WO2023173242A1

WO2023173242A1 - α-FAPBI3 PEROVSKITE QUANTUM DOT AND PREPARATION METHOD THEREFOR, AND PHOTOELECTRIC DEVICE

Info

Publication number: WO2023173242A1
Application number: PCT/CN2022/080560
Authority: WO
Inventors: 薛冬峰; 徐珂
Original assignee: 中国科学院深圳先进技术研究院
Priority date: 2022-03-14
Filing date: 2022-03-14
Publication date: 2023-09-21

Abstract

Disclosed in the present application are an α-FAPbI3 perovskite quantum dot and a preparation method therefor, and a photoelectric device. The preparation method for an α-FAPbI3 perovskite quantum dot comprises the steps of: dissolving formamidine iodide and lead iodide in a solvent to obtain a mixed solution; dissolving an organic carboxylic acid, i.e. oleic acid, an organic amine, i.e. oleylamine, and a short-chain organic carboxylic acid in the mixed solution to obtain a precursor solution, wherein the carbon chain length of the short-chain organic carboxylic acid is 1-4; and adding an anti-solvent to the precursor solution, carrying out a mixing treatment, and then separating and purifying same to obtain an α-FAPbI3 perovskite quantum dot. According to the preparation method of the present application, the organic carboxylic acid, i.e. oleic acid, and the organic amine, i.e. oleylamine, are used as synergistic passivation ligands to effectively reduce the surface defect concentration; in addition, the short-chain organic carboxylic acid is introduced to inhibit the crystal nucleation speed and inhibit the agglomeration between the quantum dots, thereby forming a ligand protection layer on the surfaces of the quantum dots, so that the stability and the light-emitting property of the perovskite quantum dots are improved.

Description

α-FAPbI3 perovskite quantum dots and preparation methods, optoelectronic devices

Technical field

This application relates to the technical field of perovskite materials, specifically to an α-FAPbI ₃ perovskite quantum dot and its preparation method, as well as an optoelectronic device.

Background technique

The statements herein merely provide background information relevant to the present application and do not necessarily constitute prior art. As a type of semiconductor fluorescent material with excellent optoelectronic properties, low preparation cost and suitable band gap, FAPbI ₃ perovskite materials have good optoelectronic application prospects. In terms of composition, the FAPbI ₃ perovskite structure is a typical ABX ₃ -type perovskite structure. The A position is FA ⁺ with large size, the B position is Pb ²⁺ , and the X position is the halide ion I ^- . In terms of properties, _FAPbI3 perovskite has high fluorescence quantum yields (PLQYs), high absorption coefficient, tunable band gap and superior thermal stability, and is currently the preferred material for preparing high-performance perovskite solar cells. one. Structurally, it usually has a photoactive black phase (α phase) and a non-photoactive yellow phase (δ phase). Studies have found that when stored at room temperature, the photoactive black phase α-FAPbI ₃ is easily transformed into a non-photoactive phase. Reactive yellow phase of δ-FAPbI ₃ , leading to degradation of the material.

At present, the synthesis of FAPbI ₃ perovskite quantum dots usually uses three processes: hot injection method, solution phase method for low-temperature synthesis, and solution phase method for room temperature synthesis. Compared with the solution phase method, the hot injection method is time-consuming and cumbersome, and it is easy to react to generate a mixture of δ-FAPbI ₃ and α-FAPbI _3. The operation process is more sensitive to the experimental environment. The low-temperature synthesis of the solution phase method has the disadvantage of low quality of the FAPbI ₃ crystals produced. However, the solution phase method of room temperature synthesis, that is, the ligand-assisted reprecipitation (LAPR) method at room temperature, has the disadvantages of simple operation, short time consumption, and tolerance to the external environment. Due to its strong properties, it is one of the preferred synthesis processes for synthesizing FAPbI ₃ perovskite quantum dots.

However, currently synthesized FAPbI ₃ perovskite quantum dots are mostly a mixture of photoactive black phase α-FAPbI ₃ and inactive yellow phase δ-FAPbI _3. It is difficult to synthesize a single component α-FAPbI ₃ perovskite. ore quantum dots; even if a single-component α-FAPbI ₃ perovskite quantum dot is synthesized, it is difficult to store for a long time and has strong instability; and the fluorescence quantum yield (PLQYs) of the synthesized FAPbI ₃ perovskite quantum dots is ) lower.

technical problem

One of the purposes of the embodiments of the present application is to provide an α-FAPbI ₃ perovskite quantum dot and a preparation method thereof, as well as an optoelectronic device, aiming to solve the problem of difficulty in synthesizing a single-component α-FAPbI ₃ perovskite quantum dot. point, and the problem of poor storage stability.

Technical solutions

In order to solve the above technical problems, the technical solutions adopted in the embodiments of this application are:

In the first aspect, a preparation method of α-FAPbI ₃ perovskite quantum dots is provided, including the following steps:

Dissolve formamidine iodine and lead iodide in the solvent to obtain a mixed solution;

The organic carboxylic acid oleic acid, organic amine oleylamine and short-chain organic carboxylic acid are dissolved in the mixed solution to obtain a precursor solution; the carbon chain length of the short-chain organic carboxylic acid is 1 to 4;

An antisolvent is added to the precursor solution for mixing, and then separated and purified to obtain α-FAPbI ₃ perovskite quantum dots.

In a second aspect, an α-FAPbI ₃ perovskite quantum dot is provided. The surface of the α-FAPbI ₃ perovskite quantum dot is combined with an organic carboxylic acid oleic acid ligand, an organic amine oleylamine ligand and a short chain. Organic carboxylic acid ligand, the carbon chain length of the short-chain organic carboxylic acid ligand is 1 to 4.

