Preparation and application of core-shell structure perovskite quantum dot material with peelable coating layer

Abstract

The application belongs to the technical field of nanometer luminescent materials, and particularly relates to a perovskite quantum dot material with a peelable coating layer structure and a preparation method thereof. (II) X3 is a core, and a low-dimensional peroviskite A4B (II) X6 / AB2 (II) X5 / A2B (IV) X6 / A3B (III) X6 is a shell layer, forming a core-shell structure; the low-dimensional peroviskite shell layer is peeled off through polar solvent washing, and then AB (II) X3 is a core. Through the core-shell protection and desorption peeling strategy, the shell layer is peeled off after the surface passivation and protection of the quantum dot core based on the shell layer, and the charge transmission in the device operation can be maximized, and the performance of the electroluminescent device is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of nanoluminescent materials technology, specifically a perovskite quantum dot material with a peelable coating structure, its preparation method, and its application in electroluminescent devices, active matrix displays, quantum dot lasers, and fluorescent conversion photovoltaic cells. Background Technology

[0002] Perovskite quantum dots (PQDs) have emerged as a candidate material for next-generation displays and lighting due to their advantages such as high color purity, high luminous efficiency, and solution-processability. However, small-sized AB... (II) X3 quantum dots have a high surface defect density, making them prone to ligand detachment, quantum dot aggregation, phase transitions, and fluorescence quenching during purification, film formation, and service. This results in unstable performance, leading to a roll-off in device efficiency and a reduction in lifetime, making it difficult to meet high device performance requirements.

[0003] To address size-dependent instability and limitations in achieving high device performance, researchers have explored various improvement strategies, including core-shell structure coating (such as polymer-coated AB). (II) X3, Oxide-coated AB (II) X3, Perovskite-coated AB (II) Methods such as X3, surface ligand modification (e.g., chelation or zwitterionic ligands), and surface chemical engineering (e.g., selective removal of defect-rich external components from PQDs using HCl or HI) are employed. However, these methods often suffer from the following problems: the shells of existing core-shell perovskite quantum dots are mostly irreversible coating structures, meaning the outer shell cannot be removed individually during subsequent use, ultimately leading to poor conductivity, charge injection imbalance, efficiency roll-off, and shortened lifetime in material applications; removing the shell often requires strong polar solvents, strong acids, or high-temperature treatment, which can easily cause lattice collapse of the core perovskite, a surge in surface defects, and even complete loss of quantum dot luminescence performance; the coating process causes energy level mismatch between the two materials, resulting in poor or even non-conductive conductivity of the shell, and the core-shell structure affects the charge transport performance of the intrinsic quantum dot material, thus affecting device performance and lifetime; furthermore, modified surface ligands are prone to detachment, and surface etching strategies are difficult to control.

[0004] Therefore, how to develop a method that can protect the perovskite quantum dot core from external environmental damage without affecting its intrinsic photoelectric transmission performance, thereby enabling the reliable construction of high-performance, long-life PQDs-based optoelectronic devices, has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of the above-described background technology, the present invention proposes a core-shell structured perovskite quantum dot material with a peelable coating layer and its preparation method, and studies its application in electroluminescent diode devices.

[0006] This invention employs a core-shell protection and desorption / stripping strategy. While performing surface passivation and protecting the quantum dot core based on the shell, the desorption of the shell maximizes charge transport during device operation. Specifically, a one-step method is used in AB... (II) A low-dimensional perovskite shell is grown in situ on the X3 surface. This shell not only confines the growth of the core quantum dot but also significantly improves the environmental stability of the quantum dot. In subsequent use, the surface shell is directionally peeled off by washing with a weakly polar solvent to obtain a light-emitting core AB with low defect density. (II) X3 quantum dot materials ultimately significantly improved the performance of electroluminescent devices.

[0007] The inventive concept of this invention is as follows:

[0008] Traditional perovskite quantum dots (PQDs) are difficult to form into shell structures through heterostructures due to their soft ionic crystal structure. However, with three-dimensional (3D) perovskite quantum dots (AB)... (II) X3 has a similar crystal structure to low-dimensional perovskite A4B. (II) X6 / AB2 (II) X5 / A2B (IV) X6 / A3B (III) X6 can effectively solve this problem. Low-dimensional perovskite, as a shell structure, can significantly improve the environmental tolerance of the core quantum dot material. Furthermore, due to its loose structure, low-dimensional perovskite can be exfoliated in an orderly manner using polar solvents, thereby exposing the core quantum dots, which possess high crystallinity, low defect density, and high luminescence performance, undamaged by the environment. Therefore, this invention utilizes three-dimensional (3D) perovskite quantum dots AB... (II) Using X3 as the core and also as a seed crystal, a one-step in-situ method was employed to grow low-dimensional perovskite A4B on the surface of quantum dots. (II) X6 / AB2 (II) X5 / A2B (IV) X6 / A3B (III) An X6 shell is used to prepare perovskite-coated perovskite heterojunction perovskite quantum dot luminescent materials, followed by ordered exfoliation of the low-dimensional perovskite shell using a weakly polar solvent. Compared to traditional shell-coated perovskite quantum dot materials, the low-dimensional shell strategy employed in this invention not only allows for more efficient generation of perovskite quantum dots with strong quantum confinement effects during growth due to the shell's confinement effect, but also effectively improves the environmental tolerance of the core quantum dots through the shell's passivation effect. Furthermore, the directional exfoliation using a polar solvent exposes quantum dot materials with low defect density, high luminescence performance, and high conductivity, enabling them to exhibit superior device performance in fields such as electroluminescence and photovoltaic cells.

[0009] Based on the above inventive concept, and to achieve the above objectives, the technical solution provided by this invention is as follows:

[0010] A core-shell perovskite quantum dot material with a peelable coating, using three-dimensional (3D) perovskite quantum dots AB (II) X3 is the core, with a low-dimensional perovskite A4B layer in situ coated on the surface. (II) X6 / AB2 (II) X5 / A2B (IV) X6 / A3B (III) The X6 shell forms a core-shell structure; the shell is peeled off by washing with a polar solvent, thus exposing the AB layer. (II) X3 core;

[0011] Wherein: A is a positively charged cation; B is one or more of transition metal ions or rare earth ions; X is one or more of negatively charged halide ions; and the polar solvent is one or more of methyl acetate, ethyl acetate, dimethyl carbonate, tert-butanol, acetonitrile, and acetone.

