Colloidal quantum dot liquid-phase ligand exchange matrix material recycling method based on purification and recrystallization
By recovering halide matrix materials from the liquid-phase ligand exchange process through purification and recrystallization, the problems of resource waste and environmental pollution are solved, achieving efficient and environmentally friendly resource recycling, reducing production costs and improving the performance of quantum dot films.
Patent Information
- Application Number
- CN202511330002.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-17
- Publication Date
- 2025-12-16
AI Technical Summary
In existing technologies, the halide matrix materials generated during liquid-phase ligand exchange are not effectively recovered, leading to resource waste and environmental pollution. The lack of effective recovery and reuse methods limits the sustainability and economy of the process.
The mixture after liquid-phase ligand exchange was centrifuged using a purification and recrystallization method. Immiscible alkane and organic solvents were used for separation to recover unreacted halide matrix materials. High-purity, reusable matrix materials were prepared by drying, and halide precursor solutions were reconstituted.
It significantly improves the utilization rate of halide matrix materials, reduces production costs, reduces environmental pollution, and the prepared quantum dot films have stable performance and are easy to scale up.
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Figure CN121134823A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of nanomaterial preparation and resource recycling, and specifically relates to a method for recycling and reusing a colloidal quantum dot liquid phase ligand exchange substrate material based on purification and recrystallization. BACKGROUND
[0002] Colloidal quantum dots are widely used in short-wave infrared detectors, solar cells, light-emitting diodes, display devices and other fields due to their excellent photoelectric properties (such as adjustable band gap, high quantum yield and wide spectral coverage). Among them, lead sulfide (PbS) quantum dots have become a research and application hotspot due to their mature synthesis process and wide spectral response characteristics. In the preparation of PbS quantum dot films, the liquid phase ligand exchange technology is a key step to improve the electronic transmission performance. In general, inorganic halide ligands (such as lead iodide and lead bromide) are used to replace the original long-chain organic ligands (such as oleic acid) on the surface of quantum dots to enhance the electrical performance of the film.
[0003] However, during the liquid phase ligand exchange process, the halide substrate material exists in the form of a solution, and part of the halide precursor solution that does not participate in the ligand exchange reaction is usually discarded as waste liquid, which leads to the following problems: Resource waste: The utilization rate of high-cost halide materials (such as PbI2 and PbBr2) is low, increasing the preparation cost.
[0004] Environmental pollution: Direct discharge of waste liquid containing heavy metals (such as lead) may cause environmental pollution, and the treatment cost is high.
[0005] Technical gap: There is a lack of effective recycling and reusing method for halide substrate materials in the existing technology, which limits the sustainability and economy of the process. SUMMARY
[0006] In view of the above deficiencies of the prior art, the purpose of the present application is to provide a method for recycling and reusing colloidal quantum dot liquid phase ligand exchange substrate materials based on purification and recrystallization. The present application recycles unreacted halide substrate materials (such as PbI2 and PbBr2) from the waste liquid generated during the liquid phase ligand exchange process and purifies them to prepare high-purity reusable substrate materials. The present application develops an efficient, environmentally friendly and easy-to-implement halide substrate material recycling technology to realize resource recycling, reduce production cost and reduce environmental pollution.
[0007] To solve the above technical problems, the present application adopts the following technical scheme: A method for recycling and reusing colloidal quantum dot liquid phase ligand exchange substrate materials based on purification and recrystallization, comprising the following steps: The mixture after the liquid ligand exchange reaction is centrifuged to obtain the quantum dot solid precipitate after ligand exchange and the supernatant containing the halide matrix.
[0008] The immiscible alkane solvent is added to the supernatant containing the halide matrix, and after mixing, the organic ligand in the supernatant is transferred to the alkane solvent. The lower layer of the purified supernatant is taken and mixed with an organic solvent, and the halide matrix material is precipitated after stirring. After centrifugation, the precipitate is obtained.
[0009] The precipitate is collected and dried to obtain the purified recrystallized colloidal quantum dot liquid ligand exchange matrix material.
