Method for preparing FAPbBr3 quantum dots

Abstract

The invention provides a method for preparing FAPbBr3 quantum dots, which comprises the following steps: S1, preparation of a precursor solution: respectively dissolving a lead source precursor, a bromine source precursor and acid in water and stirring to obtain the precursor solution; s2, formation of nucleation sites: adding an FA precursor into the precursor solution prepared in the step S1, stirring, and reacting and crystallizing in water to form floccules capable of being used as the nucleation sites; s3, construction of a substrate layer: adding silane into the solution prepared in the step S2, stirring, heating and drying to obtain a FAPbBr3-coated SiO2 quantum dot crude product, and coating the exterior of FAPbBr3 with SiO2 generated by hydrolysis of the silane in an acidic solution to serve as the substrate layer; s4, ball-milling recrystallization: carrying out ball-milling recrystallization on the FAPbBr3-coated SiO2 quantum dot crude product prepared in the step S3; wherein the object of ball milling is a substrate layer, and the object of recrystallization is FAPbBr3 quantum dots. The solvent of the system is an aqueous solution, so that the problems of recycling, discharging and the like of organic solvents are solved.

Description

Technical Field

[0001] This invention belongs to the field of perovskite quantum dot synthesis technology, and particularly relates to a method for preparing FAPbBr3 quantum dots. Background Technology

[0002] The structural formula of perovskite materials is ABX3, where element A is a monovalent cation, such as methylamine cation, formamidinium cation, cesium cation, etc., and element B is usually a divalent metal cation, such as lead (Pb). 2+ ), Tin (Sn) 2+ ) etc., where X is a monovalent halogen anion such as chlorobromoiodine (Cl... - ,Br - I - ).

[0003] Perovskite quantum dots (PDOs) are structurally unstable due to their strong ionicity, readily decomposing under conditions of water, oxygen, light, heat, and strong blue light. Therefore, improving the stability of PDOs has become a top priority in research both domestically and internationally. In 2018, González-Pedro et al. reported the use of APTES as a ligand to hydrolyze and generate silica-cesium lead bromine core-shell structured quantum dots, which effectively enhanced photoluminescence properties and stability after encapsulation. These research findings have significantly advanced the research progress on encapsulated structures of perovskite quantum dots.

[0004] Chinese Patent Publication No. CN 111139058 A discloses a perovskite quantum dot structure and its preparation method. The structure consists of perovskite quantum dots composed of formamidine lead bromine encapsulated in silica nanospheres. The preparation method is as follows: first, the prepared formamidine lead bromine quantum dots are dispersed in n-hexane; then, the bifunctional ligand is added to the quantum dot solution and stirred at high speed. Once a precipitate forms, the resulting precipitate is the perovskite quantum dot composed of formamidine lead bromine encapsulated in silica nanospheres. The emission peak position of the FAPbBr3 quantum dots prepared by the above method is between 525-535 nm, and the stability of the quantum dots can be improved.

[0005] Similarly, Chinese patent CN107474821A discloses a method for coating quantum dots with silica (publication date: 20171215). This silica is prepared by adding a silanizing agent to an anhydrous organic solvent containing quantum dots, where the mass ratio of the silanizing agent to the quantum dots is 0.1–10:1. To avoid quenching of the quantum dots by introduced catalysts such as water, ammonia, and mercapto groups during the silica formation process, the principle is to directly add the silanizing agent to the anhydrous organic solvent containing the quantum dots to prepare silica-coated quantum dot nanomaterials. The anhydrous organic solvent mentioned refers to analytically pure organic solvents or completely anhydrous organic solvents. The silanizing agent undergoes a hydrolysis reaction relying on residual moisture in the organic solvent or residual moisture in the air to obtain the silica coating layer. Alternatively, the silica coating layer can be obtained through high-temperature pyrolysis.

[0006] Because perovskite quantum dots readily react with water (hydroxyl groups), thereby reducing their luminescence performance, the field of perovskite display luminescence research often suffers from a technical bias that "water must be isolated during perovskite preparation." Therefore, existing technologies often use organic solvents or mixed solvents with organic solvents as the main component, such as the aforementioned hexane and DMF as reaction solvents.

[0007] Given the aforementioned technical context, those skilled in the art often avoid synthesizing quantum dots in an aqueous environment. However, this approach introduces environmental issues related to the use of organic solvents. Furthermore, the recovery and discharge of organic solvents during the factory scale-up phase increases production costs for enterprises, thereby raising the cost of product preparation. Therefore, improvements are needed. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing FAPbBr3 quantum dots. The solvent in this method is an aqueous solution, which avoids problems such as the recovery and discharge of organic solvents.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing FAPbBr3 quantum dots includes the following steps:

[0011] S1. Preparation of precursor solution: Dissolve lead source precursor, bromine source precursor and acid in water and stir to obtain precursor solution;

[0012] S2. Formation of nucleation sites: Add FA precursor to the precursor solution obtained in step S1 and stir. React and crystallize in water to form flocculents that can serve as nucleation sites.

