Method for passivating surface defects of red light perovskite quantum dots

Abstract

The application discloses a method for passivating surface defects of red light perovskite quantum dots, which comprises the following steps: adding acyl chloride in the process of cooling the high-temperature synthesized quantum dots, changing the dynamic balance among the organic ligands in the reaction system, reducing the long-chain organic ligands on the surface of the quantum dots, and introducing chlorine atoms to fill the iodine atom vacancies on the surface, so that the passivation of the surface defects is realized while the quantum dots are synthesized. The red light perovskite quantum dots obtained by the method have more excellent optical performance, and the complicated post-processing ligand exchange is avoided, which has great significance for promoting the development and application of the perovskite quantum dots in the field of semiconductor devices.

Description

Technical Field

[0001] This invention belongs to the field of perovskite quantum dot preparation technology, and particularly relates to a method for passivating surface defects of red perovskite quantum dots in the fluorescence emission band of 620-760nm. Background Technology

[0002] Colloidal quantum dots, as a novel semiconductor material, possess a band gap that can be adjusted by controlling their size. They exhibit high luminous efficiency and narrow fluorescence emission linewidth, and can be processed using solution methods, resulting in low cost. They hold great promise for applications in solar cells, light-emitting diodes, photodetectors, and lasers. In 2015, Kovalenko et al. at ETH Zurich successfully prepared small, regularly shaped CsPbX3 (X = Cl, Br, I) perovskite quantum dots using a hot-injection method. Their emission spectrum covered the entire visible light region and was easier to control, greatly boosting research enthusiasm for this material in the field.

[0003] However, due to the large specific surface area of ​​perovskite quantum dots (quantum dots), their surfaces are prone to numerous defects. Furthermore, the binding between quantum dots and their surface organic ligands exists in a dynamic equilibrium; ligand detachment leads to an increase in surface defects. These surface defects reduce the luminescence performance and stability of perovskite quantum dots. Currently, researchers mainly use two methods to passivate surface defects in perovskite quantum dots: ligand engineering and surface coating. Ligand engineering introduces long-chain organic ligands with stronger binding affinity to quantum dots, while surface coating encapsulates quantum dots within SiO2 or polymer matrices. Both methods can effectively improve the luminescence efficiency of perovskite quantum dots; however, these long-chain organic ligands, polymers, and oxides themselves have poor conductivity, and the insulating layer they form on the quantum dot surface severely affects the overall conductivity of the quantum dot, thus limiting its further application in semiconductor electronic devices. Therefore, it is urgent to find suitable methods for passivating surface defects and preparing high-efficiency perovskite quantum dots, which is of great significance for promoting the development and application of perovskite quantum dots in the semiconductor field. Summary of the Invention

[0004] The purpose of this invention is to provide a method for passivating surface defects in red-light perovskite quantum dots. This invention improves the luminescence efficiency of red-light perovskite quantum dots by passivating defects through the injection of acyl chlorides during the reaction cooling process. The red-light perovskite quantum dots prepared by this method exhibit extremely high photoluminescence quantum yield (~100%) and other excellent optical properties.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A monovalent cation precursor is provided, the monovalent cation precursor being composed of at least one monovalent cation selected from cesium (Cs), rubidium (Rb), formamidine (FA), methylammonium (MA), and aminoformamidine (GA) and an acid;

[0007] A mixed precursor containing an iodine source, a lead source, an organic acid, and an organic amine is provided;

[0008] The monovalent cation precursor is added to the mixed precursor for reaction at a temperature of 150-190°C.

[0009] During the cooling process after the reaction, acyl chloride is added at a temperature range of 100-140℃ to achieve passivation.

[0010] In the reaction, the reaction temperature is 150-190℃. During the reaction, some of the organic acids and organic amines are adsorbed onto the quantum dot surface as ligands, while the other part remains free in the colloidal system, and a dynamic equilibrium exists between these two parts. This scheme uses a hot-injection method to prepare colloidal quantum dots. The quantum dots are formed after rapid nucleation and growth of the system following the injection of a monovalent cation precursor at high temperature. Therefore, the effective composition of the quantum dots is determined by the precursor in the reaction system at that time. The red-light perovskite quantum dots prepared by this scheme are generally iodine-based perovskite crystals. If acyl chloride is directly injected at the reaction temperature, chloride ions will be introduced prematurely, preventing the formation of the intrinsic perovskite phase of pure iodine. Furthermore, the organic acids and amines necessary for the nucleation and growth of the quantum dots will react prematurely, affecting the formation of the quantum dots.

