Zero-dimensional perovskite nanocrystal large-scale preparation process

Abstract

The invention belongs to the field of synthesis of nano materials, discloses a large-scale preparation process of zero-dimensional perovskite nanocrystals, and aims to solve the technical problems that an existing liquid phase method is complex in process, difficult to scale and poor in product purity and optical performance. The preparation method comprises the following steps: mixing a precursor with a core-shell structure with a dynamic functional solvent containing a temperature-sensitive phase separation eutectic solvent and a sublimable solid template, reacting in a continuous mechanical force chemical reaction device with multiple temperature zones, and coupling mechanical energy with a thermal field to obtain the temperature-sensitive phase separation eutectic solvent. The generation and size confinement of the nanocrystal and in-situ surface passivation guided by temperature-triggered phase separation are realized in sequence; and finally, the template is removed through vacuum sublimation to finish purification. According to the method, a plurality of steps are integrated, the process is simplified, the method is green and free of waste liquid, continuous and large-scale preparation of the high-quality nanocrystalline is achieved, and the product has high crystalline phase purity, uniform and controllable particle size and excellent optical performance.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial synthesis technology, specifically to a process for the large-scale preparation of zero-dimensional perovskite nanocrystals. Background Technology

[0002] Zero-dimensional inorganic lead halide perovskites, especially those represented by cesium lead bromide (Cs4PbBr5), have shown great application potential in cutting-edge technology fields such as solid-state lighting, high-definition displays, and high-energy ray scintillation detection due to their unique optical properties, such as excellent photoluminescence performance, high quantum yield, large Stokes shift, and better chemical stability compared to three-dimensional perovskites. They have become a hot topic in the field of optoelectronic materials research.

[0003] Currently, the mainstream methods for preparing high-quality zero-dimensional perovskite nanocrystals still heavily rely on traditional solution chemical synthesis routes, such as high-temperature thermal injection and ligand-assisted antisolvent precipitation. These methods typically involve dissolving metal halide precursors in specific organic solvents and inducing crystal nucleation and growth by injection or altering the solvent environment under precisely controlled temperature and atmosphere. However, these long-established liquid-phase synthesis methods have revealed a series of inherent and insurmountable defects in their progress towards practical application and industrial production.

[0004] Existing technological processes are often cumbersome and highly dependent on solvents, typically involving multiple separate unit operations such as reaction, centrifugation, repeated washing, and redispersion. The entire process is time-consuming and difficult to scale up continuously. This multi-step batch production model is not only inefficient, but also, during scale-up production, the non-uniformity of heat and mass transfer within the reactor is drastically amplified, leading to significant differences in particle size, morphology, and optical properties between different batches, making it difficult to guarantee quality uniformity. Furthermore, the reliance on large amounts of high-boiling-point, toxic organic solvents, and the large amounts of organic waste generated during purification, also pose serious environmental burdens and potential safety risks.

[0005] More importantly, at the technical level, existing methods have limited control over the reaction process. Prolonged reactions at high temperatures or drastic changes in the solvent environment make precise control of the reaction pathway difficult, often resulting in the formation of thermodynamically unstable intermediates or three-dimensional perovskite impurity phases with poor luminescence performance. This severely damages the crystal phase purity and optical properties of the final product. Furthermore, although adding organic ligands can passivate the nanocrystal surface to improve luminescence efficiency, this passivation effect is often unsatisfactory, and these surface ligands are easily detached during repeated centrifugation and washing, leading to decreased product performance and stability. Therefore, there is an urgent need to develop a novel, efficient, green, and easily scalable preparation technology to overcome the many bottlenecks of existing technologies and achieve the controllable preparation of high-quality zero-dimensional perovskite nanocrystals. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the defects in existing zero-dimensional perovskite nanocrystal preparation processes, such as reliance on large amounts of organic solvents, difficulty in achieving large-scale and continuous production, poor batch-to-batch repeatability, high production costs, and complex process flow.

[0007] To address the aforementioned technical problems, the first aspect of this invention provides a method for the continuous preparation of zero-dimensional perovskite nanocrystals.

[0008] The technical solution provided by this invention combines a specially designed core-shell structure precursor with a dynamic functional solvent system with phase separation characteristics, and uses mechanical energy to drive the reaction and temperature field to trigger in-situ passivation in a multi-temperature zone continuous mechanochemical reaction device. Finally, it is purified by a solvent-free method, thus constructing a complete, large-scale, green and environmentally friendly new paradigm for the preparation of zero-dimensional perovskite nanocrystals.

[0009] Specifically, the technical solution provided by this invention includes the following steps:

[0010] First, the reactants are prepared and designed. This step aims to pre-determine the microstructure and chemical environment of the reaction for subsequent continuous synthesis. In one specific embodiment, this step includes preparing a core-shell structured precursor powder. For example, cesium halide is used as the core and lead halide as the shell, prepared by dry methods such as solid-phase mechanical chemical coating. The technical mechanism of this core-shell structure design lies in the regional pre-organization of the two reactants at the microscale of individual particles, forming a well-defined reaction interface. When mechanical energy is subsequently applied, the reaction proceeds controllably from the shell to the core of the particle, thereby ensuring controlled local stoichiometry and creating favorable initial conditions for the precise generation of the target zero-dimensional crystalline phase and the suppression of impurity phases.

