Lead sulfide quantum dot and preparation method thereof

Abstract

The invention provides a lead sulfide quantum dot and a preparation method thereof, and the preparation method comprises the following steps: carrying out ion exchange on a perovskite quantum dot and a sulfur source in a liquid-phase medium to obtain the lead sulfide quantum dot. According to the invention, the perovskite quantum dots are used as a template, and the perovskite quantum dots and a sulfur source are subjected to ion exchange by using the ion characteristics of the perovskite quantum dots, so that the perovskite quantum dots are converted into lead sulfide quantum dots; therefore, the lead sulfide quantum dots with different wavelengths can be obtained by regulating and controlling the particle size and the shape of the perovskite quantum dots. According to the preparation method of the lead sulfide quantum dot, the lead sulfide quantum dot with the high peak-to-valley ratio and the good monodispersity can be prepared under the room temperature condition, the preparation process is simple, the raw material source is wide, the raw material cost is low, the preparation condition requirement is low, environment friendliness is high, and the preparation method is suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis technology, and particularly relates to a lead sulfide quantum dot and its preparation method. Background Technology

[0002] Solution processing is an effective way to achieve low cost, large area, flexibility, and lightweight characteristics in optoelectronic devices. Near-infrared PbS quantum dots, as a high-performance light conversion material, show great promise for applications in solar cells and photodetectors. PbS quantum dots possess tunable bandgap, excellent light absorption properties, and low carrier binding energy, giving them unique advantages in solar cells and infrared detection.

[0003] Currently, the hot-injection method using (TMS)₂S (hexamethyldisiloxane) as the sulfur source is the most common synthetic route for lead sulfide quantum dots. Compared with other sulfur sources, lead sulfide quantum dots prepared using (TMS)₂S as the sulfur source have better quality, exhibiting better monodispersity and a higher peak-to-valley ratio. However, (TMS)₂S is expensive, highly volatile, and has a certain degree of toxicity, which greatly limits the large-scale promotion and application of lead sulfide quantum dots. Summary of the Invention

[0004] This application provides a lead sulfide quantum dot and its preparation method, aiming to solve the problems of high sulfur source price, high volatility and certain toxicity in existing lead sulfide quantum dot preparation methods, which limit the large-scale promotion and application of lead sulfide quantum dots.

[0005] To solve the above-mentioned technical problems, one technical solution adopted in this application is: to provide a method for preparing lead sulfide quantum dots, comprising the following steps: Lead sulfide quantum dots are obtained by ion exchange between perovskite quantum dots and a sulfur source in a liquid medium.

[0006] Preferably, the perovskite quantum dot has the structure ABX3, wherein A is Cs, MA, BA or FA; B is Pb; and X is F, Cl, Br or I.

[0007] Preferably, the perovskite quantum dots are prepared by high-temperature hot-injection or room-temperature recrystallization.

[0008] Preferably, the sulfur source is S-OLA, S-TOP, S-TBP, S-ODE or (TMS)2S.

[0009] Preferably, the liquid medium is one or more of toluene, chloroform, hexane, heptane, octane, dodecane, octadecene, N,N-dimethylformamide, and dimethyl sulfoxide.

[0010] Preferably, the temperature of the ion exchange is 0~300℃.

[0011] Preferably, the temperature of the ion exchange is 10~40℃.

[0012] Preferably, the temperature of the ion exchange is 25°C.

[0013] Preferably, the ion exchange time is 10 s to 30 min.

[0014] Preferably, the step of ion-exchanging perovskite quantum dots and a sulfur source in a liquid medium to obtain lead sulfide quantum dots specifically includes: The perovskite quantum dots and the sulfur source are subjected to ion exchange in the liquid phase to obtain a product liquid. The product solution was mixed with a precipitant, centrifuged, and dried to obtain the lead sulfide quantum dots.

[0015] Preferably, the precipitant is one or more selected from ethanol, isopropanol, acetone, ethyl acetate, methyl acetate, and ethyl formate.

[0016] Preferably, the centrifugation speed is 500~20000 rpm.

[0017] To solve the above-mentioned technical problems, another technical solution adopted in this application is to provide a lead sulfide quantum dot, which is prepared by the lead sulfide quantum dot preparation method as described in any of the above claims.

