min to remove unreacted large particle impurities. The supernatant was taken, and three times the volume of methyl acetate was added as a precipitant. After mixing well, it was centrifuged at 8000rcf for 10min. The supernatant was discarded, and the green precipitate at the bottom was redispersed with a small amount of n-hexane and purified by centrifugation again. The purified FAPbBr3 quantum dots were dispersed in 10mL of anhydrous n-hexane and stored at 5°C in the dark.

[0088] Example 5

[0089] Preparation of MAPbBr3 quantum dots:

[0090] (1) Preparation of precursor solution:

[0091] At room temperature, 3.0mmol of methylamine lead bromide (MABr, 336.0mg) and 3.6mmol of PbBr2(1316.4mg) were weighed and dissolved in a mixed solvent of 90mL of DMF and 10mL of isopropyl alcohol. Oleic acid (final concentration 0.1M) and oleylamine (final concentration 0.05M) were added, and the precursor solution was obtained after stirring for 35min.

[0092] (2) Installation and debugging of equipment:

[0093] A 5mL glass syringe was used to load the precursor solution, and a 30mL glass syringe was used to load the toluene anti-solvent. The syringes were installed on two high-precision syringe pumps (precision ±0.5%) respectively. A PTFE pipeline with an inner diameter of 2.0mm was used to connect the syringes to the two inlet channels of the confined impinging jet mixer. The mixer uses a head-on design, with a mixing chamber volume of about 2mL, an inlet channel outlet diameter of 0.5mm, and a two-channel axis angle of 180°. In addition, to achieve long-term continuous liquid supply, the syringe pump can be connected to an external liquid storage bottle, or under laboratory conditions, the same collection volume can be achieved by replacing the syringe multiple times, so the volume of the quantum dot solution collected subsequently can be greater than the nominal volume of a single syringe, without affecting the residence time and mixing conditions.

[0094] (3) Preparation of MAPbBr3 quantum dots:

[0095] The precursor feeding speed was 4.8mL / min (0.0254m / s), and the toluene feeding speed was 52.8mL / min (0.280m / s) (feeding volume ratio 1:11), the residence time was 5 seconds (pipeline length 153cm), and the turbulent mixing time in the mixer was about 3.5 milliseconds. During the preparation process, it was observed that the solution showed green fluorescence. The collection time was 12min, and about 691mL of product was obtained.

[0096] (4) Separation and purification:

[0097] The collected product was transferred to a centrifuge tube, first centrifuged at 3000rcf for 3min to remove unreacted large particle impurities. The supernatant was taken, and three times the volume of methyl acetate was added as a precipitant. After mixing well, it was centrifuged at 8000rcf for 10min. The supernatant was discarded, and the green precipitate at the bottom was redispersed with a small amount of n-hexane and purified by centrifugation again. The purified MAPbBr3 quantum dots were dispersed in 10mL anhydrous n-hexane and stored at 5°C in the dark.

[0098] Example 6

[0099] (1) Preparation of precursor solution:

[0100] Mixed halide quantum dots were prepared to achieve wavelength tuning of luminescence. At room temperature, 1.5mmol of CsBr (318.8mg), 1.5mmol of CsI (778.8mg), 1.8mmol of PbBr2(658.2mg) and 1.8mmol of PbI2(831.0mg) were weighed and dissolved in 110mL of DMSO. Due to the complexity of the mixed system, it was necessary to stir at 40°C for 60min to ensure complete dissolution. Oleic acid (final concentration 0.11M) and oleylamine (final concentration 0.055M) were added to obtain the precursor solution.

[0101] (2) Installation and commissioning of equipment:

[0102] A 5mL glass syringe was used to load the precursor solution, and a 30mL glass syringe was used to load the toluene anti-solvent. The syringes were installed on two high-precision syringe pumps (precision ±0.5%) respectively. A PTFE pipeline with an inner diameter of 2.0mm was used to connect the syringes to the two inlet channels of the confined impinging jet mixer. The mixer used a head-on design, with a mixing chamber volume of about 2mL, an inlet channel outlet diameter of 0.5mm, and a two-channel axis angle of 180°. In addition, to achieve continuous liquid supply for a long time, the syringe pump can be connected to an external liquid storage bottle, or under laboratory conditions, the same collection volume can be achieved by replacing the syringe multiple times, so the volume of the quantum dot solution collected subsequently can be greater than the nominal volume of a single syringe, without affecting the residence time and mixing conditions.

[0103] (3) CsPbBr 1.5 I 1.5 Quantum dot preparation:

[0104] The precursor feeding speed was 4.2mL / min (0.0223m / s), and the toluene feeding speed was 50.4mL / min (0.268m / s) (feeding volume ratio 1:12), the residence time was 6 seconds (pipeline length 174cm), and the turbulent mixing time in the mixer was about 3.7 milliseconds. During the preparation process, it was observed that the solution exhibited yellow-green fluorescence. The collection time was 14min, and about 764mL of product was obtained.