[0010] The recovered purified recrystallized colloidal quantum dot liquid ligand exchange matrix material is used to reconfigure the halide precursor solution.
[0011] In a preferred embodiment of the present application, the preparation method of the quantum dot dispersion liquid to be exchanged in S1 is to disperse oleic acid-coated PbS colloidal quantum dots in an octane solution to obtain a quantum dot dispersion liquid, and the concentration is 5 mg / mL-200 mg / mL.
[0012] In a preferred embodiment of the present application, the preparation method of the halide precursor solution in S1 is to weigh lead halide and dissolve it in N,N-dimethylformamide, and stir until completely dissolved to form a halide precursor solution. The halide is one or a mixture of several of lead iodide, lead bromide, and lead chloride, and the concentration of the halide is 0.1 mmol / mL-6 mmol / mL.
[0013] In a preferred embodiment of the present application, in the ligand exchange reaction in S1, the oleic acid ligand is replaced by halide ions, and the quantum dots are transferred from the nonpolar octane phase to the polar dimethylformamide phase to form a stable dimethylformamide phase quantum dot dispersion liquid.
[0014] In a preferred embodiment of the present application, the volume ratio of the quantum dot dispersion liquid to be exchanged in S1 to the halide precursor solution is between 5:1 and 1:5.
[0015] In a preferred embodiment of the present application, the centrifugation speed of the mixture after the liquid ligand exchange reaction is 1500rmp-8000rpm, and the time is 10s-10min.
[0016] In a preferred embodiment of the present application, the immiscible alkane solvent is one or a mixture of several of n-hexane, cyclohexane, and n-octane, and the volume ratio of the immiscible alkane solvent to the supernatant containing the halide matrix is between 0.1 and 5.
[0017] In the preferred embodiment of the present application, the alkane solvent used for purification in S3 is octane, and the volume ratio of octane to waste liquid is 1:1.
[0018] In the preferred embodiment of the present application, the organic solvent is one of toluene, chlorobenzene and chloroform.
[0019] In the preferred embodiment of the present application, the volume ratio of the purified supernatant to the organic solvent is 1-5:1, preferably 5:1, and the stirring time is 10s-10min; the centrifugal speed of the mixture of the purified supernatant and the organic solvent is 1500rmp-8000rpm, and the centrifugal time is 10s-10min.
[0020] In the preferred embodiment of the present application, the drying time is 30min-2h.
[0021] In the preferred embodiment of the present application, according to the ICP-MS element analysis results, the proportion of halide in the halide-based matrix material based on colloidal quantum dot liquid phase ligand exchange is determined, chlorine element is supplemented to correct the proportion, the precursor solution is prepared by redissolving, and the obtained solution can be directly used for liquid phase ligand exchange of the next batch of quantum dots, and the recovery rate of the halide-based matrix material is 85%-98%.
[0022] Another object of the present application is to provide a colloidal quantum dot liquid phase ligand exchange matrix material based on purification and recrystallization obtained by the recycling and reuse method.
[0023] The colloidal quantum dot liquid phase ligand exchange matrix material based on purification and recrystallization described in the present application is applied to short-wave infrared detectors, photoelectric devices and display devices.
[0024] Compared with the prior art, the present application has the beneficial effects that: 1. The present application relates to a kind of based on purification recrystallization colloidal quantum dot liquid phase ligand exchange substrate material recycling method, the mixed liquid after liquid phase ligand exchange reaction is centrifuged, obtains the solid precipitate of quantum dot after ligand exchange and the supernatant containing halide substrate, add immiscible alkane solvent in supernatant, fully mix and make organic conversion in supernatant transfer to alkane solvent, purified supernatant is mixed after adding organic solvent and stir, make halide substrate material precipitate, after centrifugation, obtain precipitate, after collecting precipitate, dry, recycle based on purification recrystallization colloidal quantum dot liquid phase ligand exchange substrate material, using recycled based on purification recrystallization colloidal quantum dot liquid phase ligand exchange substrate material to prepare halide precursor solution, using reagent with greater boiling point difference to reduce waste liquid containing halide substrate, it is favorable to the recovery separation of waste liquid.A kind of efficient, environmental protection and easy to implement halide substrate material recovery technology is developed, to realize the recycling of resources, reduce production cost and reduce environmental pollution, stable performance, easy to scale up the recovery technology of popularization.
