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

Abstract

The application discloses a long-time high-temperature-resistant lead sulfide colloidal quantum dot film and a preparation method thereof, and comprises the following steps: obtaining first PbS quantum dot solids, wherein the surface ligand of the first PbS quantum dot solids is a first ligand; dissolving the first PbS quantum dot solids in a first non-polar solvent to form a first PbS quantum dot solution; adding a mercaptan ligand into the first PbS quantum dot solution; obtaining second PbS quantum dot solids, wherein the surface of the quantum dots is the mercaptan ligand; dissolving the quantum dots with the mercaptan ligand on the surface in a second non-polar solvent to obtain a second PbS quantum dot solution; and spin-coating the second PbS quantum dot solution on a substrate to prepare a PbS colloidal quantum dot film; and the mercaptan ligand is one or a combination of mercaptoethanol (ME) or butanethiol. According to the application, mercaptoethanol (ME) or butanethiol is used as the PbS quantum dot solid ligand, the high-temperature-resistant mercaptan ligand is used to replace the high-temperature-unstable metal halide ligand, and the long-time high-temperature stability of the PbS quantum dot film is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of electronic materials technology, and specifically relates to a long-term high-temperature resistant lead sulfide colloidal quantum dot film and its preparation method. Background Technology

[0002] Infrared detectors are one of the foundations of infrared optical sensing technology and are widely used in emerging fields such as machine vision, material identification, and bioimaging. The demand for easily manufactured, low-cost, and tunable infrared photoelectric materials in third-generation infrared photodetectors has driven the development of infrared colloidal quantum dots (CQDs). Among them, lead sulfide (PbS) CQDs have an extended light absorption range into the near-infrared region, strong light absorption capacity, a large exciton Bohr radius, and a band gap tunable range comparable to the solar spectrum, making them a research hotspot in infrared photodetectors. Currently, research on the high-temperature stability of PbS CQD quantum dot thin films for infrared photodetectors mainly focuses on 85℃, and the high-temperature resistance time is relatively short, which cannot fully meet market needs. Therefore, there is an urgent need for a PbS CQD thin film with long-term high-temperature resistance. Summary of the Invention

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

[0004] To address the aforementioned technical problems, this invention provides a method for preparing long-term high-temperature resistant lead sulfide colloidal quantum dot films, comprising the following steps:

[0005] S1: Obtain a first PbS quantum dot solid, the surface ligand of which is the first ligand; dissolve the first PbS quantum dot solid in a first nonpolar solvent to form a first PbS quantum dot solution.

[0006] S2: Add thiol ligands to the first PbS quantum dot solution, shake the reaction thoroughly for 1 min to 100 min, then add antisolvent to the reaction system to form a mixed solution; let stand, and the PbS quantum dots precipitate from the mixed solution to obtain a precipitate solution;

[0007] S3: Remove the supernatant from the precipitate solution and vacuum for 5 min to 50 min to obtain the second PbS quantum dot solid. At this time, the surface of the quantum dot is a thiol ligand.

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

[0009] S5: Dissolve 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-coat the second PbS quantum dot solution onto the substrate, then cover the substrate surface with a thiol ligand solution, let it stand, spin-coat again, and then wash it multiple times with the first polar solvent.

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

[0012] 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 nonpolar 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 antisolvent is one or more of isopropanol, chloroform, or acetone.

[0017] Preferably, in step S4, the second nonpolar 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 or 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 10 s to 60 s, and the spin coating acceleration is 100 r / s to 1000 r / s.

[0020] Preferably, in step S6, the thiol ligand solution is allowed to stand 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.

[0021] This invention also provides a long-term high-temperature resistant lead sulfide colloidal quantum dot film, which is prepared by the above-described method for preparing long-term high-temperature resistant lead sulfide colloidal quantum dot films.

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

[0023] (1) In this embodiment of the invention, a layer-by-layer exchange method is used to prepare the thin film, which allows for ligand exchange. The exchanged ligands are one or more combinations of mercaptoethanol or butanethiol. The functional group -SH of the short-chain ligands mercaptoethanol and butanethiol has a strong binding force with the metal sites on the surface of PbS quantum dots, which can fully exchange the original ligands on the quantum dot surface. Furthermore, by using high-temperature resistant thiol short-chain ligands instead of high-temperature unstable metal halide short-chain ligands, the long-term high-temperature stability of the PbS quantum dot film is greatly improved. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A flowchart illustrating a method for preparing a long-term high-temperature resistant lead sulfide colloidal quantum dot film for the purpose of implementing this invention;

[0026] Figure 2 An absorption spectrum of a long-term high-temperature resistant lead sulfide colloidal quantum dot film is provided for the implementation of this invention;

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

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] like Figure 1As shown in this embodiment, a method for preparing a long-term high-temperature resistant lead sulfide colloidal quantum dot film is disclosed. The method for preparing the long-term high-temperature resistant lead sulfide colloidal quantum dot film includes the following steps:

[0030] S1: Obtain a first PbS quantum dot solid, the surface ligand of which is the first ligand; dissolve the first PbS quantum dot solid in a first nonpolar solvent to form a first PbS quantum dot solution.