[0018] The beneficial effects of this application's embodiments are as follows: Unlike existing technologies, this application provides lead sulfide quantum dots and a method for preparing the same. The method for preparing lead sulfide quantum dots includes: ion exchange between perovskite quantum dots and a sulfur source in a liquid medium to obtain lead sulfide quantum dots. By using perovskite quantum dots as a template, the ionic properties of the perovskite quantum dots are utilized to induce ion exchange with the sulfur source, thereby converting the perovskite quantum dots into lead sulfide quantum dots. Furthermore, the preparation method for perovskite quantum dots is simple, and the particle size and shape of the perovskite quantum dots are highly controllable; therefore, lead sulfide quantum dots prepared by ion exchange using perovskite quantum dots as a template can maintain their particle size and shape well, and thus, lead sulfide quantum dots of different wavelengths can be obtained by controlling the particle size and shape of the perovskite quantum dots. Compared to traditional preparation methods that are limited to using (TMS)2S as a sulfur source and require a high-temperature environment, the lead sulfide quantum dot preparation method provided in this application can prepare lead sulfide quantum dots with a peak-to-valley ratio and good monodispersity at room temperature. The preparation process is simple, the raw materials are widely available, the raw material cost is low, the preparation conditions are low, the environmental friendliness is strong, and it is suitable for large-scale production. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application 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 embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 This is the infrared absorption spectrum of the PbS quantum dots provided in Embodiment 1 of this application; Figure 2 This is the XRD pattern of the PbS quantum dots provided in Embodiment 1 of this application; Figure 3 This is a TEM image of the PbS quantum dots provided in Embodiment 1 of this application; Figure 4 This is the infrared absorption spectrum of the PbS quantum dots provided in Embodiment 2 of this application. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0022] The terms "first," "second," and "third" in this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movements between components in a specific orientation (as shown in the figures). If the specific orientation changes, the directional indications also change accordingly. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] This application provides a method for preparing lead sulfide quantum dots, which includes the following steps: Step S1: Ion exchange is performed between perovskite quantum dots and a sulfur source in a liquid medium to obtain lead sulfide quantum dots.

[0025] In the specific implementation process, step S1 specifically includes: Step S11: Ion exchange is performed between perovskite quantum dots and sulfur source in the liquid phase to obtain product liquid.

[0026] In specific implementation, the preferred structure of the perovskite quantum dots is ABX3, wherein A is preferably Cs, MA (methylamine), BA (butylamine), or FA (methylammonium); B is preferably Pb; and X is preferably F, Cl, Br, or I. For example, the structure of the perovskite quantum dots can be any structure such as CsPbBr3, CsPbI3, CsPbCl3, or CsPbF3.

[0027] In practice, perovskite quantum dots are preferably prepared by high-temperature hot injection or room-temperature recrystallization.

[0028] Specifically, taking the preparation of perovskite quantum dots CsPbBr3 as an example, the preferred process for preparation using the high-temperature hot-injection method includes: Oleic acid (OA) and / or 1-octadecene (ODE) are added to Cs2CO3 and heated under vacuum until all Cs2CO3 is dissolved to form a cesium source. PbBr2 is dissolved in one or more of OA, oleylamine (OLA), and ODE under heating and vacuum conditions to form a lead source. The cesium source is injected into the lead source under high temperature conditions and reacted for a period of time to obtain a crude CsPbBr3 quantum dot solution. The crude CsPbBr3 quantum dot solution is mixed with a precipitant, centrifuged and dried to obtain CsPbBr3. The preferred ratio of OA, ODE, and Cs2CO3 is (2~8) mL:(10~30) mL:1 mmol, more preferably 4 mL:20 mL:1 mmol; the preferred ratio of PbBr2, OA, OLA, and ODE is 1 mmol:(1~5) mL:(1~5) mL:(10~50) mL, more preferably 1 mmol:3 mL:3 mL:25 mL; the preferred molar ratio of cesium source to lead source is 1:5~1:20, more preferably 1:10; the preferred high temperature is 80~120℃, more preferably 100℃; the preferred reaction time is 10~60 s, more preferably 30 s; the preferred precipitant is ethyl acetate; the preferred volume ratio of precipitant to CsPbBr3 quantum dot crude solution is 2:1~5:1, more preferably 3:1.