[0105] (4) Separation and purification:

[0106] The collected product was transferred to a centrifuge tube, first centrifuged at 3000rcf for 3min to remove unreacted large particle impurities. Take the supernatant, add three volumes of methyl acetate as precipitant, mix well and centrifuge at 8000rcf for 10min. Discard the supernatant, and the green precipitate at the bottom was redispersed with a small amount of n-hexane and purified by centrifugation again. The purified CsPbBr 1.5 I 1.5 The quantum dots were dispersed in 10 mL of anhydrous n-hexane and stored in the dark at 5°C.

[0107] Example 7

[0108] (1) Preparation of precursor solution:

[0109] In order to improve the yield, a high concentration precursor solution was prepared. At room temperature, 6.0 mmol of CsBr (1275.0 mg) and 7.2 mmol of PbBr2(2632.8 mg) were dissolved in 80 mL of DMF, with the concentration increased to 1.5 times the original. The amount of ligand was increased accordingly: oleic acid (final concentration 0.15 M), oleylamine (final concentration 0.075 M). Stirring for 45 min ensured complete dissolution, and the precursor solution was obtained.

[0110] (2) Installation and commissioning of equipment:

[0111] A 5 mL glass syringe was used to load the precursor solution, and a 30 mL glass syringe was used to load the toluene anti-solvent. The syringes were installed on two high-precision syringe pumps (precision ±0.5%) respectively. A PTFE pipeline with an inner diameter of 2.0 mm was used to connect the syringes to the two feed channels of the limited impinging jet mixer. The mixer uses a head-on design, with a mixing chamber volume of about 2 mL, an outlet diameter of 0.5 mm for the feed channels, and an included angle of 180° between the two channel axes. In addition, in order to realize continuous liquid supply for a long time, the syringe pump can be connected to an external liquid storage bottle, or under laboratory conditions, the same collection volume can be achieved by replacing the syringe multiple times, so the volume of the quantum dot solution collected subsequently can be greater than the nominal volume of a single syringe, without affecting the residence time and mixing conditions.

[0112] (3) Preparation of high-concentration CsPbBr3 quantum dots:

[0113] Due to the increased concentration, process parameters need to be adjusted. The precursor feed rate is 3.0 mL / min (0.0159 m / s), the toluene feed rate is 45.0 mL / min (0.239 m / s) (feed volume ratio 1:15, increasing the dilution factor), the residence time is 7 seconds (line length 178 cm), and the turbulent mixing time in the mixer is about 4.2 milliseconds. During the preparation process, it is observed that the solution exhibits bright green fluorescence, and the fluorescence intensity is significantly enhanced compared to the standard concentration. The collection time is 20 min, and about 960 mL of product is obtained, which is further separated and purified.

[0114] (4) Separation and purification:

[0115] The collected product is transferred to a centrifuge tube, first centrifuged at 3000 rcf for 3 min to remove unreacted large particle impurities. Take the supernatant, add three times the volume of methyl acetate as a precipitant, mix thoroughly, and centrifuge at 8000 rcf for 10 min. Discard the supernatant, and the green precipitate at the bottom is redispersed with a small amount of n-hexane and centrifuged again for purification. The purified CsPbBr3 quantum dots are dispersed in 10 mL of anhydrous n-hexane and stored at 5°C in the dark.

[0116] Example 8

[0117] (1) Continuous preparation equipment preparation:

[0118] To verify the continuous production capacity of the process, a long-time continuous preparation experiment is carried out. A large-volume syringe (100 mL of precursor solution, 1000 mL of toluene) is used, and the precursor solution formulation and optimized conditions of Example 1 are used.

[0119] (2) Continuous preparation process:

[0120] The precursor feed rate is 5.0 mL / min (0.0265 m / s), the toluene feed rate is 50.0 mL / min (0.265 m / s), the residence time is 5 seconds (line length 146 cm), and the turbulent mixing time in the mixer is about 3.6 milliseconds. Continuous preparation for 2 h, sampling every 10 min to monitor the stability of product quality. During the preparation process, it is observed that the product quality is stable, and the fluorescence color and intensity remain consistent. The total collection time is 120 min, and about 6600 mL of product is obtained.

[0121] (3) Separation and purification:

[0122] The collected product was transferred to a centrifuge tube, first centrifuged at 3000rcf for 3min to remove unreacted large particle impurities. Take the supernatant, add three volumes of methyl acetate as precipitant, mix well and centrifuge at 8000rcf for 10min. Discard the supernatant, and the green precipitate at the bottom was redispersed with a small amount of n-hexane and purified by centrifugation again. The purified CsPbBr3 quantum dots were dispersed in 10mL anhydrous n-hexane and stored at 5℃ in the dark.