[0031] S2: Add thiol ligands to the first PbS quantum dot solution, shake the reaction thoroughly for 1 min to 100 min, then add antisolvent to the reaction system to form a mixed solution; let stand, and the PbS quantum dots precipitate from the mixed solution to obtain a precipitate solution;

[0032] S3: Remove the supernatant from the precipitate solution and vacuum for 5 min to 50 min to obtain the second PbS quantum dot solid. At this time, the surface of the quantum dot is a thiol ligand.

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

[0034] S5: Dissolve 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-coat the second PbS quantum dot solution onto the substrate, then cover the substrate surface with a thiol ligand solution, let it stand, spin-coat again, and then wash it multiple times with the first polar solvent.

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

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

[0038] The method for preparing long-term high-temperature resistant lead sulfide colloidal quantum dot films employs a layer-by-layer exchange method to exchange ligands. The exchanged ligands are one or more combinations of mercaptoethanol or butanethiol. The -SH functional group of the short-chain ligands mercaptoethanol and butanethiol has a strong binding force with the metal sites on the PbS quantum dot surface, effectively exchanging the original ligands on the quantum dot surface. Furthermore, by using high-temperature resistant short-chain thiol ligands instead of high-temperature unstable short-chain metal halide ligands, the long-term high-temperature stability of the PbS quantum dot film is significantly improved.

[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 nonpolar 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 antisolvent is one or more of isopropanol, chloroform, or acetone. The settling time is 1 to 15 minutes.

[0041] In step S4, the second nonpolar 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 or methanol.

[0043] In 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 10 s to 60 s, 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 10 s to 100 s, the spin-coating speed is 1000 r / min to 10000 r / min, the spin-coating time is 10 s to 60 s, and the spin-coating acceleration is 100 r / s to 1000 r / s. The number of washing cycles is 1 to 10.

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

[0045] Specifically, the present invention provides a method for preparing a long-term high-temperature resistant lead sulfide colloidal quantum dot film and a method for preparing a lead sulfide colloidal quantum dot film using metal halides as short-chain ligands.

[0046] Example 1

[0047] The method for preparing a long-term high-temperature resistant lead sulfide colloidal quantum dot film according to the present invention is carried out in an inert environment in all steps, and the specific steps are as follows:

[0048] (1) Obtain PbS quantum dot solids coated with oleic acid, dissolve the PbS quantum dot solids in the nonpolar solvent toluene, and prepare a PbS quantum dot solution with a concentration of 50 mg / mL.

[0049] (2) Take 3 mL of the PbS quantum dot solution from step (1) into a centrifuge tube, add 60 μL of mercaptoethanol (ME), and shake for 30 min. Then take 5 mL of the antisolvent isopropanol and mix it with the quantum dot solution in the centrifuge tube. Let it stand for 10 min, and the quantum dots will precipitate from the mixed solution.

[0050] (3) Centrifuge the mixed solution obtained in step (2) at a speed of 9000 r / min for 5 min, discard the supernatant, place the centrifuge tube in a vacuum chamber and evacuate for 15 min to obtain quantum dot solids. At this time, the surface of PbS quantum dots is thiol ligand.

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

[0052] (5) Take a certain amount of butanethiol and mix 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, and 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 onto the substrate, and spin coat at 2500 r / min for 30 s; then use the butanethiol acetonitrile solution in step (5) to completely cover the substrate surface, let it stand for 30 s, and spin coat at 2500 r / min for 30 s; then use the polar solvent acetonitrile to spin coat at 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, the high-temperature stability absorption of PbS colloidal quantum dot films prepared by pretreatment with mercaptoethanol, using butanethiol as the exchange solution, and employing a layer-by-layer exchange method was tested at 125 °C for different durations.

[0056] See Figure 2 , Figure 2 The images show the absorption spectra of the lead sulfide colloidal quantum dot film prepared by the method described in Example 1 for long-term high-temperature resistant lead sulfide colloidal quantum dot film at different times. After aging at 125℃ for 72 hours, the absorption intensity of the lead sulfide colloidal quantum dot film remained at the same level as that of the unaged lead sulfide colloidal quantum dot film, indicating good stability.

[0057] Comparative Example 1

[0058] A method for preparing lead sulfide colloidal quantum dot films 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) Obtain PbS quantum dots encapsulated with oleic acid ligands, dissolve the quantum dots in the nonpolar solvent n-octane to prepare a PbS quantum dot solution with a concentration of 10 mg / mL; filter the PbS quantum dot solution into a clean glass bottle using an organic filter with a specification of 0.22 μm.

