Long-time high-temperature-resistant lead sulfide colloid quantum dot film and preparation method thereof

Abstract

The invention discloses a lead sulfide colloid quantum dot film resistant to high temperature for a long time and a preparation method thereof.The preparation method comprises the steps that a first PbS quantum dot solid is obtained, a surface ligand of the first PbS quantum dot solid is a first ligand, and the first PbS quantum dot solid is dissolved in a first non-polar solvent to form a first PbS quantum dot solution; adding a thiol ligand into the first PbS quantum dot solution; at the moment, the surface of the quantum dot is a thiol ligand; dissolving the quantum dots of which the surfaces are thiol ligands in a second non-polar solvent to obtain a second PbS quantum dot solution; spin-coating the second PbS quantum dot solution on a substrate to prepare a PbS colloidal quantum dot film; the thiol ligand is one or a combination of more of mercaptoethanol (ME) and butyl mercaptan. According to the embodiment of the invention, mercaptoethanol (ME) or butyl mercaptan is used as a PbS quantum dot solid ligand, and a high-temperature-resistant mercaptan ligand is used for replacing a high-temperature unstable metal halide ligand, so that the long-time high-temperature stability of the PbS quantum dot film is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic materials, and particularly relates to a lead sulfide colloidal quantum dot film that is resistant to high temperatures for a long time and a preparation method thereof. Background Art

[0002] Infrared detectors are one of the foundations of infrared light sensing technology and are widely used in emerging fields such as machine vision, material identification, and biological imaging. The demand for easy-to-manufacture, low-cost, and adjustable infrared photoelectric materials in the third-generation infrared photodetectors has promoted the development of infrared colloidal quantum dots (CQDs). Among them, the light absorption range of lead sulfide (PbS) CQDs can be extended to the near-infrared range, with strong light absorption ability, a large exciton Bohr radius, and its adjustable band gap range is equivalent to the solar spectrum range, which has become a research hotspot for infrared photodetectors. At present, the high-temperature stability research and development of PbS CQDs quantum dot films for infrared photodetectors based on PbS CQDs mainly stays at 85°C, and the high-temperature resistance time is short, which cannot fully meet market needs. Therefore, a PbS CQDs film with long-term high-temperature resistance is urgently needed. Summary of the invention

[0003] The technical problem to be solved by the present invention is that, since the existing lead sulfide colloidal quantum dot film cannot withstand high temperature for a long time, the present invention provides a lead sulfide colloidal quantum dot film that can withstand high temperature for a long time and a preparation method thereof.

[0004] In order to solve the above technical problems, an embodiment of the present invention provides a method for preparing a lead sulfide colloidal quantum dot film that is resistant to high temperatures for a long time, comprising the following steps:

[0005] S1: obtaining a first PbS quantum dot solid, whose surface ligand is a first ligand, and dissolving the first PbS quantum dot solid in a first non-polar solvent to form a first PbS quantum dot solution;

[0006] S2: adding a thiol ligand to the first PbS quantum dot solution, fully oscillating the reaction for 1 min to 100 min, then adding an antisolvent to the reaction system to form a mixed solution; standing the solution to allow the PbS quantum dots to precipitate from the mixed solution to obtain a precipitated solution;

[0007] S3: removing the supernatant from the precipitation solution, and evacuating the solution for 5 to 50 minutes to obtain a second PbS quantum dot solid, wherein the surface of the quantum dot is a thiol ligand;

[0008] S4: dissolving quantum dots with thiol ligands on the surface in a second non-polar solvent to obtain a second PbS quantum dot solution with a concentration of 10 mg / mL to 500 mg / mL;

[0009] S5: dissolving the thiol ligand in the first polar solvent to obtain a thiol ligand solution with a volume percentage of 0.01 to 1%;

[0010] S6: spin-coating the second PbS quantum dot solution on the substrate, then covering the surface of the substrate with a thiol ligand solution, allowing it to stand, spin-coating, and then washing it with a first polar solvent for multiple times;

[0011] S7: Repeat step S6 multiple times until a PbS colloidal quantum dot film is prepared;

[0012] Wherein, the thiol ligand is one or more combinations of mercaptoethanol (ME) or butanethiol.

[0013] Preferably, in step S1, the first ligand is a long-chain ligand containing 8 to 16 C atoms, including one or more combinations of oleic acid and oleylamine.

