Preparation path of hyperstable perovskite quantum dots

Abstract

The invention relates to the field of nano functional materials, and discloses a preparation path of a hyperstable perovskite quantum dot. An A site (containing at least two cations, and the molar ratio of FA < + > or MA < + > is greater than or equal to 50%), a B site (containing Mn < 2 + > and at least four metal cations, and the total molar ratio of the four metal cations is 25%-40%) and an X site (at least two anions) are selected to form an ABX3 type perovskite precursor. S2-S5 are sequentially subjected to ball-milling nucleation with a fluxing agent, reaction with lengthened-chain organic amine to form a layered structure, dispersing, reagent adding for reaction, centrifugal drying and reaction with maleic anhydride to form a coating layer, and the quantum dots are prepared. According to the technology, the performance of the perovskite quantum dots is comprehensively improved by virtue of unique material design and a preparation process. The environment stability is excellent, the photoelectric property is excellent, and the lead-free and environment-friendly effects and good biocompatibility are achieved; the method has the advantages of low process cost, high efficiency, strong stability and obvious advantages compared with the prior art.

Description

Technical Field

[0001] The present invention relates to the field of nano functional materials, and in particular to a preparation method of ultra-stable perovskite quantum dots. Background Art

[0002] Perovskite quantum dots, with their outstanding properties such as excellent luminescence efficiency and tunable band gap, have attracted considerable attention in recent years in fields such as optoelectronic displays and photovoltaics. In the optoelectronic display field, their outstanding luminescence performance is expected to lead to higher-quality displays; in the photovoltaic field, the tunable band gap provides new possibilities for improving solar energy conversion efficiency.

[0003] However, perovskite quantum dots still face many urgent challenges, which have severely restricted their commercialization and have kept them mainly in the laboratory research stage. The specific issues are as follows: 1. Stability Issues: Poor stability to moisture and light exposure stems primarily from their inherent structural and physicochemical properties. For one thing, the crystal structure contains defects and ions have diffusion characteristics; for another, their high surface energy makes them highly susceptible to environmental corrosion. Furthermore, at room temperature, perovskite quantum dots are in a thermodynamically metastable state and prone to phase transitions. While surface modification, doping, or alloying methods are currently being employed to improve stability, achieving a 10,000-hour lifespan remains difficult with a single approach.

[0004] 2. Toxicity issue: Although lead-containing perovskite quantum dots have the best performance and higher efficiency, their lead-containing properties are highly toxic, which greatly limits their widespread application in the commercial field.

[0005] 3. Lifespan: The current short lifespan of perovskite quantum dots requires improvements in packaging technology. Technically, perovskites must achieve an external quantum efficiency of at least 30% and a lifetime of 15,000-20,000 hours to meet the basic requirements for commercialization.

[0006] 4. Environmentally friendly perovskite efficiency issues: To address the toxicity of lead-containing perovskites, research is underway to develop hybrid, single-, or multi-doped lead-free, environmentally friendly perovskites. However, the efficiency of these lead-free, environmentally friendly perovskites remains low, not yet reaching mainstream levels and failing to meet the demands of practical applications.

[0007] Therefore, there is an urgent need for a perovskite quantum dot preparation path that combines structural stability, surface protection, and environmental friendliness to achieve ultra-long life and commercial applications. Summary of the Invention

[0008] The present invention aims to provide a systematic preparation path to solve the problems of poor environmental stability, high ion migration activity, easy phase change and lead toxicity of perovskite quantum dots, break through the existing lifespan bottleneck, improve their continuous working performance in extreme environments, and realize non-toxic, replaceable and ultra-stable perovskite quantum dot materials.