[0011] Simultaneously, this step also includes the preparation of a multifunctional, dynamically responsive phase-separated eutectic solvent. This solvent system consists of three key components: hydrogen bond donors, such as choline chloride, which form one of the components constituting the eutectic solvent framework; and hydrogen bond acceptors, such as long-chain carboxylic acids, which have a dual function. First, they serve as another component constituting the eutectic solvent; second, their long-chain alkyl structure allows them to act as surface passivation ligands for nanocrystals in subsequent steps.

[0012] Removable solid guest molecules, such as sublimable cyclic hydrocarbon molecules. The technical mechanism lies in the fact that these molecules, through steric hindrance, act as a "sacrificial" dynamic size control template during the reaction stage, filling the hydrogen bond network of the eutectic solvent, thereby physically confining and controlling the size of the generated nanocrystal nuclei.

[0013] The eutectic solvent system composed of the above two or more components has a key physicochemical property: the upper critical dissolution temperature. That is, below a certain temperature (e.g., the reaction temperature in the first temperature zone), the components are mutually soluble to form a homogeneous liquid phase; while above this temperature (e.g., the passivation temperature in the second temperature zone), the system undergoes phase separation and decomposes into two independent phases rich in different components.

[0014] Secondly, a continuous mechanochemical reaction and in-situ passivation are performed. This step is the core of the invention, achieving nanocrystal generation, size control, and surface passivation in a continuous process. In one specific embodiment, the core-shell structured precursor powder prepared in the previous step is mixed with the phase-separated eutectic solvent (e.g., at a ratio of 8–12 wt% of the total mass of the precursor powder) to obtain a reactant. Subsequently, the reactant is continuously fed into a mechanochemical reaction apparatus, such as a twin-screw extruder, at a preset rate (e.g., 15–40 g / min). This apparatus has at least two independently controllable temperature zones.

[0015] In the first temperature zone (reaction zone): the temperature is set below the upper critical dissolution temperature of the eutectic solvent (e.g., 25–35°C), where the eutectic solvent is a homogeneous liquid phase. Within this zone, a device (such as the screw of an extruder) applies strong mechanical energy (shearing, extrusion), driving the core-shell precursor to undergo a solid-state reaction at a controlled interface, generating nuclei for zero-dimensional perovskite nanocrystals. Simultaneously, the solid guest molecules dissolved in the homogeneous eutectic solvent phase provide the aforementioned size confinement control.

[0016] In the second temperature zone (passivation zone): the material is transported to this region, and the temperature is set above the upper critical dissolution temperature of the eutectic solvent (e.g., 55–65°C). The increase in temperature triggers phase separation in the eutectic solvent system. At this point, long-chain carboxylic acids, acting as hydrogen bond acceptors, accumulate from the system and form an independent nonpolar phase. Due to the hydrophobic surface of the newly formed perovskite nanocrystals, they are spontaneously and preferentially captured and coated by this nonpolar long-chain carboxylic acid phase, thus instantly achieving high-quality in-situ surface passivation. This mechanism cleverly utilizes the system's endogenous physicochemical phase transition, achieving an instantaneous and seamless connection between the reaction termination and surface passivation processes, effectively avoiding excessive growth or aggregation of nanocrystals.

[0017] Finally, solvent-free product purification is performed. This step aims to remove guest molecules that act as temporary templates during the reaction, obtaining a pure target product. In one specific embodiment, the reaction product obtained in the previous step is processed. Specifically, the product can be placed under vacuum and moderately heated (e.g., to a temperature near the sublimation point of the guest molecules), causing the solid guest molecules to sublimate directly and be removed from the product. Since this purification method does not require washing or centrifugation with any solvent, it fundamentally avoids the generation of organic waste liquid, simplifies the post-processing procedure, and preserves the original state of the product to the greatest extent possible.

[0018] In summary, by organically combining the above steps, especially by introducing a core-shell precursor and a phase-separable dynamic functional solvent system, and by utilizing multiple temperature zones in a continuous reaction apparatus to achieve spatiotemporal separation of reaction and passivation, this invention successfully constructs a novel method for preparing zero-dimensional perovskite nanocrystals that is efficient, green, controllable, and easily scalable.

[0019] This invention provides a process for the large-scale preparation of zero-dimensional perovskite nanocrystals. It has the following beneficial effects:

[0020] 1. This invention achieves a fundamental transformation from traditional batch-type reactors to continuous, large-scale production by employing a continuous mechanochemical reaction device. This method couples mechanical energy and precisely controlled thermal fields as the core driving force of the reaction, effectively overcoming the problem of uneven heat and mass transfer that is common in the scale-up production of traditional solution methods, thereby ensuring high stability of product quality and batch-to-batch consistency under industrial production conditions.

[0021] 2. This invention significantly improves the crystal phase purity and final optical quality of the target product through ingenious design of the reactant source. By pre-constructing a core-shell precursor with a specific microstructure, an ideal reaction path is predetermined at the individual particle scale, fundamentally suppressing the formation of impurity phases detrimental to luminescence performance. This technical feature ensures high reaction selectivity and is the structural basis for obtaining high-purity zero-dimensional perovskite.