[0013] S3. Substrate construction: Silane is added to the solution obtained in step S2, and after stirring, it is heated and dried to obtain crude FAPbBr3@SiO2 quantum dots. The SiO2 generated by the hydrolysis of silane in acidic solution coats the outside of FAPbBr3 as a substrate.

[0014] S4. Ball milling and recrystallization: The crude FAPbBr3@SiO2 quantum dot product obtained in step S3 is subjected to ball milling and recrystallization.

[0015] Wherein: the object of ball milling is the substrate layer, and the object of recrystallization is FAPbBr3 quantum dots. In this application, the aforementioned flocculent material is interpreted as a substance insoluble in water.

[0016] Furthermore, the lead source precursor is lead bromide;

[0017] The bromine source precursor is at least one of potassium bromide, sodium bromide, and zinc bromide.

[0018] The preferred molar ratio of Pb:Br is 1:3.

[0019] The aforementioned lead bromide can actually be used as both a lead source precursor and a bromine source precursor. Those skilled in the art can arbitrarily select appropriate raw materials as lead and bromine source precursors according to their needs and the motivation of this invention, and the scope of protection of this invention should cover both.

[0020] Furthermore, the acid is at least one of citric acid and oxalic acid.

[0021] Furthermore, the FA precursor is formamidine acetate.

[0022] Furthermore, the stirring time in step S2 is 15-60 minutes; the stirring time in step S3 is at least 2 hours.

[0023] The drying temperature in step S3 is 60-80℃.

[0024] Furthermore, the silane is one or more of tetraethyl silicate, hexamethyldisilazane, and silane coupling agents.

[0025] The silane coupling agent includes at least one of 3-aminopropyltriethoxysilane, tetramethoxysilane, (3-mercaptopropyl)trimethoxysilane, bis-[3-(triethoxysilane)-propyl]-tetrasulfide, and octadecyltrimethoxysilane.

[0026] Furthermore, in step S4, the ball milling speed is 200-800 r / min; the ball milling time is at least 1 hour.

[0027] Furthermore, the substrate layer has at least one layer, and the SiO2 serves as the substrate layer during the ball milling and recrystallization stage of FAPbBr3 quantum dots.

[0028] During the ball milling stage, the substrate layer will inevitably be damaged; therefore, in this application, the substrate layer includes complete sacrifice and partial sacrifice.

[0029] Furthermore, the silane is a mixture of tetraethyl silicate and 3-aminopropyltriethoxysilane.

[0030] Furthermore, the ball milling recrystallization step S4 can convert δ-FAPbBr3 into α-FAPbBr3.

[0031] By adopting the above technical solution: δ-FAPbBr3 is a non-luminescent or weakly luminescent impurity phase with numerous defects. These defects act as non-radiative recombination centers, leading to a decrease in luminescence performance. In this application, δ-FAPbBr3 refers to the non-luminescent phase, while α-FAPbBr3 is a more stable luminescent phase that improves defect passivation.

[0032] The beneficial effects of this invention are mainly reflected in:

[0033] (1) In step S1 of this invention, the acid increases the solubility of the lead and bromine source precursors in aqueous solution and provides an acidic solution environment for the subsequent silane hydrolysis. In step S2, the flocculent material is mainly the non-luminescent phase of FAPbBr3. This invention selects the non-luminescent phase of FAPbBr3 as the nucleation site to avoid the destruction of quantum dots by the intermediate product ethanol (containing hydroxyl functional groups) generated by the subsequent silane hydrolysis. In step S3, silane undergoes hydrolysis under acidic conditions to generate silicon dioxide (SiO2), which chemically bonds with FAPbBr3, thereby coating the outside of FAPbBr3 as a substrate layer. At the same time, drying in step S3 can also remove some volatile substances, such as acids and alcohols. In step S4, the ball milling of this invention directly targets the substrate layer, not the FAPbBr3 quantum dots. The substrate layer has the following three functions:

[0034] 1. It can protect the inner layer of FAPbBr3 quantum dots and prevent ball milling from damaging the FAPbBr3 quantum dots;

[0035] 2. The heat generated during the ball milling process is transferred to the FAPbBr3 quantum dots inside through the substrate, causing the FAPbBr3 quantum dots to recrystallize and transform the non-luminescent phase of FAPbBr3 into the luminescent phase.

[0036] 3. The substrate layer can be used as a grinding aid to improve ball milling efficiency.

[0037] (2) The solvent of the system of the present invention is an aqueous solution, and there are no problems such as the recovery and discharge of organic solvents. Attached Figure Description

[0038] Figure 1 This is a comparison diagram of PLQY between Examples 1-3 and Comparative Examples 1-3 of the present invention;

[0039] Figure 2 This is a physical image of the FAPbBr3 quantum dots prepared in Example 3 of this invention;

[0040] Figure 3 This is a physical image of the FAPbBr3 quantum dots prepared in Comparative Example 3 of this invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0042] Example 1:

[0043] This embodiment provides a method for preparing FAPbBr3 quantum dots, including the following steps:

[0044] 0.6 g KBr, 1.84 g PbBr2, and 0.95 g citric acid were weighed and added to 500 g deionized water. The mixture was stirred at 60 °C for 30 min to obtain a precursor solution. 0.55 g formamidine acetate was added to the precursor solution, and the mixture was stirred for 30 min to form a non-luminescent white flocculent. Then, 8 g tetraethyl silicate was added, and the mixture was stirred for 3 h. After drying (at 60 °C), crude FAPbBr3@SiO2 quantum dots were obtained. The crude FAPbBr3@SiO2 quantum dot product was then ball-milled at 600 r / min for 3 h.