[0123] To further illustrate the beneficial effects of the embodiments of the present application, the following comparative examples are constructed.

[0124] Comparative Example 1

[0125] To verify the superiority of the method of the present application, a comparative experiment was conducted using the traditional ligand-assisted precipitation method:

[0126] (1) Preparation of precursor solution:

[0127] At room temperature, 3mmol CsBr and 3.6mmol PbBr2 were dissolved in 100mL DMF, and oleic acid (final concentration 0.1M) and oleylamine (final concentration 0.05M) were added to prepare a precursor solution with the same concentration as Example 1.

[0128] (2) Traditional LARP preparation process:

[0129] At room temperature, 10mL of the precursor solution was quickly injected into 100mL of vigorously stirred toluene (V 前驱体 :V 抗溶剂 =1:10) with a syringe. The injection speed was about 5mL / s, and local color unevenness was observed during the injection process. After the injection was completed, the stirring was continued for 5min.

[0130] (3) Collection and purification:

[0131] The mixture was centrifuged and the supernatant was discarded, and the obtained precipitate was redispersed in anhydrous n-hexane.

[0132] Comparative Example 2

[0133] This comparative example provides a method for preparing perovskite quantum dots, which is different from Example 1 in that the classical hot injection method is used for comparison, and the preparation process is as follows:

[0134] (1) Preparation of Cs precursor:

[0135] At room temperature, 1.0mmol Cs2CO3 and 4mL oleic acid were dried in 20mL octadecene (ODE) at 120℃ for 1h, then heated to 150℃ under nitrogen protection until completely dissolved to form a Cs-oleate precursor. It needs to be preheated to 100℃ before use.

[0136] (2) PbBr2 precursor preparation:

[0137] 1.8 mmol of PbBr2 was mixed with 10 mL of oleylamine (final concentration 0.45 M) and 10 mL of oleic acid (final concentration 0.43 M) in 50 mL of ODE, dried under vacuum at 120 °C for 30 min, and then warmed up to 170 °C under nitrogen until complete dissolution.

[0138] (3) Hot-injection preparation process:

[0139] The PbBr2 precursor was kept at 170 °C, and 4 mL of preheated Cs precursor was injected rapidly. The reaction was immediately transferred to an ice bath for rapid cooling after 5 s. The whole process was carried out under nitrogen protection.

[0140] Comparative Example 3

[0141] This comparative example provides a preparation method of perovskite quantum dots, which is different from Example 1 in that a microfluidic nanoscale precipitation technology is used for comparison, and the preparation process is as follows:

[0142] (1) Precursor solution preparation:

[0143] At room temperature, 3.0 mmol of CsBr (637.5 mg) and 3.6 mmol of PbBr2 (1316.4 mg) were dissolved in 100 mL of N,N-dimethylformamide (DMF), and oleic acid (final concentration 0.1 M) and oleylamine (final concentration 0.05 M) were added as ligands. Stirring until complete dissolution, the same concentration of precursor solution as Example 1 was prepared.

[0144] (2) Microfluidic device design:

[0145] A T-shaped microfluidic chip was used, with a main channel width of 200 μm and a depth of 100 μm, and a side channel width of 100 μm. The precursor solution entered from the main channel, and the toluene anti-solvent entered from the two side channels.

[0146] (3) Microfluidic preparation process:

[0147] At room temperature, the precursor solution was fed at a speed of 45 mL / h, and toluene was fed at a speed of 450.0 mL / h (feed volume ratio 1:10), and the total flow rate was low to maintain a laminar flow state. The two streams contacted at the T-shaped intersection and mixed by molecular diffusion. Due to the low flow rate, the mixing process was slow, and a long mixing channel (about 30 cm) was needed to ensure complete mixing. During the preparation process, quantum dots were observed to gradually form in the mixing channel, and the solution color gradually changed from transparent to green.

[0148] (4) Collection and purification:

[0149] The product was collected at the outlet of the device, and due to the low yield, it took 1 h to obtain about 500 mL of product continuously. It was found that the microchannel was easily blocked by the formed quantum dots during the preparation process, and the device needed to be cleaned frequently. The collected product was centrifuged and purified according to the method of Example 1.

[0150] Detection of photoluminescence quantum yield (PLQY) of perovskite quantum dots:

[0151] The perovskite quantum dots prepared in Examples 1-8 and Comparative Examples 1-3 were subjected to TEM (the average particle size was calculated), PL peak position, PL full width at half maximum (FWHM), and photoluminescence quantum yield (PLQY) tests, and the results are shown in Table 1.