[0009] The present invention provides a preparation method of ultra-stable perovskite quantum dots, comprising the following steps: S1, select A-site cations and B-site metal cations to form an ABX3 type perovskite precursor, where: A-site cations include formamidinium (FA + ), cesium ions (Cs + ) and methylammonium (MA + ) and A is a cation FA + or MA + The molar proportion is ≥50%; the metal cation at the B position is Mn 2+ With Sn 2+ 、Bi 3+ 、Zn 2+ 、In 3+ There are at least four combinations of Sn 2+ 、Bi 3+ 、Zn 2+ 、In 3+ The total molar proportion of metal cations at the B position is 25%-40%; the X position is Cl - Br - , I - At least two of the following; S2, mixing the perovskite precursor with a flux at a mass ratio of 5:1, wherein the flux is choline chloride, using zirconium oxide grinding balls with a ball-to-material ratio of 15:1, and ball milling at a speed of 800-1000 rpm for 30 minutes under argon protection to directly form high-entropy perovskite crystal nuclei, with a particle size of ≤30 nm after ball milling; S3, adding a long-chain organic amine with a carbon chain length of C12-C18 to the product of step S2, and reacting at 180-200° C. for 0.5-1 hour to form a 2D / Ruddlesden–Popper (RP) type layered structure, wherein the molar ratio of the long-chain organic amine to the metal cation at the B site is 3:1-5:1; S4, dispersing the quantum dots obtained in step S3 in toluene, and sequentially adding trioctylphosphine oxide (TOPO), triphenylphosphine oxide (TPPO) and oleic acid, wherein the molar ratio of TOPO:TPPO:oleic acid is 1:0.5:2, stirring and reacting at 90° C. for 1 hour, and centrifugally drying to obtain quantum dot powder; S5. The quantum dot powder and maleic anhydride are mixed in a mass ratio of 8:1, and reacted in a vacuum at 130° C. for 20 minutes to form a polymaleic anhydride coating layer with a thickness of 2-5 nm.

[0010] Preferably, in step S1, the molar ratio of the metal cations at position B is Mn 2+ With Sn 2+ 、Bi 3+ 、Zn 2+ 、In 3+ =65:12:10:8:5.

[0011] Preferably, in step S2, the ball milling speed is 900 rpm, and the pressure of the inert gas argon filled in the ball milling tank is 0.5-1.0 MPa.

[0012] Preferably, step S4 further includes adding 0.1-0.5 wt % of fluorosilane to modify the surface of the quantum dots together with TOPO / TPPO to form a fluorinated hydrophobic layer.

[0013] Preferably, step S4 further includes adding 0.5 wt% of polytetrafluoroethylene (PTFE) nanoparticles to modify the surface of the quantum dots together with fluorosilane to form a multi-layer hydrophobic barrier with a contact angle of ≥150°.

[0014] Preferably, in step S3, the C12-C18 long-chain organic amine is selected from octadecylamine, hexadecylamine or dodecylamine.

[0015] Preferably, in step S3, the reaction temperature is 190° C., the reaction time is 40 minutes, and nitrogen is introduced as a carrier gas during the reaction at a flow rate of 10-20 mL / min.

[0016] Compared with the prior art, the present invention has the following beneficial effects: Ultra-long environmental stability: resistant to high temperature and humidity, extreme temperature cycles and salt spray erosion, and maintains good performance.

[0017] High-efficiency optoelectronic performance: high external quantum efficiency, excellent performance in the visible and near-infrared bands, wide color gamut, meeting ultra-high-definition display requirements.

[0018] Lead-free and environmentally friendly: It does not contain heavy metals such as lead and cadmium, meets environmental protection standards, has good biocompatibility, and is suitable for biological imaging.

[0019] Process cost advantage: high-energy ball milling one-step synthesis greatly shortens process time and reduces energy consumption; low-temperature process is suitable for low-cost flexible substrates, and mass production cost is low.

[0020] Multi-dimensional synergistic stabilization mechanism: Through strategies such as high entropy doping, two-dimensional RP structure, and super-hydrophobic composite layer, the material stability is effectively improved.

[0021] Commercial adaptability: It performs well in flexible devices and outdoor applications, is suitable for scenarios such as foldable displays, and has strong outdoor durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A roadmap for the preparation of ultra-stable perovskite quantum dots; Figure 2 This is the TEM image of the quantum dots in Example 1. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to specific embodiments. The illustrative embodiments and descriptions of the present invention are intended to explain the present invention but are not intended to limit the present invention.