[0014] Preferably, in step S1, the first non-polar solvent includes: one or more combinations of n-hexane, n-octane, toluene, and tetrachloroethylene.

[0015] Preferably, in step S1, the concentration of the first PbS quantum dot solution is 1 mg / mL to 1000 mg / mL.

[0016] Preferably, in step S2, the anti-solvent is a mixture of one or more of isopropanol, chloroform or acetone.

[0017] Preferably, in step S4, the second non-polar solvent includes: one or more combinations of n-hexane, n-octane, toluene, and tetrachloroethylene.

[0018] Preferably, in step S5, the first polar solvent includes: one or more combinations of acetonitrile and methanol.

[0019] Preferably, in step S6, the spin coating speed of the second PbS quantum dot solution on the substrate is 1000 r / min to 10000 r / min, the spin coating time is 10s to 60s, and the spin coating acceleration is 100r / s to 1000r / s.

[0020] Preferably, in step S6, the standing time of the thiol ligand solution on the substrate is 10s to 100s, the spin coating speed is 1000r / min to 10000r / min, the spin coating time is 10s to 60s, and the spin coating acceleration is 100r / s to 1000r / s.

[0021] An embodiment of the present invention also provides a lead sulfide colloidal quantum dot film that is resistant to high temperatures for a long time. The lead sulfide colloidal quantum dot film that is resistant to high temperatures for a long time is prepared by the above-mentioned method for preparing a lead sulfide colloidal quantum dot film that is resistant to high temperatures for a long time.

[0022] The implementation of the embodiments of the present invention has the following beneficial effects:

[0023] (1) The embodiment of the present invention adopts a layer-by-layer exchange film preparation method to exchange ligands, and the ligands after exchange are one or more combinations of mercaptoethanol or butanethiol. The functional group -SH of the short-chain ligand mercaptoethanol and butanethiol has a strong binding force with the metal site on the surface of the PbS quantum dot, and can fully exchange the original ligand on the surface of the quantum dot. And because the high-temperature resistant thiol short-chain ligand is used to replace the high-temperature unstable metal halide short-chain ligand, the long-term high-temperature stability of the PbS quantum dot film has been greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A flow chart of a method for preparing a lead sulfide colloidal quantum dot film with long-term high temperature resistance provided for the implementation of the present invention;

[0026] Figure 2 An absorption spectrum of a lead sulfide colloidal quantum dot film that is resistant to high temperatures for a long time provided for the implementation of the present invention;

[0027] Figure 3 Absorption spectrum of lead sulfide colloidal quantum dot film with metal halide as short-chain ligand provided for the implementation of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] like Figure 1As shown, this embodiment discloses a method for preparing a lead sulfide colloidal quantum dot film that is resistant to high temperatures for a long time. The method for preparing a lead sulfide colloidal quantum dot film that is resistant to high temperatures for a long time comprises the following steps:

[0030] S1: obtaining a first PbS quantum dot solid, whose surface ligand is a first ligand, and dissolving the first PbS quantum dot solid in a first non-polar solvent to form a first PbS quantum dot solution;

[0031] S2: adding a thiol ligand to the first PbS quantum dot solution, fully oscillating the reaction for 1 min to 100 min, then adding an antisolvent to the reaction system to form a mixed solution; standing the solution to allow the PbS quantum dots to precipitate from the mixed solution to obtain a precipitated solution;

[0032] S3: removing the supernatant from the precipitation solution, and evacuating the solution for 5 to 50 minutes to obtain a second PbS quantum dot solid, wherein the surface of the quantum dot is a thiol ligand;

[0033] S4: dissolving quantum dots with thiol ligands on the surface in a second non-polar solvent to obtain a second PbS quantum dot solution with a concentration of 10 mg / mL to 500 mg / mL;

[0034] S5: dissolving the thiol ligand in the first polar solvent to obtain a thiol ligand solution with a volume percentage of 0.01 to 1%;

[0035] S6: spin-coating the second PbS quantum dot solution on the substrate, then covering the surface of the substrate with a thiol ligand solution, allowing it to stand, spin-coating, and then washing it with a first polar solvent for multiple times;

[0036] S7: Repeat step S6 multiple times until a PbS colloidal quantum dot film is prepared;

[0037] Wherein, the thiol ligand is one or more combinations of mercaptoethanol (ME) or butanethiol.