[0152] Table 1

[0153]

[0154]

[0155] As can be seen from Table 1, the high-quality quantum dots can be successfully prepared by changing different ligands and solvents in Examples 1-8 of the present application. Compared with the traditional LARP method (Comparative Example 1), the PLQY of the examples of the present application is significantly improved. Among them, the PLQY of the all-inorganic CsPbBr3 system (Examples 1, 7, and 8) can reach 88-94%, the PLQY of the mixed halogen CsPbBr 1.5 I 1.5 system (Example 6) reaches 80%, and the PLQY of the organic-inorganic hybrid systems FAPbBr3 and MAPbBr3 (Examples 4 and 5) is 87% and 83%, respectively.

[0156] Compared with the hot injection method (Comparative Example 2, PLQY is 85%), the examples of the present application still obtain higher photoluminescence quantum yield under mild conditions, and the PLQY of Examples 1 and 8 can reach 92-94% at the highest. Compared with the microfluidic nanosecond precipitation technology (Comparative Example 3, PLQY is 72%), the quantum yield of the examples of the present application is significantly higher, which is mainly due to the fact that the limited impact jet mixing technology can achieve more uniform and rapid mixing, reducing the formation of defect states.

[0157] The quantum dots prepared in the embodiments 1-8 of the present application have excellent size and luminescence characteristics by changing different ligands and solvents. Compared with the traditional LARP method (comparative example 1), the quantum dots prepared in the embodiments of the present application have more uniform size distribution and narrower luminescence half-peak width. In particular, the CsPbBr3system (embodiments 1, 7, 8), the particle size is controlled in the range of 7.3-9.2 nm, and the half-peak width is only 17-20 nm, while the particle size distribution of the quantum dots prepared in comparative example 1 is wider (12.1±2.8 nm), and the half-peak width reaches 35 nm.

[0158] Compared with the hot injection method (comparative example 2), the perovskite quantum dots synthesized in the embodiments of the present application are quite uniform in size, but the preparation process is more mild and does not need to be cooled rapidly from high temperature. Compared with the microfluidic nanodispersion technology (comparative example 3), the quantum dots prepared in the embodiments of the present application have better size uniformity (standard deviation 1.1-1.7 nm vs 2.5 nm) and narrower luminescence half-peak width (17-35 nm vs 38 nm). More importantly, the embodiments of the present application have a significant yield advantage, and 50-960 mL of product can be obtained in a single preparation, while the microfluidic method can only prepare 500 mL in 1 h, and the production efficiency is increased by about 20-40 times.

[0159] In addition, the microfluidic nanodispersion technology has key technical bottlenecks such as complex equipment manufacturing process, easy clogging of microchannels, and low yield, which limits its industrial application. In contrast, the confined impingement jet mixing technology of the present application has the advantages of simple equipment, convenient operation, easy scaling up, ensuring product quality while realizing high-efficiency continuous production, and has significant process advantages and industrialization potential.

[0160] Figure 2 TEM image of the CsPbBr3quantum dots prepared in the embodiment 1 of the present application.

[0161] Figure 3 Particle size distribution graph of the CsPbBr3quantum dots prepared in the embodiment 1 of the present application.

[0162] Figure 4 TEM image of the CsPbBr3quantum dots prepared in the comparative example 1 of the present application.

[0163] Figure 5 Particle size distribution graph of the CsPbBr3quantum dots prepared in the comparative example 1 of the present application.

[0164] The above-described embodiments only describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for preparing perovskite quantum dots using nanosecond transient precipitation, characterized in that, The method comprises the following steps: A-site cation halide of ABX3 type perovskite quantum dots, B-site metal ion halide and ligand are dispersed in a polar solvent to obtain a precursor solution; the precursor solution and a non-polar antisolvent are mixed by jet flow to induce turbulent mixing, and the perovskite quantum dots are obtained after staying; The volume ratio of the precursor solution to the non-polar antisolvent is 1:5-20 during the jet flow mixing; The flow rate of the precursor solution is 0.005-0.05 m / s, and the flow rate of the non-polar antisolvent is 0.05-1.06 m / s during the jet flow mixing; The turbulent mixing time is 1-10 milliseconds; The staying time is 2-10 seconds. 2.The method for preparing perovskite quantum dots using nano-transient precipitation according to claim 1, characterized in that, The molar ratio of the A-site cation of the A-site cation halide to the B-site metal ion of the B-site metal ion halide is 1:1-2. 3.The method of claim 1, wherein the method is characterized by, The ligand is composed of an acid ligand and an amine ligand at a molar ratio of 2:1, and the concentration of the acid ligand in the precursor solution is 0.05-0.2 M. 4.The method of claim 1, wherein the method is characterized by, The preparation temperature of the precursor solution is 20-60 DEG C. 5.The method for preparing perovskite quantum dots using nano-transient precipitation according to claim 1, wherein, The staying is followed by a purification step.

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