[0029] In the specific implementation process, taking the preparation of perovskite quantum dots CsPbI3 as an example, the preferred specific process for preparation using the high-temperature hot-injection method includes: Oleic acid (OA) and / or 1-octadecene (ODE) are added to Cs₂CO₃ and heated under vacuum until all Cs₂CO₃ is dissolved to form a cesium source. PbI₂ is dissolved in one or more of OA, oleylamine (OLA), and ODE under heating and vacuum conditions to form a lead source. The cesium source is injected into the lead source under high temperature conditions and reacted for a period of time to obtain a crude CsPbI₃ quantum dot solution. The crude CsPbI₃ quantum dot solution is mixed with a precipitant, centrifuged and dried to obtain CsPbI₃. The preferred ratio of OA, ODE, and Cs2CO3 is (2~8) mL:(10~30) mL:1 mmol, more preferably 4 mL:20 mL:1 mmol; the preferred ratio of PbI2, OA, OLA, and ODE is 1 mmol:(1~5) mL:(1~5) mL:(10~50) mL, more preferably 1 mmol:3 mL:3 mL:25 mL; the preferred molar ratio of cesium source to lead source is 1:5~1:20, more preferably 1:15; the preferred high temperature is 80~120℃, more preferably 90℃; the preferred reaction time is 10~60 s, more preferably 20 s; the preferred precipitant is ethyl acetate; the preferred volume ratio of precipitant to CsPbI3 quantum dot crude solution is 2:1~5:1, more preferably 4:1.

[0030] In the specific implementation process, taking the preparation of perovskite quantum dots CsPbBr3 as an example, the preferred specific process for preparation using the room temperature recrystallization method includes: PbBr2 and CsBr were dissolved in N,N-dimethylformamide (DMF) to obtain a precursor solution; oleic acid and oleylamine were added to the precursor solution to obtain a mixed solution; the mixed solution was injected into toluene and stirred to obtain a CsPbBr3 nanocrystal solution; the CsPbBr3 nanocrystal solution was mixed with a precipitant, centrifuged and dried to obtain CsPbBr3. The preferred molar ratio of PbBr2 to CsBr is 1:(0.5~2), more preferably 1:1; the preferred molar ratio of PbBr2 to N,N-dimethylformamide is (0.2~0.6) mmol:10 mL, more preferably 0.4 mmol:10 mL; the preferred molar ratio of PbBr2 to oleic acid is (0.2~0.6) mmol:1 mL, more preferably 0.4 mmol:1 mL; the preferred molar ratio of PbBr2 to oleylamine is (0.2~0.6) mmol:0.5 mL, more preferably 0.4 mmol:0.5 mL; the preferred volume ratio of the mixed solution to toluene is 1:5~1:20, more preferably 1:10; the preferred precipitant is ethyl acetate; the preferred volume ratio of CsPbBr3 nanocrystal solution to precipitant is 1:2~1:8, more preferably 1:4; the preferred centrifugation speed is 6000~12000 rpm, more preferably 8000 rpm. The centrifugation time is preferably 2-8 min, more preferably 5 min.

[0031] In specific implementation, the preferred sulfur source is S-OLA (sulfur-oleylamine, i.e., a mixture of sulfur and oleylamine), S-TOP (sulfur-trioctylphosphine, i.e., a mixture of sulfur and trioctylphosphine), S-TBP (sulfur-tributylphosphine, i.e., a mixture of sulfur and tributylphosphine), S-ODE (sulfur-octadecene, i.e., a mixture of sulfur and 1-octadecene), or (TMS)2S (hexamethyldisilazane); the sulfur content in the sulfur source is preferably 0.2~2 mmol / mL, specifically 0.2 mmol / mL, 0.3 mmol / mL, 0.4 mmol / mL, 0.5 mmol / mL, 0.6 mmol / mL, 0.7 mmol / mL, 0.8 mmol / mL, 0.9 mmol / mL, 1 mmol / mL, 1.1 mmol / mL, 1.2 mmol / mL, 1.3 mmol / mL, 1.4 mmol / mL, 1.5 mmol / mL, 1.6 mmol / mL, 1.7 mmol / mL, etc. mmol / mL, 1.8 mmol / mL, 1.9 mmol / mL or 2 mmol / mL.