[0012] Further specifying, the monovalent cation is a cesium ion (Cs). + ), rubidium ions (Rb + ), methylamine ions (CH3NH3) + MA + ) and formamidinium ion (HC(NH2)2 + FA + One or more of the following; B is lead ion (Pb). 2+ ), tin ions (Sn) 2+ germanium ions (Ge) 2+ ), copper ions (Cu) + ), manganese ions (Mn) 2+ ), Bismuth ions (Bi 3+ ), antimony ions (Sb) 3+ ) and europium ions (Eu) 2+ One or more of the following; the monovalent halide ion is chloride ion (Cl... - ), bromide ions (Br) - ) and iodide ions (I - One or more of the following.

[0013] Further specifying, the shell layer is pre-formed in the precursor through the dissolution of ligands to form a precursor solution of BX / BX2 / BX3-ligand coordination compound containing BX / BX2 / BX3 nanoclusters; then reacts with A ligand coordination compound to grow in situ on the core surface; the precursor solvent is generally an inert solvent; the ligand is an organic molecule containing coordinating functional groups.

[0014] Furthermore, the thickness of the shell is controlled by adjusting the molar ratio of BX / BX2 / BX3 nanoclusters to BX / BX2 / BX3-ligand coordination compounds at a ratio of 0.1:1 to 4:1.

[0015] A method for preparing the core-shell structured perovskite quantum dot material with a peelable coating layer includes the following steps:

[0016] Step 1: Prepare a precursor solution of BX / BX2 / BX3-ligand coordination compound containing BX / BX2 / BX3 nanoclusters;

[0017] Step 2: Core-shell perovskite quantum dots were prepared by mixing an A-ligand coordination compound precursor solution with a BX / BX2 / BX3-ligand coordination compound precursor solution containing BX / BX2 / BX3 nanoclusters using a hot-injection or room-temperature ligand-assisted reprecipitation method.

[0018] Step 3: Wash the core-shell perovskite quantum dots at least once with a polar solvent to obtain the core-shell perovskite quantum dots.

[0019] Further specifying, step 2, the preparation of core-shell perovskite quantum dots using the hot-injection method, specifically includes the following processes:

[0020] A precursor solution of BX / BX2 / BX3-ligand coordination compound containing BX / BX2 / BX3 nanoclusters was prepared by controlling the content of ligands. The A-ligand coordination compound precursor solution was injected into the BX / BX2 / BX3-ligand coordination compound precursor solution containing BX / BX2 / BX3 nanoclusters at a molar ratio of A:B = 1.5:1 to 2.5:1. The reaction was terminated in an ice-water bath after 5 to 60 s to obtain core-shell perovskite quantum dots.

[0021] Further specifying, step 2, the preparation of core-shell perovskite quantum dots using the room-temperature ligand reprecipitation method, specifically includes the following processes:

[0022] A precursor solution of BX / BX2 / BX3 ligand coordination compounds containing BX / BX2 / BX3 nanoclusters was prepared by controlling the content of ligands. Under room temperature conditions, the A-ligand coordination compound precursor solution was injected into the BX / BX2 / BX3-ligand coordination compound precursor solution containing BX / BX2 / BX3 nanoclusters at a molar ratio of A:B = 1.5:1 to 2.5:1. Subsequently, the mixed solution was injected into an antisolvent, and the rapid nucleation and crystallization at room temperature was triggered based on the solubility difference between the good solvent and the antisolvent to generate core-shell perovskite quantum dots.

[0023] Further specifying, after step 3, the following steps are also included: adding a polar solvent to the core-shell structured perovskite quantum dot material, selectively exfoliating the shell layer to obtain perovskite quantum dots through a polar solvent exfoliation strategy, and dispersing them in a non-polar good solvent.

[0024] Applications of core-shell perovskite quantum dot materials with peelable coatings as photoelectric conversion materials in the fabrication of electroluminescent devices, active matrix displays, quantum dot lasers, and fluorescent conversion photovoltaic cells.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. This invention utilizes low-dimensional perovskite A4B (II) X6 / AB2 (II) X5 / A2B (IV) X6 / A3B (III) X6 serves as a shell-coated three-dimensional (3D) perovskite quantum dot AB (II) The X3 core was used to construct a perovskite / perovskite homogeneous core-shell quantum dot material. Subsequently, the low-dimensional perovskite shell was orderly desorbed and peeled off using a weakly polar solvent, thereby exposing the highly crystallinity, low defect density AB core. (II) The X3 core retains the same luminescence peak position after in-situ desorption and stripping of the quantum dots. This homogeneous core-shell structure design effectively solves the technical challenges of soft core quantum dot lattice, high lattice mismatch between shell and core phases, and difficulty in controllably constructing heterogeneous core-shell structures.

[0027] 2. This invention utilizes a one-step method to develop luminescent perovskite quantum dots AB. (II) In-situ growth of low-dimensional perovskite A4B on X3 surface (II) X6 / AB2 (II) X5 / A2B (IV) X6 / A3B (III) Compared with existing methods (which mostly employ two or more steps, first preparing the core quantum dots and then coating the shell through secondary dispersion, ligand exchange, etc.), the X6 shell requires no additional post-processing steps, significantly shortens the preparation cycle, reduces reagent consumption and quantum dot loss, and improves yield while being more suitable for large-scale production.

[0028] 3. The perovskite / perovskite homogeneous core-shell quantum dots of different dimensions prepared in this invention possess a unique in-situ growth control mechanism: during the nucleation and growth stages of the luminescent core quantum dots, the low-dimensional perovskite shell is simultaneously generated and continuously consumes the precursor solution in the system, thereby forming a growth confinement effect on the luminescent core quantum dots. This growth confinement effect can effectively suppress the excessive growth of the luminescent core particles, allowing the size of the core quantum dots to be easily controlled to below their exciton Bohr radius, thus endowing the core-shell structure quantum dot material with significant quantum confinement characteristics.