[0045] Example 2:

[0046] The difference from Example 1 is that citric acid is replaced with the same molar amount of oxalic acid. Specifically, 0.95g of citric acid is replaced with 0.45g of oxalic acid.

[0047] Example 3:

[0048] The difference from Example 1 is that the silane is a mixture of tetraethyl silicate and 3-aminopropyltriethoxysilane. Specifically, it consists of 8g of tetraethyl silicate and 1g of 3-aminopropyltriethoxysilane.

[0049] Comparative Example 1:

[0050] The difference from Example 1 is that citric acid is not added.

[0051] Comparative Example 2:

[0052] The difference from Example 1 is that tetraethyl silicate is not added.

[0053] Comparative Example 3:

[0054] The difference from Example 3 is that it does not react in water.

[0055] Weigh out 0.6g KBr, 1.84g PbBr2, 0.95g citric acid, and 0.55g formamidine acetate, and ball mill them for 30 minutes. Then add 8g tetraethyl silicate, 1g 3-aminopropyltriethoxysilane, and a trace amount of water, and ball mill for 3 hours. The trace amount of water mentioned above is moisture from the air or moisture from the raw materials.

[0056] The initial fluorescence efficiency and emission peak of the FAPbBr3 quantum dots prepared in Examples 1-3 and Comparative Examples 1-3 were tested, and the results are shown in Table 1.

[0057] Table 1: Emission peaks and fluorescence quantum yields of FAPbBr3 quantum dots from different schemes

[0058]

[0059]

[0060] The present invention has been illustrated with the above embodiments to explain the detailed preparation method of the present invention. However, the present invention is not limited to the above detailed preparation method, that is, it does not mean that the present invention must rely on the above product and detailed preparation method to be implemented. Those skilled in the art should understand that any improvement to the present invention, or the combination or equivalent substitution of the raw materials of the present invention, falls within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing FAPbBr3 quantum dots, characterized in that, Includes the following steps: S1. Preparation of precursor solution: Dissolve lead source precursor, bromine source precursor and acid in water and stir to obtain precursor solution; S2. Formation of nucleation sites: Add FA precursor to the precursor solution obtained in step S1 and stir. React and crystallize in water to form flocculents that can serve as nucleation sites. S3. Substrate construction: Silane is added to the solution obtained in step S2, and after stirring, it is heated and dried to obtain crude FAPbBr3@SiO2 quantum dots. The SiO2 generated by the hydrolysis of silane in acidic solution coats the outside of FAPbBr3 as a substrate. S4. Ball milling and recrystallization: The crude FAPbBr3@SiO2 quantum dot product obtained in step S3 is subjected to ball milling and recrystallization. Wherein: the object of ball milling is the substrate layer, and the object of recrystallization is FAPbBr3 quantum dots.

2. The method for preparing FAPbBr3 quantum dots according to claim 1, characterized in that, The lead source precursor is lead bromide; The bromine source precursor is at least one of potassium bromide, sodium bromide, and zinc bromide.

3. The method for preparing FAPbBr3 quantum dots according to claim 1, characterized in that, The acid is at least one of citric acid and oxalic acid.

4. The method for preparing FAPbBr3 quantum dots according to claim 1, characterized in that, The FA precursor is formamidine acetate.

5. The method for preparing FAPbBr3 quantum dots according to claim 1, characterized in that, The stirring time in step S2 is 15-60 min; the stirring time in step S3 is at least 2 h. The drying temperature in step S3 is 60-80℃.

6. The method for preparing FAPbBr3 quantum dots according to claim 1, characterized in that, The silane is one or more of tetraethyl silicate, hexamethyldisilazane, and silane coupling agents.

7. The method for preparing FAPbBr3 quantum dots according to claim 1, characterized in that, The ball milling speed in step S4 is 200-800 r / min.

8. The method for preparing FAPbBr3 quantum dots according to claim 1, characterized in that, The substrate layer has at least one layer, and the SiO2 serves as the substrate layer during the ball milling and recrystallization stage of FAPbBr3 quantum dots.

9. The method for preparing FAPbBr3 quantum dots according to claim 6, characterized in that, The silane is a mixture of tetraethyl silicate and 3-aminopropyltriethoxysilane.

10. The method for preparing FAPbBr3 quantum dots according to claim 8, characterized in that, The ball milling and recrystallization step S4 can convert δ-FAPbBr3 into α-FAPbBr3.

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