A method for preparing perovskite quantum dots by coupling microfluidics and supercritical carbon dioxide

Abstract

The application discloses a method for preparing perovskite quantum dots by coupling microfluidics and supercritical carbon dioxide, and belongs to the technical field of nanomaterial and optoelectronic material preparation. The method comprises the following steps: 1) dispersing A-site cation halide and B-site metal ion halide in a polar solvent until completely dissolved, adding a ligand, stirring until homogeneous, and forming a precursor solution; 2) preheating a micro-reaction zone and a reaction channel, increasing the pressure of a high-pressure injection pump connected with a CO2 cylinder to a specified pressure, and stabilizing the pressure; 3) simultaneously conveying the precursor solution in step 1) and supercritical carbon dioxide to the micro-reaction zone, and controlling the residence time of the mixed solution by flow rate; 4) obtaining a crude sample after quenching the product with different residence times in step 3) through a low-temperature reaction zone; and 5) obtaining a target product by purifying the obtained crude sample. The method is efficient and controllable, and the prepared perovskite quantum dots can be used in the field of display.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and optoelectronic materials preparation technology, and particularly relates to a method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide. Background Technology

[0002] Perovskite quantum dots (PQDs) possess excellent optoelectronic properties, including high photoluminescence quantum yield (PLQY), tunable emission wavelength, high color purity, and low operating threshold. They hold immense application potential in fields such as biology, solar cells, light-emitting diodes (LEDs), and lasers, attracting widespread attention and research. However, the poor dimensional stability, wide particle size distribution, and poor batch-to-batch reproducibility of the synthesis process of perovskite PQDs severely restrict their large-scale mass production and practical application. Therefore, achieving continuous fabrication of high-performance perovskite PQDs with controllable size and uniform particle size is a crucial technical challenge that urgently needs to be addressed. Currently, the mainstream methods for synthesizing perovskite quantum dots mainly include hot injection and ligand-assisted reprecipitation. Hot injection requires high-boiling-point solvents and an inert atmosphere. The precursor is rapidly injected into a high-boiling-point solution containing PbX2 and ligands, resulting in the uniform formation of crystal nuclei with a concentrated size distribution within a short time. Rapid cooling then prevents nucleus growth. However, hot injection, requiring high temperatures and an inert atmosphere, and necessitating rapid cooling, results in high operational costs and difficulty in controlling product quality, hindering large-scale production. Ligand-assisted reprecipitation involves adding a stoichiometric ratio of mixed metal halides to a polar solvent containing organic ligands at room temperature. After heating and vigorous stirring, a non-polar solvent is added, inducing nucleation and growth of perovskite quantum dots through a transient supersaturation state. While ligand-assisted reprecipitation exhibits ultrafast reaction kinetics, the dynamic evolution of the interface between the polar and non-polar systems directly affects the quality of crystallization, and the presence of locally high concentrations leads to poor batch reproducibility. These factors limit the widespread application of existing methods in industrial settings, necessitating the development of a novel method for the continuous preparation of perovskite quantum dots that offers high mixing efficiency, controllable reactions, stable product quality, and high batch reproducibility. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide (scCO2). This invention controls the growth of perovskite quantum dots by precisely controlling the fluid dynamics in a supercritical carbon dioxide environment, thereby preparing high-quality perovskite quantum dots.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide includes the following steps: Step 1: Disperse the A-site cation halide and the B-site metal ion halide together in a polar solvent until completely dissolved, add the ligand and stir the solution until homogeneous to form a precursor solution; Step 2: Preheat the micro-reaction zone and reaction channel, and pressurize the high-pressure injection pump connected to the CO2 cylinder to the specified pressure to stabilize the pressure. Step 3: The precursor solution from Step 1 and supercritical carbon dioxide are simultaneously introduced into the micro-reaction zone, and the residence time of the mixed solution is controlled by controlling the flow rate. Step 4: The products with different residence times are quenched and grown in a low-temperature reaction zone to obtain a crude sample; Step 5: Purify the sample obtained in Step 4 to obtain the perovskite quantum dots.

[0005] The principle of this invention: This invention effectively solves the problems of low mixing efficiency, uncontrollable nucleation process, wide particle size distribution, and poor batch reproducibility in traditional liquid-phase synthesis processes. The microchannel reaction zone utilizes microscale flow channels to enhance mass and heat transfer, giving the precursor solution and supercritical CO2 high diffusion capacity and adjustable solubility characteristics, improving reactant transfer efficiency and reducing local concentration differences. Furthermore, this invention employs a continuous flow system combined with a subsequent continuous low-temperature control region to improve the uniformity of quantum dot particle size. Moreover, the continuous operation mode adopted in this invention overcomes the difficulties in scale-up and insufficient reproducibility of traditional batch reactions, providing a new technical path for the efficient, controllable, and large-scale preparation of perovskite quantum dots.

[0006] Furthermore, in step one, after adding the ligand, the reaction temperature is 20~60 ℃.

[0007] Further, in step one, the polar solvent is selected from at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), isopropanol, 2-methoxyethanol (2ME), acetonitrile (ACN), and 2-pyrrolidone (2P).

[0008] Furthermore, in step one, the ligand is selected from two of oleic acid (OA), oleylamine (OAm), tri-n-octylphosphine (TOP), octadecylamine (ODA), dialcyldimethylammonium bromide (DDeA), and guanidine bromide (GuaBr).

[0009] Furthermore, when the ligands are oleic acid and oleylamine, their molar ratio is 2:1.

[0010] Furthermore, in step one, the concentration of the ligand in the precursor solution is 0.05~0.15 M.

[0011] Furthermore, in step two, the preheating temperature is 35~37 ℃.

[0012] Furthermore, in step two, after the supercritical carbon dioxide is introduced, the temperature is 35~90 ℃ and the pressure is 8~40 MPa.