[0024] Example 1: (Five-element high-entropy Mn-based quantum dots) 1. Specific steps: 1) Precursor preparation: Position A: FA + :Cs + =6:4 (molar ratio); B position: Mn 2+ :Sn 2+ :Bi 3+ :Zn 2+ :In 3+ =65:12:10:8:5 (total doping ratio 50%); X position: Br - :I - =7:3; add choline chloride (flux, 20% of the precursor mass).

[0025] 2) High-energy ball milling: zirconia grinding balls (ball-to-material ratio 15:1), argon pressure 0.8 MPa, 900 rpm, ball milling for 30 min, particle size 25 ± 3 nm.

[0026] 3) Two-dimensional layered construction: Add octadecylamine (molar ratio of 4:1 to metal cation at B site) and react at 190°C in nitrogen atmosphere for 40 minutes.

[0027] 4) Multi-ligand modification: TOPO:TPPO:oleic acid = 1:0.5:2 (molar ratio), add 0.5 wt% PTFE nanoparticles, and react at 90°C for 1 hour.

[0028] 5) In situ polymerization: Quantum dot powder and maleic anhydride were mixed in a mass ratio of 8:1, and reacted in a vacuum at 130°C for 20 minutes. The coating thickness was 3 nm.

[0029] 2. The test results are as follows: Double 85 test: PLQY remains at 86% after 10,000 hours; EQE: 28.5%; Heavy metals: lead and cadmium were not detected (ICP-MS detection limit 0.001 wt%); Hydrophobicity: contact angle 152°.

[0030] Example 2: (Quaternary High Entropy + Low-Temperature Rapid Synthesis) 1. Specific steps: Based on Example 1, B position: Mn 2+ :Sn 2+ :Bi 3+ :In 3+ =65:15:15:10 (total doping ratio 40%) The ball milling speed was 800 rpm for 30 minutes, the reaction temperature was 180°C, and the reaction time was 30 minutes.

[0031] 2. The test results are as follows: Double 85 test: PLQY remains at 83% after 9500 hours; EQE: 27.8%; Energy consumption: 40% lower than that of Example 1.

[0032] Example 3: (Six-element high entropy + super-hydrophobic reinforcement) 1. Specific steps: On the basis of Example 2, Sb is added to the B position. 3+ , B position: Mn 2+ :Sn 2+ :Bi 3+ :Zn 2+ :In 3+ :Sb 3+ =45:18:12:8:5:12 (total doping ratio 55%) Surface modification was performed by adding 1.0 wt% PTFE.

[0033] 2. The test results are as follows: Double 85 test: PLQY remains at 83% after 8800 hours; Contact angle: 158° (superhydrophobic); Salt spray test: PLQY remains at 82% after 1000 hours; EQE: 26.5%.

[0034] Comparative Example 1: (Single Mn doping, no high entropy effect) Step: B position contains only Mn 2+ , other conditions are the same as in Example 1.

[0035] The test results are as follows: EQE: 15.2% Dual 85 life: 1200 hours; XRD: impurity phases (MnI2, MnBr2) appear, and the crystallinity is poor.

[0036] Comparative Example 2: (Traditional ball milling + heat treatment process) Procedure: ball milling at 600 rpm for 6 hours, heat treatment at 200° C. for 2 hours, without adding PTFE, and other conditions were the same as in Example 1.

[0037] The test results are as follows: EQE: 21.5%; Particle size distribution: 30-80 nm (uneven); Energy consumption: 3 times that of Example 1.

[0038] Comparative Example 3: (No two-dimensional layered structure) Steps: octadecylamine was replaced with octylamine (C8), the molar ratio of organic amine to B-position metal was 1:1, and other conditions were the same as in Example 1.

[0039] The test results are as follows: Ion migration rate: 3.2 times that of Example 1; Dual 85 life: 2500 hours; TEM: The surface coating is discontinuous.

[0040] Comparison Data Table

[0041] Analysis Conclusion Necessity of high-entropy doping (Comparative Example 1 vs. Example 1): The five-element high-entropy design improves EQE by 88% and extends lifetime by 7 times, demonstrating the core role of multi-element synergy in stabilizing the lattice.

[0042] Advantages of high-energy ball milling (Comparative Example 2 vs. Example 1): Short-term high-energy ball milling (30 minutes) reduces energy consumption by 67% compared to the traditional process (6 hours + heat treatment), and significantly improves particle size uniformity.