[0011] Therefore, this application requires the addition of acyl chloride during the cooling process at a temperature range of 100-140°C after the reaction is complete. At this temperature, the acyl chloride reacts with the organic acids and amines in the system, consuming a portion of them to alter the original ligand equilibrium. When the free acids and amines are consumed by the acyl chloride reaction, the long-chain organic ligands originally coordinated on the quantum dots are deprotonated and desorbed from the quantum dot surface. This desorption of the long-chain organic ligands from the quantum dot surface has the following two technical effects:

[0012] 1. The desorption of long-chain organic ligands from the surface of quantum dots can increase the conductivity of quantum dots;

[0013] 2. Long-chain organic ligands are desorbed from the quantum dot surface to create vacancies on the quantum dot surface. At the same time, the reaction of acyl chloride with organic acids and organic amines can release chloride ions. Chloride atoms can fill the iodine atom vacancies on the quantum dot surface (the presence of iodine atom vacancies will seriously affect the luminescence performance of perovskite quantum dots), thus achieving passivation of surface defects.

[0014] In this application, the desorption of long-chain organic ligands from the quantum dot surface and the filling of iodine atom vacancies on the quantum dot surface by chlorine atoms occur simultaneously. Compared to iodine atoms, chlorine atoms have a stronger binding affinity to lead atoms, resulting in better stability and optical properties for the quantum dots.

[0015] Further, the monovalent cation precursor includes one or more of the following: cesium carbonate (Cs2CO3), cesium formate (CsHCOO), cesium acetate (CsAc), rubidium carbonate (Rb2CO3), rubidium formate (RbHCOO), rubidium acetate (RbAc), formamidine formate (FAHCOO), formamidine acetate (FA-Ac), methylamine formate (MAHCOO), guanidine carbonate (GA2CO3), and guanidine acetate (GA-Ac).

[0016] Furthermore, the iodine source in the mixed precursor includes one or more of hydrogen iodide (HI), potassium iodide (KI), magnesium iodide (MgI2), lead iodide (PbI2), zinc iodide (ZnI2), manganese iodide (MnI2), strontium iodide (SrI2), tin iodide (SnI2), zirconium iodide (ZrI4), and cobalt iodide (CoI2).

[0017] Furthermore, the lead source in the mixed precursor includes lead iodide (PbI2), lead bromide (PbBr2), lead chloride (PbCl2), lead acetate (Pb(Ac)2), lead oleate (Pb(OA)2), and lead stearate ([CH3(CH2)2]). 16 One or more of [COO]2Pb).

[0018] Furthermore, in the mixed precursor, the volume ratio of acid to amine is close to 1, preferably 1:1-1.5.

[0019] Furthermore, the acyl chloride refers to an organic compound containing the following structure:

[0020]

[0021] In this system, R represents hydrogen or an organic group, and M represents one of carbon, nitrogen, phosphorus, or sulfur. When adding acyl chloride, the preferred reaction temperature is 100-140℃. The role of acyl chloride is primarily to react with organic acids and amines in the reaction solution, altering the ligand balance of the original system. This causes some of the long-chain organic ligands originally coordinated to the quantum dot surface to deprotonate and desorb from the quantum dot surface. This allows the chlorine atoms released from the reaction of acyl chloride with acids and amines to fill the iodine atom vacancies on the quantum dot surface. Compared to iodine atoms, chlorine atoms have a stronger binding affinity to lead atoms, resulting in better stability and optical properties for the quantum dots.

[0022] Furthermore, the passivation method for surface defects described in this application is only applicable to red-light perovskite quantum dots with a wavelength range of 620-760 nm, and not to blue or green-light perovskite quantum dots. This is because blue and green quantum dots are generally based on perovskite structures with bromine as the halogen atom, and the introduction of chlorine would form a mixed halogen structure, leading to problems such as spectral shift and phase separation. The halogen component of red-light perovskite quantum dots is generally iodine, and the introduction of chlorine can effectively passivate surface defects without causing spectral or structural problems.