In a third aspect, an optoelectronic device is provided, wherein the functional layer of the optoelectronic device contains α-FAPbI ₃ perovskite quantum dots prepared by the above method, or the above-mentioned α-FAPbI ₃ perovskite quantum dots.

The beneficial effect of the preparation method of α-FAPbI ₃ perovskite quantum dots provided in the embodiments of this application is that: the organic carboxylic acid oleic acid (OA) and the organic amine oleylamine (OAm) are used as surface passivation ligands, which are combined in the quantum dots. The dot surface can effectively passivate defects on the surface of FAPbI ₃ perovskite crystals and improve the stability of quantum dot materials. At the same time, short-chain organic carboxylic acids with a carbon chain length of 1 to 4 are used as additives to slow down the nucleation speed of FAPbI ₃ perovskite quantum dots, thereby making the reaction more controllable and reducing defective sites introduced by grain boundaries. It also effectively adjusts the pH of the reaction system, making it easier for the reaction to generate α-FAPbI ₃ and achieving the purpose of improving the stability of α-FAPbI ₃ perovskite quantum dots to environmental humidity (H ₂ O) and temperature. Moreover, -COO ^- in short-chain carboxylic acids has a strong affinity with FA ⁺ and Pb ²⁺ , which can effectively enhance the stability of α-FAPbI ₃ perovskite quantum dots, reduce the concentration of cationic defect states, and constrain the black phase α -FAPbI ₃ transforms into a yellow phase δ-FAPbI ₃ perovskite quantum dot structure, thereby allowing the reaction to generate high purity and high stability of photoactive black phase α-FAPbI ₃ perovskite quantum dots. If the carbon chain length of the short-chain organic carboxylic acid is too long, δ-FAPbI ₃ will be generated at the same time, which is not conducive to the generation of pure-phase α-FAPbI ₃ perovskite quantum dots. The preparation method of α-FAPbI ₃ perovskite quantum dots in this application uses the organic carboxylic acid oleic acid (OA) and the organic amine oleylamine (OAm) as synergistic passivation ligands to effectively reduce the surface defect concentration, and at the same time introduces short-chain organic carboxyl Acid is used to inhibit the crystal nucleation speed, inhibit the agglomeration between quantum dots, effectively improve the stability and luminescence performance of α-FAPbI ₃ perovskite quantum dots, and form a complex structure on the surface of the prepared α-FAPbI ₃ perovskite quantum dots. body protective layer, thereby improving its adaptability to the environment, improving its stability, and enabling long-term storage. Specifically, by reducing the impact of quantum dot aggregation or phase transition on optical properties, the fluorescence quantum yields (PLQYs) and optical stability of quantum dot materials are improved.

The beneficial effect of the α-FAPbI ₃ perovskite quantum dots provided by the embodiments of this application is that: the surface is bound with organic carboxylic acid oleic acid (OA) ligands, organic amine oleylamine (OAm) ligands and short-chain organic carboxylic acid ligands. Among them, the organic carboxylic acid oleic acid (OA) and the organic amine oleylamine (OAm) combined on the surface of quantum dots can effectively passivate defects on the surface of FAPbI ₃ perovskite crystals and improve the stability of quantum dot materials. Short-chain organic carboxylic acids with a carbon chain length of 1 to 4 are combined on the surface of perovskite quantum dots, which can reduce defect sites introduced by grain boundaries, reduce the concentration of cationic defect states, and constrain the black phase α-FAPbI ₃ to yellow phase δ -FAPbI ₃ perovskite quantum dot structural transformation improves the stability of α-FAPbI ₃ perovskite quantum dots to humidity (H ₂ O) and temperature in the environment. Thereby improving its ability to adapt to the environment, improving its stability, and enabling long-term storage. Reduce the impact of quantum dot aggregation or phase transition on optical properties, thereby improving the fluorescence quantum yields (PLQYs) and optical stability of quantum dot materials.

The beneficial effects of the optoelectronic device provided by the embodiments of the present application are: the α-FAPbI ₃ perovskite quantum dots contained in the functional layer of the optoelectronic device have good structural stability and are stable against humidity (H ₂ O) and temperature in the environment. High, perovskite quantum dot materials are not easy to agglomerate or undergo phase transition, so they have good optical stability and high fluorescence quantum yields (PLQYs). This improves the photoelectric performance and photoelectric stability of the optoelectronic device.

Description of the drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments or exemplary technologies will be briefly introduced below. Obviously, the drawings in the following description are only for the purpose of the present application. For some embodiments, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a schematic flow chart of the preparation method of α-FAPbI ₃ perovskite quantum dots provided by the embodiments of the present application;

Figure 2 is an X-ray diffraction pattern of α-FAPbI ₃ perovskite quantum dots provided in Example 1 of the present application;

Figure 3 is the ultraviolet absorption spectrum and fluorescence emission spectrum of α-FAPbI ₃ perovskite quantum dots provided in Example 2 of the present application;

Figure 4 is the ultraviolet absorption spectrum and fluorescence emission spectrum of δ-FAPbI ₃ and α-FAPbI ₃ perovskite quantum dots prepared in Comparative Example 1 of the present application;

Figure 5 is a test chart of the fluorescence quantum yields (PLQYs) of the _FAPbI3 perovskite quantum dots prepared in Example 1 and Comparative Example 1 of the present application.

Embodiments of the invention

In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it can be directly on the other component or indirectly on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc. are based on the orientation or positional relationship shown in the drawings. They are only for convenience of description and do not indicate or imply the device to which they are referred. Or elements must have specific orientations, be constructed and operated in specific orientations, and therefore cannot be construed as limitations to the application. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances. The terms "first" and "second" are only used for convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of technical features. "Plural" means two or more, unless otherwise expressly and specifically limited.