[0022] 3. This invention innovatively designs and uses a multifunctional dynamic reaction medium that can trigger phase separation based on temperature changes during the reaction process, achieving "extraction-style" in-situ surface passivation of newly formed nanocrystals. This intelligent passivation process, completed by the reaction medium itself, can efficiently repair crystal surface defects, thereby significantly improving the photoluminescence efficiency and environmental stability of the product, which is impossible to achieve with traditional inert solvent systems.

[0023] 4. This invention greatly simplifies the process flow, highly integrating multiple key steps into a single continuous equipment. It cleverly couples several originally independent unit operations, such as nanocrystal generation, surface defect passivation and repair, and preliminary separation, into different functional sections of the reaction device for automatic completion. This "process enhancement" design significantly shortens the production cycle, reduces energy consumption and operational complexity, and eliminates the generation of organic waste liquid by eliminating the need for solvent washing, achieving green production throughout the entire process.

[0024] 5. This invention introduces a novel, orthogonal dimension for product performance regulation, greatly facilitating the customized production of materials. By adding removable solid guest molecules as "sacrificial" physical templates to the reaction system, the final nanocrystal size can be precisely controlled simply by adjusting the amount of these template molecules without altering the main process parameters. This innovative control method enhances the designability and flexibility of the process. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the specification of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: This example provides a method for preparing zero-dimensional perovskite nanocrystals, the specific steps of which are as follows:

[0027] (1) Preparation of core-shell structure precursor: Cesium bromide powder and lead bromide powder were placed in a zirconia ball mill jar at a molar ratio of 4.0:1.0, and zirconia grinding balls were added, with the ball-to-material mass ratio controlled at 17.5:1. Under an inert atmosphere, the mixture was ground for 2 hours using a planetary ball mill at a speed of 475 rpm to obtain core-shell structure precursor powder.

[0028] (2) Preparation of dynamic functional solvent system: Choline chloride and decanoic acid were mixed at a molar ratio of 1.0:2.0 and heated and stirred at 65°C to form a clear eutectic solvent. Subsequently, while stirring, the temperature was lowered and adamantane was added to make the molar ratio of adamantane to choline chloride 0.03:1.0. After stirring until completely dissolved, the mixture was cooled to room temperature for later use.

[0029] (3) Continuous Mechanochemical Synthesis of Zero-Dimensional Perovskite Nanocrystals: The precursor powder obtained in step (1) was mixed with the solvent system obtained in step (2) to make the solvent system account for 10 wt% of the total mass of the material, forming a uniform paste. The material was continuously fed into a co-rotating twin-screw extruder at a rate of 27.5 g / min, and the screw speed was set to 250 rpm. The temperatures of each zone of the extruder were set as follows: Zone 1 30℃, Zone 2 60℃, and Zone 3 25℃. The powdered coarse product was collected from the end of the extruder.

[0030] (4) Solvent-free purification of the product: The collected crude product powder was processed in a dynamic vacuum drying system. Under a vacuum of 0.3 mbar, the temperature was raised to 78 °C and maintained for 4 hours to allow the adamantane to sublimate and be removed. After the treatment, the final zero-dimensional perovskite nanocrystal dry powder was obtained.

[0031] Example 2

[0032] This embodiment provides a method for preparing zero-dimensional perovskite nanocrystals, the specific steps of which are as follows:

[0033] (1) Preparation of core-shell structure precursor: Cesium bromide powder and lead bromide powder were placed in a zirconia ball mill jar at a molar ratio of 4.0:1.0, and zirconia grinding balls were added, with the ball-to-material mass ratio controlled at 15:1. Under an inert atmosphere, the mixture was ground for 1 hour at a speed of 400 rpm using a planetary ball mill to obtain core-shell structure precursor powder.

[0034] (2) Preparation of dynamic functional solvent system: Choline chloride and decanoic acid (DA) were mixed at a molar ratio of 1.0:1.8 and heated and stirred at 60°C to form a clear eutectic solvent. Subsequently, while stirring, the temperature was lowered and adamantane was added to make the molar ratio of adamantane to choline chloride 0.01:1.0. After stirring until completely dissolved, the mixture was cooled to room temperature for later use.

[0035] (3) Continuous Mechanochemical Synthesis of Zero-Dimensional Perovskite Nanocrystals: The precursor powder obtained in step (1) was mixed with the solvent system obtained in step (2) to make the solvent system account for 8 wt% of the total mass of the material, forming a uniform paste. The material was continuously fed into a co-rotating twin-screw extruder at a rate of 15 g / min, and the screw speed was set to 150 rpm. The temperatures of each zone of the extruder were set as follows: Zone 1 25℃, Zone 2 55℃, and Zone 3 20℃. The powdered coarse product was collected from the end of the extruder.

[0036] (4) Solvent-free purification of the product: The collected crude product powder was processed in a dynamic vacuum drying system. Under a vacuum of 0.5 mbar, the temperature was raised to 70 °C and maintained for 3 hours to allow the adamantane to sublimate and be removed. After the treatment, the final zero-dimensional perovskite nanocrystal dry powder was obtained.