[0025] 2, the present application is based on a kind of purification recrystallization colloidal quantum dot liquid phase ligand exchange substrate material recycling method, recycle 85%-95% of halide substrate material in waste liquid, significantly improve raw material utilization, prepare two batches of similar performance PbS quantum dot film, precursor material cost reduces about 50%-60%, effectively reduce production cost, the photoelectric performance of quantum dot film prepared using recycled powder is excellent, dark current only about 1.5 times of original process, still meet the needs of short-wave infrared detector and other devices, reduce the direct discharge of waste liquid containing heavy metals, reduce environmental pollution and waste liquid treatment cost, meet the green manufacturing requirements, recovery process is simple, equipment demand is low, easy to promote and apply in laboratory and industrial production, wide applicability. BRIEF DESCRIPTION OF DRAWINGS
[0026] Figure 1 It is the flow chart of example 1~example 7 in the present application.
[0027] Figure 2 It is the comparison of device dark current of the process of example 1 and the original process of comparative example 1, wherein a is the device dark current of the process of example, b is the device dark current of the original process of comparative example 1.
[0028] Figure 3 It is the recovery rate comparison histogram of the process of example 1~example 5 and the recovery rate comparison histogram of the process of example 3, example 6 and example 7, wherein a is the recovery rate comparison histogram of the process of example 1~example 5, b is the recovery rate comparison histogram of the process of example 3, example 6 and example 7. DETAILED DESCRIPTION
[0029] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.
[0030] It should be noted that all technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.
[0031] Example 1 A method for recycling and reusing colloidal quantum dot liquid-phase ligand exchange matrix materials based on purification and recrystallization includes the following steps: (1) Disperse oleic acid-coated PbS colloidal quantum dots in octane solution at a concentration of 50 mg / mL to prepare 15 mL of quantum dot dispersion.
[0032] (2) Weigh 1.84g lead iodide (PbI2, purity ≥99%) and 0.64g lead bromide (PbBr2, purity ≥99%), dissolve them in 15 mL N,N-dimethylformamide (DMF, analytical grade), stir until completely dissolved, and form a homogeneous halide precursor solution.
[0033] (3) Mix the quantum dot dispersion and the halide precursor solution at a volume ratio of 1:1 (15mL:15mL), and stir at room temperature for 30 minutes under the protection of inert gas (nitrogen) to allow the ligand exchange reaction to proceed fully.
[0034] (4) Place the mixture after reaction in a centrifuge and centrifuge at 5000 rpm for 3 min to separate the supernatant (waste liquid containing unreacted halides and other impurities) and the precipitate (solid containing quantum dots after exchange). The supernatant is yellow and contains unreacted PbI2, PbBr2 and a small amount of organic impurities.
[0035] (5) Take the above yellow supernatant, add 15 mL of octane for purification, and then add toluene (analytical grade) to the purified yellow supernatant and mix at a volume ratio of 1:5 (supernatant: toluene). Stir for 10 min to precipitate the halide matrix material, and centrifuge at 8000 rpm for 5 min to obtain a white or light yellow matrix material precipitate.
[0036] (6) Collect the precipitate and then dry it in a vacuum drying oven at 60 °C for 4 hours. The recovered purified and recrystallized colloidal quantum dot liquid ligand exchange substrate material (mainly composed of PbI2and PbBr2) is obtained.
[0037] (7) The recovered purified and recrystallized colloidal quantum dot liquid ligand exchange substrate material is subjected to component analysis by EDS, and it is confirmed that the main components are PbI2and PbBr2, and the recovery rate is 95.1%.