In order to illustrate the technical solution described in this application, a detailed description will be given below with reference to specific drawings and embodiments.

As shown in Figure 1, the first aspect of the embodiment of the present application provides a method for preparing α- _FAPbI3 perovskite quantum dots, which includes the following steps:

S10. Dissolve formamidine iodide (FAI) and lead iodide (PbI ₂ ) in the solvent to obtain a mixed solution;

S20. Dissolve the organic carboxylic acid oleic acid (OA), organic amine oleylamine (OAm) and short-chain organic carboxylic acid in the mixed solution to obtain a precursor solution; the carbon chain length of the short-chain organic carboxylic acid is 1 to 4;

S30. Add the precursor solution to the antisolvent for mixing and separation and purification to obtain α-FAPbI ₃ perovskite quantum dots.

The preparation method of α-FAPbI ₃ perovskite quantum dots provided in the first aspect of the embodiments of this application uses formamidine iodide (FAI) and lead iodide (PbI ₂ ) as raw materials. After dissolving them in a solvent, adding organic Carboxylic acid oleic acid (OA), organic amine oleylamine (OAm) and short-chain organic carboxylic acid are dissolved to form a precursor solution, and then an antisolvent is added for reaction, which promotes the self-assembly of the raw material components to generate α-FAPbI ₃ perovskite quantum point. Among them, organic carboxylic acid oleic acid (OA) and organic amine oleylamine (OAm) are used as surface passivation ligands. When combined on the surface of quantum dots, they can effectively passivate defects on the surface of FAPbI ₃ perovskite crystals and improve the stability of quantum dot materials. sex. Short-chain organic carboxylic acids with a carbon chain length of 1 to 4 are used as additives. On the one hand, they can slow down the nucleation speed of _FAPbI3 perovskite quantum dots, thereby making the reaction more controllable and reducing defective sites introduced by grain boundaries. , and effectively adjust the pH of the reaction system, making the reaction easier to generate α-FAPbI ₃ , and achieving the purpose of improving the stability of α-FAPbI ₃ perovskite quantum dots to environmental humidity (H ₂ O) and temperature; on the other hand, , the short-chain carboxylic acid -COO ^- has a strong affinity with FA ⁺ and Pb ²⁺ , which can effectively enhance the stability of α-FAPbI ₃ perovskite quantum dots, reduce the concentration of cationic defect states, and constrain the black phase α- FAPbI ₃ transforms into a yellow phase δ-FAPbI ₃ perovskite quantum dot structure, thereby allowing the reaction to generate high purity and high stability of photoactive black phase α-FAPbI ₃ perovskite quantum dots. If the carbon chain length of the short-chain organic carboxylic acid is too long, δ-FAPbI ₃ will be generated at the same time, which is not conducive to the generation of pure-phase α-FAPbI ₃ perovskite quantum dots. The preparation method of α-FAPbI ₃ perovskite quantum dots in the embodiment of this application uses the organic carboxylic acid oleic acid (OA) and the organic amine oleylamine (OAm) as synergistic passivation ligands to effectively reduce the surface defect concentration and introduce short chains at the same time. Organic carboxylic acid is used to inhibit the crystal nucleation speed, inhibit the agglomeration between quantum dots, effectively improve the stability and luminescence performance of α-FAPbI ₃ perovskite quantum dots, and make the surface of the prepared α-FAPbI ₃ perovskite quantum dots Forming a protective layer on the ligand, thereby improving its adaptability to the environment, improving its stability, and enabling long-term storage. Reduce the impact of quantum dot aggregation or phase transition on optical properties, thereby improving the fluorescence quantum yields (PLQYs) and optical stability of quantum dot materials.

In some embodiments, in the above step S10, formamidine iodide (FAI) and lead iodide (PbI ₂ ) are completely dissolved in the solvent by sufficient stirring or other methods to form a mixed solution. Using formamidine iodide (FAI) and lead iodide (PbI ₂ ) as raw materials, it has good solubility and high self-assembly efficiency. It can be self-assembled into ABX ₃ type FAPbI ₃ perovskite quantum dots, in which the A position has a large size. FA ⁺ , B position is Pb ²⁺ , and X position is halide ion I ^- .

In some embodiments, the molar ratio of formamidine iodine (FAI) and lead iodide (PbI ₂ ) is (0.1~1):1. This ratio is conducive to the self-assembly of FA ⁺ , Pb ²⁺ , and I ^- into α -FAPbI ₃ perovskite quantum dot material. In some embodiments, the molar ratio of formamidine iodine (FAI) and lead iodide (PbI ₂ ) is 0.2~0.5.

In some embodiments, the solvent is selected from at least one of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF). These solvents are resistant to formamidine iodide (FAI) and lead iodide ( PbI ₂ ), as well as the subsequent additives organic carboxylic acid oleic acid (OA), organic amine oleylamine (OAm) and short-chain organic carboxylic acids all have good solubility properties and provide a solution environment for the formation of perovskite quantum dot materials. .

In some specific embodiments, formamidine iodine (FAI) and lead iodide (PbI ₂ ) are weighed and placed in a flask equipped with a stirrer, and then dimethyl sulfoxide (DMSO) or N,N-dimethyl is added. Formamide (DMF) solvent, the added volume of the solvent can be 5 to 80 times the total volume of formamidine iodide (FAI) and lead iodide (PbI ₂ ), or 20 to 80 times, ensuring that the solvent formamidine iodide ( FAI) and lead iodide (PbI ₂ ) can be fully dissolved in the solvent. Then place the mixture solution on a stirring table and stir at room temperature for about 30 minutes until it is completely dissolved, and set aside for later use.