[0013] Furthermore, in step two, the pressure of the high-pressure injection pump is 8~40 MPa.

[0014] Furthermore, in step three, the dwell time is 5-15 seconds.

[0015] Furthermore, in step four, the temperature of the low-temperature reaction zone is 5~15 ℃.

[0016] This invention also provides a quantum dot synthesis system for implementing the above method, comprising a precursor container, a carbon dioxide cylinder, a high-pressure injection pump, a microreactor zone, a low-temperature reaction zone, and a reservoir. The system is arranged according to a feed-mixing reaction-temperature control-product collection flow. The precursor container and the CO2 cylinder are located on the left side, serving as two active feed paths. The CO2 cylinder is connected to the high-pressure injection pump to provide a stable high-pressure supercritical CO2 flow. The precursor solution and supercritical carbon dioxide are simultaneously injected into the microreactor zone to achieve quantum dot nucleation and growth reactions. The outlet of the microreactor zone is connected to the downstream low-temperature reaction zone, where cooling stops quantum dot growth. Finally, the reaction products are collected in the reservoir at the end.

[0017] Furthermore, in the quantum dot synthesis system for implementing the above method, the precursor container is used to store and transport the solution; the carbon dioxide cylinder is used to provide the supercritical carbon dioxide reaction medium. The microreaction zone is used for the nucleation and growth of perovskite quantum dots; The low-temperature reaction zone is used to stop the growth of quantum dots; The reservoir is used to store the synthesized perovskite quantum dot solution.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects: This invention uses supercritical carbon dioxide as an antisolvent, enabling the preparation of perovskite quantum dots under mild and environmentally friendly conditions, avoiding the use of toxic antisolvents in traditional methods. Microfluidics allows for precise control of the size and optical properties of quantum dots by accurately adjusting parameters such as flow rate and residence time. The use of supercritical fluids reduces viscosity, enhances mass transfer, and provides high repeatability, making it easy to achieve industrial-scale continuous production. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A diagram of a perovskite quantum dot device for supercritical CO2 coupled microfluidic control. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] Embodiments of the present invention provide a method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide, comprising the following steps: Step 1: Disperse the A-site cation halide and the B-site metal ion halide together in a polar solvent until completely dissolved, add the ligand and stir the solution until homogeneous to form a precursor solution; Step 2: Preheat the micro-reaction zone and reaction channel, and pressurize the CO2 cylinder to the specified pressure using a high-pressure injection pump, and stabilize the pressure (preferably for 3 minutes). Step 3: The precursor solution from Step 1 and supercritical carbon dioxide are simultaneously introduced into the micro-reaction zone, and the residence time of the mixed solution is controlled by controlling the flow rate. Step 4: The products with different residence times are quenched and grown in a low-temperature reaction zone to obtain a crude sample; Step 5: Purify the sample obtained in Step 4 to obtain perovskite quantum dots.

[0026] In a preferred embodiment of the present invention, in step one, the molar ratio of the A-site cation halide to the B-site metal ion halide is (3~7.2):(3~6).

[0027] In a preferred embodiment of the present invention, in step one, the A-position cation halide is selected from lead formamidinium bromide (FABr), lead methylamine bromide (MABr), bromide (CsBr), CsI, or CsCl, and the B-position cation halide is selected from lead bromide (PbBr2), PbI2, or PbCl2.

[0028] In a preferred embodiment of the present invention, in step one, after adding the ligand, the reaction temperature is 20~60 ℃.

[0029] In a preferred embodiment of the present invention, in step one, the polar solvent is selected from at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), isopropanol, 2-methoxyethanol (2ME), acetonitrile (ACN), and 2-pyrrolidone (2P).

[0030] In a preferred embodiment of the present invention, in step one, the ligand is selected from any two of oleic acid (OA), oleylamine (OAm), tri-n-octylphosphine (TOP), octadecylamine (ODA), dialcyldimethylammonium bromide (DDeA), and guanidine bromide (GuaBr).

[0031] In a preferred embodiment of the present invention, when the ligands are oleic acid and oleylamine, the molar ratio of the two is 2:1.

[0032] In a preferred embodiment of the present invention, in step one, the concentration of the ligand in the precursor solution is 0.05~0.15 M.

[0033] In a preferred embodiment of the present invention, in step one, the stirring rate is 500 rpm and the stirring time is 1~40 min.

[0034] In a preferred embodiment of the present invention, in step two, the preheating temperature is 35~37 ℃, preferably 35.6 ℃.

[0035] In a preferred embodiment of the present invention, in step two, after supercritical carbon dioxide is introduced, the temperature is 35~90 ℃ and the pressure is 8~40 MPa.

[0036] In a preferred embodiment of the present invention, in step two, the pressure of the high-pressure injection pump is 8~40 MPa.

[0037] In a preferred embodiment of the present invention, the dwell time in step three is 5 to 15 seconds.

[0038] In a preferred embodiment of the present invention, in step four, the temperature of the low-temperature reaction zone is 5~15 ℃.

[0039] The present invention also provides a quantum dot synthesis system for implementing the above method (structural schematic diagram shown in Figure 1). Figure 1 As shown in the diagram, the system includes a precursor container, a carbon dioxide cylinder, a high-pressure injection pump, a microreactor zone, a cryogenic reaction zone, and a reservoir. The system is arranged according to a feed-mixing-temperature control-product collection flow. The precursor container and CO2 cylinder are located on the left side, serving as two active feed paths. The CO2 cylinder is connected to the high-pressure injection pump to provide a stable high-pressure supercritical CO2 flow. The precursor solution and supercritical carbon dioxide are simultaneously injected into the microreactor zone to achieve quantum dot nucleation. The outlet of the microreactor zone connects to the downstream cryogenic reaction zone, where cooling stops quantum dot growth. Finally, the reaction products are collected in the reservoir at the end. Precursor containers are used for storing and transporting solutions; Carbon dioxide cylinders are used to provide supercritical carbon dioxide reaction media; The micro-reaction zone is used for the nucleation and growth of perovskite quantum dots; The low-temperature reaction zone is used to stop the growth of quantum dots; The reservoir is used to store the synthesized perovskite quantum dot solution.