[0038] Example 2 A method for recycling a purified and recrystallized colloidal quantum dot liquid ligand exchange substrate material, comprising the following steps: (1) Disperse oleic acid-coated PbS colloidal quantum dots in an octane solution at a concentration of 50 mg / mL to prepare 15 mL of quantum dot dispersion.
[0039] (2) Weigh 1.84 g of lead iodide (PbI2, purity ≥ 99%) and 0.64 g of lead bromide (PbBr2, purity ≥ 99%) and dissolve them in 15 mL of N,N-dimethylformamide (DMF, analytical pure) to form a uniform halide precursor solution.
[0040] (3) Mix the quantum dot dispersion and the halide precursor solution in a volume ratio of 1:1 (15 mL:15 mL) and shake under inert gas (nitrogen) protection at room temperature for 30 minutes to allow the ligand exchange reaction to proceed fully.
[0041] (4) Centrifuge the mixed solution after the reaction at a speed of 5000 rpm for 3 min to separate the supernatant (waste liquid containing unreacted halide and other impurities) and the precipitate (solid containing exchanged quantum dots). The supernatant is yellow and contains unreacted PbI2, PbBr2and a small amount of organic impurities.
[0042] (5) Take the yellow supernatant and add 15 mL of octane for purification. Mix the yellow supernatant after purification with toluene (analytical pure) in a volume ratio of 1:4 (supernatant:toluene) and stir for 10 min to precipitate the halide substrate material. Centrifuge at 8000 rpm for 5 min to obtain white or light yellow substrate material precipitate.
[0043] (6) Collect the precipitate and then dry it in a vacuum drying oven at 60 °C for 4 hours. The recovered purified and recrystallized colloidal quantum dot liquid ligand exchange substrate material (mainly composed of PbI2and PbBr2) is obtained.
[0044] (7) The recovered colloidal quantum dot liquid ligand exchange substrate material based on purification and recrystallization was subjected to component analysis by EDS, and it was confirmed that the main components were PbI2 and PbBr2, and the recovery rate was 94.6%.
[0045] Example 3 A method for recycling a colloidal quantum dot liquid ligand exchange substrate material based on purification and recrystallization, comprising the following steps: (1) Disperse oleic acid-coated PbS colloidal quantum dots in an octane solution at a concentration of 50 mg / mL to prepare 15 mL of quantum dot dispersion.
[0046] (2) Weigh 1.84 g of lead iodide (PbI2, purity ≥ 99%) and 0.64 g of lead bromide (PbBr2, purity ≥ 99%) and dissolve them in 15 mL of N,N-dimethylformamide (DMF, analytical pure) to form a uniform halide precursor solution.
[0047] (3) Mix the quantum dot dispersion and the halide precursor solution in a volume ratio of 1:1 (15 mL:15 mL) under the protection of inert gas (nitrogen) and shake at room temperature for 30 minutes to allow the ligand exchange reaction to proceed fully.
[0048] (4) Centrifuge the mixed solution after the reaction at 8000 rpm for 5 min to separate the supernatant (waste liquid containing unreacted halide and other impurities) and the precipitate (solid containing exchanged quantum dots), and the supernatant is yellow, containing unreacted PbI2, PbBr2 and a small amount of organic impurities.
[0049] (5) Take the yellow supernatant and add 15 mL of octane for purification. Mix the yellow supernatant after purification with toluene (analytical pure) in a volume ratio of 1:3 (supernatant:toluene) and stir for 10 min to precipitate the halide substrate material. Centrifuge at 8000 rpm for 5 min to obtain white or light yellow substrate material precipitate.
[0050] (6) Collect the precipitate and then dry it in a vacuum drying oven at 60°C for 2 hours to recover the colloidal quantum dot liquid ligand exchange substrate material based on purification and recrystallization (main components are PbI2 and PbBr2).
[0051] (7) The recovered colloidal quantum dot liquid ligand exchange substrate material based on purification and recrystallization was subjected to component analysis by EDS, and it was confirmed that the main components were PbI2 (about 76.6%) and PbBr2 (about 23.4%), and the recovery rate was 93.9%.