[0023] Furthermore, the volume ratio of the added acyl chloride to the reaction solution should be less than 1:10, preferably 1:20-200. If the ratio is greater than 1:10, i.e., too much acyl chloride is added, it will deplete the acid and amine in the reaction solution. Since the stability of quantum dots in colloidal systems is due to the presence of their surface ligands (organic acids and organic amines) that create gaps between the quantum dots, allowing them to disperse in the solvent and maintain relative stability, the depletion of organic acids and amines will lead to structural instability or even destruction of the perovskite quantum dots, initiating a phase transition.

[0024] Furthermore, the auxiliary reagent includes one or more of benzene-based and alkane-based reagents. The auxiliary reagent can be used to dilute a portion of the acyl chloride with a smaller molecular weight or to dissolve a portion of the acyl chloride that is solid at room temperature.

[0025] The beneficial effects of this invention are mainly reflected in:

[0026] By directly adding acyl chloride during the cooling process of high-temperature quantum dot synthesis, the dynamic equilibrium of organic ligands in the reaction system is altered, reducing the number of long-chain organic ligands on the quantum dot surface and introducing chlorine atoms to fill iodine vacancies, thus passivating surface defects simultaneously with quantum dot synthesis. The red-light perovskite quantum dots obtained through this method exhibit superior optical properties and photostability, while avoiding complex post-processing ligand exchange. This method is of great significance for promoting the development and application of perovskite quantum dots in semiconductor devices.

[0027] Furthermore, this invention improves the conductivity of quantum dots by removing the poorly conductive long-chain organic ligands from the surface of the quantum dots and replacing the organic ligands with chloride ions, which have strong binding capacity and good conductivity, on the surface of the quantum dots. Attached Figure Description

[0028] Figure 1 This invention describes the reaction mechanism of acyl chloride passivation of surface defects in red light perovskite quantum dots.

[0029] Figure 2 The UV-Vis absorption spectrum and fluorescence emission spectrum of the CsPbI3 quantum dots obtained in Example 1 are shown.

[0030] Figure 3 This is a comparison of the fluorescence quantum yield and fluorescence lifetime of the CsPbI3 quantum dot solution before and after passivation in Example 1.

[0031] Figure 4 This is a comparison of the fluorescence quantum yield and fluorescence lifetime of the CsPbI3 quantum dot films before and after passivation in Example 1.

[0032] Figure 5 This is a comparison of the variable excitation fluorescence quantum yield of CsPbI3 quantum dot films before and after passivation in Example 1.

[0033] Figure 6 This is a comparison chart of the conductivity of CsPbI3 quantum dot films before and after passivation in Example 1.

[0034] Figure 7 This is a comparison of the fluorescence quantum yield of CsPbI3 quantum dot solutions before passivation and after passivation at different temperatures in Example 1. Detailed Implementation

[0035] This invention provides a method for passivating surface defects in red-light perovskite quantum dots. 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.

[0036] According to a specific embodiment of the present invention, a method for passivating surface defects of red perovskite quantum dots mainly includes the following steps:

[0037] S10, provides a monovalent cationic precursor composed of one or more cations selected from cesium (Cs), rubidium (Rb), formamidine (FA), methylammonium (MA), and aminoformamidine (GA) and an acid;

[0038] S20 provides a mixed precursor containing an iodine source, a lead source, an organic acid, and an organic amine;

[0039] S30, the monovalent cation precursor is added to the mixed precursor to carry out a reaction at a temperature of 150-190°C;

[0040] S40 is passivated by adding acyl chloride (which can be dispersed in auxiliary reagents) during the cooling process after the reaction.