In some embodiments, in the above step S20, the step of dissolving the organic carboxylic acid oleic acid (OA), the organic amine oleylamine (OAm) and the short-chain organic carboxylic acid in the mixed solution includes: dissolving the organic carboxylic acid oleic acid (OAm) OA) and organic amine oleylamine (OAm) are sequentially dissolved in the mixed solution, and short-chain organic carboxylic acid is added for dissolution to obtain a precursor solution. In the embodiment of this application, the organic carboxylic acid oleic acid (OA) is first dissolved in the mixed solution, and then the organic amine oleylamine (OAm) is added for dissolution, which is beneficial to obtaining a transparent and clear precursor solution. If the organic carboxylic acid oleic acid (OA) and the organic amine oleylamine (OAm) are added to the mixed solution at the same time for dissolution, or the organic amine oleylamine (OAm) is dissolved first and then the organic carboxylic acid oleic acid (OA) is dissolved, the precursor The bulk solution is not easy to be completely dissolved and is easy to form a gel-like liquid, thereby affecting the passivation effect of the ligand on the surface defects of α-FAPbI ₃ perovskite quantum dot materials. In addition, after the organic carboxylic acid oleic acid (OA) and the organic amine oleylamine (OAm) are sequentially dissolved in the mixed solution, a short-chain organic carboxylic acid is added for dissolution, so that each component has a better dissolving and dispersing effect, which is beneficial to short-term use. Chain organic carboxylic acid regulates the nucleation speed of FAPbI ₃ perovskite quantum dots and improves the structure and optical stability of perovskite quantum dot materials.

In some embodiments, the molar ratio of the organic carboxylic acid oleic acid (OA) and lead iodide (PbI ₂ ) is (0.1~0.6):1. In some embodiments, the molar ratio of organic amine oleylamine (OAm) and lead iodide (PbI ₂ ) is (0.05~0.4):1. The organic amine oleylamine (OAm) and the organic carboxylic acid oleic acid (OA) in the embodiments of this application not only play the role of passivating the surface defects of quantum dots, but also play the role of adjusting the pH value of the reaction system, especially the organic carboxylic acid oil. Acid (OA) is a long-chain carboxylic acid, which plays a great role in regulating the pH value of the reaction system, thereby having a greater impact on the phase state of the generated FAPbI ₃ perovskite quantum dots. The above ratio is not only beneficial to the passivation effect of the organic amine oleylamine (OAm) and the organic carboxylic acid oleic acid (OA) on the surface defects of FAPbI ₃ perovskite quantum dots, but also makes the reaction system have a suitable pH value, promoting the generation of The product is α-FAPbI ₃ perovskite quantum dots, which reduces the generation of δ-FAPbI ₃ perovskite quantum dots. If the amount of organic carboxylic acid oleic acid (OA) is added too much or too little, it will affect the purity and environmental stability of α-FAPbI ₃ perovskite quantum dots. When organic amine oleylamine (OAm) and organic carboxylic acid oil When the amount of acid (OA) added is too high, it will affect the pH value of the reaction system and hinder the binding between ligands and quantum dots, resulting in the inability to form FAPbI ₃ perovskite quantum dots. In some specific embodiments, the molar ratio of the organic carboxylic acid oleic acid (OA) and lead iodide (PbI ₂ ) is (0.2~0.5):1.

In some embodiments, the molar ratio of short-chain organic carboxylic acid and lead iodide (PbI ₂ ) is (2~15):1. This addition ratio enables the short-chain organic carboxylic acid to controllably slow down the nucleation speed of α-FAPbI ₃ perovskite quantum dots, and the strong affinity between FA ⁺ and Pb ²⁺ and -COO ^- in the short-chain carboxylic acid , enhances the stability of perovskite quantum dots and reduces the concentration of cationic defect states. At the same time, the pH of the reaction system can be effectively adjusted, making it easier for the reaction to generate α-FAPbI ₃ . If the amount of short-chain organic carboxylic acid added is too low, δ-FAPbI ₃ perovskite quantum dots will be generated, making it difficult to obtain single-phase α-FAPbI ₃ perovskite quantum dots, and also reducing the stability of the quantum dots; if Adding too high an amount of short-chain organic carboxylic acid will also affect the formation of α-FAPbI ₃ perovskite quantum dots, and may even hinder the binding between ligands and quantum dots. In some specific embodiments, the molar ratio of short-chain organic carboxylic acid and lead iodide (PbI ₂ ) is (5~10):1.

In some embodiments, the short-chain organic carboxylic acid is selected from at least one of formic acid, acetic acid, propionic acid, and butyric acid. These short-chain organic carboxylic acids can controllably slow down the formation of α- _FAPbI3 perovskite quantum dots. The strong affinity between nuclear speed, FA ⁺ and ^Pb2+ and ^-COO- in short-chain carboxylic acids enhances the stability of perovskite quantum dots and reduces the cationic defect state concentration. At the same time, the pH of the reaction system can be effectively adjusted, making it easier for the reaction to generate α-FAPbI ₃ perovskite quantum dots.

In some embodiments, in the above-mentioned step S30, the precursor solution is added to the antisolvent for a mixing process. The duration of the mixing process is 1 to 10 minutes, and an α-FAPbI ₃ perovskite quantum dot solution is initially obtained. If the reaction time is too short, the reaction will not be sufficient, that is, the surface ligands will not be fully passivated, the fluorescence quantum yield (PLQYs) of the perovskite quantum dots will be low, and the corresponding stability will also be affected by moisture due to the exposure of the surface ligands. Stability decreases due to contact with oxygen.