[0029] 4. The present invention utilizes a dense, low-dimensional perovskite shell grown in situ to form a dual effect of physical barrier and chemical passivation. On the one hand, it isolates external corrosive factors such as water, oxygen, light, and heat, inhibiting ion migration and phase separation of the core quantum dots. On the other hand, the coordinating groups of the low-dimensional perovskite shell can precisely passivate dangling bonds and vacancy defects on the core surface, reducing non-radiative recombination centers. Compared with core-shell quantum dots prepared by traditional methods, the product of the present invention has a higher fluorescence quantum yield, a narrower emission peak width, and significantly improved stability under long-term storage, light exposure, or humid and hot environments.

[0030] 5. In the one-step in-situ growth process of this invention, the thickness, dimensionality, and composition (A4B) of the low-dimensional shell can be controlled by adjusting parameters such as the proportion of precursors, ligand concentration, reaction temperature, and injection system. (II) X6 / AB2 (II) X5 / A2B (IV) X6 / A3B (III) The ratio of X6 allows for targeted control of the band gap, emission wavelength, and carrier transport characteristics of core-shell quantum dots, thus solving the problems of difficult shell parameter control, uneven shell thickness, and composition deviation in traditional multi-step methods.

[0031] 6. Existing core-shell perovskite quantum dots often have irreversible shell structures. Removing these shells typically requires strong polar solvents, strong acids, or high temperatures, which can easily cause lattice collapse of the core perovskite, a surge in surface defects, and even complete loss of the quantum dot's luminescence properties. This invention utilizes a low-dimensional perovskite shell with a weak interaction interface between it and the 3D perovskite core. By using a weak polar solvent to solvate the shell, the bonding force between the shell and the core is precisely disrupted, achieving complete and non-destructive exfoliation of the shell. Furthermore, the exfoliated 3D perovskite core retains its original crystal structure and photoelectric properties.

[0032] 7. The core-shell perovskite quantum dots prepared by this invention have excellent stability and can be stored stably in environmental conditions for a long time, making them suitable for perovskite optoelectronic conversion devices with low requirements for conductivity. When the shell is peeled off, the core quantum dot material with high luminescence performance and low defect density is exposed, making it suitable for constructing perovskite light-emitting diode devices. It can also be used for high-resolution displays and high-brightness lighting driven by active matrix, thereby broadening the application scenarios of perovskite quantum dots in high-end optoelectronic devices.

[0033] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0034] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0035] Figure 1 A schematic diagram of the synthesis and shell desorption process of perovskite quantum dots with a peelable core-shell structure;

[0036] Figure 2 High-resolution transmission electron microscopy (HRTEM) comparison images of perovskite quantum dots before and after shell peeling;

[0037] Figure 3 A comparison of transmission electron microscopy (TEM) images of perovskite quantum dots before and after shell peeling;

[0038] Figure 4 A comparison of the fluorescence and UV-Vis absorption spectra of perovskite quantum dots before and after shell exfoliation;

[0039] Figure 5 The X-ray diffraction (XRD) patterns of perovskite quantum dots before and after shell exfoliation;

[0040] Figure 6 This is a comparison chart of stability tests;

[0041] Figure 7 The image shows the current density-voltage-luminance-external quantum efficiency (JVL-EQE) curves of the core quantum dots after shell stripping applied to light-emitting diodes, and a schematic diagram of their application in active matrix perovskite quantum dot light-emitting diodes. Detailed Implementation

[0042] The present invention and the resulting technology will be clearly and completely described below with reference to embodiments, so as to fully understand the purpose and effects of the present invention. The embodiments described in detail below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0044] This invention provides a core-shell perovskite quantum dot material with a peelable coating, a preparation method thereof, and the application of the material in electroluminescent devices, active matrix displays, and fluorescent photovoltaic cells.

[0045] This invention utilizes a ligand regulation strategy to generate BX / BX2 / BX3 / BX4 nanoclusters in a precursor solution, and in AB... (II) X3 Quantum Dot Surface In-situ Growth A4B (II) X6 / AB2 (II) X5 / A2B (IV) X6 / A3B (III) X6 low-dimensional perovskite shells were used to construct perovskite / perovskite homojunction core-shell quantum dot materials with different dimensions, exhibiting excellent environmental stability. Furthermore, this low-dimensional perovskite shell can be gently desorbed and exfoliated using a weakly polar solvent washing strategy, exposing the highly crystallized, low-defect-density, and high-luminescence-performance AB core. (II) The X3 luminescent core enables an integrated "core-shell desorption" process. After the shell is peeled off, the core quantum dots can maintain their original lattice, size, and emission peak position, and can be stably dispersed in non-polar solvents such as hexane, octane, and toluene, making them suitable for the fabrication of high-performance perovskite photoelectric conversion devices.

[0046] See Figure 1 The present invention discloses a method for preparing a core-shell structured perovskite quantum dot material with a peelable coating layer, the specific steps of which are as follows:

[0047] First, a precursor solution containing BX / BX2 / BX3 / BX4 nanoclusters is prepared. Specifically, a precursor solution of BX / BX2 / BX3 / BX4-ligand coordination compound containing BX / BX2 / BX3 / BX4 nanoclusters is pre-formed in the precursor through the dissolution of ligands. The thickness of the shell is controlled by adjusting the molar ratio of BX / BX2 / BX3 / BX4 nanoclusters to BX / BX2 / BX3 / BX4-ligand coordination compound from 0.1:1 to 4:1.

[0048] Preferably, the precursor solvent is generally an inert solvent that has the functions of dispersing and stabilizing ligands and quantum dots. Common examples include octadecene, hexadecene, diphenyl ether, and phenyl ether-biphenyl eutectic.