[0040] In a preferred embodiment of the present invention, the microreaction zone employs a microchannel structure with a length of 500 mm and a width of 250 mm, including a 100 mm mixing zone and a 400 mm growth zone. The mixing zone is used for rapid mixing and nucleation of precursors, while the growth zone is used for quantum dot growth regulation. A low-temperature reaction zone is connected downstream of the microreaction zone, which features a temperature gradient of 5–15 °C along the sample flow direction to achieve precise control of the quantum dot growth process.

[0041] This invention solves the problems of high solvent contamination, difficulty in controlling the size of perovskite quantum dots, and wide size distribution of perovskite quantum dots in traditional methods. The specific steps of this method include: 1) dispersing A-site cation halides and B-site metal ion halides together in a polar solvent until completely dissolved, adding ligands and stirring until homogeneous to form a precursor solution; 2) preheating the micro-reaction zone and reaction channel, and pressurizing to a specified pressure using a high-pressure injection pump connected to a carbon dioxide cylinder, stabilizing the pressure; 3) simultaneously delivering the precursor solution from step 1) and supercritical carbon dioxide to the micro-reaction zone, controlling the residence time of the mixed solution by the flow rate; 4) quenching and growing the products from step 3) at different residence times in a low-temperature reaction zone to obtain a crude sample; 5) purifying the crude sample obtained in step 4) to obtain the target product, and storing the target product in a storage container. This method is efficient and controllable, and the prepared perovskite quantum dots can be used in fields such as displays.

[0042] Unless otherwise specified, the room temperature in this invention is 25±2 ℃.

[0043] All raw materials used in the embodiments of the present invention were obtained through commercial purchase.

[0044] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0045] The technical solution of the present invention will be further illustrated by the following embodiments.

[0046] Example 1 A method for preparing perovskite quantum dots (specifically CsPbBr3 quantum dots) by coupling microfluidics with supercritical carbon dioxide, comprising the following steps: (1) Preparation of precursor solution At 20 °C, 3 mmol lead bromide and 3 mmol cesium bromide were mixed with 80 mL N,N-dimethylformamide (DMF) and stirred until completely dissolved. Then, 8 mL oleylamine and 16 mL oleic acid were added, and the mixture was stirred at 500 rpm for 1 min to obtain the precursor solution.

[0047] (2) Equipment installation and commissioning The precursor solution was loaded into a 5 mL glass syringe and mounted on a high-precision syringe pump (accuracy ±0.3%). A PTFE tubing syringe with an inner diameter of 2.0 mm was used. The microreaction zone consisted of a channel 500 mm long and 250 mm wide, including a 100 mm mixing zone and a 400 mm growth zone. The temperature of the low-temperature reaction zone was adjusted to maintain a temperature of 5–15 °C from the inlet to the outlet.

[0048] (3) Preparation of CsPbBr3 quantum dots This embodiment employs a supercritical carbon dioxide coupled microchannel device to prepare perovskite quantum dots. First, the microreaction system is preheated to 35.6 °C, supercritical CO2 is introduced, and the pressure is adjusted to 10 MPa, maintaining this temperature and pressure for 3 min. Then, the precursor solution is delivered at a flow rate of 0.025 m / s and simultaneously introduced into the micromixing zone along with the supercritical CO2. After reacting in the microreaction zone for 5 s, a quantum dot dispersion is formed. The resulting product is then cooled in a low-temperature reaction zone at 5–15 °C, and subsequently collected in a storage tank and stirred at 850 rpm to obtain a stable, dispersed perovskite quantum dot solution.

[0049] (4) Separation and purification The collected product was transferred to centrifuge tubes and centrifuged at 4000 RCF for 4 min to remove unreacted large particles. The supernatant was collected, and three volumes of excess methyl acetate were added as a precipitant. After thorough mixing, the mixture was centrifuged at 8000 RCF for 8 min. The precipitated solid particles were collected, redispersed in toluene, and purified by centrifugation again. Finally, the purified CsPbBr3 quantum dots were dispersed in 8 mL of toluene and stored at 8 °C in the dark.

[0050] Example 2 A method for preparing perovskite quantum dots (specifically CsPbI3 quantum dots) using microfluidic coupling with supercritical carbon dioxide, comprising the following steps: (1) Preparation of precursor solution At 25 °C, since the CsI and PbI2 system has poor solubility in acetonitrile, 10 mL of DMSO was first placed in a 250 mL round-bottom flask, and 3.2 mmol of PbI2 was added. After complete dissolution, 3.0 mmol of CsI was added, and after complete dissolution, 90 mL of acetonitrile was added. After complete dissolution, tri-n-octylphosphine (final concentration 0.18 M) was added, and stirring was continued until clear and free of precipitate, yielding the precursor solution (hereinafter referred to as the solution).

[0051] (2) Equipment installation and commissioning: The solution was loaded into a 5 mL glass syringe, which was then mounted on a high-precision injection pump (accuracy ±0.3%). A PTFE tubing syringe with an inner diameter of 2.0 mm was used. The microreaction zone consisted of a 500 mm long and 250 mm wide channel, including a 100 mm mixing zone and a 400 mm growth zone. The temperature of the low-temperature reaction zone was adjusted to maintain a temperature of 5–15 °C from the inlet to the outlet.