[0037] Example 3

[0038] This embodiment provides a method for preparing zero-dimensional perovskite nanocrystals, the specific steps of which are as follows:

[0039] (1) Preparation of core-shell structure precursor: Cesium bromide powder and lead bromide powder were placed in a zirconia ball mill jar at a molar ratio of 4.0:1.0, and zirconia grinding balls were added, with the ball-to-material mass ratio controlled at 20:1. Under an inert atmosphere, the mixture was ground for 3 hours using a planetary ball mill at a speed of 550 rpm to obtain core-shell structure precursor powder.

[0040] (2) Preparation of dynamic functional solvent system: Choline chloride and decanoic acid were mixed at a molar ratio of 1.0:2.2 and heated and stirred at 70°C to form a clear eutectic solvent. Subsequently, while stirring, the temperature was lowered and adamantane was added to make the molar ratio of adamantane to choline chloride 0.05:1.0. After stirring until completely dissolved, the mixture was cooled to room temperature for later use.

[0041] (3) Continuous Mechanochemical Synthesis of Zero-Dimensional Perovskite Nanocrystals: The precursor powder obtained in step (1) was mixed with the solvent system obtained in step (2) to make the solvent system account for 12 wt% of the total mass of the material, forming a uniform paste. The material was continuously fed into a co-rotating twin-screw extruder at a rate of 40 g / min, and the screw speed was set to 350 rpm. The temperatures of each zone of the extruder were set as follows: Zone 1 35℃, Zone 2 65℃, and Zone 3 30℃. The powdered coarse product was collected from the end of the extruder.

[0042] (4) Solvent-free purification of the product: The collected crude product powder was processed in a dynamic vacuum drying system. Under a vacuum of 0.1 mbar, the temperature was raised to 85°C and maintained for 5 hours to allow the adamantane to sublimate and be removed. After the treatment, the final zero-dimensional perovskite nanocrystal dry powder was obtained.

[0043] Comparative Example 1: Compared with Example 1, the difference is that adamantane was not added in step (2) when preparing the dynamic functional solvent system. The remaining steps are the same as in Example 1.

[0044] Comparative Example 2: Compared with Example 1, the difference is that in step (1), the core-shell structure precursor is not prepared. Instead, cesium bromide powder and lead bromide powder with a molar ratio of 4.0:1.0 are directly physically mixed and used. The remaining steps are the same as in Example 1.

[0045] Comparative Example 3: The difference from Example 1 is that a dynamic functional solvent system was not used. In step (3), the precursor powder obtained in step (1) was mixed with 10 wt% of octadecene, a conventional high-boiling-point solvent that does not have phase separation properties, to form a paste. The remaining steps were the same as in Example 1.

[0046] Comparative Example 4: Compared with Example 1, the difference is that the temperature of the second temperature zone of the twin-screw extruder in step (3) is also set to 30°C, which is the same as the temperature of the first temperature zone. The remaining steps are the same as in Example 1.

[0047] Comparative Example 5: Compared with Example 1, the solvent-free purification step (4) is omitted. The powdery crude product collected from the end of the extruder is the final product.

[0048] Test Example 1: Test on the Influence of Dynamic Guest Molecules on Product Size Uniformity

[0049] Experimental instructions

[0050] This test aims to verify the effectiveness of introducing removable solid guest molecules into a phase-separated eutectic solvent system in controlling the particle size and distribution of the final product in the method of this invention.

[0051] 1. Experimental Samples

[0052] Sample A: Zero-dimensional perovskite nanocrystal dry powder prepared and purified according to the complete steps of Example 1.

[0053] Sample B: Zero-dimensional perovskite nanocrystal dry powder prepared and purified according to the steps of Comparative Example 1 (i.e., without adding adamantane when preparing the solvent system).

[0054] 2. Experimental Procedure

[0055] Sample preparation: Accurately weigh 0.05 g of sample A and place it in 20 mL of anhydrous hexane. Use an ultrasonic cell disruptor (probe type, power set to 200 W) to sonicate the suspension for 2 minutes under ice-water bath conditions to ensure that the powder is fully dispersed.

[0056] Repeat the operation: Repeat step (1) on sample B to prepare the suspension to be tested.

[0057] Particle size testing: Transfer the suspension of sample A into the sample cell of the laser particle size analyzer and start the instrument for measurement. The instrument records and calculates the particle size distribution parameters of the sample, including D10, D50, D90, and the distribution width (Span). Each sample is measured three times, and the average value is taken.

[0058] Repeat test: After thoroughly cleaning the instrument tubing with anhydrous hexane, inject the suspension of sample B into the sample cell and repeat the test in step (3).

[0059] Experimental data

[0060] Table 1: Comparison of particle size distribution test data between Example 1 and Comparative Example 1

[0061] sample D10(μm) D50(μm) D90(μm) Particle size distribution width (Span) Example 1 0.64 0.88 1.21 0.65 Comparative Example 1 1.13 2.86 8.05 2.42

[0062] Experiment Summary

[0063] As can be clearly seen from the data in Table 1, the product prepared by the method of the present invention (Example 1) has a significantly smaller median D50 particle size than the product of Comparative Example 1, and its particle size distribution width (Span) is also much smaller than that of Comparative Example 1. This indicates that the product of Example 1 not only has finer particles, but also its size uniformity is greatly improved, and the particle size distribution of the product is more concentrated.