[0049] Preferably, the ligand is an organic molecule containing a coordination functional group (one or more of common functional groups such as amino, carboxyl, phosphonic acid, and thiol groups), characterized by having dual functions: first, it achieves the dissolution and dispersion of BX / BX2 / BX3 powder by forming a coordination bond with B in BX through the functional group; second, it stabilizes the BX / BX2 / BX3 nanoclusters through coordination, providing uniform reaction sites for subsequent shell growth.

[0050] Next, after mixing the BX / BX2 / BX3 / BX4 precursor solution containing BX / BX2 / BX3 / BX4 nanoclusters with the A-site cation precursor, AB was preferentially generated. (II)X3 quantum dot core; subsequently, the remaining BX / BX2 / BX3 / BX4 nanoclusters and excess A-site precursors in the system, in AB (II) X3 quantum dots were used as seed crystals to grow A4B in situ on their surface. (II) X6 / AB2 (II) X5 / A2B (IV) X6 / A3B (III) X6 low-dimensional perovskite shell to prepare core-shell structured perovskite quantum dots.

[0051] Preferably, the core-shell perovskite quantum dots are prepared by a hot injection method. Specifically, this involves preparing a precursor solution of BX / BX2 / BX3 / BX4-ligand coordination compounds containing BX / BX2 / BX3 / BX4 nanoclusters by controlling the content of the injected ligands; injecting the A-site precursor solution into the precursor solution of BX / BX2 / BX3 / BX4-ligand coordination compounds containing BX / BX2 / BX3 / BX4 nanoclusters at a molar ratio of A:B of 1.5:1 to 2.5:1; terminating the reaction in an ice-water bath after 5 to 60 seconds to obtain core-shell perovskite quantum dots.

[0052] Preferably, a room-temperature ligand reprecipitation method is used to prepare core-shell perovskite quantum dots. Specifically, a precursor solution of BX / BX2 / BX3 / BX4-ligand coordination compounds containing BX / BX2 / BX3 / BX4 nanoclusters is prepared by controlling the content of injected ligands. Under room temperature conditions, the A-site precursor solution is injected into the precursor solution of BX / BX2 / BX3 / BX4-ligand coordination compounds containing BX / BX2 / BX3 / BX4 nanoclusters at a molar ratio of A:B = 1.5:1 to 2.5:1. Subsequently, the mixed solution is injected into an antisolvent, and core-shell perovskite quantum dots are rapidly crystallized.

[0053] Finally, wash at least once with a polar solvent to remove byproducts, and the product is obtained.

[0054] Furthermore, by adding a weakly polar solvent to the core-shell perovskite quantum dots, the directional desorption and exfoliation of the shell was achieved through the polar solvent, exposing the perovskite AB. (II) The X3 core remains unchanged after desorption and stripping of the quantum dot emission peak.

[0055] Preferably, the above-mentioned A4B (II) X6 / AB2 (II) X5 / A2B (IV) X6 low-dimensional perovskite and perovskite AB (II) In X3 quantum dots, A is a positively charged monovalent cation; B is one or more of transition metal ions or rare earth ions; and X is one or more of negatively charged monovalent halide ions.

[0056] Preferably, the positively charged cation is one or more of Cs ions, Rb ions, CH3NH3 ions and HC(NH2)2 ions; B is one or more of Pb ions, Sn ions, Ge ions, Cu ions, Mn ions, Bi ions, Sb ions and Eu ions; and the negatively charged halide ion is one or more of Cl ions, Br ions and I ions.

[0057] Preferably, the polar solvent is one or more selected from methyl acetate, ethyl acetate, dimethyl carbonate, tert-butanol, acetonitrile, and acetone.

[0058] The technical solution of the invention is described in detail with specific embodiments, and the technical effect of the invention is verified by performance testing.

[0059] It should be noted that, unless otherwise specified, the chemicals and reagents used in the following embodiments are all commercially available products commonly used in the field.

[0060] It should be noted that, unless otherwise specified, the operations and testing methods used in the following embodiments are conventional operations and existing standard testing methods in the art.

[0061] Example 1

[0062] This embodiment uses a hot-injection method to prepare core-shell perovskite quantum dot materials with a peelable coating layer. The specific steps are as follows:

[0063] Step 1: Preparation of Cs-OA precursor solution

[0064] 0.154 mmol (50 mg) of cesium carbonate (Cs₂CO₃) and 5 mL of octadecene (ODE) were added to a 50 mL three-necked flask; the mixture was placed under vacuum at 120 °C and continuously stirred for 1 h to degas. Then, 0.5 mL of pre-dehydrated oleic acid (OA) was added, and the system was heated to 150 °C under a nitrogen atmosphere. After the Cs₂CO₃ was completely dissolved, the Cs-OA precursor solution was obtained.

[0065] Step 2: Preparation of precursor solution containing PbI2 nanoclusters

[0066] A 50 mL three-necked flask was used as the reaction vessel. 0.188 mmol of lead iodide (PbI2) and 0.564 mmol of zinc iodide (ZnI2) solid powder were added to it sequentially. Then, 5 mL of ODE was injected, followed by the addition of 1.6 mL of oleic acid (OA) and 1.5 mL of oleylamine (OAm) as ligand dissolution precursors. The reaction system was placed at 120 °C under vacuum for 1 h to completely remove moisture and oxygen from the system, finally obtaining a clear and homogeneous pale yellow Pb-I-OAm precursor solution with PbI2 nanoclusters.

[0067] Step 3: Synthesis of core-shell perovskite quantum dots

[0068] The Pb-I-OAm precursor solution containing PbI2 nanoclusters from step 2 was heated to 165 °C and held at that temperature. 1 mL of a 0.125 mol / L Cs-OA precursor solution (prepared in step 1) was rapidly injected using a syringe. After reacting for 8 s, the reaction flask was immediately placed in an ice bath to quench to room temperature, thereby achieving the in-situ construction of the CsPbI3@CsPb2I5 core-shell structure and obtaining the reaction stock solution.

