Application of a polyionic liquid in preparation of perovskite quantum dots, and a preparation method of perovskite quantum dots

Abstract

The application relates to the technical field of quantum dot materials, in particular to application of a polyionic liquid in preparation of perovskite quantum dots and a preparation method of the perovskite quantum dots. The application provides the application of the polyionic liquid in the preparation of the perovskite quantum dots, and the polyionic liquid has a structural formula of formula I or formula II; wherein n in the formula I and the formula II is independently selected from integers from 10 to 15. By taking the polyionic liquid as a ligand, halogens in the polyionic liquid participate in synthesis of quantum dots in a reprecipitation process, the polyionic liquid is more firmly wrapped on surfaces of perovskite quantum dots, and then surface defects of the perovskite quantum dots are reduced, so that the stability of the perovskite is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of quantum dot materials, and particularly relates to application of a polyionic liquid in preparation of perovskite quantum dots and a preparation method of perovskite quantum dots. BACKGROUND

[0002] Metal halide perovskite has the advantages of adjustable band gap, low binding energy, wide visible light absorption range, high photoluminescence quantum yield, fast carrier transfer and the like, so that the metal halide perovskite can be applied in the fields of solar cells, photodetectors, light-emitting devices, photocatalysis and X-ray imaging and the like.

[0003] At present, the preparation methods for synthesizing perovskite nanocrystals mainly include liquid phase chemical synthesis and physical vapor deposition (the liquid phase chemical synthesis mainly includes high-temperature hot injection, normal-temperature coprecipitation, solvent thermal synthesis and microwave-assisted synthesis and the like), but these preparation technologies still have many defects at the present stage, such as the high-temperature hot injection method needing severe reaction conditions (high temperature, inert gas and the like), a complex preparation process, the microwave-assisted synthesis method not meeting the demand of large-scale production and the like.

[0004] The ligand-assisted reprecipitation method is an effective method for synthesizing perovskite quantum dots, and is based on the difference in solubility of ions in different solvents, and perovskite quantum dots are synthesized through the reprecipitation technology. Compared with the preparation method of perovskite nanocrystals, the ligand-assisted reprecipitation method has the advantages of simplifying the preparation process and improving the quantum yield, and is more advantageous in practicability.

[0005] However, the application of perovskite quantum dots is limited by its instability, for example, the influence of moisture, oxygen and temperature will cause the structure of the perovskite quantum dots to degrade and the photoluminescence (PL) to be quenched. At present, inorganic ligands (SiO2, Al2O3, TiO2, molecular sieve) or organic ligands (oleic acid, oleylamine) are often introduced to passivate the surface of the perovskite quantum dots, for example, inorganic SiO2 is covered on the quantum dots to protect the internal material from the influence of the external environment. In 2019, Yinzi et al. disclosed in the article “Preparation of MAPbBr3 by ligand-assisted reprecipitation method” that the ligands 3-aminopropyl triethoxysilane (APTES) and oleic acid (OA) are added into a precursor solution formed by MABr and PbBr2, and then the precursor is added into a toluene solution (anti-solvent) under vigorous stirring to obtain a sample with green fluorescence and adjustable grain size. Although the inorganic ligand coating can improve the stability of the perovskite quantum dots, it will greatly block the transmission path of the electron-hole in the quantum dots, affecting the optical performance and photocatalytic performance of the quantum dots. The commonly used organic ligands such as oleic acid and oleylamine are unstable and easy to fall off, thereby affecting the stability of the perovskite quantum dots. SUMMARY

[0006] The application aims to provide an application of a polyionic liquid in preparation of perovskite quantum dots, and solve the problem of poor stability of perovskite quantum dots prepared by a current ligand-assisted reprecipitation method.

[0007] The second object of the application is to provide a preparation method of perovskite quantum dots, and solve the problem of poor stability of perovskite quantum dots prepared by a current ligand-assisted reprecipitation method.

[0008] To solve the above technical problems, the technical scheme of the application of a polyionic liquid in preparation of perovskite quantum dots is as follows:

[0009] The application of a polyionic liquid in preparation of perovskite quantum dots, the polyionic liquid has a structural formula of formula I or formula II.