[0064] The technical mechanism behind this significant difference lies in the innovative introduction of removable solid guest molecules into the phase-separated eutectic solvent system. During the mechanochemical reaction stage in the first temperature region, these guest molecules, acting as dynamic templates, physically fill the hydrogen bond network of the eutectic solvent through steric hindrance, effectively confining the nascent perovskite nuclei. This confinement acts like setting up countless tiny "reaction cages" for the growth of nanocrystals, thereby inhibiting further growth of the nuclei and aggregation between particles.

[0065] In contrast, the reaction system of Comparative Example 1 lacked this crucial guest molecule, leading to uncontrolled growth and aggregation of the generated crystal nuclei under the continuous action of mechanical energy, ultimately forming large and highly unevenly distributed particles. Therefore, the test results strongly demonstrate that introducing specific, removable guest molecules as "sacrificial" templates into the reaction system is one of the core technical means of this invention to achieve precise control over the physical morphology (especially particle size and uniformity) of the final product, reflecting the advanced nature of this invention in reaction system design.

[0066] Test Example 2: Test on the Influence of Precursor Structure on the Crystal Phase Purity of the Product

[0067] Experimental instructions

[0068] This test aims to verify the decisive role of using a core-shell structured precursor in improving the crystal phase purity of the final product in the method of this invention.

[0069] 1. Experimental Samples

[0070] Sample C: Zero-dimensional perovskite nanocrystal dry powder prepared and purified according to the complete steps of Example 1 (using a core-shell precursor).

[0071] Sample D: Zero-dimensional perovskite nanocrystal dry powder prepared and purified according to the steps of Comparative Example 2 (using a simple physical mixture of powders as a precursor).

[0072] 2. Experimental Procedure

[0073] Sample preparation: Take approximately 100 mg of the dry powder from sample C and lightly grind it in an agate mortar to eliminate the influence of preferred particle orientation. The ground powder is then uniformly filled into the grooved sample holder of the powder X-ray diffractometer, and the surface is smoothed with a glass slide.

[0074] Repeat the operation: Repeat step (1) on sample D to prepare the sample to be tested.

[0075] Diffraction test: The sample holder of sample C was placed in an X-ray diffractometer. Using a Cu Kα radiation source (λ=1.5406Å), diffraction data were acquired in 0.02-degree steps within a 2θ scan range of 10 to 50 degrees.

[0076] in:

[0077] Cu Kα:

[0078] Note: Refers to the characteristic Kα X-ray radiation produced by a copper (Cu) target.

[0079] λ (Greek letter, Lambda):

[0080] Note: The symbol commonly used in physics to represent wavelength.

[0081] Å (Ångström, abbreviated as "Å"):

[0082] Note: A unit of length. It is defined as 1 Å = 10⁻¹⁰. -10 A meter (m) equals 0.1 nanometers (nm). This unit is very commonly used in crystallography and atomic physics because its size is comparable to the atomic radius and the interatomic spacing in a crystal.

[0083] Here, λ = 1.5406 Å precisely indicates that the wavelength of the Cu Kα X-rays used in the experiment is 1.5406 × 10⁻⁶ Å. -10 rice.

[0084] θ (Greek letter, Theta):

[0085] Note: In X-ray diffraction, the Bragg angle or incident angle specifically refers to the angle between the incident X-ray beam and the crystal plane that produces diffraction.

[0086] 2θ(Two-theta):

[0087] Note: The diffraction angle is the total angle between the direction of the incident X-ray beam and the direction of the diffracted beam, and its value is twice the Bragg angle θ. It is the abscissa of the XRD pattern.

[0088] Data Analysis and Repeat Testing: After the initial test, the sample holder was replaced with sample D, and the test was conducted under the exact same instrument parameters. The two sets of diffraction patterns were analyzed, and the intensities of the main characteristic peak of the zero-dimensional Cs4PbBr5 phase (located at 2θ ≈ 31.4°) and the characteristic peak of the three-dimensional CsPbBr3 impurity phase (located at 2θ ≈ 15.2°) were identified and integrated. The relative content of the impurity phase was calculated using the intensity ratio of the two peaks.

[0089] Experimental data

[0090] Table 2: X-ray diffraction data analysis of the products of Example 1 and Comparative Example 2

[0091] sample 3D impurity phase characteristic peak relative intensity (%) Example 1 0.7 Comparative Example 2 26.4

[0092] Experiment Summary

[0093] The test data in Table 2 clearly reveal that the content of the three-dimensional impurity phase in the product prepared using the method described in this invention (Example 1) is extremely low, almost negligible. In stark contrast, the product prepared using a simple physically mixed precursor (Comparative Example 2) exhibits a relative intensity of 26.4% for the three-dimensional impurity phase, indicating a serious problem of crystalline phase impurity. This result directly demonstrates the significant advantage of this invention in ensuring high product purity.