[0060] (2) Weigh PbI2 (2.6 mmol) and PbBr2 (0.26 mmol) into a clean glass bottle, add 10 mL of N,N-dimethylformamide, shake thoroughly for 10 min to obtain a metal halide ligand solution; filter the ligand solution into a clean glass bottle using an organic filter with a specification of 0.22 μm 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) and mix them in a 50 ml glass bottle; seal tightly and shake thoroughly for 1 min. The upper octane phase turns clear and the lower N,N-dimethylformamide phase turns 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 the solution will continue to separate into layers;

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

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

[0065] (7) Take a certain amount of quantum dot powder from step (5) and a certain volume of dispersant from step (6) to prepare a PbS quantum dot solution with a concentration of 300 mg / ml, and shake it thoroughly for 10 min; use a centrifuge at a speed of 5000 r / min for 1 min or use an organic filter head with a specification of 0.22 μm to filter the PbS quantum dot solution.

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

[0067] In an inert environment, the high-temperature stability absorption of PbS CQDs films prepared by exchanging oleic acid long ligands on the surface of PbS quantum dots with metal halides as short ligands was tested at 125 °C for different durations.

[0068] See Figure 3 , Figure 3 This is a lead sulfide colloidal quantum dot film prepared using the method described in Comparative Example 1, which uses metal halides as short-chain ligands. With prolonged aging, the absorption intensity of the lead sulfide colloidal quantum dot film clearly decreases, indicating poor stability.

[0069] A comparison between Example 1 and Comparative Example 1 reveals that the method for preparing the long-term high-temperature resistant lead sulfide colloidal quantum dot film employs a layer-by-layer exchange method, resulting in ligand exchange. The exchanged ligands are one or more combinations of mercaptoethanol or butanethiol. The -SH functional group of the short-chain ligands mercaptoethanol and butanethiol exhibits strong binding affinity to the metal sites on the PbS quantum dot surface, effectively exchanging the original ligands. Furthermore, by using high-temperature resistant short-chain thiol ligands instead of high-temperature unstable metal halide short-chain ligands, the long-term high-temperature stability of the PbS quantum dot film is significantly improved.

[0070] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for preparing a long-time high-temperature-resistant lead sulfide colloidal quantum dot film, characterized in that, Includes the following steps: S1: Obtain a first PbS quantum dot solid, the surface ligand of which is the first ligand; dissolve the first PbS quantum dot solid in a first nonpolar solvent to form a first PbS quantum dot solution. S2: Add thiol ligands to the first PbS quantum dot solution, shake the reaction thoroughly for 1 min to 100 min, then add antisolvent to the reaction system to form a mixed solution; let stand, and the PbS quantum dots precipitate from the mixed solution to obtain a precipitate solution; S3: Remove the supernatant from the precipitate solution and vacuum for 5 min to 50 min to obtain the second PbS quantum dot solid. At this time, the surface of the quantum dot is a thiol ligand. S4: Dissolve quantum dots with thiol ligands on the surface in a second nonpolar solvent to obtain a second PbS quantum dot solution with a concentration of 10 mg / mL to 500 mg / mL; S5: Dissolve the thiol ligand in the first polar solvent to obtain a thiol ligand solution with a volume percentage of 0.01~1%; S6: Spin-coat the second PbS quantum dot solution onto the substrate, then cover the substrate surface with the thiol ligand solution from step S5, let it stand, spin-coat again, and then wash it multiple times with the first polar solvent. S7: Repeat step S6 multiple times until the PbS colloidal quantum dot film is formed; In step S2, the thiol ligand is mercaptoethanol (ME); in step S5, the thiol ligand is butanethiol. The antisolvent is one or a mixture of isopropanol, chloroform, or acetone; 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.

2. The method for preparing long-term high-temperature resistant lead sulfide colloidal quantum dot thin films according to claim 1, characterized in that, In step S1, the first nonpolar solvent includes one or more combinations of n-hexane, n-octane, toluene, and tetrachloroethylene.

3. The method for preparing long-term high-temperature resistant lead sulfide colloidal quantum dot thin films according to claim 1, characterized in that, In step S1, the concentration of the first PbS quantum dot solution is 1 mg / mL to 1000 mg / mL.

4. The method for preparing long-term high-temperature resistant lead sulfide colloidal quantum dot thin films according to claim 1, characterized in that, In step S4, the second nonpolar solvent includes one or more combinations of n-hexane, n-octane, toluene, and tetrachloroethylene.

5. The method for preparing long-term high-temperature resistant lead sulfide colloidal quantum dot thin films according to claim 1, characterized in that, In step S5, the first polar solvent includes one or more combinations of acetonitrile or methanol.

6. The method for preparing long-term high-temperature resistant lead sulfide colloidal quantum dot thin films according to claim 1, characterized in that, In step S6, the spin coating speed of the second PbS quantum dot solution on the substrate is 1000 r / min ~ 10000 r / min, the spin coating time is 10s ~ 60s, and the spin coating acceleration is 100 r / s ~ 1000 r / s.

7. The method for preparing long-term high-temperature resistant lead sulfide colloidal quantum dot thin films according to claim 1, characterized in that, In step S6, the thiol ligand solution is left to stand 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.

8. A long-time high-temperature-resistant lead sulfide colloidal quantum dot film, characterized in that, The long-term high-temperature resistant lead sulfide colloidal quantum dot film is prepared by any one of the long-term high-temperature resistant lead sulfide colloidal quantum dot film preparation methods according to claims 1-7.

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