[0032] Specifically, the preferred ratio of perovskite quantum dots to sulfur source (in terms of sulfur content) is 100 mg: (0.5~2) mmol, specifically 100 mg: 0.5 mmol, 100 mg: 0.6 mmol, 100 mg: 0.7 mmol, 100 mg: 0.8 mmol, 100 mg: 0.9 mmol, 100 mg: 1 mmol, 100 mg: 1.1 mmol, 100 mg: 1.2 mmol, 100 mg: 1.3 mmol, 100 mg: 1.4 mmol, 100 mg: 1.5 mmol, 100 mg: 1.6 mmol, 100 mg: 1.7 mmol, 100 mg: 1.8 mmol, 100 mg: 1.9 mmol, or 100 mg: 2 mmol.

[0033] In specific implementation, the liquid medium is preferably one or more of toluene, chloroform, hexane, heptane, octane, dodecane, octadecene, N,N-dimethylformamide, and dimethyl sulfoxide; hexane is preferably n-hexane; and octane is preferably n-octane.

[0034] Specifically, the content of perovskite quantum dots in the liquid medium is preferably 5~25 mg / mL, specifically 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, 10 mg / mL, 11 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL, 15 mg / mL, 16 mg / mL, 17 mg / mL, 18 mg / mL, 19 mg / mL, 20 mg / mL, 21 mg / mL, 22 mg / mL, 23 mg / mL, 24 mg / mL or 25 mg / mL.

[0035] Furthermore, ion exchange is preferably carried out under stirring conditions; the stirring speed is preferably 100~1000 rpm, specifically 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm or 1000 rpm.

[0036] In the specific implementation process, the ion exchange temperature is preferably 0~300℃, more preferably 10~40℃, specifically 10℃, 15℃, 20℃, 25℃ (room temperature), 30℃, 35℃ or 40℃. The ion exchange time is preferably 10 s~30 min, more preferably 5~30 min, specifically 5 min, 10 min, 15 min, 20 min, 25 min or 30 min.

[0037] Step S12: Mix the product liquid with the precipitant, centrifuge, and dry to obtain lead sulfide quantum dots.

[0038] In the specific implementation process, after the ion exchange is completed, the obtained product solution is preferably post-treated; that is, the product solution obtained in step S11 is mixed with a precipitant, and the mixture is centrifuged and dried to obtain lead sulfide quantum dots. The precipitant is preferably one or more of ethanol, isopropanol, acetone, ethyl acetate, methyl acetate, and ethyl formate; the volume ratio of the product solution to the precipitant is preferably 1:2 to 1:6, specifically 1:2, 1:3, 1:4, 1:5, or 1:6.

[0039] Specifically, the centrifugation speed is preferably 500~20000 rpm, more preferably 5000~10000 rpm, and can be 5000 rpm, 5500 rpm, 6000 rpm, 6500 rpm, 7000 rpm, 7500 rpm, 8000 rpm, 8500 rpm, 9000 rpm, 9500 rpm or 10000 rpm; the centrifugation time is preferably 0.5~5 min, and can be 0.5 min, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min or 5 min.

[0040] The method for preparing lead sulfide quantum dots provided in this application has at least the following beneficial effects: 1) Pioneeringly using perovskite quantum dots as templates, utilizing the ionic properties of perovskite quantum dots to enable them to exchange ions with sulfur sources, thereby converting perovskite quantum dots into lead sulfide quantum dots; 2) Currently, quantum dots synthesized at room temperature do not have a good peak-to-valley ratio, and quantum dots with a high peak-to-valley ratio are all synthesized at high temperature. However, the method of this application can synthesize quantum dots with a high peak-to-valley ratio at room temperature, filling the technological gap in the synthesis of quantum dots at room temperature. The synthesis process is simple, the equipment requirements are low, and it is suitable for large-scale production. 3) Lead sulfide quantum dots prepared by the currently widely used hot injection method have poor performance (wider absorption peak and smaller peak-to-valley ratio), while lead sulfide quantum dots prepared by the method proposed in this application have narrower absorption peak and higher peak-to-valley ratio.

[0041] 4) The raw material cost for the preparation of lead sulfide quantum dots is currently high (e.g., (TMS)2S, 200 yuan / g), while the method of this application uses a wide variety of sulfur sources, which can be selected according to market conditions, and has a cost advantage (e.g., sulfur powder, 0.5~5 yuan / g).