[0069] Step 4: Mix the reaction stock solution obtained in Step 3 with methyl acetate at a volume ratio of 1:3, place it in a centrifuge tube and centrifuge at 12000 rpm for 3 min. Discard the supernatant (containing unreacted precursors and free ligands), collect the bottom precipitate, and you will get high-purity core-shell perovskite quantum dot material, denoted as CsPbI3@CsPb2I5;

[0070] Step 5: Add 1 mL of hexane to the above core-shell structured quantum dot material, followed by slowly adding 4 mL of methyl acetate solution. At this time, the low-dimensional perovskite shell (CsPb2I5 shell) is selectively desorbed and peeled off due to solvation. Then, centrifuge the mixture at 12000 rpm for 3 min, discard the supernatant containing the peeled shell, and collect the bottom precipitate, which is the CsPbI3 core quantum dot.

[0071] In this embodiment, the performance of the prepared perovskite quantum dot material was tested.

[0072] Test 1

[0073] High-resolution transmission electron microscopy (HRTEM) images of perovskite quantum dots before and after shell peeling, as shown below. Figure 2 As shown.

[0074] from Figure 2 It can be seen that the boundary between the shell and the core of the perovskite quantum dots with a core-shell structure is clearly distinguishable; after the shell is peeled off, only the core quantum dots remain in the sample, and their size is basically the same as the core size in the core-shell structure.

[0075] Test 2

[0076] Transmission electron microscopy (TEM) comparison images of perovskite quantum dots before and after shell peeling, as shown below. Figure 3 As shown.

[0077] from Figure 3 It can be seen that both the core-shell perovskite quantum dots and the core quantum dots after the shell is removed exhibit a regular nanocubic morphology and a uniform particle size distribution; the size of the core quantum dots after the shell is removed is not much different from that of the core-shell quantum dots.

[0078] Test 3

[0079] Comparison of fluorescence and UV-Vis absorption spectra of perovskite quantum dots before and after shell peeling, as shown in the figure. Figure 4 As shown.

[0080] Depend on Figure 4 It can be seen that before the shell is peeled off, the spectrum clearly shows the exciton absorption peak and characteristic emission peak corresponding to the low-dimensional perovskite shell; after directional peeling, the characteristic peaks related to the shell completely disappear.

[0081] Test 4

[0082] X-ray diffraction (XRD) patterns of perovskite quantum dots before and after shell exfoliation, such as Figure 5 As shown.

[0083] Depend on Figure 5 It can be seen that in the quantum dot pattern of the core-shell structure before peeling, the low-dimensional perovskite shell and AB (II) The characteristic diffraction peaks of the X3 core quantum dot coexist; after shell-exfoliation, the characteristic peaks of the low-dimensional perovskite shell completely disappear, leaving only AB. (II) Characteristic diffraction peaks of the X3 core quantum dot.

[0084] The above performance tests show that the core-shell perovskite quantum dot material prepared in Example 1 can maintain its original lattice, size and emission peak position after the core quantum dot is peeled off. The core quantum dot has low defect density, high luminescence performance and high conductivity, and is suitable for preparing high-performance perovskite photoelectric conversion devices.

[0085] Comparative Example 1

[0086] This comparative example uses a hot-injection method to prepare core-shell-free perovskite quantum dot materials. Specific steps include:

[0087] Step 1: Add 0.188 mmol lead iodide (PbI2) and 0.564 mmol zinc iodide (ZnI2) to a three-necked flask containing 5 mL of octadecene (ODE). Degas the resulting mixture under vacuum at 120 °C for approximately 1 h; then, under a nitrogen atmosphere, sequentially inject 1.6 mL of pre-degassed oleic acid (OA) and 1.6 mL of pre-degassed oleylamine (OAm) into the flask. Continue heating to 165 °C to ensure complete dissolution of the precursors.

[0088] Step 2: Quickly inject 1 mL of the 0.125 mol / L Cs-OA precursor solution from Example 1 into the reaction mixture. The color of the precursor solution changes rapidly from pale yellow to bright red. After the reaction lasts for 5 seconds, quickly transfer the flask to an ice-water bath to cool to room temperature.

[0089] Step 3: Wash the material according to steps 4 and 5 in Example 1 to obtain a perovskite quantum dot material without a shell structure, denoted as CsPbI3.

[0090] The performance of the core-shell perovskite quantum dot material (CsPbI3@CsPb2I5) prepared in Example 1 and the perovskite quantum dot material (CsPbI3) prepared in Comparative Example 1 were tested.

[0091] Test 5

[0092] A comparison of the stability tests of CsPbI3@CsPb2I5 and CsPbI3 is shown in the figure. Figure 6 As shown.

[0093] from Figure 6 It is evident that core-shell perovskite quantum dots exhibit significantly better stability under heating, ultraviolet irradiation, and water-oxygen environments compared to perovskite quantum dots without core-shell structures.

[0094] Test 6

[0095] The current density-voltage-luminance-external quantum efficiency (JVL-EQE) curves of the core quantum dot after shell stripping of CsPbI3@CsPb2I5 in Example 1 and the CsPbI3 in Comparative Example 1 applied to a light-emitting diode are shown in the following figures. Figure 7 As shown in Figures (ab), devices fabricated from CsPbI3 quantum dots with the exfoliated shell exhibit superior electrical conductivity and electroluminescence properties compared to directly synthesized CsPbI3.

[0096] A schematic diagram of the application of the core quantum dot after the CsPbI3@CsPb2I5 shell was stripped in an active matrix perovskite quantum dot light-emitting diode, as shown in Example 1. Figure 7As can be seen from (cd), the perovskite quantum dot material prepared by this method can be applied to active matrix displays and has high resolution.