[0052] Example 4 A method for recycling a matrix material of ligand exchange of colloidal quantum dots in liquid phase based on purification and recrystallization, comprising the following steps: (0) Disperse oleic acid-coated PbS colloidal quantum dots in an octane solution at a concentration of 50 mg / mL to prepare 15 mL of a quantum dot dispersion.
[0053] (1) Weigh 1.84 g of lead iodide (PbI2, purity ≥ 99%) and 0.64 g of lead bromide (PbBr2, purity ≥ 99%) and dissolve them in 15 mL of N,N-dimethylformamide (DMF, analytical pure) to form a uniform halide precursor solution.
[0054] (2) Mix the quantum dot dispersion and the halide precursor solution at a volume ratio of 1:1 (15 mL:15 mL) and shake under inert gas (nitrogen) protection at room temperature for 30 minutes to allow the ligand exchange reaction to proceed fully.
[0055] (3) Centrifuge the reaction mixture at 8000 rpm for 5 min to separate the supernatant (waste liquid containing unreacted halide and other impurities) and the precipitate (solid containing exchanged quantum dots). The supernatant is yellow and contains unreacted PbI2, PbBr2 and a small amount of organic impurities.
[0056] (4) Take the yellow supernatant and purify it with 15 mL of octane. Mix the purified yellow supernatant with toluene (analytical pure) at a volume ratio of 1:2 (supernatant:toluene) and stir for 10 min to precipitate the halide matrix material. Centrifuge at 8000 rpm for 5 min to obtain white or light yellow matrix material precipitate.
[0057] (5) Collect the precipitate and then dry it in a vacuum drying oven at 60°C for 2 hours to recover the matrix material of ligand exchange of colloidal quantum dots in liquid phase based on purification and recrystallization (main components are PbI2 and PbBr2).
[0058] (6) The recovered matrix material of ligand exchange of colloidal quantum dots in liquid phase based on purification and recrystallization is analyzed by EDS to confirm that the main components are PbI2 and PbBr2, and the recovery rate is 75.5%.
[0059] Example 5 A method for recycling a matrix material of ligand exchange of colloidal quantum dots in liquid phase based on purification and recrystallization, comprising the following steps: (7) Disperse oleic acid-coated PbS colloidal quantum dots in an octane solution at a concentration of 50 mg / mL to prepare 15 mL of a quantum dot dispersion.
[0060] (8) Weigh 1.84 g of lead iodide (PbI2, purity≥99%) and 0.64 g of lead bromide (PbBr2, purity≥99%) and dissolve them in 15 mL of N,N-dimethylformamide (DMF, analytical pure) to form a uniform halide precursor solution after stirring until complete dissolution.
[0061] (9) Mix the quantum dot dispersion liquid with the halide precursor solution at a volume ratio of 1:1 (15 mL:15 mL) and shake under inert gas (nitrogen) protection at room temperature for 30 minutes to allow the ligand exchange reaction to proceed fully.
[0062] (10) Centrifuge the mixed solution after the reaction at a speed of 5000 rpm for 3 min to separate the supernatant (waste liquid containing unreacted halide and other impurities) and the precipitate (solid containing exchanged quantum dots). The supernatant is yellow and contains unreacted PbI2, PbBr2 and a small amount of organic impurities.
[0063] (11) Take the yellow supernatant and add 15 mL of octane for purification. Mix the yellow supernatant after purification with toluene (analytical pure) at a volume ratio of 1:1 (supernatant:toluene) and stir for 10 min to precipitate the halide matrix material. Centrifuge at a speed of 8000 rpm for 5 min to obtain white or light yellow matrix material precipitate.
[0064] (12) Collect the precipitate and then dry it in a vacuum drying oven at 60°C for 4 hours to recover the purified and recrystallized colloidal quantum dot liquid phase ligand exchange matrix material (mainly composed of PbI2 and PbBr2).
[0065] (13) The recovered purified and recrystallized colloidal quantum dot liquid phase ligand exchange matrix material is analyzed by EDS to confirm that the main components are PbI2 and PbBr2, and the recovery rate is 47.8%.