In some embodiments, the volume ratio of the precursor solution to the antisolvent is (0.01~0.1): (4~20), and the amount of the antisolvent can ensure that the raw material components in the precursor solution fully self-assemble to generate α-FAPbI ₃ perovskite quantum dots and precipitate. If the amount of antisolvent is too small, it will not be conducive to the precipitation of perovskite quantum dots; if the amount of antisolvent is too much, changing the pH value of the reaction system will also be detrimental to the precipitation of perovskite quantum dots. In some specific embodiments, the volume ratio of the precursor solution to the antisolvent is (0.03~0.08): (8~14).

In some embodiments, the antisolvent is selected from at least one of n-hexane, toluene, dichloromethane, and chloroform; these antisolvents are beneficial to the precipitation of α-FAPbI ₃ perovskite quantum dots.

In some specific embodiments, 8 to 14 mL of at least one antisolvent among n-hexane, toluene, dichloromethane, and chloroform is added to a reaction vessel equipped with a stirrer, placed on a stirring table for stirring, and then Inject 0.03~0.08 mL of the precursor solution into the antisolvent at one time and stir quickly at room temperature for 1~10 minutes to initially obtain the α-FAPbI ₃ perovskite quantum dot solution.

In some embodiments, the step of separation and purification includes: using centrifugal washing to purify the mixed reaction solution; the rotation speed of centrifugal washing is 4000~15000 r/min, the duration is 15~20 min, and the number of times is 3~4 times. Free raw materials, ligands and intermediate products that are not involved in the reaction in the reaction system are removed by centrifugal washing. The two conditions for centrifugal purification are centrifugation time and rotational speed. Excessive time and rotational speed will cause damage to the perovskite quantum dots, causing the surface ligands to detach from the surface of the perovskite quantum dots, resulting in the agglomeration of quantum dots. However, time and rotational speed If it is too short, the purification will be incomplete, and impurities without fluorescence effect will accumulate, reducing the fluorescence quantum yield (PLQYs) and stability. In some embodiments, the rotation speed of centrifugal washing is 4000~15000 r/min.

In some embodiments, solvents used for centrifugal washing and purification include but are not limited to toluene, chlorobenzene, dichloromethane, chloroform, n-hexane, etc.

The second aspect of the embodiment of the present application provides an α-FAPbI ₃ perovskite quantum dot. The surface of the α-FAPbI ₃ perovskite quantum dot is combined with an organic carboxylic acid oleic acid (OA) ligand and an organic amine oleylamine (OAm). ) ligand and short-chain organic carboxylic acid ligand. The carbon chain length of the short-chain organic carboxylic acid ligand is 1 to 4.

The α-FAPbI ₃ perovskite quantum dots provided in the second aspect of the embodiments of this application have organic carboxylic acid oleic acid (OA) ligands, organic amine oleylamine (OAm) ligands and short-chain organic carboxylic acid ligands bound to their surface. ; Among them, the combination of organic carboxylic acid oleic acid (OA) and organic amine oleylamine (OAm) on the surface of quantum dots can effectively passivate defects on the surface of FAPbI ₃ perovskite crystals and improve the stability of quantum dot materials. Short-chain organic carboxylic acids with a carbon chain length of 1 to 4 are combined on the surface of perovskite quantum dots, which can reduce defect sites introduced by grain boundaries, reduce the concentration of cationic defect states, and constrain the black phase α-FAPbI ₃ to yellow phase δ -FAPbI ₃ perovskite quantum dot structural transformation improves the stability of α-FAPbI ₃ perovskite quantum dots to humidity (H ₂ O) and temperature in the environment. Based on this, this will improve its adaptability to the environment, improve its stability, enable long-term storage, and reduce the impact of quantum dot agglomeration or phase transition on optical properties, thereby increasing the fluorescence quantum yields (PLQYs) of quantum dot materials. ) and optical stability.

The third aspect of the embodiments of the present application provides an optoelectronic device. The functional layer of the optoelectronic device contains α-FAPbI ₃ perovskite quantum dots prepared by the above method, or the above-mentioned α-FAPbI ₃ perovskite quantum dots.

The α-FAPbI ₃ perovskite quantum dots contained in the functional layer of the optoelectronic device provided in the third aspect of the embodiment of the present application have good structural stability and high stability against humidity (H ₂ O) and temperature in the environment. Mineral quantum dot materials are not easy to agglomerate or undergo phase transition, so they have good optical stability and high fluorescence quantum yields (PLQYs). This improves the photoelectric performance and photoelectric stability of the optoelectronic device.

In some embodiments, optoelectronic devices include, but are not limited to, perovskite solar cells.

In order to make the above implementation details and operations of the present application clearly understood by those skilled in the art, and to significantly reflect the progressive performance of the α-FAPbI ₃ perovskite quantum dots and preparation methods and optoelectronic devices in the embodiments of the present application, the following is provided through a number of Examples are provided to illustrate the above technical solutions.