[0041] In some embodiments, the volume ratio of the added acyl chloride to the reaction solution is less than 1:10, preferably 1:20-200. If the ratio is greater than 1:10, i.e., too much acyl chloride is added, the acid and amine in the reaction solution will be depleted, leading to the structural destruction of the perovskite quantum dots and initiating a phase transition. Furthermore, the reaction temperature when adding the acyl chloride is preferably 100-140°C. At this temperature, the reaction rate of the acyl chloride with the acid and amine is moderate. Too high a temperature will cause some low-boiling-point acyl chloride and auxiliary reagents to vaporize, causing them to leave the colloidal system in a gaseous state, thus weakening the passivation effect; too low a temperature will result in a too slow reaction rate, preventing the effective release of chlorine atoms and making it difficult to effectively fill the iodine atom vacancies on the quantum dot surface. It is also preferable to insert the syringe needle below the liquid surface when adding the acyl chloride to ensure that the hydrogen chloride produced by the reaction can fully react with the solution.

[0042] In some embodiments, the added auxiliary reagents include one or more of benzene-based and alkane-based reagents, including but not limited to toluene, xylene, chlorobenzene, hexane, octane, etc., as well as mixed solvents composed of them in different proportions. The auxiliary reagents can be used to dilute portions of acyl chlorides with smaller molecular weights or to dissolve portions of acyl chlorides that are solid at room temperature.

[0043] In some embodiments, the monovalent cation in the monovalent cation precursor in S10 is a mixture of one or more of the following in different proportions: cesium carbonate (Cs₂CO₃), cesium formate (CsHCOO), cesium acetate (CsAc), rubidium carbonate (Rb₂CO₃), rubidium formate (RbHCOO), rubidium acetate (RbAc), formamidine formate (FAHCOO), formamidine acetate (FA-Ac), methylamine formate (MAHCOO), guanidine carbonate (GA₂CO₃), and guanidine acetate (GA-Ac). For example, Cs₂CO₃ and RbAc constitute a mixed monovalent cation in a 5:1 ratio.

[0044] In some embodiments, the monovalent cation precursor in S10 can be cesium oleate (Cs-OA), which can be prepared by: weighing 100 mg of cesium carbonate (Cs₂CO₃) and adding it to a three-necked flask; then adding 0.4 mL of oleic acid (OA) to the three-necked flask to dissolve the cesium carbonate (Cs₂CO₃), and adding 3.5 mL of octadecene (ODE) as a solvent; preheating the three-necked flask to 80°C; evacuating and stirring for a period of time; then filling the three-necked flask with an inert atmosphere; and cooling it down after the solid has completely dissolved. When using, the precursor is then heated to 100-120°C.

[0045] In some embodiments, the monovalent cation precursor in S10 can be formamidine acetate (FA-AC), and the preparation method can be as follows: weigh 5 mmol of FA-AC and add it to a three-necked flask, then add 20 mL of oleic acid (OA) to the three-necked flask, evacuate the three-necked flask and stir for a period of time, then fill the three-necked flask with an inert atmosphere and stir for later use.

[0046] In some embodiments, the iodine source in the mixed precursor in S20 is a mixture of one or more of hydrogen iodide (HI), potassium iodide (KI), magnesium iodide (MgI2), lead iodide (PbI2), zinc iodide (ZnI2), manganese iodide (MnI2), strontium iodide (SrI2), tin iodide (SnI2), zirconium iodide (ZrI4), and cobalt iodide (CoI2) in different proportions.

[0047] In some embodiments, the lead source in the mixed precursor in S20 is lead iodide (PbI2), lead bromide (PbBr2), lead chloride (PbCl2), lead acetate (Pb(Ac)2), lead oleate (Pb(OA)2), or lead stearate ([CH3(CH2)2]). 16 A mixture of one or more of COO]2Pb in different proportions.

[0048] In some embodiments, the organic acid in the monovalent cation precursor of S10 and the organic acid in the mixed precursor of S20 include, but are not limited to, octanoic acid, lauric acid, oleic acid, octylphosphonic acid, octadecylphosphonic acid, bis(2,4,4-trimethylpentyl)phosphonic acid, benzenesulfonic acid, etc. The organic amine in the mixed precursor of S20 includes, but is not limited to, n-octylamine, di-n-octylamine, dodecylamine, bis(dodecylamine), hexadecylamine, octadecylamine, oleylamine, etc. Furthermore, the mixed precursor may also contain a solvent, such as octadecene, mesitylene, etc. In addition, the volume ratio of acid to amine is close to 1, preferably 1:1-1.5. An acid-amine ratio close to 1 is beneficial for the nucleation and growth of perovskite quantum dots, synthesizing quantum dots with fewer surface defects, while a slight excess of amine is beneficial for the dissolution of the mixed precursor.