[0010] Formula I;

[0011] Formula II;

[0012] In the formula, n in the formula I and the formula II is independently selected from an integer of 10-15.

[0013] The application is an improvement on the prior art, and provides the application of a polyionic liquid in preparation of perovskite quantum dots, in which a polyionic liquid formed by poly 1-butyl (3-hydroxy) -3-methyl imidazole chloride or poly 1-butyl (3-hydroxy) -3-methyl imidazole bromide is used as a ligand in the process of preparing perovskite quantum dots by a ligand-assisted reprecipitation method, halogen in the polyionic liquid can participate in the formation of quantum dots as a halogen source in the reprecipitation process, and the polyionic liquid can be coated on the surface of perovskite quantum dots, has good wrapping stability, is wrapped more firmly, can reduce the surface defects of perovskite quantum dots, and thus improves the stability of perovskite.

[0014] The technical scheme of the preparation method of perovskite quantum dots is as follows:

[0015] The preparation method of perovskite quantum dots comprises the following steps: using the polyionic liquid as a ligand and perovskite precursors to prepare perovskite quantum dots by a ligand-assisted reprecipitation method.

[0016] The application uses the ligand-assisted reprecipitation method to prepare perovskite materials, which has simple reaction equipment, mild reaction conditions, and an easy-to-operate reaction process, has the advantages of simple synthesis process, low cost and low risk, and overcomes the shortcomings of complicated preparation process, harsh reaction conditions and difficulty in large-scale preparation of the high-temperature hot injection method, the anion exchange method and the vapor deposition method.

[0017] The commonly used lead halide perovskite, such as CsPbBr3, Cs4PbBr6, MAPbBr3, has a relatively large toxicity of Pb element, which has potential harm to human health and environment. Therefore, in order to obtain a non-lead perovskite quantum dot, preferably, the perovskite quantum dot is a Cs3Bi2X9 perovskite quantum dot, wherein X is Cl or Br.

[0018] In order to further improve the synthesis efficiency of the Cs3Bi2X9 perovskite quantum dot, preferably, the Cs3Bi2X9 perovskite quantum dot is obtained by mixing the polyionic liquid and the perovskite precursor in a solvent to form a reaction liquid, and then adding the reaction liquid into an anti-solvent under stirring to precipitate.

[0019] In order to further regulate the structure of the perovskite and improve the coating rate of the polyionic liquid on the perovskite, preferably, the molar ratio of Cs element in the Cs source to Bi element in the Bi source is (0.8-5):(0.5-2), and 50-200 mg of the polyionic liquid is added for each 0.08-0.5 mmol of the Cs element. More preferably, the molar ratio of Cs element in the Cs source to Bi element in the Bi source is (0.8-5):(1.5-2), and 100-200 mg of the polyionic liquid is added for each 0.08-0.5 mmol of the Cs element.

[0020] In order to further improve the synthesis efficiency of the quantum dot, preferably, the temperature during the mixing to form the reaction liquid is 25-80℃, and the time is 15-30 min.

[0021] In order to further improve the coating efficiency of the polyionic liquid, preferably, the reaction liquid is obtained by dissolving the Cs source and the Bi source in a polyionic liquid solution, and the concentration of the polyionic liquid in the polyionic liquid solution is 10-40 mg / mL. More preferably, the concentration of the polyionic liquid in the polyionic liquid solution is 20-40 mg / mL.

[0022] In order to further regulate the size and morphology of the perovskite quantum dot, preferably, the anti-solvent is isopropanol, and the volume ratio of the reaction liquid to the anti-solvent is 1:(10-20).