[0038] The method for preparing a long-term high-temperature resistant lead sulfide colloidal quantum dot film uses a layer-by-layer exchange film preparation method to exchange its ligands, and the exchanged ligands are one or more combinations of mercaptoethanol or butanethiol. The functional group -SH of the short-chain ligand mercaptoethanol and butanethiol has a strong binding force with the metal site on the surface of the PbS quantum dot, and can fully exchange the original ligand on the surface of the quantum dot. And because the high-temperature resistant thiol short-chain ligand is used to replace the high-temperature unstable metal halide short-chain ligand, the PbS quantum dot film has a great improvement in long-term high-temperature stability.

[0039] Specifically, in step S1, the first ligand is a long-chain ligand containing 8 to 16 carbon atoms, including one or more combinations of oleic acid and oleylamine. The first non-polar solvent includes one or more combinations of n-hexane, n-octane, toluene, and tetrachloroethylene. The concentration of the first PbS quantum dot solution is 1 mg / mL to 1000 mg / mL.

[0040] In step S2, the anti-solvent is a mixture of one or more of isopropanol, chloroform or acetone. The standing time is 1 to 15 minutes.

[0041] In the step S4, the second non-polar solvent includes: one or more combinations of n-hexane, n-octane, toluene, and tetrachloroethylene.

[0042] In step S5, the first polar solvent includes: one or more combinations of acetonitrile and methanol.

[0043] In the step S6, the amount of the second PbS quantum dot solution added to the substrate is 10 μL to 100 μL. The spin coating speed of the second PbS quantum dot solution on the substrate is 1000 r / min to 10000 r / min, the spin coating time is 10s to 60s, and the spin coating acceleration is 100 r / s to 1000 r / s. The standing time of the thiol ligand solution on the substrate is 10s to 100s, the spin coating speed is 1000 r / min to 10000 r / min, the spin coating time is 10s to 60s, and the spin coating acceleration is 100 r / s to 1000 r / s. The number of cleaning times is 1 to 10 times.

[0044] In the step S6, the number of repetitions of the step S6 is 10 to 50 times.

[0045] Specifically, the present invention provides a method for preparing a lead sulfide colloidal quantum dot film that is resistant to high temperatures for a long time and a method for preparing a lead sulfide colloidal quantum dot film that uses metal halides as short-chain ligands.

[0046] Embodiment 1

[0047] All steps of the method for preparing a lead sulfide colloidal quantum dot film with long-term high temperature resistance described in the present invention are carried out in an inert environment, and the specific steps are as follows:

[0048] (1) Obtain oleic acid-coated PbS quantum dot solid, dissolve the PbS quantum dot solid in a non-polar solvent, toluene, to prepare a PbS quantum dot solution with a concentration of 50 mg / mL.

[0049] (2) Take 3 mL of the PbS quantum dot solution in step (1) in a centrifuge tube, add 60 μL of mercaptoethanol (ME), and oscillate for 30 minutes; then take 5 mL of anti-solvent isopropanol and mix it with the quantum dot solution in the centrifuge tube, let it stand for 10 minutes, and the quantum dots are precipitated from the mixed solution.

[0050] (3) The mixed solution obtained in step (2) is centrifuged at a speed of 9000 r / min for 5 min, the supernatant is discarded, and the centrifuge tube is placed in a vacuum chamber for evacuation for 15 min to obtain a quantum dot solid, at which point the surface of the PbS quantum dots is a thiol ligand.

[0051] (4) Dissolving the PbS quantum dot solid in step (3) in a non-polar solvent n-octane solution to prepare a PbS quantum dot solution with a concentration of 20 mg / mL; filtering the PbS quantum dot solution into a clean glass bottle using an organic filter with a specification of 0.22 μm for later use.

[0052] (5) taking a certain amount of butanethiol and mixing it with the polar solvent acetonitrile to prepare a butanethiol acetonitrile solution with a volume percentage of 1%;

[0053] (6) Turn on the spin coating equipment, set the spin coating speed to 2500 r / min, the spin coating time to 30 s, the spin coating acceleration to 500 r / min, and place the substrate in the center of the spin coating equipment; take 50 μL of the PbS quantum dot solution obtained in step (4) and drop it on the substrate, and spin coat it at a speed of 2500 r / min for 30 s; then use the butanethiol acetonitrile solution in step (5) to completely cover the surface of the substrate, let it stand for 30 s, and spin coat it at a speed of 2500 r / min for 30 s; then use the polar solvent acetonitrile to spin coat it at a speed of 2500 r / min for 30 s, and wash three times;

[0054] (7) Repeat step (6) 15 times to form a PbS colloidal quantum dot colloidal film.