[0066] Example 6 A method for recycling a purified and recrystallized colloidal quantum dot liquid phase ligand exchange matrix material, comprising the following steps: (1) Disperse the oleic acid-coated PbS colloidal quantum dots in an octane solution at a concentration of 50 mg / mL to prepare 15 mL of quantum dot dispersion liquid.
[0067] (2) Weigh 1.84 g of lead iodide (PbI2, purity≥99%) and 0.64 g of lead bromide (PbBr2, purity≥99%) and dissolve them in 15 mL of N,N-dimethylformamide (DMF, analytical pure) to form a uniform halide precursor solution after stirring until complete dissolution.
[0068] (3) The quantum dot dispersion liquid and the halide precursor solution are mixed in a volume ratio of 1:1 (15 mL:15 mL), and under the protection of inert gas (nitrogen), the mixture is stirred at room temperature for 30 minutes to fully carry out the ligand exchange reaction.
[0069] (4) The mixed solution after reaction is placed in a centrifuge, and centrifuged at a speed of 8000 rpm for 5 minutes to separate the supernatant (waste liquid containing unreacted halide and other impurities) and the precipitate (solid containing exchanged quantum dots). The supernatant is yellow, containing unreacted PbI2, PbBr2 and a small amount of organic impurities.
[0070] (5) The above yellow supernatant is taken, 15 mL of octane is added for purification, and the yellow supernatant after purification is mixed with chlorobenzene (analytical pure) in a volume ratio of 1:3 (supernatant:chlorobenzene), and stirred for 10 minutes to precipitate the halide matrix material. The white or light yellow matrix material precipitate is obtained by centrifugation at 8000 rpm for 5 minutes.
[0071] (6) The precipitate is collected and then dried in a vacuum drying oven at 60°C for 2 hours. The recovered colloidal quantum dot liquid phase ligand exchange matrix material based on purification and recrystallization (mainly containing PbI2 and PbBr2) is obtained.
[0072] (7) The recovered colloidal quantum dot liquid phase ligand exchange matrix material based on purification and recrystallization is analyzed by EDS, and it is confirmed that the main components are PbI2 and PbBr2, and the recovery rate is 92.6%.
[0073] Example 7 A method for recycling a colloidal quantum dot liquid phase ligand exchange matrix material based on purification and recrystallization, comprising the following steps: (1) The oleic acid-coated PbS colloidal quantum dots are dispersed in an octane solution at a concentration of 50 mg / mL to prepare 15 mL of quantum dot dispersion liquid.
[0074] (2) 1.84 g of lead iodide (PbI2, purity ≥ 99%) and 0.64 g of lead bromide (PbBr2, purity ≥ 99%) are weighed and dissolved in 15 mL of N,N-dimethylformamide (DMF, analytical pure) to form a uniform halide precursor solution.
[0075] (3) The quantum dot dispersion liquid and the halide precursor solution are mixed in a volume ratio of 1:1 (15 mL:15 mL), and under the protection of inert gas (nitrogen), the mixture is stirred at room temperature for 30 minutes to fully carry out the ligand exchange reaction.
[0076] (4) Place the mixture after reaction in a centrifuge and centrifuge at 8000 rpm for 5 min to separate the supernatant (waste liquid containing unreacted halides and other impurities) and the precipitate (solid containing quantum dots after exchange). The supernatant is yellow and contains unreacted PbI2, PbBr2 and a small amount of organic impurities.
[0077] (5) Take the above yellow supernatant, add 15 mL of octane for purification, and then add chloroform (analytical grade) to the yellow supernatant at a volume ratio of 1:3 (supernatant: chloroform). Stir for 10 min to precipitate the halide matrix material, and centrifuge at 8000 rpm for 5 min to obtain a white or light yellow matrix material precipitate.
[0078] (6) Collect the precipitate and then dry it in a vacuum drying oven at 60°C for 2 hours to recover the colloidal quantum dot liquid phase ligand exchange matrix material based on purification and recrystallization (the main components are PbI2 and PbBr2).