[0052] (3) Preparation of CsPbI3 quantum dots This embodiment utilizes a supercritical carbon dioxide coupled microchannel device to prepare perovskite quantum dots. First, the microreaction system was preheated to 35.6 °C, supercritical CO2 was introduced, and the pressure was adjusted to 15 MPa, maintaining this temperature and pressure for 3 min. Subsequently, the precursor solution was delivered at a flow rate of 0.022 m / s and simultaneously introduced into the micromixing zone along with the supercritical CO2. After reacting in the microreaction zone for approximately 5 s, a quantum dot dispersion was formed. The resulting product was then cooled in a low-temperature reaction zone at a temperature controlled between 5 and 15 °C. It was subsequently collected in a storage tank and stirred at 850 rpm to obtain a stable, dispersed perovskite quantum dot solution.

[0053] (4) Separation and purification: The collected product was transferred to centrifuge tubes and centrifuged at 4000 RCF for 4 min to remove unreacted large particles. The supernatant was collected, and three volumes of excess methyl acetate were added as a precipitant. After thorough mixing, the mixture was centrifuged at 8000 RCF for 8 min. The precipitated solid particles were collected, redispersed in toluene, and purified by centrifugation again. Finally, the purified CsPbI3 quantum dots were dispersed in 8 mL of toluene and stored at 8 °C in the dark.

[0054] Example 3 A method for preparing perovskite quantum dots (specifically CsPbCl3 quantum dots) using microfluidic coupling with supercritical carbon dioxide, comprising the following steps: (1) Preparation of precursor solution Weigh 3.0 mmol CsCl and 3.2 mmol PbCl2 into a 250 mL round-bottom flask at 25 °C, and dissolve them in 100 mL DMF. Since chlorides dissolve slowly in DMF, stirring at 500 rpm and 60 °C for 40 min is necessary. After complete dissolution, cool to room temperature, add oleic acid (final concentration 0.12 M) and oleylamine (final concentration 0.06 M), and continue stirring until clear and free of precipitate to obtain the precursor solution (hereinafter referred to as the solution).

[0055] (2) Equipment installation and commissioning The solution was loaded into a 5 mL glass syringe, which was then mounted on a high-precision injection pump (accuracy ±0.3%). A PTFE tubing syringe with an inner diameter of 2.0 mm was used. The microreaction zone consisted of a 500 mm long and 250 mm wide channel, including a 100 mm mixing zone and a 400 mm growth zone. The temperature of the low-temperature reaction zone was adjusted to maintain a temperature of 5–15 °C from the inlet to the outlet.

[0056] (3) Preparation of CsPbCl3 quantum dots This embodiment utilizes a supercritical carbon dioxide-coupled microchannel device to prepare perovskite quantum dots. First, the microreaction system was preheated to 35.6 °C, supercritical CO2 was introduced, and the pressure was adjusted to 14 MPa, maintaining this temperature and pressure for 3 min. Subsequently, the precursor solution was delivered at a flow rate of 0.020 m / s and simultaneously introduced into the micromixing zone along with the supercritical CO2. After reacting in the microreaction zone for approximately 5 s, a quantum dot dispersion was formed. The resulting product was then cooled in a low-temperature reaction zone at a temperature controlled between 5 and 15 °C. It was subsequently collected in a storage tank and stirred at 850 rpm to obtain a stable, dispersed perovskite quantum dot solution.

[0057] (4) Separation and purification The collected product was transferred to centrifuge tubes and centrifuged at 4000 RCF for 4 min to remove unreacted large particles. The supernatant was collected, and three volumes of excess methyl acetate were added as a precipitant. After thorough mixing, the mixture was centrifuged at 8000 RCF for 8 min. The solid particles were collected, redispersed in toluene, and purified by centrifugation again. Finally, the purified CsPbCl3 quantum dots were dispersed in 8 mL of toluene and stored at 8 °C in the dark.

[0058] Example 4 A method for preparing perovskite quantum dots (FAPbBr3 quantum dots) by coupling microfluidics with supercritical carbon dioxide includes the following steps: (1) Preparation of precursor solution At 30 °C, 3.0 mmol of formamidinium lead bromide (FABr) and 3.2 mmol of PbBr2 were dissolved in 100 mL of DMF. Since FA-based perovskites have better thermal stability, the ligand concentration can be appropriately increased by adding octadecylamine (ODA, final concentration 0.18 M). The mixture was stirred at 500 rpm for 40 min at 60 °C until completely clear to obtain the precursor solution (hereinafter referred to as the solution).

[0059] (2) Equipment installation and commissioning The solution was loaded into a 5 mL glass syringe, which was then mounted on a high-precision injection pump (accuracy ±0.3%). A PTFE tubing syringe with an inner diameter of 2.0 mm was used. The microreaction zone consisted of a 500 mm long and 250 mm wide channel, including a 100 mm mixing zone and a 400 mm growth zone. The temperature of the low-temperature reaction zone was adjusted to maintain a temperature of 5–15 °C from the inlet to the outlet.

[0060] (3) Preparation of FAPbBr3 quantum dots This embodiment utilizes a supercritical carbon dioxide coupled microchannel device to prepare perovskite quantum dots. First, the microreaction system was preheated to 35.6 °C, supercritical CO2 was introduced, and the pressure was adjusted to 16 MPa, maintaining this temperature and pressure for 3 min. Subsequently, the precursor solution was delivered at a flow rate of 0.025 m / s and simultaneously introduced into the micromixing zone along with the supercritical CO2. After reacting in the microreaction zone for approximately 5 s, a quantum dot dispersion was formed. The resulting product was then cooled in a low-temperature reaction zone at a temperature controlled between 5 and 15 °C. It was subsequently collected in a storage tank and stirred at 850 rpm to obtain a stable, dispersed perovskite quantum dot solution.