[0023] In order to further regulate the structure of the perovskite quantum dot, preferably, the Cs source is selected from one or more of Cs2CO3, CH3COOCs and Cs2SO4; and the Bi source is selected from one or both of Bi(NO3)3 and Bi2(SO4)3. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 XRD pattern of the Cs3Bi2Br9 perovskite quantum dot prepared in Example 2 of the present application;

[0025] Figure 2 Infrared spectrum of Cs3Bi2Br9 perovskite quantum dots prepared for Example 2 of the present application;

[0026] Figure 3 Photo of aqueous dispersion of Cs3Bi2Br9 perovskite quantum dots prepared for Example 2 of the present application placed in a dark environment at room temperature for one month;

[0027] Figure 4 Ultraviolet spectrum of aqueous dispersion of Cs3Bi2Br9 perovskite quantum dots prepared for Example 2 of the present application placed for one month;

[0028] Figure 5 Comparison chart of aqueous dispersion of Cs3Bi2Br9 perovskite quantum dots prepared for Example 2 and Comparative Example 1 placed in a dark environment at room temperature for one month. DETAILED DESCRIPTION

[0029] The technical concept of the application of the polyionic liquid in the preparation of perovskite quantum dots is as follows:

[0030] In the prior art, ligand-assisted reprecipitation method is used to prepare perovskite quantum dots, and the ligand is generally an organic ligand oleic acid or an inorganic ligand SiO2 to passivate the surface of the perovskite quantum dots, but the inorganic ligand affects the optical properties of the quantum dots, and the organic ligand is easy to fall off, resulting in poor stability of the perovskite quantum dots; and in the present application, the polyionic liquid is used as the ligand, and in the reprecipitation process, the halogen in the polyionic liquid participates in the synthesis of the quantum dots, and the wrapping of the polyionic liquid on the surface of the perovskite quantum dots is more firm, thereby reducing the surface defects of the perovskite quantum dots and improving the stability of the perovskite.

[0031] The preparation method of the perovskite quantum dots of the present application comprises the following steps: adding a Cs source and a Bi source into a polyionic liquid solution, stirring at 25-80℃ for 15-30min until complete dissolution to form a reaction liquid, adding the reaction liquid into isopropyl alcohol under the condition of vigorous stirring, stirring for 5-10min for precipitation, instant formation of Cs3Bi2X9 quantum dots with the addition of the reaction liquid, and then solid-liquid separation, washing, and drying to obtain Cs3Bi2X9 quantum dots.

[0032] In the specific embodiment, the polyionic liquid is prepared by referring to the preparation method disclosed in patent CN108409964A, and only the anion of the polyionic liquid is changed to Br - and Cl - . Specifically, the polyionic liquid is obtained by ring-opening addition reaction of imidazole and halogenated propylene oxide in a solvent, the halogenated propylene oxide is epichlorohydrin or epibromohydrin, and the molar ratio of the imidazole and the halogenated propylene oxide is 1: (0.9-1.1).

[0033] In specific embodiments, the ring-opening addition reaction is stirring the imidazole aqueous solution and the halogenated propylene oxide under ice bath conditions for 12-15 h, and then reacting at 95-110℃ for 7-9 days; the concentration of the imidazole aqueous solution is 1-2 mol / L.

[0034] In specific embodiments, after the ring-opening addition reaction is completed, an extractant is added to the reaction system to extract the synthesized polyionic liquid from the aqueous phase to the organic phase, and then a solid waxy sample is obtained after drying.

[0035] In specific embodiments, the polyionic liquid solution is obtained by dissolving the polyionic liquid in dimethyl sulfoxide (DMSO).

[0036] In specific embodiments, the solid-liquid separation in the preparation of the Cs3Bi2X9 perovskite quantum dots is centrifugation, and the centrifugation speed is 8000-10000 rpm and the centrifugation time is 5-10 min.

[0037] In specific embodiments, the washing in the preparation of the Cs3Bi2X9 perovskite quantum dots is washing twice with isopropanol; and the drying is drying in a vacuum drying box.

[0038] The application will be further described in detail below with reference to specific embodiments. The chemical reagents involved in the following examples are commercially available conventional goods, unless otherwise specified.

[0039] I. Specific embodiments of the application of the polyionic liquid in the preparation of perovskite quantum dots

[0040] Example 1

[0041] The application of the polyionic liquid in the preparation of perovskite quantum dots in this embodiment is to apply the polyionic liquid as a ligand in the preparation of Cs3Bi2X9 perovskite quantum dots.

[0042] The polyionic liquid has a structural formula of Formula I:

[0043] Formula I;

[0044] In Formula I, n is an integer selected from 10-15.