[0079] (7) The recovered colloidal quantum dot liquid phase ligand exchange matrix material based on purification and recrystallization was analyzed by EDS and the main components were confirmed to be PbI2 and PbBr2, with a recovery rate of 91.6%.
[0080] Comparative Example 1 A device fabrication method using the original process (lead sulfide quantum dots with inorganic ligands prepared from non-recycled lead halides) includes the following steps: (1) Disperse oleic acid-coated PbS colloidal quantum dots in octane solution at a concentration of 50 mg / mL to prepare 15 mL of quantum dot dispersion.
[0081] (2) Weigh 1.84g lead iodide (PbI2, purity ≥99%) and 0.64g lead bromide (PbBr2, purity ≥99%), dissolve them in 15 mL N,N-dimethylformamide (DMF, analytical grade), stir until completely dissolved, and form a homogeneous halide precursor solution.
[0082] (3) Mix the quantum dot dispersion and the halide precursor solution at a volume ratio of 1:1 (15mL:15mL), and stir at room temperature for 30 minutes under the protection of inert gas (nitrogen) to allow the ligand exchange reaction to proceed fully.
[0083] (4) Place the mixture after reaction in a centrifuge and centrifuge at 8000 rpm for 5 min to separate the supernatant (waste liquid containing unreacted halides and other impurities) and the precipitate (solid containing quantum dots after exchange). The supernatant is yellow and contains unreacted PbI2, PbBr2 and a small amount of organic impurities.
[0084] (5) The above-mentioned separated precipitate is the inorganic ligand lead sulfide quantum dot after ligand exchange, which can be used for device fabrication. In (2), the lead halide weighed is a non-recycled drug, which can be replaced by the lead halide recovered in Example 1 to prepare inorganic ligand lead sulfide quantum dots for device fabrication.
[0085] Results Analysis The fabrication method of the ITO / ZnO / PbS-ink / PbS-EDT / MoOx / Ag device involves spin-coating zinc oxide onto a customized ITO electrode as an electron transport layer, then configuring the ligand-exchanged quantum dots prepared in Example 1 and Comparative Example 1 into an ink, which is then spin-coated onto the zinc oxide electrode as a photoactive layer. Lead sulfide quantum dots with EDT as the ligand are then used as a hole transport layer. Finally, molybdenum oxide and silver are deposited on the hole transport layer as the top electrode to obtain the ITO / ZnO / PbS-ink / PbS-EDT / MoOx / Ag device.
[0086] Figure 1 The flowcharts for Examples 1 to 7 of this invention illustrate the process from ligand exchange to waste liquid recovery into solid lead halide powder. Specifically, the process includes several steps such as waste liquid separation and purification, halide precipitation and separation, precipitate drying, and halide precursor preparation. The recovered solid lead halide powder can be used for new ligand exchange to achieve the recycling of lead halide powder, thereby reducing costs and heavy metal emissions.
[0087] Table 1 shows the EDS composition characterization results of the recovered powder in Example 1 of the present invention. Through EDS characterization analysis, the main components of the recovered powder are bromine, iodine and lead, with lead bromide and lead iodide contents of 23.4% and 76.6%, respectively.
[0088] Table 1 shows the characterization results of the recovered powdered EDS in Example 1 of the present invention. Figure 2 This is a comparison chart showing the dark current performance of the device using the process of Embodiment 1 of the present invention and the device using the original process of Comparative Example 1, where a represents the dark current of the device using the process of Embodiment 1, and b represents the dark current of the device using the original process of Comparative Example 1. Figure 2 In the image, b represents the device fabricated using the original process, with a dark current density of 314 nA / cm². 2 , Figure 2 In Figure 'a', the dark current density of the device prepared using the powder recovered in Example 1 is 470 nA / cm². 2 The dark current density of the recycled powder increased by about 1.5 times.