[0061] (4) Separation and purification The collected product was transferred to centrifuge tubes and centrifuged at 4000 RCF for 4 min to remove unreacted large particles. The supernatant was collected, and three volumes of excess methyl acetate were added as a precipitant. After thorough mixing, the mixture was centrifuged at 8000 RCF for 8 min. The solid particles were collected, redispersed in toluene, and purified by centrifugation again. Finally, the purified FAPbBr3 quantum dots were dispersed in 8 mL of toluene and stored at 8 °C in the dark.

[0062] Example 5 A method for preparing perovskite quantum dots (MAPbBr3 quantum dots) by coupling microfluidics with supercritical carbon dioxide includes the following steps: (1) Preparation of precursor solution Weigh 3.0 mmol of methylamine lead bromide (MABr) and 3.62 mmol of PbBr2 at 25 °C, and dissolve them in a mixed solvent of 95 mL DMF and 10 mL isopropanol. Add oleic acid (final concentration 0.1 M) and oleylamine (final concentration 0.05 M), and stir at 500 rpm and 60 °C for 30 min to obtain the precursor solution (hereinafter referred to as the solution).

[0063] (2) Equipment installation and commissioning The solution was loaded into a 5 mL glass syringe, which was then mounted on a high-precision injection pump (accuracy ±0.3%). A PTFE tubing syringe with an inner diameter of 2.0 mm was used. The microreaction zone consisted of a 500 mm long and 250 mm wide channel, including a 100 mm mixing zone and a 400 mm growth zone. The temperature of the low-temperature reaction zone was adjusted to maintain a temperature of 5–15 °C from the inlet to the outlet.

[0064] (3) Preparation of MAPbBr3 quantum dots This embodiment utilizes a supercritical carbon dioxide-coupled microchannel device to prepare perovskite quantum dots. First, the microreaction system was preheated to 35.6 °C, supercritical CO2 was introduced, and the pressure was adjusted to 16 MPa, maintaining this temperature and pressure for 3 min. Subsequently, the precursor solution was delivered at a flow rate of 0.0254 m / s and simultaneously introduced into the micromixing zone along with the supercritical CO2. After reacting in the microreaction zone for approximately 5 s, a quantum dot dispersion was formed. The resulting product was then cooled in a low-temperature reaction zone at a temperature controlled between 5 and 15 °C. It was subsequently collected in a storage tank and stirred at 850 rpm to obtain a stable, dispersed perovskite quantum dot solution.

[0065] (4) Separation and purification The collected product was transferred to centrifuge tubes and centrifuged at 4000 RCF for 4 min to remove unreacted large particles. The supernatant was collected, and three volumes of excess methyl acetate were added as a precipitant. After thorough mixing, the mixture was centrifuged at 8000 RCF for 8 min. The solid particles were collected, redispersed in toluene, and purified by centrifugation again. Finally, the purified MAPbBr3 quantum dots were dispersed in 8 mL of toluene and stored at 8 °C in the dark.

[0066] Example 6 A method for preparing perovskite quantum dots (CsPbBr) by coupling microfluidics with supercritical carbon dioxide. 1.5 I 1.5 The preparation method of quantum dots is as follows: (1) Preparation of precursor solution Mixed halogen quantum dots were prepared to achieve wavelength modulation of emission. At room temperature, 1.5 mmol CsBr, 1.5 mmol CsI, 1.6 mmol PbBr2, and 1.6 mmol PbI2 were weighed and dissolved in 100 mL DMSO. Due to the complexity of the mixture, stirring at 500 rpm and 60 °C for 50 min was required to ensure complete dissolution. Guanidine bromide (final concentration 0.18 M) was added to obtain the precursor solution (hereinafter referred to as the solution).

[0067] (2) Equipment installation and commissioning The solution was loaded into a 5 mL glass syringe, which was then mounted on a high-precision syringe pump (accuracy ±0.3%). A PTFE tubing syringe with an inner diameter of 2.0 mm was used. The microreaction zone consisted of a 500 mm long and 250 mm wide channel, including a 100 mm mixing zone and a 400 mm growth zone. The temperature of the low-temperature reaction zone was adjusted to maintain a temperature of 5–15 °C from the inlet to the outlet.

[0068] (3) CsPbBr 1.5 I 1.5Quantum dot preparation This embodiment utilizes a supercritical carbon dioxide-coupled microchannel device to prepare perovskite quantum dots. First, the microreaction system was preheated to 35.6 °C, supercritical CO2 was introduced, and the pressure was adjusted to 16 MPa, maintaining this temperature and pressure for 3 min. Subsequently, the precursor solution was delivered at a flow rate of 0.0254 m / s and simultaneously introduced into the micromixing zone along with the supercritical CO2. After reacting in the microreaction zone for approximately 5 s, a quantum dot dispersion was formed. The resulting product was then cooled in a low-temperature reaction zone at a temperature controlled between 5 and 15 °C. It was subsequently collected in a storage tank and stirred at 850 rpm to obtain a stable, dispersed perovskite quantum dot solution.

[0069] (4) Separation and purification The collected product was transferred to centrifuge tubes and centrifuged at 4000 RCF speed for 4 min to remove unreacted large particles. The supernatant was collected, and three volumes of excess methyl acetate were added as a precipitant. After thorough mixing, the mixture was centrifuged at 8000 RCF speed for 8 min. The solid particles were collected, redispersed with toluene, and purified again by centrifugation. Finally, the purified CsPbBr... 1.5 I 1.5 The quantum dots were dispersed in 8 mL of toluene and stored at 8 °C in the dark.