[0042] 5) The wavelength of lead sulfide prepared by the method proposed in this application is controllable, and lead sulfide quantum dots of different wavelength bands can be prepared, which can be applied in the fields of infrared light-emitting diodes, infrared detectors, and solar cells. 6) The method proposed in this application can also be used to prepare lead sulfide nanowires and nanosheets, and has a wide range of potential applications.

[0043] The invention will now be described in more detail with reference to the following embodiments and accompanying drawings. However, the embodiments and comparative examples provided below are merely illustrative and the scope of this application is not limited thereto.

[0044] Example 1 (1) Add 4 mL of OA and 20 mL of ODE to 1 mmol of Cs2CO3, heat and pump until all Cs2CO3 is dissolved to form a cesium source; (2) Dissolve 1 mmol of PbBr2 under heating and vacuum conditions in a mixed solvent of 3 mL OA, 3 mL OLA and 25 mL ODE to form a lead source; (3) At 100℃, the cesium source was injected into the lead source at a molar ratio of 1:10 and reacted for 30 s to obtain a crude liquid of CsPbBr3 quantum dots. (4) Add ethyl acetate to the crude CsPbBr3 quantum dot solution, with a volume ratio of ethyl acetate:crude solution = 3:1, centrifuge and dry to obtain CsPbBr3; (5) Add n-hexane to CsPbBr3 to prepare a 10 mg / mL CsPbBr3 solution; (6) Dissolve sulfur powder (0.5~5 yuan / g, the same below) in oleylamine to prepare a sulfur source (S-OLA) with a concentration of 1 mmol / mL. (7) Take 1 mL of S-OLA and add it to 10 mL of CsPbBr3 solution; (8) Stir the reaction at 300 rpm for 10 min at room temperature; (9) After the reaction is complete, transfer the product liquid to a centrifuge tube, add three times the volume of methyl acetate, and shake until homogeneous; (10) Then, centrifuge at 7000 rpm for 3 min, and after drying the precipitate, obtain PbS quantum dots.

[0045] The PbS quantum dots prepared in this embodiment were characterized, and the results are as follows: Figures 1-3 As shown. Figure 1 The infrared absorption spectrum of the PbS quantum dots provided in Example 1 of this application shows that the PbS has a narrow absorption peak, indicating that the prepared PbS has good monodispersity. Figure 2The XRD pattern of the PbS quantum dots provided in Example 1 of this application shows that the prepared PbS has a truncated octahedral phase structure. Figure 3 This is a TEM image of the PbS quantum dots provided in Example 1 of this application, showing that the prepared quantum dots have good monodispersity and an average particle size of 3.5 nm.

[0046] Example 2 (1) Add 0.4 mmol of PbBr2 and 0.4 mmol of CsBr to 10 mL of DMF and sonicate until completely dissolved to obtain the precursor solution; (2) Take 1 mL of oleic acid and 0.5 mL of oleylamine and add them to the above precursor solution, then sonicate for 10 min to obtain a mixed solution; (3) Then, 1 mL of the above mixed solution was injected into 10 mL of toluene and stirred at room temperature to ensure complete reaction. The stirring speed was 800 r / min to obtain CsPbBr3 nanocrystal solution. (4) Add ethyl acetate to the CsPbBr3 nanocrystal solution, the ratio of CsPbBr3 nanocrystal solution to ethyl acetate is 1:4 (volume ratio), centrifuge at 8000 r / min for 5 min, and dry to obtain CsPbBr3; (5) Disperse CsPbBr3 in n-octane to prepare a 15 mg / mL CsPbBr3 solution; (6) Dissolve sulfur powder in oleylamine to prepare a sulfur source (S-OLA) of 0.5 mmol / mL. (7) Take 3 mL of S-OLA and add it to 10 mL of CsPbBr3 solution; (8) The reaction was stirred at 400 rpm for 15 min at room temperature; (9) After the reaction is complete, transfer the product liquid to a centrifuge tube, add three times the volume of ethyl acetate, and shake until homogeneous; (10) Then, centrifuge at 8000 rpm for 3 min, dry the precipitate, and obtain PbS quantum dots.

[0047] The PbS quantum dots prepared in this embodiment were characterized, and the results are as follows: Figure 4 As shown. Figure 4 The infrared absorption spectrum of the PbS quantum dots provided in Example 2 of this application shows that the PbS has a narrow absorption peak, indicating that the prepared PbS has good monodispersity.