Example 1

An α-FAPbI ₃ perovskite quantum dot , its preparation includes the steps:

① Dissolve formamidine iodine (FAI) and lead iodide (PbI ₂ ) in the dimethyl sulfoxide (DMSO) solvent at a material ratio of 0.3:1 and stir until completely dissolved; lead iodide (PbI ₂ ) The initial concentration is 0.01 mol/L, in which the volume of dimethyl sulfoxide (DMSO) solvent is 0.2 mL; then, organic carboxylic acid oleic acid (OA) and organic amine oleylamine (OAm) are added in sequence and stirred to dissolve, where, The ratio of the amount of organic carboxylic acid oleic acid (OA) to lead iodide (PbI ₂ ) is 0.4:1, and the ratio of the amount of organic amine oleylamine (OAm) to lead iodide (PbI ₂ ) is 0.3:1; finally, add short-chain organic carboxylic acid acetic acid, the mass ratio of short-chain organic carboxylic acid acetic acid to lead iodide (PbI ₂ ) is 8:1, stir at room temperature for 1 to 2 minutes to fully dissolve to obtain FAPbI ₃ Precursor solution of perovskite quantum dots;

② According to the volume ratio of precursor solution to anti-solvent toluene is 0.05:10, inject the precursor solution of FAPbI ₃ perovskite quantum dots into toluene, in which the volume of anti-solvent toluene is 10 mL; react at room temperature for 2-5 minutes to obtain α-FAPbI ₃ perovskite quantum dot solution;

③Centrifuge, wash and purify the α-FAPbI ₃ perovskite quantum dot solution obtained from ② reaction at a speed of 8000r/min. Centrifuge for 18 minutes each time to collect the precipitate. Centrifuge 3 times to separate and obtain the purified solution. of α-FAPbI ₃ perovskite quantum dots, and finally store them in a vacuum drying oven at room temperature.

Example 2

① Dissolve formamidine iodine (FAI) and lead iodide (PbI ₂ ) in a N,N-dimethylformamide (DMF) solvent at a material ratio of 0.3:1 and stir until completely dissolved; lead iodide ( The initial concentration of PbI ₂ ) is 0.01 mol/L, in which the volume of N,N-dimethylformamide (DMF) solvent is 0.2 mL; then, the organic carboxylic acid oleic acid (OA) and the organic amine oleylamine ( OAm) and stir to dissolve. The ratio of the amount of organic carboxylic acid oleic acid (OA) to lead iodide (PbI ₂ ) is 0.4:1, and the amount of organic amine oleylamine (OAm) to lead iodide. The mass ratio of (PbI ₂ ) substances is 0.3:1; finally, add short-chain organic carboxylic acid acetic acid, the mass ratio of short-chain organic carboxylic acid acetic acid and lead iodide (PbI ₂ ) is 8:1, and stir at room temperature. Fully dissolve in 1~2 minutes to obtain the precursor solution of FAPbI ₃ perovskite quantum dots;

② According to the volume ratio of precursor solution to anti-solvent chloroform is 0.05:10, inject the precursor solution of FAPbI ₃ perovskite quantum dots into chloroform, in which the volume of anti-solvent chloroform is 10 mL; at room temperature React for 2-5 minutes to obtain α-FAPbI ₃ perovskite quantum dot solution;

Example 3

① Dissolve formamidine iodine (FAI) and lead iodide (PbI ₂ ) in the dimethyl sulfoxide (DMSO) solvent at a material ratio of 0.3:1 and stir until completely dissolved; lead iodide (PbI ₂ ) The initial concentration is 0.01 mol/L, in which the volume of dimethyl sulfoxide (DMSO) solvent is 0.2 mL; then, organic carboxylic acid oleic acid (OA) and organic amine oleylamine (OAm) are added in sequence and stirred to dissolve, where, The ratio of the amount of organic carboxylic acid oleic acid (OA) to lead iodide (PbI ₂ ) is 0.4:1, and the ratio of the amount of organic amine oleylamine (OAm) to lead iodide (PbI ₂ ) is 0.3:1; finally, add short-chain organic carboxylic acid formic acid, the mass ratio of short-chain organic carboxylic acid formic acid to lead iodide (PbI ₂ ) is 8:1, stir at room temperature for 1 to 2 minutes to fully dissolve to obtain FAPbI ₃ Precursor solution of perovskite quantum dots;

Example 4

① Dissolve formamidine iodine (FAI) and lead iodide (PbI ₂ ) in the dimethyl sulfoxide (DMSO) solvent at a material ratio of 0.3:1 and stir until completely dissolved; lead iodide (PbI ₂ ) The initial concentration is 0.01 mol/L, in which the volume of dimethyl sulfoxide (DMSO) solvent is 0.2 mL; then, organic carboxylic acid oleic acid (OA) and organic amine oleylamine (OAm) are added in sequence and stirred to dissolve, where, The ratio of the amount of organic carboxylic acid oleic acid (OA) to lead iodide (PbI ₂ ) is 0.4:1, and the ratio of the amount of organic amine oleylamine (OAm) to lead iodide (PbI ₂ ) is 0.3:1; finally, add short-chain organic carboxylic acid acetic acid, the mass ratio of short-chain organic carboxylic acid acetic acid to lead iodide (PbI ₂ ) is 12:1, stir at room temperature for 1 to 2 minutes to fully dissolve to obtain FAPbI ₃ Precursor solution of perovskite quantum dots;

Comparative Example 1 (no short-chain organic carboxylic acid added)

A kind of FAPbI ₃ perovskite quantum dot , its preparation includes the steps:

① Dissolve formamidine iodine (FAI) and lead iodide (PbI ₂ ) in the dimethyl sulfoxide (DMSO) solvent at a material ratio of 0.3:1 and stir until completely dissolved; lead iodide (PbI ₂ ) The initial concentration is 0.01 mol/L, in which the volume of dimethyl sulfoxide (DMSO) solvent is 0.2 mL; then, organic carboxylic acid oleic acid (OA) and organic amine oleylamine (OAm) are added in sequence and stirred to dissolve, where, The ratio of the amount of organic carboxylic acid oleic acid (OA) to lead iodide (PbI ₂ ) is 0.4:1, and the ratio of the amount of organic amine oleylamine (OAm) to lead iodide (PbI ₂ ) The ratio is 0.3:1. Stir for 1 to 2 minutes at room temperature to fully dissolve the solution to obtain the precursor solution of FAPbI ₃ perovskite quantum dots;

② According to the volume ratio of precursor solution to anti-solvent toluene is 0.05:10, inject the precursor solution of FAPbI ₃ perovskite quantum dots into toluene, in which the volume of anti-solvent toluene is 10 mL; react at room temperature for 2-5 minutes to obtain FAPbI ₃ perovskite quantum dot solution;

③Centrifuge, wash and purify the FAPbI ₃ perovskite quantum dot solution obtained from ② reaction at a speed of 8000r/min. Centrifuge for 18 minutes each time to collect the precipitate. Centrifuge 3 times to separate and obtain the purified δ. -Perovskite quantum dot mixture of _FAPbI3 and α- _FAPbI3 .