[0055] In an inert environment, high temperature stability absorption tests of different lengths were carried out at 125°C on PbS colloidal quantum dot films that were pretreated with mercaptoethanol and prepared using a layer-by-layer exchange method using butanethiol as the exchange solution.

[0056] See also Figure 2 , Figure 2 The absorption spectra of the lead sulfide colloidal quantum dot film prepared by the method for preparing the lead sulfide colloidal quantum dot film with long-term high temperature resistance in Example 1 at different times. After aging at 125°C for 72 hours, the absorption intensity of the lead sulfide colloidal quantum dot film is still at the same level as that of the unaged lead sulfide colloidal quantum dot film, and the stability is good.

[0057] Comparative Example 1

[0058] A method for preparing a lead sulfide colloidal quantum dot film using metal halides as short-chain ligands, wherein all steps are performed in an inert environment, and the specific steps are as follows:

[0059] (1) Obtaining PbS quantum dots wrapped with oleic acid ligands, dissolving the quantum dots in a non-polar solvent n-octane to prepare a PbS quantum dot solution with a concentration of 10 mg / mL; using an organic filter head with a specification of 0.22 μm to filter the PbS quantum dot solution into a clean glass bottle for later use.

[0060] (2) Weigh PbI2 (2.6 mmol) and PbBr2 (0.26 mmol) into a clean glass bottle, add 10 mL of N,N-dimethylformamide, and shake thoroughly for 10 min to obtain a metal halide ligand solution; use an organic filter with a specification of 0.22 μm to filter the ligand solution into a clean glass bottle for later use.

[0061] (3) Take 10 ml of the PbS quantum dot solution in step (1) and the metal halide ligand solution in step (2) respectively, mix them in a 50 ml glass bottle; strictly seal and shake thoroughly for 1 min. The upper octane phase changes to clear and the lower N,N-dimethylformamide phase changes to black.

[0062] (4) Use a pipette to remove and discard the upper layer of solution, add the same volume of n-octane to the glass bottle, shake for 1 min, and continue to separate the solution;

[0063] (5) Repeat step (4) three times, divide the lower quantum dot mixed solution evenly into two 10 mL centrifuge tubes, and centrifuge at 9000 r / min for 5 min; after centrifugation, remove the upper clear liquid, place the centrifuge tube in a vacuum chamber and evacuate for 60 min to obtain a metal halide modified quantum dot solid.

[0064] (6) Prepare a dispersant according to the ratio of N,N-dimethylformamide: 3-pyridinemethylamine: dimethyl sulfoxide: n-butylamine = 34%: 1%: 25%: 40%.

[0065] (7) taking a certain amount of quantum dot powder in step (5) and a certain volume of dispersant in step (6), preparing a PbS quantum dot solution with a concentration of 300 mg / ml, and fully oscillating for 10 min; using a centrifuge at a speed of 5000 r / min for 1 min or using an organic filter head with a specification of 0.22 μm to filter the PbS quantum dot solution.

[0066] (8) Turn on the spin coating equipment, set the spin coating speed to 3000 r / min, the spin coating time to 30 s, and the spin coating acceleration to 500 r / min; place the substrate on the spin coater, take 60 μL of the quantum dot solution obtained in step (7) and drop it in the middle of the substrate, and start spin coating.

[0067] In an inert environment, the high temperature stability absorption test of PbS CQDs films prepared by using metal halides as short ligands to exchange the long oleic acid ligands on the surface of PbS quantum dots was carried out for different lengths at 125°C.

[0068] See also Figure 3 , Figure 3 The lead sulfide colloidal quantum dot film is prepared by the lead sulfide colloidal quantum dot film preparation method using the metal halide as a short-chain ligand in Comparative Example 1. As the aging time of the lead sulfide colloidal quantum dot film increases, it can be clearly seen that the absorption intensity of the lead sulfide colloidal quantum dot film gradually decreases, and the stability is poor.