[0097] Example 2

[0098] This embodiment employs a ligand-assisted reprecipitation method to prepare core-shell perovskite quantum dot materials with exfoliable coating layers. Specific steps include:

[0099] Step 1: Preparation of Cs-OA precursor solution

[0100] The Cs-OA precursor solution was prepared by dissolving 0.154 mmol (50 mg) of cesium carbonate (Cs2CO3) in 0.5 mL of pre-dehydrated oleic acid (OA);

[0101] Step 2: Preparation of precursor solution containing PbI2 nanoclusters

[0102] 0.188 mmol PbI2 and 0.564 mmol ZnI2 were added to a mixed solution of 1.6 mL OA and 1.5 mL OAm. The solution was degassed under vacuum at 120 °C for 1 h to remove water and oxygen from the system. Finally, a clear and uniform pale yellow Pb-I-OAm precursor solution with PbI2 nanoclusters was obtained.

[0103] Step 3: Measure 0.1 mL of the Cs-OA precursor solution cooled to room temperature and quickly add it to the Pb-I-OAm precursor solution containing PbI2 nanoclusters that has been cooled to room temperature. Stir magnetically for 3-5 min at room temperature to ensure that the two systems are fully mixed and homogeneous.

[0104] Step 4: Accurately transfer 1 mL of the above-mentioned well-mixed precursor solution and quickly add it to 10 mL of toluene solution to prepare CsPbI3@CsPb2I5 core-shell perovskite quantum dots through antisolvent-induced crystallization process to obtain the reaction stock solution;

[0105] Step 5: Mix the reaction stock solution obtained in Step 4 with methyl acetate at a volume ratio of 1:3, place it in a centrifuge tube and centrifuge at 12000 rpm for 3 min. Discard the supernatant (containing unreacted precursors and free ligands), collect the bottom precipitate, and you will get high-purity core-shell perovskite quantum dot material, denoted as CsPbI3@CsPb2I5;

[0106] Step 6: Add 1 mL of hexane to the above core-shell quantum dot precipitate, followed by slowly adding 4 mL of methyl acetate solution. At this time, the low-dimensional perovskite shell (CsPb2I5 shell) is selectively desorbed and peeled off due to solvation. Centrifuge the mixture at 12000 rpm for 3 min, discard the supernatant containing the peeled shell, and collect the bottom precipitate, which is the CsPbI3 core quantum dot.

[0107] Comparative Example 2

[0108] This comparative example uses a ligand-assisted reprecipitation method to prepare core-shell-free perovskite quantum dot materials. The specific steps are as follows:

[0109] Step 1: Add 0.188 mmol PbI2 and 0.564 mmol ZnI2 to 1.6 mL of pre-degassed OA and 1.6 mL of pre-degassed OAM; continue heating to 165 °C to ensure complete dissolution of the precursors, and finally obtain a clear and homogeneous pale yellow Pb-I-OAm precursor solution with PbI2 nanoclusters;

[0110] Step 2: Take 0.1 mL of the Cs-OA precursor solution cooled to room temperature from Example 2 and quickly add it to the Pb-I-OAm precursor solution containing PbI2 nanoclusters that has been cooled to room temperature. Stir magnetically for 3-5 min at room temperature to ensure that the two systems are fully mixed and homogeneous.

[0111] Step 3: Accurately transfer 1 mL of the above-mentioned well-mixed precursor solution and quickly add it to 10 mL of toluene solution to prepare a shell-less perovskite quantum dot material, denoted as CsPbI3, through an antisolvent-induced crystallization process.

[0112] Example 3

[0113] This embodiment uses a hot-injection method to prepare core-shell perovskite quantum dot materials with peelable coatings of different shell thicknesses, specifically including the following steps:

[0114] Step 1: Preparation of precursor solution containing PbI2 nanoclusters

[0115] A 50 mL three-necked flask was used as the reaction vessel. 0.188 mmol of lead iodide (PbI2) and 0.714 mmol of zinc iodide (ZnI2) solid powder were added to it sequentially. Then, 5 mL of ODE was injected, followed by the addition of 1.6 mL of OA and 1.65 mL of OAm as ligand dissolution precursors. The reaction system was placed at 120 °C under vacuum for 1 h to completely remove moisture and oxygen from the system, finally obtaining a clear and homogeneous pale yellow Pb-I-OAm precursor solution containing PbI2 nanoclusters.

[0116] Step 2: Take the Pb-I-OAm precursor solution containing PbI2 nanoclusters from Step 1, heat it to 165 ℃ and keep it at that temperature; use a syringe to quickly inject 1 mL of the 0.125 mol / L Cs-OA precursor solution from Example 1. After reacting for 8 seconds, immediately place the reaction flask in an ice bath system to quench it to room temperature to achieve in-situ construction of the CsPbI3@CsPb2I5 core-shell structure and obtain the reaction stock solution;

[0117] Step 3: Wash the material as described in Step 4 of Example 1 to obtain high-purity core-shell perovskite quantum dot material, denoted as CsPbI3@CsPb2I5.

[0118] In the core-shell perovskite quantum dot material prepared in this embodiment, the thickness of the low-dimensional perovskite shell (CsPb2I5 shell) is slightly thicker than that in Example 1.

[0119] Example 4

[0120] This embodiment uses a hot-injection method to prepare core-shell perovskite quantum dot materials with peelable coatings of different shell thicknesses, specifically including the following steps:

[0121] Step 1: Preparation of precursor solution containing PbI2 nanoclusters

[0122] A 50 mL three-necked flask was used as the reaction vessel. 0.188 mmol of lead iodide (PbI2) and 0.864 mmol of zinc iodide (ZnI2) solid powder were added to it sequentially. Then, 5 mL of ODE was injected, followed by the addition of 1.6 mL of OA and 1.8 mL of OAM as ligand dissolution precursors. The reaction system was placed at 120 °C for vacuum degassing for 1 h to fully remove moisture and oxygen from the system, finally obtaining a clear and homogeneous pale yellow Pb-I-OAm precursor solution containing PbI2 nanoclusters.

[0123] Step 2: Take the Pb-I-OAm precursor solution containing PbI2 nanoclusters from Step 1, heat it to 165 ℃ and keep it at that temperature; use a syringe to quickly inject 1 mL of the 0.125 mol / L Cs-OA precursor solution from Example 1, react for 8 seconds, and immediately place the reaction flask in an ice bath to cool it to room temperature to achieve in-situ construction of the CsPbI3@CsPb2I5 core-shell structure;

[0124] Step 3: Wash the material as described in Step 4 of Example 1 to obtain high-purity core-shell perovskite quantum dot material, denoted as CsPbI3@CsPb2I5.