[0070] Example 7 A method for preparing perovskite quantum dots (high-concentration CsPbCl3 quantum dots) by coupling microfluidics with supercritical carbon dioxide includes the following steps: (1) Preparation of precursor solution To increase yield, a high-concentration precursor solution was prepared. At room temperature, 6.0 mmol CsCl and 7.2 mmol PbCl2 were dissolved in 90 mL DMF, doubling the original concentration. The amounts of ligands were correspondingly increased: oleic acid (final concentration 0.18 M) and oleylamine (final concentration 0.09 M). The solution was stirred at 850 rpm and 60 °C for 45 min to ensure complete dissolution, yielding the precursor solution (hereinafter referred to as the solution).

[0071] (2) Equipment installation and commissioning The solution was loaded into a 5 mL glass syringe, which was then mounted on a high-precision syringe pump (accuracy ±0.3%). A PTFE tubing syringe with an inner diameter of 2.0 mm was used. The microreaction zone consisted of a 500 mm long and 250 mm wide channel, including a 100 mm mixing zone and a 400 mm growth zone. The temperature of the low-temperature reaction zone was adjusted to maintain a temperature of 5–15 °C from the inlet to the outlet.

[0072] (3) Preparation of high-concentration CsPbCl3 quantum dots This embodiment uses a supercritical carbon dioxide coupled microchannel device to prepare perovskite quantum dots. Due to the increased concentration, process parameters need to be adjusted. First, the microreaction system is preheated to 35.6 °C, supercritical CO2 is introduced and the pressure is adjusted to 15 MPa, and the system is stabilized at this temperature and pressure for 3 min. Then, the precursor solution is delivered at a flow rate of 0.02 m / s and simultaneously introduced into the micromixing zone along with the supercritical CO2. After reacting in the microreaction zone for approximately 5 s, a quantum dot dispersion is formed. The resulting product is then cooled in a low-temperature reaction zone at a temperature controlled between 5 and 15 °C, and subsequently collected in a storage tank and stirred at 850 rpm to obtain a stable, dispersed perovskite quantum dot solution.

[0073] (4) Separation and purification The collected product was transferred to centrifuge tubes and centrifuged at 4000 RCF for 4 min to remove unreacted large particles. The supernatant was collected, and three volumes of excess methyl acetate were added as a precipitant. After thorough mixing, the mixture was centrifuged at 8000 RCF for 8 min. The solid particles were collected, redispersed in toluene, and purified by centrifugation again. Finally, the purified CsPbCl3 quantum dots were dispersed in 8 mL of toluene and stored at 8 °C in the dark.

[0074] Example 8 A method for preparing perovskite quantum dots (high-concentration CsPbBr3 quantum dots) by coupling microfluidics with supercritical carbon dioxide includes the following steps: (1) Preparation of continuous preparation equipment To verify the continuous production capability of the process, a long-term continuous preparation experiment was conducted. A large-volume syringe (100 mL precursor) was used, along with the precursor solution from Example 1 and optimized conditions.

[0075] (2) Continuous preparation process This embodiment employs a supercritical carbon dioxide coupled microchannel device to prepare perovskite quantum dots. First, the microreaction system is preheated to 35.6 °C, supercritical CO2 is introduced, and the pressure is adjusted to 15 MPa, maintaining this temperature and pressure for 3 min. Subsequently, the precursor solution is delivered at a flow rate of 0.025 m / s and simultaneously introduced into the micromixing zone along with the supercritical CO2. After reacting in the microreaction zone for approximately 5 s, a quantum dot dispersion is formed. The resulting product is then cooled in a low-temperature reaction zone at a temperature controlled between 5 and 15 °C. It is then collected in a storage tank and stirred at 850 rpm to obtain a stable, dispersed perovskite quantum dot solution.

[0076] (3) Separation and purification The collected product was transferred to centrifuge tubes and centrifuged at 4000 RCF for 4 min to remove unreacted large particles. The supernatant was collected, and three volumes of excess methyl formate were added as a precipitant. After thorough mixing, the mixture was centrifuged at 8000 RCF for 8 min. The solid particles were collected, redispersed in toluene, and purified again by centrifugation. Finally, the purified CsPbBr3 quantum dots were dispersed in 8 mL of toluene and stored at 8 °C in the dark.

[0077] Example 9 A method for preparing perovskite quantum dots (high-concentration CsPbI3 quantum dots) by coupling microfluidics with supercritical carbon dioxide includes the following steps: (1) Preparation of precursor solution Weigh 6.0 mmol CsI and 6.4 mmol PbI2 into a 250 mL round-bottom flask at 25 °C, add 100 mL 2-methoxyethanol, and dissolve completely at room temperature. Then add dialcyldimethylammonium bromide (final concentration 0.18 M) and continue stirring until no precipitate is obtained to obtain the precursor solution.

[0078] (2) Equipment installation and commissioning: The solution was loaded into a 5 mL glass syringe, which was then mounted on a high-precision injection pump (accuracy ±0.3%). A PTFE tubing syringe with an inner diameter of 2.0 mm was used. The microreaction zone consisted of a 500 mm long and 250 mm wide channel, including a 100 mm mixing zone and a 400 mm growth zone. The temperature of the low-temperature reaction zone was adjusted to maintain a temperature of 5–15 °C from the inlet to the outlet.

[0079] (3) Preparation of CsPbI3 quantum dots This embodiment utilizes a supercritical carbon dioxide coupled microchannel device to prepare perovskite quantum dots. First, the microreaction system was preheated to 35.6 °C, supercritical CO2 was introduced, and the pressure was adjusted to 15 MPa, maintaining this temperature and pressure for 3 min. Subsequently, the precursor solution was delivered at a flow rate of 0.022 m / s and simultaneously introduced into the micromixing zone along with the supercritical CO2. After reacting in the microreaction zone for approximately 5 s, a quantum dot dispersion was formed. The resulting product was then cooled in a low-temperature reaction zone at a temperature controlled between 5 and 15 °C. It was subsequently collected in a storage tank and stirred at 850 rpm to obtain a stable, dispersed perovskite quantum dot solution.