[0069] By comparing Example 1 with Comparative Example 1, it can be learned that the method for preparing the lead sulfide colloidal quantum dot film with long-term high temperature resistance uses a layer-by-layer exchange film preparation method to exchange its ligands, and the exchanged ligands are one or more combinations of mercaptoethanol or butanethiol. The functional groups -SH of the short-chain ligands mercaptoethanol and butanethiol have a strong binding force with the metal sites on the surface of the PbS quantum dots, and can fully exchange the original ligands on the surface of the quantum dots. And because the high-temperature resistant thiol short-chain ligands are used to replace the high-temperature unstable metal halide short-chain ligands, the PbS quantum dot film has a great improvement in long-term high-temperature stability.

[0070] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for preparing a lead sulfide colloidal quantum dot film that is resistant to high temperatures for a long time, characterized in that: The following steps are involved: S1: obtaining a first PbS quantum dot solid, whose surface ligand is a first ligand, and dissolving the first PbS quantum dot solid in a first non-polar solvent to form a first PbS quantum dot solution; S2: adding a thiol ligand to the first PbS quantum dot solution, fully oscillating the reaction for 1 min to 100 min, then adding an antisolvent to the reaction system to form a mixed solution; standing the solution to allow the PbS quantum dots to precipitate from the mixed solution to obtain a precipitated solution; S3: removing the supernatant from the precipitation solution, and evacuating the solution for 5 to 50 minutes to obtain a second PbS quantum dot solid, wherein the surface of the quantum dot is a thiol ligand; S4: dissolving quantum dots with thiol ligands on the surface in a second non-polar solvent to obtain a second PbS quantum dot solution with a concentration of 10 mg / mL to 500 mg / mL; S5: dissolving the thiol ligand in the first polar solvent to obtain a thiol ligand solution with a volume percentage of 0.01 to 1%; S6: spin-coating the second PbS quantum dot solution on the substrate, then covering the surface of the substrate with a thiol ligand solution, allowing it to stand, spin-coating, and then washing it with a first polar solvent for multiple times; S7: Repeat step S6 multiple times until a PbS colloidal quantum dot film is prepared; Wherein, the thiol ligand is one or more combinations of mercaptoethanol (ME) or butanethiol.

2. The method for preparing a lead sulfide colloidal quantum dot film with long-term high temperature resistance according to claim 1, characterized in that: In the step S1, the first ligand is a long-chain ligand containing 8 to 16 carbon atoms, including one or more combinations of oleic acid and oleylamine.

3. The method for preparing a lead sulfide colloidal quantum dot film with long-term high temperature resistance according to claim 1, characterized in that: In the step S1, the first non-polar solvent includes: one or more combinations of n-hexane, n-octane, toluene, and tetrachloroethylene.

4. The method for preparing a lead sulfide colloidal quantum dot film with long-term high temperature resistance according to claim 1, characterized in that: In the step S1, the concentration of the first PbS quantum dot solution is 1 mg / mL to 1000 mg / mL.

5. The method for preparing a lead sulfide colloidal quantum dot film with long-term high temperature resistance according to claim 1, characterized in that: In step S2, the anti-solvent is a mixture of one or more of isopropanol, chloroform or acetone.

6. The method for preparing a lead sulfide colloidal quantum dot film with long-term high temperature resistance according to claim 1, characterized in that: In the step S4, the second non-polar solvent includes: one or more combinations of n-hexane, n-octane, toluene, and tetrachloroethylene.

7. The method for preparing a lead sulfide colloidal quantum dot film with long-term high temperature resistance according to claim 1, characterized in that: In step S5, the first polar solvent includes: one or more combinations of acetonitrile and methanol.

8. The method for preparing a lead sulfide colloidal quantum dot film with long-term high temperature resistance according to claim 1, characterized in that: In the step S6, the second PbS quantum dot solution is spin-coated on the substrate at a speed of 1000 r / min to 10000 r / min, a spin-coating time of 10s to 60s, and a spin-coating acceleration of 100r / s to 1000r / s.

9. The method for preparing a lead sulfide colloidal quantum dot film with long-term high temperature resistance according to claim 1, characterized in that: In the step S6, the thiol ligand solution is left on the substrate for 10s to 100s, the spin coating speed is 1000r / min to 10000r / min, the spin coating time is 10s to 60s, and the spin coating acceleration is 100r / s to 1000r / s.

10. A lead sulfide colloidal quantum dot film with long-term high temperature resistance, characterized in that: The lead sulfide colloidal quantum dot film that can withstand high temperatures for a long time is prepared by any one of the methods for preparing a lead sulfide colloidal quantum dot film that can withstand high temperatures for a long time as recited in claims 1-9.

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