[0043] Value of the two-dimensional layered structure (Comparative Example 3 vs. Example 1): The RP structure constructed with a long-chain organic amine (C18) reduced the ion migration rate by 68% and extended the lifetime by 3.4 times.

[0044] Super-hydrophobic enhancement (Example 3): PTFE+fluorosilane multi-layer modification makes the material super-hydrophobic, and its lifespan in salt spray environment is increased by 30%, making it suitable for marine equipment applications.

[0045] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A preparation method of ultra-stable perovskite quantum dots, characterized by: The following steps are involved: S1, select A-site cations and B-site metal cations to form an ABX3 type perovskite precursor, where: A-site cations include formamidinium (FA + ), cesium ions (Cs + ) and methylammonium (MA + ) and A is a cation FA + or MA + The molar proportion is ≥50%; the metal cation at the B position is Mn 2+ With Sn 2+ 、Bi 3+ 、Zn 2+ 、In 3+ There are at least four combinations of Sn 2+ 、Bi 3+ 、Zn 2+ 、In 3+ The total molar proportion of metal cations at the B position is 25%-40%; the X position is Cl - Br - , I - At least two of the following; S2, mixing the perovskite precursor with a flux at a mass ratio of 5:1, wherein the flux is choline chloride, using zirconium oxide grinding balls with a ball-to-material ratio of 15:1, and ball milling at a speed of 800-1000 rpm for 30 minutes under argon protection to directly form high-entropy perovskite crystal nuclei, with a particle size of ≤30 nm after ball milling; S3, adding a long-chain organic amine with a carbon chain length of C12-C18 to the product of step S2, and reacting at 180-200° C. for 0.5-1 hour to form a 2D / Ruddlesden–Popper (RP) type layered structure, wherein the molar ratio of the long-chain organic amine to the metal cation at the B site is 3:1-5:1; S4, dispersing the quantum dots obtained in step S3 in toluene, and sequentially adding trioctylphosphine oxide (TOPO), triphenylphosphine oxide (TPPO) and oleic acid, wherein the molar ratio of TOPO:TPPO:oleic acid is 1:0.5:2, stirring and reacting at 90° C. for 1 hour, and centrifugally drying to obtain quantum dot powder; S5. The quantum dot powder and maleic anhydride are mixed in a mass ratio of 8:1, and reacted in a vacuum at 130° C. for 20 minutes to form a polymaleic anhydride coating layer with a thickness of 2-5 nm.

2. The preparation method of ultra-stable perovskite quantum dots according to claim 1, characterized in that: In step S1, the molar ratio of the metal cation at position B is Mn 2+ With Sn 2+ 、Bi 3+ 、Zn 2+ 、In 3+ =65:12:10:8:

5.

3. The preparation method of ultra-stable perovskite quantum dots according to claim 1, characterized in that: In step S2, the ball milling speed is 900 rpm, and the pressure of the inert gas argon filled in the ball milling tank is 0.5-1.0 MPa.

4. The preparation method of ultra-stable perovskite quantum dots according to claim 1, characterized in that: Step S4 also includes adding 0.1-0.5 wt% of fluorosilane to modify the surface of the quantum dots together with TOPO / TPPO to form a fluorinated hydrophobic layer.

5. The preparation method of ultra-stable perovskite quantum dots according to claim 4, characterized in that: Step S4 also includes adding 0.5 wt% of polytetrafluoroethylene (PTFE) nanoparticles to modify the surface of the quantum dots together with fluorosilane to form a multi-layer hydrophobic barrier with a contact angle ≥150°.

6. The preparation method of ultra-stable perovskite quantum dots according to claim 1, characterized in that: In step S3, the C12-C18 long-chain organic amine is selected from octadecylamine, hexadecylamine or dodecylamine.

7. The preparation method of ultra-stable perovskite quantum dots according to claim 1, characterized in that: In step S3, the reaction temperature is 190° C., the reaction time is 40 minutes, and nitrogen is introduced as a carrier gas during the reaction at a flow rate of 10-20 mL / min.

Images