[0094] The underlying mechanism of this advantage lies in the pre-defined structure of the reactants at the microscopic scale. By preparing the reactants into a core-shell structure, this invention constructs an ideal reaction interface and controlled local stoichiometry at the scale of individual particles before the reaction begins. When mechanical energy drives the reaction, the reaction proceeds orderly from the lead-rich shell to the cesium salt core, which greatly ensures that the reaction pathway always develops in the direction of generating the target zero-dimensional Cs4PbBr5 phase.

[0095] In contrast, the simple physical mixing method used in Comparative Example 2 resulted in a macroscopic mixing of the two precursor powders in the reactor, while microscopically, numerous random, stoichiometrically imbalanced contact points existed. Under mechanical force, the reactions in these regions were disordered and uncontrollable, readily forming thermodynamically favorable three-dimensional CsPbBr3 impurity phases. Therefore, this test strongly confirms that the key innovation of this invention lies in designing and employing core-shell structured precursors, rather than simple physical mixtures, to control reaction selectivity from the source and ensure high crystalline phase purity of the final product.

[0096] Test Example 3: Test on the Influence of Phase Separation Solvent System on the Optical Properties of the Product

[0097] Experimental instructions

[0098] This test aims to verify the superiority of the dynamic functional solvent system with phase separation characteristics used in this invention in improving the optical performance of the final product.

[0099] 1. Experimental Samples

[0100] Sample E: Zero-dimensional perovskite nanocrystal dry powder prepared and purified according to the complete steps of Example 1 (using a phase-separated eutectic solvent).

[0101] Sample F: Zero-dimensional perovskite nanocrystal dry powder prepared and purified according to the steps of Comparative Example 3 (using the conventional high-boiling-point solvent octadecene to replace the phase separation eutectic solvent).

[0102] 2. Experimental Procedure

[0103] Sample preparation: Accurately weigh 20 mg of sample E and disperse it in 10 mL of anhydrous toluene to prepare a suspension with a concentration of 2 mg / mL.

[0104] Repeat the operation: Repeat step (1) for sample F to prepare a test suspension of the same concentration.

[0105] Optical testing: The suspension of sample E was placed in a fluorescence spectrometer equipped with an integrating sphere. The excitation wavelength was set to 365 nm, and the emission spectrum and the spectrum of excitation light not absorbed by the sample were measured. The instrument software automatically calculated and provided the photoluminescence quantum yield (PLQY) of the sample based on the measured number of photons.

[0106] Repeat test: Inject the suspension of sample F into the sample cell and repeat the test in step (3) under exactly the same instrument parameters. To ensure the accuracy of the results, three parallel samples from different batches were measured for each sample, and the average value was taken.

[0107] Experimental data

[0108] Table 3: Comparison of photoluminescence quantum yield of products from Example 1 and Comparative Example 3

[0109] sample Photoluminescence quantum yield (PLQY, %) Example 1 87.3 Comparative Example 3 13.8

[0110] Experiment Summary

[0111] Table 3 shows that the product prepared using the method of the present invention (Example 1) has a photoluminescence quantum yield of 87.3%, while the product of Comparative Example 3, which uses a conventional solvent, has a quantum yield of only 13.8%. The significant difference in optical properties between the two fully demonstrates the remarkable technical advantages of the method described in this invention in preparing high-quality luminescent materials.

[0112] The fundamental reason for this performance difference lies in the originality of the reaction medium designed in this invention. The phase-separated eutectic solvent used in this method is not merely a reaction carrier, but also an active actuator integrating passivation function. When the material enters the second temperature zone of the reaction device, the temperature rise triggers phase separation in the solvent system, causing long-chain carboxylic acids, acting as passivation ligands, to accumulate and precipitate from the system. The newly formed, hydrophobic perovskite nanocrystals are instantly captured and coated by the precipitated phase, and the defect states on their surface that would seriously affect luminescence efficiency are efficiently repaired instantaneously.

[0113] In contrast, the octadecene used in Comparative Example 3 is a chemically inert conventional solvent that only provides a site for the reaction but does not possess any surface passivation function. Therefore, the nanocrystals formed therein have numerous exposed defects on their surfaces. These defects become the main non-radiative recombination centers, causing most of the excitation energy to be consumed through non-luminescent pathways, ultimately resulting in extremely low photoluminescence efficiency. This test clearly demonstrates that designing and utilizing a temperature-sensitive phase-separation solvent system to achieve "in-situ passivation" is the core technical concept and key innovation of this invention for obtaining high-performance products.

[0114] Test Example 4: Test on the effect of temperature zone setting on in-situ passivation of products

[0115] Experimental instructions

[0116] This test aims to verify the key role of setting different temperature zones in the continuous reaction apparatus to trigger phase separation of the solvent system in achieving high-quality passivation of the product and improving its environmental stability in the method of the present invention.

[0117] 1. Experimental Samples

[0118] Sample G: Zero-dimensional perovskite nanocrystal dry powder prepared and purified according to the complete steps of Example 1 (the second temperature zone was set to 60 °C).