[0080] (4) Separation and purification The collected product was transferred to centrifuge tubes and centrifuged at 4000 RCF for 4 min to remove unreacted large particles. The supernatant was collected, and three volumes of excess methyl acetate were added as a precipitant. After thorough mixing, the mixture was centrifuged at 8000 RCF for 8 min. The precipitated solid particles were collected, redispersed in toluene, and purified by centrifugation again. Finally, the purified CsPbI3 quantum dots were dispersed in 8 mL of toluene and stored at 8 °C in the dark.

[0081] To further illustrate the beneficial effects of the embodiments of the present invention, the following comparative examples are constructed.

[0082] Comparative Example 1 To verify the superiority of the method of this invention, a comparative experiment was conducted using the traditional ligand-assisted precipitation method: (1) Preparation of precursor solution At 20 °C, 3 mmol lead bromide and 3 mmol cesium bromide were mixed with 80 mL DMF and stirred until completely dissolved. Then, 8 mL of oleylamine and 16 mL of oleic acid were added, and the mixture was stirred for 1 min. A precursor solution (hereinafter referred to as solution) with the same concentration as in Example 1 was prepared.

[0083] (2) Traditional LARP preparation process: At 20 °C, accurately measure 10 mL of the solution using a syringe and inject it into the mixing zone. At the same time, introduce supercritical carbon dioxide to 10 MPa and mix at a stirring rate of 850 rpm for 25 min until the solution is clear and transparent.

[0084] (3) Collection and purification The collected product was transferred to centrifuge tubes and centrifuged at 4000 RCF for 4 min to remove unreacted large particles. The supernatant was collected, and three volumes of excess methyl acetate were added as a precipitant. After thorough mixing, the mixture was centrifuged at 8000 RCF for 8 min. The solid particles were collected, redispersed in toluene, and purified again by centrifugation. Finally, the purified CsPbBr3 quantum dots were dispersed in 8 mL of toluene and stored at 8 °C in the dark.

[0085] Comparative Example 2 This comparative example provides a method for preparing perovskite quantum dots. The difference from Example 1 is that it uses the traditional hot-injection method. The preparation process is as follows: (1) Preparation of cesium oleate precursor At 20 °C, 1 g Cs2CO3, 4 mL OA and 80 mL octadecene (ODE) were added to a three-necked flask, evacuated, and purged with nitrogen three times. The mixture was then stirred at 120 °C under nitrogen protection for 30 min until completely dissolved to obtain the cesium oleate precursor, which was kept at 155 °C for later use.

[0086] (2) Preparation of PbBr2 precursor 0.752 mmol PbBr2 and 80 mL ODE were added to a three-necked flask and stirred for 30 min under nitrogen protection at 120 °C. 1 mL OA and 1 mL OLAm were added until completely dissolved, and the temperature was raised to 180 °C to obtain the PbBr2 precursor.

[0087] (3) Thermal injection reaction 1.6 mL of cesium oleate precursor was rapidly injected into the PbBr2 precursor obtained in step (2), and the reaction was immediately quenched in an ice bath after 10 s to obtain CsPbBr3 quantum dots.

[0088] Comparative Example 3 This comparative example provides a method for preparing perovskite quantum dots. The difference from Example 1 is that supercritical CO2 is used as the antisolvent, and a ligand-assisted precipitation method is used to prepare perovskite quantum dots. The preparation process is as follows: (1) Preparation of PbBr2 precursor At 20 °C, 3 mmol of lead bromide was mixed with 100 mL of DMF, and 10.7 mL of oleylamine was added. The mixture was stirred vigorously until PbBr2 was completely dissolved. The mixture was then cooled to room temperature to obtain the PbBr2 precursor.

[0089] (2) Preparation of CsBr precursor At 20 °C, 3 mmol of cesium bromide was mixed with 100 mL of DMSO, and 20 mL of oleic acid was added. The mixture was stirred vigorously until completely dissolved and then cooled to room temperature. 10 mL of the solution was injected into the premixing vessel of the apparatus, and supercritical carbon dioxide was introduced to 10 MPa and stirred until homogeneous. This yielded the CsBr precursor.

[0090] (3) Preparation of CsPbBr3 quantum dots by supercritical CO2 and process detection: At 20 °C, 25 mL of toluene was injected into the reactor. A homogeneous mixture of supercritical carbon dioxide and CsBr precursor was introduced into the reactor from the premixing vessel, and the pressure was increased to 10 MPa while stirring. The initial absorption baseline of the system was monitored using UV-vis spectroscopy.

[0091] The PbBr2 precursor from step (1) was pumped into 12 mL at a rate of 120 mL / min using a plunger pump. The mixture was stirred vigorously at 850 rpm for 10 s, and the redshift evolution of the UV-vis absorption peak was monitored in real time. The increasing intensity trend of the PL emission spectrum was also monitored simultaneously. After stirring was stopped for 5 s, the real-time particle size distribution was obtained by rapid DLS analysis.

[0092] After uniform nucleation and growth of the crystals, the pressure relief valve was opened to rapidly release pressure for 5 seconds. Spectral changes during the pressure relief process were monitored to ensure product stability. The collection vessel was then opened to obtain CsPbBr3 perovskite quantum dots.

[0093] Comparative Example 4 This comparative example provides a method for preparing perovskite quantum dots. The difference from Example 1 is that toluene is used as the antisolvent, and microfluidic technology is employed to prepare the perovskite quantum dots. The preparation process is as follows: (1) Preparation of precursor solution At 20 °C, 3 mmol lead bromide and 3 mmol cesium bromide were mixed with 80 mL DMF and stirred until completely dissolved. Then, 8 mL oleylamine and 16 mL oleic acid were added, and the mixture was stirred at 500 rpm for 1 min to obtain the precursor solution (hereinafter referred to as the solution).