Comparative Example 2 (no organic carboxylic acid oleic acid added)

① Dissolve formamidine iodine (FAI) and lead iodide (PbI ₂ ) in the dimethyl sulfoxide (DMSO) solvent at a material ratio of 0.3:1 and stir until completely dissolved; lead iodide (PbI ₂ ) The initial concentration is 0.01 mol/L, in which the volume of dimethyl sulfoxide (DMSO) solvent is 0.2 mL; then, organic amine oleylamine (OAm) is added and stirred to dissolve, where the added amount of organic amine oleylamine (OAm) The mass ratio of the short-chain organic carboxylic acid acetic acid to lead iodide (PbI ₂ ) is 0.3:1; finally, the short-chain organic carboxylic acid acetic acid is added, and the mass ratio of the short-chain organic carboxylic acid acetic acid to lead iodide (PbI ₂ ) is 8:1. Stir for 1 to 2 minutes at room temperature to fully dissolve the solution to obtain the precursor solution of FAPbI ₃ perovskite quantum dots;

② According to the volume ratio of precursor solution to anti-solvent toluene is 0.05:10, inject the precursor solution of FAPbI ₃ perovskite quantum dots into toluene, in which the volume of anti-solvent toluene is 10 mL; react at room temperature for 2-5 minutes to obtain δ-FAPbI ₃ and α-FAPbI ₃ perovskite quantum dot solutions;

③Centrifuge, wash and purify the δ-FAPbI ₃ and α-FAPbI ₃ perovskite quantum dot solutions obtained from ② reaction at a speed of 8000r/min. Centrifuge for 18 minutes each time to collect the precipitate, and centrifuge 3 times, that is The purified δ-FAPbI ₃ and α-FAPbI ₃ perovskite quantum dots can be separated and obtained, and finally stored in a vacuum drying oven at room temperature.

Comparative Example 3 (no organic amine oleylamine added)

① Dissolve formamidine iodine (FAI) and lead iodide (PbI ₂ ) in the dimethyl sulfoxide (DMSO) solvent at a material ratio of 0.3:1 and stir until completely dissolved; lead iodide (PbI ₂ ) The initial concentration is 0.01 mol/L, in which the volume of dimethyl sulfoxide (DMSO) solvent is 0.2 mL; then, the organic carboxylic acid oleic acid (OA) is added and stirred to dissolve, where the organic carboxylic acid oleic acid (OA) The amount of addition and the amount of lead iodide (PbI ₂ ) are 0.4:1; finally, the short-chain organic carboxylic acid acetic acid is added, and the amount of short-chain organic carboxylic acid acetic acid and lead iodide (PbI ₂ ) is 8: 1. Stir for 1 to 2 minutes at room temperature to fully dissolve the solution to obtain the precursor solution of FAPbI ₃ perovskite quantum dots;

② According to the volume ratio of precursor solution to anti-solvent toluene is 0.05:10, inject the precursor solution of FAPbI ₃ perovskite quantum dots into toluene, in which the volume of anti-solvent toluene is 10 mL; react at room temperature for 2-5 minutes, and it cannot Obtain FAPbI ₃ perovskite quantum dot solution.

In order to verify the progress of the embodiments of the present application, the following performance tests were conducted on the embodiments and comparative examples:

1. The characteristic peaks of the crystal structure of the α-FAPbI ₃ perovskite quantum dots prepared in Example 1 were tested using an X-ray diffractometer testing instrument. The test results are shown in Figure 2, and the corresponding characteristic peaks are the α phase. FAPbI ₃ perovskite quantum dots.

2. The characteristic peaks of the UV absorption spectrum and fluorescence emission spectrum of the α- _FAPbI3 perovskite quantum dots prepared in Example 2 were tested using UV-visible spectrophotometer and fluorescence spectrophotometer testing instruments. The test results are as attached As shown in Figure 3, the corresponding characteristic peaks are 795 nm and 798 nm respectively.

3. The characteristic peaks of the ultraviolet absorption spectrum and fluorescence emission spectrum of the δ-FAPbI ₃ and α-FAPbI ₃ perovskite quantum dots prepared in Comparative Example 1 were tested using UV-visible spectrophotometer and fluorescence spectrophotometer testing instruments. , The test results are shown in Figure 4, in which the characteristic peaks corresponding to the absorption peaks/emission peaks of δ-FAPbI ₃ and α-FAPbI ₃ perovskite quantum dots are 570/576 nm and 775/782 nm respectively.

4. Use the integrating sphere of the fluorescence spectrophotometer tester to test the stability of Examples 1-4 and Comparative Examples 1 and 2. The stability test conditions are an ambient temperature of 25°C and a relative humidity of 70%. The test results are as follows As shown in Table 1.