[0119] Sample H: Zero-dimensional perovskite nanocrystal dry powder prepared and purified according to the steps of Comparative Example 4 (the temperature of the second temperature zone is also set to 30 ℃, the same as the first temperature zone).

[0120] 2. Experimental Procedure

[0121] Initial optical performance test: Dry powders of sample G and sample H were taken respectively, and the initial photoluminescence quantum yield of the two sets of samples was measured at an excitation wavelength of 365 nm using a fluorescence spectrometer and its integrating sphere accessory.

[0122] Stability aging test: Two samples were pressed into thin sheets of the same thickness and diameter, and placed side by side in a constant temperature and humidity chamber. The chamber environment was set at a temperature of 45 ℃ and a relative humidity of 55%.

[0123] Timed monitoring: Samples were removed and their photoluminescence (PL) spectra were rapidly measured at 0, 24, 48, and 72 hours after the start of the test. The integrated intensity of the main emission peak of each sample was recorded under 365 nm excitation.

[0124] Data processing: The PL intensity of each sample at different time points is compared with its own initial (0-hour) intensity, and the retention rate of its relative photoluminescence intensity is calculated and recorded.

[0125] Experimental data

[0126] Table 4: Comparison of optical properties and stability of products under different temperature settings

[0127] sample Initial photoluminescence quantum yield (PLQY, %) Relative PL strength retention rate (%) after 72 hours Example 1 88.1 93.7 Comparative Example 4 21.3 15.2

[0128] Experiment Summary

[0129] The data in Table 4 clearly show that the product prepared using the multi-temperature zone setup described in this invention (Example 1) not only has a very high initial photoluminescence quantum yield, but also exhibits excellent stability under harsh humid and hot aging conditions. In contrast, the product of Comparative Example 4, prepared under isothermal conditions, already had very poor initial optical quality, and its luminescence intensity rapidly decayed during aging tests, almost completely failing.

[0130] This significant performance difference profoundly reveals the core mechanism of the multi-temperature zone thermal field design in this invention. This invention does not simply involve continuous production, but rather actively regulates the chemical reaction process by constructing a precisely controlled temperature gradient. In Example 1, the second temperature zone was intentionally set at a temperature higher than the phase separation critical point of the solvent system. This heating step acts as a "switch" for achieving high-quality in-situ passivation. The temperature increase precisely triggers phase separation in the solvent system, causing the long-chain carboxylic acid ligands to instantly accumulate and spontaneously coat the surface of the newly formed nanocrystals, thereby effectively repairing surface defects and endowing the product with excellent optical properties and resistance to environmental corrosion.

[0131] In contrast, Comparative Example 4, due to the failure of its second temperature zone to provide the energy input required to trigger phase separation (the temperature was too low), failed to activate the key role of the dynamic functional solvent system. Under these conditions, the passivating ligands could not be effectively precipitated from the system, and the nanocrystal surface remained in an unprotected or insufficiently passivated state. This directly resulted in poor initial optical quality, and in subsequent humid and hot environments, its surface defects would quickly become sites for attack by moisture and oxygen, triggering structural decomposition and luminescence quenching. Therefore, this test irrefutably demonstrates that constructing a specific, segmented temperature field in a continuous reaction device is the core technology driving the "in-situ passivation" key step in this invention, and is the key embodiment of the inventiveness of this method.

[0132] Test Example 5: Effect of Solvent-Free Purification Step on Final Product Purity

[0133] Experimental instructions

[0134] This test aims to verify the necessity and effectiveness of the solvent-free purification step included in the method of the present invention for removing guest molecules from the reaction system and ensuring the purity of the final product.

[0135] 1. Experimental Samples

[0136] Sample I: Zero-dimensional perovskite nanocrystal dry powder prepared according to the complete steps of Example 1 and after undergoing a final vacuum sublimation purification step.

[0137] Sample J: Prepared according to the steps of Comparative Example 5, i.e., crude product dry powder collected from the end of the extruder without any purification treatment.

[0138] 2. Experimental Procedure

[0139] Sample preparation: Accurately weigh approximately 8.0 mg of sample I and place it in a clean alumina crucible.

[0140] Thermogravimetric analysis (TGA) test: Place the crucible containing sample I into the thermogravimetric analyzer. Under nitrogen atmosphere protection (flow rate 50 mL / min), heat the sample from 30 ℃ to 400 ℃ at a heating rate of 10 ℃ / min, and record the mass change curve of the sample in real time.

[0141] Repeat the test: After the furnace body has cooled down, remove the crucible and clean it. Accurately weigh approximately 8.0 mg of sample J, place it in the crucible, and perform thermogravimetric analysis under the exact same conditions as in step (2).

[0142] Data Analysis: The percentage of total mass loss for both groups of samples before reaching 250 °C was analyzed. The mass loss in this range was primarily attributed to the removal of residual, volatile organic compounds.