[0045] In other embodiments, the polyionic liquid has a structural formula of Formula II:

[0046] Formula II;

[0047] In Formula II, n is an integer selected from 10-15.

[0048] Two, the preparation method of the perovskite quantum dots provided by the application

[0049] Example 2

[0050] The preparation method of the perovskite quantum dots of this example is as follows:

[0051] (1) 0.0512 g of Cs2CO3 and 0.0595 g of Bi(NO3)3 were added to 5 mL of a polyionic liquid solution, and stirring was performed at 25°C for 15 min until complete dissolution to form a reaction solution, the polyionic liquid being a polyionic liquid having Formula II dissolved in dimethyl sulfoxide (DMSO) to obtain, wherein n = 12, and the concentration of the polyionic liquid was 40 mg / mL.

[0052] (2) The reaction solution in step (1) was added to 50 mL of isopropyl alcohol under vigorous stirring, and stirring was performed for 5 min for precipitation.

[0053] (3) The reaction product in step (2) was moved to a centrifuge tube using a pipette, centrifugation was performed at 8000 rpm for 5 min, the supernatant was discarded and the precipitate was retained, the precipitate was washed twice using isopropyl alcohol, and then dried using a vacuum drying oven to obtain Cs3Bi2Br9 perovskite quantum dots.

[0054] Example 3

[0055] The preparation method of the perovskite quantum dots of this example is basically the same as that of Example 2, except that in step (1), 0.0816 g of Cs2CO3 and 0.0595 g of Bi(NO3)3 were added to 5 mL of a polyionic liquid solution, and stirring was performed at 25°C for 30 min until complete dissolution to form a reaction solution, the polyionic liquid being a polyionic liquid having Formula I dissolved in DMSO to obtain, wherein n = 13, and the concentration of the polyionic liquid was 40 mg / mL.

[0056] Example 4

[0057] The preparation method of the perovskite quantum dots of this example is basically the same as that of Example 2, except that in step (1), 0.04315 g of CH3COOCs and 0.0592 g of Bi(NO3)3 were added to 5 mL of a polyionic liquid solution, and stirring was performed at 50°C for 15 min until complete dissolution to form a reaction solution, the polyionic liquid being a polyionic liquid having Formula I dissolved in DMSO to obtain, wherein n = 14, and the concentration of the polyionic liquid was 20 mg / mL.

[0058] Example 3

[0059] Comparative Example 1 (preparation of perovskite quantum dots using oleic acid as a ligand)

[0060] The preparation method of the perovskite quantum dots of the present comparative example is basically the same as that of Example 2, except that in step (1), 0.04315 g CH3COOCs, 0.067 g BiBr3 and 0.5 mL of oleic acid are added into 5 mL of DMSO solvent, and the mixture is stirred at 25°C until completely dissolved to form a reaction solution.

[0061] IV. Experimental Examples

[0062] The physicochemical properties of the perovskite quantum dots prepared in the examples are characterized in the present experimental examples.

[0063] The XRD pattern of the Cs3Bi2Br9 perovskite quantum dots of Example 2 is shown in Figure 1 , where the abscissa is the diffraction angle 2θ (°), and the ordinate is the diffraction intensity (intensity). The diffraction peaks of the sample are consistent with the standard card of Cs3Bi2Br9, indicating that the Cs3Bi2Br9 perovskite quantum dots are successfully prepared.

[0064] The infrared spectrum of the Cs3Bi2Br9 perovskite quantum dots of Example 2 is shown in Figure 2 . As can be seen from Figure 2 , the strong peak at 1022 cm -1 and the relatively strong peak at 1403 cm -1 correspond to the characteristic absorption peaks of the imidazole ring, indicating that the polyionic liquid is coated on the surface of the Cs3Bi2Br9 perovskite quantum dots prepared in the present application.

[0065] The photo of the aqueous dispersion of the Cs3Bi2Br9 perovskite quantum dots of Example 2 placed in a dark environment at room temperature for one month is shown in Figure 3 , and the test result of its ultraviolet absorption spectrum is shown in Figure 4 . As can be seen from Figure 4 , the Cs3Bi2Br9 perovskite quantum dots dispersion still shows a strong absorption peak at 350 nm after being placed for one month, indicating that the Cs3Bi2Br9 perovskite quantum dots prepared in the present application have good stability.