[0089] Figure 3The charts show comparative bar graphs of the process recovery rates for Examples 1-5 and Examples 3, 6, and 7 of this invention. Specifically, bar graph a represents the comparative recovery rates for Examples 1-5, and bar graph b represents the comparative recovery rates for Examples 3, 6, and 7. Using toluene as the recovery solvent, the recovery rate of lead halide powder increased from 47.8% to 95.1% when the volume ratio increased from 1:1 to 5:1. Considering the amount of toluene used, the recovery rate of lead halide powder reached 93.9% when the volume ratio increased to 3:1, and further increases in toluene usage did not significantly improve the recovery of solid powder. When the volume ratio was 3:1, the recovery rates of lead halide powder using toluene, chlorobenzene, and chloroform were 93.9%, 92.6%, and 91.6%, respectively, with toluene being the preferred recovery solvent.
[0090] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.
Claims
1. A method for recycling and reusing colloidal quantum dot liquid-phase ligand exchange matrix materials based on purification and recrystallization, characterized in that, Includes the following steps: The mixture after the liquid-phase ligand exchange reaction was centrifuged to obtain the quantum dot solid precipitate after ligand exchange and the supernatant containing the halide matrix. Add immiscible alkane solvent to the supernatant containing the halide matrix, mix thoroughly and separate into layers, so that the organic compounds in the supernatant are transferred to the alkane solvent. Take the lower layer of purified supernatant, add organic solvent again, mix and stir to precipitate the halide matrix material, and obtain the precipitate after centrifugation. After collecting and drying the precipitate, a colloidal quantum dot liquid-phase ligand exchange matrix material based on purification and recrystallization was obtained. The halide precursor solution was reconstituted using the recovered colloidal quantum dot liquid-phase ligand exchange matrix material based on purification and recrystallization.
2. The method for recycling and reusing colloidal quantum dot liquid-phase ligand exchange matrix materials based on purification and recrystallization according to claim 1, characterized in that, The immiscible alkane solvent is one or a mixture of n-hexane, cyclohexane, and n-octane, and the volume ratio of the immiscible alkane solvent to the supernatant containing the halide matrix is 0.1-5:
1.
3. The method for recycling and reusing colloidal quantum dot liquid-phase ligand exchange matrix materials based on purification and recrystallization according to claim 1, characterized in that, The organic solvent is one of toluene, chlorobenzene, or chloroform.
4. The method for recycling and reusing colloidal quantum dot liquid-phase ligand exchange matrix materials based on purification and recrystallization according to claim 1, characterized in that, The volume ratio of purified supernatant to organic solvent is 1-5:1, and the stirring time is 10s-10min.
5. The method for recycling and reusing colloidal quantum dot liquid-phase ligand exchange matrix materials based on purification and recrystallization according to claim 1, characterized in that, After the purified supernatant is mixed with an organic solvent, it is centrifuged at 1500-8000 rpm for 10-10 minutes and dried for 30 minutes-2 hours.
6. The method for recycling and reusing colloidal quantum dot liquid-phase ligand exchange matrix materials based on purification and recrystallization according to claim 1, characterized in that, Based on the ICP-MS elemental analysis results, the proportion of halides in the halide matrix material based on colloidal quantum dot liquid-phase ligand exchange was determined. Halogens were added to correct the ratio, and the precursor solution was redissolved and prepared. The resulting solution was directly used for the liquid-phase ligand exchange of the next batch of quantum dots. The recovery rate of the halide matrix material was 85%-98%.
7. The method for recycling and reusing colloidal quantum dot liquid-phase ligand exchange matrix materials based on purification and recrystallization according to claim 1, characterized in that, The mixture after the liquid phase ligand exchange reaction was centrifuged at a speed of 1500 rpm-8000 rpm for 10 s-10 min.
8. A colloidal quantum dot liquid-phase ligand exchange matrix material based on purification and recrystallization obtained by the recycling and reuse method according to any one of claims 1-7.
9. The application of the colloidal quantum dot liquid-phase ligand exchange matrix material based on purification and recrystallization as described in claim 8 in short-wave infrared detectors, optoelectronic devices, and display devices.