[0048] Example 3 (1) Add 4 mL of OA and 20 mL of ODE to 1 mmol of Cs2CO3, heat and pump until all Cs2CO3 is dissolved to form a cesium source; (2) Dissolve 1 mmol of PbI2 under heating and vacuum conditions in a mixed solvent of 3 mL OA, 3 mL OLA and 25 mL ODE to form a lead source; (3) At 90℃, the cesium source was injected into the lead source at a molar ratio of 1:15 and reacted for 20 s to obtain a crude liquid of CsPbI3 quantum dots; (4) Add ethyl acetate to the crude CsPbI3 quantum dot solution, with a volume ratio of 4:1 (ethyl acetate: crude solution), centrifuge and dry to obtain CsPbI3; (5) Add n-hexane to CsPbI3 to prepare a 10 mg / mL CsPbI3 solution; (6) Dissolve sulfur powder in oleylamine to prepare a sulfur source (S-OLA) with a concentration of 1 mmol / mL. (7) Take 1 mL of S-OLA and add it to 10 mL of CsPbI3 solution; (8) Stir the reaction at 300 rpm for 10 min at room temperature; (9) After the reaction is complete, transfer the product liquid to a centrifuge tube, add three times the volume of methyl acetate, and shake until homogeneous; (10) Then, centrifuge at 6000 rpm for 5 min, and after drying the precipitate, obtain PbS quantum dots.

[0049] Characterization of the PbS quantum dots prepared in this embodiment revealed that they also have narrow absorption peaks, indicating that the prepared PbS has good monodispersity.

[0050] This application also provides a lead sulfide quantum dot, which is prepared by the lead sulfide quantum dot preparation method provided in the above embodiments; the lead sulfide quantum dot has low manufacturing cost and has a peak-to-valley ratio and good monodispersity.

[0051] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalent elements of the claims are intended to be included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0052] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for preparing lead sulfide quantum dots, characterized in that, Includes the following steps: Lead sulfide quantum dots are obtained by ion exchange between perovskite quantum dots and a sulfur source in a liquid medium.

2. The method for preparing lead sulfide quantum dots according to claim 1, characterized in that, The perovskite quantum dot has the structure ABX3; where A is Cs, MA, BA or FA; B is Pb; and X is F, Cl, Br or I.

3. The method for preparing lead sulfide quantum dots according to claim 1, characterized in that, The perovskite quantum dots were prepared by high-temperature hot-injection or room-temperature recrystallization.

4. The preparation method according to claim 1, characterized in that, The sulfur source is S-OLA, S-TOP, S-TBP, S-ODE or (TMS)2S.

5. The method for preparing lead sulfide quantum dots according to claim 1, characterized in that, The liquid medium is one or more of toluene, chloroform, hexane, heptane, octane, dodecane, octadecene, N,N-dimethylformamide, and dimethyl sulfoxide.

6. The method for preparing lead sulfide quantum dots according to claim 1, characterized in that, The temperature for ion exchange is 0~300℃.

7. The method for preparing lead sulfide quantum dots according to claim 6, characterized in that, The temperature for ion exchange is 10~40℃.

8. The method for preparing lead sulfide quantum dots according to claim 7, characterized in that, The ion exchange temperature is 25°C.

9. The method for preparing lead sulfide quantum dots according to claim 1, characterized in that, The ion exchange time is 10 s to 30 min.

10. The method for preparing lead sulfide quantum dots according to claim 1, characterized in that, The step of ion-exchanging perovskite quantum dots and a sulfur source in a liquid medium to obtain lead sulfide quantum dots specifically includes: The perovskite quantum dots and the sulfur source are subjected to ion exchange in the liquid phase to obtain a product liquid. The product solution was mixed with a precipitant, centrifuged, and dried to obtain the lead sulfide quantum dots.

11. The method for preparing lead sulfide quantum dots according to claim 10, characterized in that, The precipitant is one or more of ethanol, isopropanol, acetone, ethyl acetate, methyl acetate, and ethyl formate.

12. The method for preparing lead sulfide quantum dots according to claim 10, characterized in that, The centrifuge speed is 500~20000 rpm.

13. A lead sulfide quantum dot, characterized in that, Lead sulfide quantum dots were prepared using the method described in any one of claims 1-12.

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