[0143] Experimental data

[0144] Table 5: Comparison of Thermogravimetric Analysis (TGA) Data of Products from Example 1 and Comparative Example 5

[0145] sample Total mass loss (%) before 250 °C Example 1 0.11 Comparative Example 5 2.3

[0146] Experiment Summary

[0147] The test results in Table 5 clearly demonstrate that the product of Example 1, prepared according to the complete method of this invention, exhibits extremely high thermal stability, with only negligible mass loss before 250°C, proving its very high purity. In contrast, the product of Comparative Example 5, which did not undergo the final purification step, showed a significant mass loss of up to 2.3%, clearly confirming that it contained a large amount of organic residues.

[0148] The underlying mechanism of this result is directly related to the completeness and advancement of the process design in this invention. To achieve precise control over the nanocrystal size of the product, this invention creatively introduces a sublimable solid guest molecule as a "sacrificial" physical template into the reaction system. However, the introduction of this template molecule must be accompanied by an efficient removal method; otherwise, it will become an impurity in the final product. The vacuum sublimation purification step designed in this invention is a key step in completing this closed loop. Utilizing the significant difference in saturated vapor pressure between the guest molecule and the inorganic product, it can be selectively and completely vaporized and removed from the final product under gentle heating and vacuum conditions.

[0149] In contrast, Comparative Example 5, by omitting this crucial purification step, resulted in the guest molecule, which acted as a template during the reaction, being permanently embedded in the product matrix after the reaction, becoming an inherent impurity in the product. This test strongly demonstrates that the solvent-free purification step included in this invention is not a dispensable post-processing step, but an indispensable part of the entire innovative concept. It ensures that the functional additive can be completely removed after completing its phase, and is one of the core guarantees for this invention to achieve the concepts of "process enhancement" and "green and waste-free" production, and ultimately obtain a high-purity target product.

[0150] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for large-scale preparation of zero-dimensional perovskite nanocrystals, characterized in that, Includes the following steps: a. Mix the core-shell structured precursor powder with a phase-separating eutectic solvent containing hydrogen bond donors, hydrogen bond acceptors, and molecules capable of removing solid guest molecules to obtain the reactants. b. The reactants obtained in step a are continuously fed into a mechanochemical reaction device with at least two temperature zones. In the first temperature zone, mechanical energy is applied to drive the precursor reaction to generate the nuclei of the zero-dimensional perovskite nanocrystals. In the second temperature zone, where the temperature is higher than that of the first temperature zone, the eutectic solvent undergoes phase separation to complete the in-situ passivation of the nanocrystals and obtain the product. c. Process the product obtained in step b after the reaction to remove solid guest molecules, thereby obtaining the zero-dimensional perovskite nanocrystals.

2. The process for large-scale preparation of zero-dimensional perovskite nanocrystals according to claim 1, characterized in that, The preparation of the core-shell structured precursor powder described in step a includes the following sub-steps: a1. Cesium halide powder (as the core) and lead halide powder (as the shell) are placed together with grinding media in a ball mill jar according to a preset molar ratio. a2. In a planetary ball mill, the lead halide powder in step a1 is subjected to high-energy mechanical ball milling at a set rotation speed. a3. Through high-energy mechanical ball milling in step a2, a lead halide shell is formed on the surface of the cesium halide powder to obtain the precursor powder with the core-shell structure.

3. The process for large-scale preparation of zero-dimensional perovskite nanocrystals according to claim 1, characterized in that, The eutectic solvent for phase separation in step a consists of the following components: Choline chloride is used as a hydrogen bond donor; Long-chain carboxylic acids are used as hydrogen bond acceptors; The molar ratio of choline chloride to the long-chain carboxylic acid is from 1.0:1.8 to 1.0:2.

2.

4. The process for large-scale preparation of zero-dimensional perovskite nanocrystals according to claim 1, characterized in that, The removable solid guest molecule is a sublimable cyclic hydrocarbon molecule, which is used to control the size of the nanocrystals in the reaction.

5. The process for large-scale preparation of zero-dimensional perovskite nanocrystals according to claim 1, characterized in that, The mechanochemical reaction device is a twin-screw extruder.

6. The process for large-scale preparation of zero-dimensional perovskite nanocrystals according to claim 5, characterized in that, Within the first temperature zone, the temperature is controlled between 25°C and 35°C, and at this temperature, the eutectic solvent is a homogeneous liquid phase.

7. The process for large-scale preparation of zero-dimensional perovskite nanocrystals according to claim 3, characterized in that, Within the second temperature zone, the temperature is controlled between 55°C and 65°C, which is higher than the upper critical dissolution temperature of the eutectic solvent.

8. The process for large-scale preparation of zero-dimensional perovskite nanocrystals according to claim 7, characterized in that, Within the second temperature zone, the long-chain carboxylic acid precipitates from the phase separation system and coats the surface of the nanocrystals to complete passivation.

9. The process for large-scale preparation of zero-dimensional perovskite nanocrystals according to claim 4, characterized in that, The step of removing the solid guest molecules in step c is as follows: heating the product under vacuum conditions to sublimate and remove the guest molecules.

10. The process for large-scale preparation of zero-dimensional perovskite nanocrystals according to claim 1, characterized in that, In step a, the amount of the phase separation eutectic solvent added is 8% to 12 wt% of the total mass of the precursor powder, and in step b, the reactants are continuously fed into the reaction apparatus at a rate of 15 to 40 g / min.