Table 1

测试项目测试对象 test project test object	荧光量子产率初始值 % Fluorescence quantum yield initial value %	两周后的荧光量子产率 % Fluorescence quantum yield % after two weeks
实施例1 Example 1	94% 94%	91% 91%
实施例2 Example 2	92% 92%	89% 89%
实施例3 Example 3	89% 89%	87% 87%
实施例4 Example 4	90% 90%	88% 88%
对比例1 Comparative example 1	52% 52%	23% twenty three%
对比例2 Comparative example 2	7% 7%	0% 0%

It can be seen from the above test results that the initial values of the fluorescence quantum yields (PLQYs) of the α-FAPbI ₃ perovskite quantum dots prepared in Examples 1 to 4 are 94%, 92%, 89% and 90% respectively. At the ambient temperature of 25 After two weeks of storage at 70% relative humidity, the initial fluorescence quantum yields (PLQYs) dropped to 91%, 89%, 87% and 88%, showing good stability when stored in an air environment. In Comparative Examples 1 and 2, no short-chain organic carboxylic acid and organic carboxylic acid oleic acid (OA) were added respectively, and the perovskite quantum dots prepared contained non-optically active δ-FAPbI ₃ perovskite quantum dots. , the initial values of fluorescence quantum yields (PLQYs) dropped from the original 52% and 7% to 23% and 0% respectively. The storage stability in the same environment is poor and prone to decomposition. In Comparative Example 3, FAPbI ₃ perovskite quantum dots could not be produced when the organic amine oleylamine (OAm) was not added.

In addition, the stability test of the samples of Example 1 and Comparative Example 1 was conducted in the polar solvent isopropyl alcohol for 48 hours through the integrating sphere of the fluorescence spectrophotometer tester. The test results are shown in Figure 5. It can be seen that the initial values of fluorescence quantum yields (PLQYs) of the samples of Example 1 and Comparative Example 1 dropped from the original 94% and 52% to 88% and 16% respectively. Example 1 still maintains good stability, indicating that the prepared pure phase α-FAPbI ₃ perovskite quantum dots have good optical properties and stability.

The above are only optional embodiments of the present application and are not used to limit the present application. Various modifications and variations may be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this application shall be included in the scope of the claims of this application.

Claims

A method for preparing α-FAPbI 3 perovskite quantum dots, which is characterized by comprising the following steps:

Dissolve formamidine iodine and lead iodide in the solvent to obtain a mixed solution;

The organic carboxylic acid oleic acid, organic amine oleylamine and short-chain organic carboxylic acid are dissolved in the mixed solution to obtain a precursor solution; the carbon chain length of the short-chain organic carboxylic acid is 1 to 4;

The precursor solution is added to the antisolvent for mixing, and then separated and purified to obtain α-FAPbI 3 perovskite quantum dots.
The preparation method of α- FAPbI3 perovskite quantum dots as claimed in claim 1, characterized in that the organic carboxylic acid oleic acid, the organic amine oleylamine and the short-chain organic carboxylic acid are dissolved in the The steps in the mixed solution include: after sequentially dissolving the organic carboxylic acid oleic acid and the organic amine oleylamine in the mixed solution, adding the short-chain organic carboxylic acid for dissolution to obtain the precursor solution .
The preparation method of α-FAPbI 3 perovskite quantum dots according to claim 1, wherein the molar ratio of the formamidine iodine and the lead iodide is (0.1~1):1.
The preparation method of α-FAPbI 3 perovskite quantum dots according to claim 1, wherein the molar ratio of the organic carboxylic acid oleic acid and the lead iodide is (0.1~0.6):1.
The preparation method of α-FAPbI 3 perovskite quantum dots according to claim 1, wherein the molar ratio of the organic amine oleylamine and the lead iodide is (0.05~0.4):1.
The preparation method of α-FAPbI 3 perovskite quantum dots according to claim 1, wherein the molar ratio of the short-chain organic carboxylic acid and the lead iodide is (2~15):1.
The preparation method of α-FAPbI 3 perovskite quantum dots according to any one of claims 3 to 6, characterized in that the volume ratio of the precursor solution to the antisolvent is (0.01 to 0.1): (4~20).
The preparation method of α- FAPbI3 perovskite quantum dots according to claim 7, wherein the short-chain organic carboxylic acid is selected from at least one of formic acid, acetic acid, propionic acid and butyric acid.
The method for preparing α- FAPbI3 perovskite quantum dots according to claim 7, wherein the antisolvent is selected from at least one of n-hexane, toluene, dichloromethane and chloroform.
The method for preparing α-FAPbI 3 perovskite quantum dots according to claim 7, wherein the solvent is selected from at least one of dimethyl sulfoxide and N,N-dimethylformamide.
The preparation method of α-FAPbI 3 perovskite quantum dots according to any one of claims 1 to 6 and 8 to 10, characterized in that the duration of the mixing treatment is 1 to 10 minutes.
The preparation method of α-FAPbI 3 perovskite quantum dots according to claim 11, characterized in that the step of separation and purification includes: purifying the reaction solution after the mixing treatment by centrifugal washing; The rotation speed is 4000~15000r/min, the duration is 15~20 min, and the number of times is 3~4 times.
An α-FAPbI 3 perovskite quantum dot, characterized in that the surface of the α-FAPbI 3 perovskite quantum dot is combined with an organic carboxylic acid oleic acid ligand, an organic amine oleylamine ligand and a short-chain organic carboxylic acid Acid ligand, the carbon chain length of the short-chain organic carboxylic acid ligand is 1 to 4.
An optoelectronic device, characterized in that the functional layer of the optoelectronic device contains α-FAPbI 3 perovskite quantum dots prepared by the method according to any one of claims 1 to 12, or as claimed in claim 13 α-FAPbI 3 perovskite quantum dots.