[0094] (2) Equipment installation and commissioning The solution was loaded into a 5 mL glass syringe. The syringes were then mounted on a high-precision injection pump (accuracy ±0.3%). A PTFE tubing syringe with an inner diameter of 2.0 mm was used. The mixing zone was 0.1 m. The micro-reaction zone consisted of a channel 400 mm long and 250 mm wide. A T-shaped device was used. Toluene entered from the two side channels, and the precursor entered from the main channel.

[0095] (3) Toluene was used as an antisolvent, and CsPbBr3 quantum dots were prepared by microfluidic control. The solution feed rate was set to 0.025 L / s, and toluene was fed at the same rate of 0.025 L / s. The syringe pump was started so that the solution and toluene entered the mixing zone at the same time, and the formation of perovskite quantum dots on the surface was achieved. The reaction solution was then passed into the micro-reaction zone, and the solution color gradually changed from transparent to green fluorescence. After 5 s, the sample was collected in a 50 mL beaker and stirred at a constant speed of 850 rpm to prevent agglomeration.

[0096] (4) Collection and purification The product was collected at the device outlet. Due to the low yield, continuous collection for 1 hour was required to obtain approximately 90 mL of product. During the preparation process, it was found that the microchannels were easily blocked by the formed quantum dots, necessitating frequent cleaning and maintenance of the equipment.

[0097] The perovskite quantum dots prepared in Examples 1-8 and Comparative Examples 1-4 were tested by TEM (average particle size calculated), PL peak position, PL half-width (FWHM), and photoluminescence quantum yield (PLQY). The results are shown in Table 1. Table 1 As shown in Table 1, all examples 1-9 of this invention successfully prepared high-quality perovskite quantum dots by changing the reaction reagents. Compared with the traditional LARP method (Comparative Example 1), the hot injection method (Comparative Example 2), the ligand-assisted precipitation method using supercritical CO2 as an antisolvent (Comparative Example 3), and the preparation of perovskite quantum dots using microfluidic technology (Comparative Example 4), the PLQY of the embodiments of this invention is significantly improved. Among them, the PLQY of the organic-inorganic hybrid systems FAPbBr3 and MAPbBr3 (Examples 4 and 5) are 91% and 85%, respectively, and the mixed halogen CsPbBr... 1.5 I 1.5 (Example 6) PLQY can reach 81%.

[0098] Examples 1-9 of this invention, by changing the reaction reagents, yielded perovskite quantum dots with excellent size and luminescence uniformity. Compared to traditional LARP (Comparative Example 1), ligand-assisted precipitation with supercritical CO2 as the antisolvent (Comparative Example 3), and microfluidic technology (Comparative Example 4), the perovskite quantum dots prepared in the examples of this invention exhibit more uniform size distribution and narrower emission half-width. This invention possesses better reproducibility, is environmentally friendly and continuous, is more suitable for mass production, and has significant process advantages and industrial potential.

[0099] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide, characterized in that, Includes the following steps: Step 1: Disperse the A-site cation halide and the B-site metal ion halide together in a polar solvent until completely dissolved, add the ligand and stir the solution until homogeneous to form a precursor solution; Step 2: Preheat the micro-reaction zone and reaction channel, and pressurize the high-pressure injection pump connected to the CO2 cylinder to the specified pressure to stabilize the pressure. Step 3: Simultaneously transport the precursor solution from step 1) and supercritical carbon dioxide to the microreaction zone, and control the residence time of the mixed solution by the flow rate; Step 4: The products with different residence times are quenched and grown in a low-temperature reaction zone to obtain a crude sample; Step 5: Purify the sample obtained in Step 4 to obtain the perovskite quantum dots.

2. The method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide according to claim 1, characterized in that, In step one, after adding the ligand, the reaction temperature is 20~60 ℃.

3. The method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide according to claim 1, characterized in that, In step one, the polar solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, 2-methoxyethanol, acetonitrile, and 2-pyrrolidone; The ligand is selected from any two of oleic acid, oleylamine, tri-n-octylphosphine, octadecylamine, dialcyldimethylammonium bromide, and guanidine bromide.

4. The method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide according to claim 3, characterized in that, When the ligands are oleic acid and oleylamine, their molar ratio is 2:

1.

5. The method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide according to claim 1, characterized in that, In step one, the concentration of the ligand in the precursor solution is 0.02~0.15 M.

6. The method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide according to claim 1, characterized in that, In step two, the preheating temperature is 35~37 ℃.

7. The method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide according to claim 1, characterized in that, In step two, the pressure of the high-pressure injection pump is 8~40 MPa; after the supercritical carbon dioxide is introduced, the temperature is 35~90 ℃ and the pressure is 8~40 MPa.

8. The method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide according to claim 1, characterized in that, In step three, the dwell time is 5 to 15 seconds.

9. The method for preparing perovskite quantum dots by coupling microfluidics with supercritical carbon dioxide according to claim 1, characterized in that, In step four, the temperature of the low-temperature reaction zone is 5~15 ℃.

10. A quantum dot synthesis system for implementing the method according to any one of claims 1 to 9, characterized in that, The system includes a precursor container, a CO2 cylinder, a high-pressure injection pump, a microreactor zone, a cryogenic reaction zone, and a reservoir. The system is arranged according to a feed-mixing-temperature control-product collection flow. The precursor container and CO2 cylinder supply device are located on the left side, serving as two feed sources. The CO2 cylinder is connected to the high-pressure injection pump to provide a stable high-pressure supercritical CO2 flow. The precursor solution and supercritical carbon dioxide simultaneously enter the microreactor zone to achieve quantum dot nucleation and growth. The outlet of the microreactor zone connects to the downstream cryogenic reaction zone, where cooling stops quantum dot growth. Finally, the reaction products are collected in the reservoir at the end.

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