[0125] In the core-shell perovskite quantum dot material prepared in this embodiment, the thickness of the low-dimensional perovskite shell (CsPb2I5 shell) is slightly thicker than that in Example 3.

[0126] Example 5

[0127] This embodiment uses a ligand-assisted reprecipitation method to prepare core-shell perovskite quantum dot materials with peelable coatings of different shell thicknesses, specifically including the following steps:

[0128] Step 1: Preparation of PbI2 nanocluster precursor solution

[0129] 0.188 mmol PbI2 and 0.714 mmol ZnI2 were added to a mixed solution of 1.6 mL OA and 1.65 mL OAm. The solution was degassed under vacuum at 120 °C for 1 h to remove moisture and oxygen from the system, and a clear and uniform pale yellow Pb-I-OAm precursor solution containing PbI2 nanoclusters was finally obtained.

[0130] Step 2: Measure 0.1 mL of the Cs-OA precursor solution cooled to room temperature and quickly add it to the Pb-I-OAm precursor solution containing PbI2 nanoclusters that has been cooled to room temperature. Stir magnetically for 3-5 min at room temperature to ensure that the two systems are fully mixed and homogeneous.

[0131] Step 3: Accurately transfer 1 mL of the above-mentioned well-mixed precursor solution and quickly add it to 10 mL of toluene solution to prepare CsPbI3@CsPb2I5 core-shell perovskite quantum dots through antisolvent-induced crystallization process to obtain the reaction stock solution;

[0132] Step 4: Wash the material as described in Step 5 of Example 2 to obtain a core-shell perovskite quantum dot material with a peelable coating, denoted as CsPbI3@CsPb2I5.

[0133] In the core-shell perovskite quantum dot material prepared in this embodiment, the thickness of the low-dimensional perovskite shell (CsPb2I5 shell) is slightly thicker than that in Example 2.

[0134] Example 6

[0135] This embodiment uses a ligand-assisted reprecipitation method to prepare core-shell perovskite quantum dot materials with peelable coatings of different shell thicknesses, specifically including the following steps:

[0136] Step 1: Preparation of precursor solution containing PbI2 nanoclusters

[0137] 0.188 mmol PbI2 and 0.864 mmol ZnI2 were added to a mixed solution of 1.6 mL OA and 1.65 mL OAm. The solution was degassed under vacuum at 120 °C for 1 h to remove moisture and oxygen from the system. Finally, a clear and uniform pale yellow Pb-I-OAm precursor solution containing PbI2 nanoclusters was obtained.

[0138] Step 2: Measure 0.1 mL of the Cs-OA precursor solution cooled to room temperature and quickly add it to the Pb-I-OAm precursor solution containing PbI2 nanoclusters that has been cooled to room temperature. Stir magnetically for 3-5 min at room temperature to ensure that the two systems are fully mixed and homogeneous.

[0139] Step 3: Accurately transfer 1 mL of the above-mentioned well-mixed precursor solution and quickly add it to 10 mL of toluene solution to prepare CsPbI3@CsPb2I5 core-shell perovskite quantum dots through antisolvent-induced crystallization process to obtain the reaction stock solution;

[0140] Step 4: Wash the material as described in Step 5 of Example 2 to obtain a core-shell perovskite quantum dot material with a peelable coating, denoted as CsPbI3@CsPb2I5.

[0141] In the core-shell perovskite quantum dot material prepared in this embodiment, the thickness of the low-dimensional perovskite shell (CsPb2I5 shell) is slightly thicker than that in Example 5.

[0142] Example 7

[0143] This embodiment uses a hot-injection method to prepare core-shell perovskite quantum dot materials with a peelable coating layer. The specific steps are as follows:

[0144] Step 1: Preparation of precursor solution containing PbBr2 nanoclusters

[0145] A 50 mL three-necked flask was used as the reaction vessel. 0.188 mmol of lead bromide (PbBr2) and 0.564 mmol of zinc bromide (ZnBr2) solid powder were added to it sequentially. Then, 5 mL of ODE was injected, followed by the addition of 1.6 mL of OA and 1.5 mL of OAM as ligand dissolution precursors. The reaction system was placed at 120 °C under vacuum for 1 h to completely remove moisture and oxygen from the system, finally obtaining a clear and homogeneous pale yellow Pb-Br-OAm precursor solution containing PbBr2 nanoclusters.

[0146] Step 2: The Pb-Br-OAm precursor solution containing PbBr2 nanoclusters was heated to 165 °C and held at that temperature; 1 mL of the 0.125 mol / L Cs-OA precursor solution from Example 1 was rapidly injected using a syringe. After reacting for 8 s, the reaction flask was immediately placed in an ice bath to cool to room temperature, thereby achieving the in-situ construction of the CsPbBr3@CsPb2Br5 core-shell structure and obtaining the reaction stock solution.

[0147] Step 3: Wash the material as described in Step 4 of Example 1 to obtain high-purity core-shell perovskite quantum dot material, denoted as CsPbBr3@CsPb2Br5.

[0148] Example 8

[0149] This embodiment uses a hot-injection method to prepare core-shell perovskite quantum dot materials with a peelable coating layer. The specific steps are as follows:

[0150] Accurately measure 1.33 mL of the Cs-OA precursor solution from Example 1 and rapidly hot-pump it into the pale yellow Pb-I-OAm precursor solution containing PbI2 nanoclusters from Example 1. After reacting for 10 s, cool the mixture to room temperature using an ice-water bath to prepare the original quantum dot material with a CsPbI3@Cs4PbI6 core-shell structure. Wash according to step 4 in Example 1 to obtain high-purity core-shell perovskite quantum dot material, denoted as CsPbI3@Cs4PbI6.