[0066] The comparative diagram of the aqueous dispersions of the Cs3Bi2Br9 perovskite quantum dots of Example 2 and Comparative Example 1 placed in a dark environment at room temperature for one month is shown in Figure 5 , where the left side is the aqueous dispersion of the quantum dots obtained in Example 2, and the right side is the aqueous dispersion of the quantum dots obtained in Comparative Example 1. As can be seen from Figure 5It can be seen that the water dispersion liquid of Cs3Bi2Br9 quantum dots prepared in Example 2 still presents the original yellow color, indicating that the quantum dots prepared in Example 2 with polyionic liquid as ligand have good stability; the color of the water dispersion liquid of Cs3Bi2Br9 quantum dots prepared in Comparative Example 1 changes from yellow to white, indicating that the water stability of the Cs3Bi2Br9 perovskite quantum dots prepared in Comparative Example 1 with oleic acid as ligand is poor. The Cs3Bi2Br9 perovskite quantum dots prepared in Examples 3-5 also exhibit good water stability.

[0067] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the foregoing detailed description of the present application is made with reference to the foregoing embodiments, for those skilled in the art, it still can be modified, or part of the technical features of the equivalent replacement, within the spirit and principles of the present application, any modification, equivalent replacement, improvement, etc., should be included within the scope of the present application.

Claims

1. Application of a polyionic liquid in the preparation of perovskite quantum dots, characterized in that, The polyionic liquid has a structural formula of Formula I or Formula II: Formula I; Formula II; wherein n in Formula I and Formula II is independently selected from an integer of 10-15; The preparation method of the perovskite quantum dot comprises the following steps: using the polyionic liquid as a ligand and perovskite precursors to prepare Cs3Bi2X9 perovskite quantum dots by a ligand-assisted reprecipitation method, wherein X is Cl or Br; the Cs3Bi2X9 perovskite quantum dots are obtained by mixing the polyionic liquid and the perovskite precursors in a solvent to form a reaction liquid, and then precipitating the reaction liquid in an anti-solvent under stirring, the perovskite precursors comprising a Cs source and a Bi source; the Cs source is selected from one or more of Cs2CO3, CH3COOCs and Cs2SO4; and the Bi source is selected from one or both of Bi(NO3)3 and Bi2(SO4)3.

2. A method for preparing perovskite quantum dots, characterized by, The preparation method of the perovskite quantum dot comprises the following steps: using the polyionic liquid as a ligand and perovskite precursors to prepare Cs3Bi2X9 perovskite quantum dots by a ligand-assisted reprecipitation method, wherein X is Cl or Br; the Cs3Bi2X9 perovskite quantum dots are obtained by mixing the polyionic liquid and the perovskite precursors in a solvent to form a reaction liquid, and then precipitating the reaction liquid in an anti-solvent under stirring, the perovskite precursors comprising a Cs source and a Bi source; the Cs source is selected from one or more of Cs2CO3, CH3COOCs and Cs2SO4; and the Bi source is selected from one or both of Bi(NO3)3 and Bi2(SO4)3.

3. The method for preparing perovskite quantum dots as described in claim 1, characterized in that, The molar ratio of Cs in the Cs source to Bi in the Bi source is (0.8-5):(0.5-2), and 50-200 mg of the polyionic liquid is added for each 0.08-0.5 mmol of Cs.

4. The method for preparing perovskite quantum dots as described in claim 1, characterized in that, The temperature for mixing to form the reaction liquid is 25-80°C, and the time is 15-30 min.

5. The method for preparing perovskite quantum dots as described in claim 1, characterized in that, The reaction liquid is obtained by dissolving the Cs source and the Bi source in a polyionic liquid solution, and the concentration of the polyionic liquid in the polyionic liquid solution is 10-40 mg / mL.

6. The method for preparing perovskite quantum dots as described in claim 1, characterized in that, The anti-solvent is isopropyl alcohol, and the volume ratio of the reaction liquid to the anti-solvent is 1:(10-20).

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