[0151] Example 9

[0152] This embodiment uses a hot-injection method to prepare core-shell perovskite quantum dot materials with a peelable coating layer. The specific steps are as follows:

[0153] Accurately measure 1.33 mL of the Cs-OA precursor solution from Example 1 and rapidly inject it into the Pb-Br-OAm precursor solution with PbBr2 nanoclusters from Example 7. After reacting for 10 s, cool the mixture to room temperature using an ice-water bath. Wash the mixture according to step 4 in Example 1 to obtain high-purity core-shell perovskite quantum dot material, denoted as CsPbBr3@Cs4PbBr6.

[0154] It should be noted that the above performance tests were performed using the core-shell perovskite quantum dot material prepared in Example 1. When using the core-shell perovskite quantum dot materials prepared in Examples 2-9, or when the core-shell perovskite quantum dot materials prepared by replacing the ligands, A, B, X, polar solvent, and preparation parameters in Example 1 are used, the same performance as in Example 1 is exhibited.

[0155] The above are preferred embodiments of the present invention and should not be construed as limiting the technical solutions of the present invention. Any changes, modifications, substitutions and variations made by those skilled in the art to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A core-shell perovskite quantum dot material with a peelable coating layer, characterized in that, With three-dimensional perovskite AB (II) With X3 quantum dots as the core, a low-dimensional perovskite A4B layer is coated in situ on the surface. (II) X6 / AB2 (II) X5 / A2B (IV) X6 / A3B (III) The X6 shell forms a core-shell structure; the shell is peeled off by washing with a polar solvent, thus exposing the AB layer. (II) X3 core; Wherein: A is a positively charged cation; B is one or more of transition metal ions or rare earth ions; X is one or more of negatively charged halide ions; and the polar solvent is one or more of methyl acetate, ethyl acetate, dimethyl carbonate, tert-butanol, acetonitrile, and acetone.

2. The core-shell perovskite quantum dot material with a peelable coating layer according to claim 1, characterized in that, The monovalent cation is a cesium ion (Cs). + ), rubidium ions (Rb + ), methylamine ions (CH3NH3) + MA + ) and formamidinium ion (HC(NH2)2 + FA + One or more of the following; B is lead ion (Pb). 2+ ), tin ions (Sn) 2+ germanium ions (Ge) 2+ ), copper ions (Cu) + ), manganese ions (Mn) 2+ ), Bismuth ions (Bi 3+ ), antimony ions (Sb) 3+ ) and europium ions (Eu) 2+ One or more of the following; the monovalent halide ion is chloride ion (Cl... - ), bromide ions (Br) - ) and iodide ions (I - One or more of the following.

3. The core-shell perovskite quantum dot material with a peelable coating layer according to claim 1 or 2, characterized in that, The shell layer is pre-formed in the precursor solvent through the dissolution and coordination of ligands to form a precursor solution containing BX / BX2 / BX3-ligand coordination compounds containing BX / BX2 / BX3 nanoclusters; It is then mixed and reacted with A-ligand coordination compounds to form a shell layer in situ on the core surface; The precursor solvent is generally an inert solvent; the ligand is an organic molecule containing coordinating functional groups.

4. The core-shell perovskite quantum dot material with a peelable coating layer according to claim 3, characterized in that, The thickness of the shell is controlled by BX / BX2 / BX3 nanoclusters and BX / BX2 / BX3-ligand coordination compounds in a molar ratio of 0.1:1 to 4:

1.

5. A method for preparing a core-shell perovskite quantum dot material with a peelable coating as described in claim 4, characterized in that, Includes the following steps: Step 1: Prepare a precursor solution of BX / BX2 / BX3-ligand coordination compound containing BX / BX2 / BX3 nanoclusters; Step 2: Core-shell perovskite quantum dots were prepared by mixing an A-ligand coordination compound precursor solution with a BX / BX2 / BX3-ligand coordination compound precursor solution containing BX / BX2 / BX3 nanoclusters using a hot-injection or room-temperature ligand-assisted reprecipitation method. Step 3: Wash the core-shell perovskite quantum dots at least once with a polar solvent to obtain the core-shell perovskite quantum dots.

6. The preparation method according to claim 5, characterized in that, Step 2, which involves preparing core-shell perovskite quantum dots using the hot-injection method, specifically includes the following processes: A precursor solution of BX / BX2 / BX3-ligand coordination compound containing BX / BX2 / BX3 nanoclusters was prepared by controlling the content of ligands. The A-ligand coordination compound precursor solution was injected into the BX / BX2 / BX3-ligand coordination compound precursor solution containing BX / BX2 / BX3 nanoclusters at a molar ratio of A:B = 1.5:1 to 2.5:

1. The reaction was terminated in an ice-water bath after 5 to 60 s to obtain core-shell perovskite quantum dots.

7. The preparation method according to claim 5, characterized in that, Step 2, which involves preparing core-shell perovskite quantum dots using the room-temperature ligand reprecipitation method, specifically includes the following processes: A precursor solution of BX / BX2 / BX3 ligand coordination compound containing BX / BX2 / BX3 nanoclusters was prepared by controlling the content of ligands. Under room temperature conditions, the A-ligand coordination compound precursor solution was injected into the BX / BX2 / BX3-ligand coordination compound precursor solution containing BX / BX2 / BX3 nanoclusters at a molar ratio of A:B = 1.5:1 to 2.5:

1. The mixed solution was then injected into the antisolvent, and the difference in solubility between the good solvent and the antisolvent triggered rapid nucleation and crystallization at room temperature to generate core-shell perovskite quantum dots.

8. The preparation method according to claim 5, characterized in that, Following step 3, the following steps are also included: adding a polar solvent to the core-shell perovskite quantum dot material, selectively exfoliating the shell layer to obtain the core perovskite quantum dots through a polar solvent exfoliation strategy, and dispersing them in a non-polar good solvent.

9. The application of the core-shell perovskite quantum dot material with a peelable coating as described in claim 3 as a photoelectric conversion material in the fabrication of electroluminescent devices, active matrix displays, quantum dot lasers, and fluorescent conversion photovoltaic cells.

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