[0049] In some embodiments, the obtained product can be purified after passivation. The purification of quantum dots can include, but is not limited to, the following steps: transferring the quantum dot stock solution to a centrifuge tube and centrifuging at low speed; extracting the supernatant after centrifugation, adding an antisolvent, including but not limited to methyl acetate, ethyl acetate, and isopropanol, and centrifuging at high speed; discarding the supernatant after centrifugation, dispersing the precipitate in octane, and collecting it by filtration through a 0.22 μm organic filter to obtain a perovskite quantum dot solution. Under certain conditions, the above steps can be repeated, continuing to add an antisolvent to the octane solution of quantum dots and centrifuging at high speed, then taking the precipitate and dispersing it again in octane after centrifugation.

[0050] The fluorescence emission peak position of the passivated red perovskite quantum dots prepared by the method of the present invention will change with the composition and content of the precursor, the reaction temperature, and the amount of acyl chloride added. The wavelength range of the above fluorescence emission peak position is 620-760nm.

[0051] In some embodiments, these red-light perovskite quantum dots can be used to fabricate semiconductor devices such as solar cells, light-emitting diodes, photodetectors, and lasers.

[0052] The present invention will be further described in detail below through embodiments:

[0053] Example 1

[0054] Preparation of CsPbI3 quantum dots and passivation with octanoyl chloride: Weigh 88 mg PbI2 and 244 mg ZnI2 and add them to a 25 mL three-necked flask. Add 1.75 mL of oleic acid (OA), 1.8 mL of oleylamine (OAm), and 5 mL of octadecene (ODE) to the three-necked flask. Evacuate the three-necked flask for 30 min to remove water, oxygen, and other components from the apparatus. Then, fill the three-necked flask with inert gas and heat the reaction solution to 160 °C with continuous stirring. Quickly inject 0.4 mL of cesium oleate (Cs-OA) precursor into the mixed precursor. After reacting for about 5 s, continuously cool the reaction apparatus with an ice-water bath. When the solution temperature drops to 130 °C, quickly inject 0.25 mL of octanoyl chloride (which can be diluted with 5 mL of auxiliary reagent) at once for passivation. After the reaction solution cools to room temperature, the passivated CsPbI3 perovskite quantum dot stock solution is obtained. After a series of subsequent purification processes, CsPbI3 perovskite quantum dots were obtained for testing and application.

[0055] Comparative Example 1:

[0056] The difference from Example 1 is that passivation treatment with acyl chloride is not performed.

[0057] Preparation of CsPbI3 quantum dots without passivation using acyl chlorides: 88 mg PbI2 and 244 mg ZnI2 were weighed and added to a 25 mL three-necked flask. 1.75 mL of oleic acid (OA), 1.8 mL of oleylamine (OAm), and 5 mL of octadecene (ODE) were added to the flask. The flask was evacuated for 30 min to remove water, oxygen, and other components. Then, an inert gas was introduced into the flask, and the reaction solution was heated to 160 °C with continuous stirring. 0.4 mL of cesium oleate (Cs-OA) precursor was rapidly injected into the mixed precursor. After reacting for approximately 5 s, the reaction apparatus was continuously cooled using an ice-water bath. Once the reaction solution cooled to room temperature, the unpassivated CsPbI3 perovskite quantum dot stock solution was obtained. After a series of subsequent purification processes, CsPbI3 perovskite quantum dots for testing and application were obtained.

[0058] Comparative Example 2:

[0059] The difference from Example 1 is that the acyl chloride was added at a temperature below 100°C.

[0060] Preparation of CsPbI3 quantum dots and passivation with octanoyl chloride (at a lower temperature): Weigh 88 mg PbI2 and 244 mg ZnI2 and add them to a 25 mL three-necked flask. Add 1.75 mL of oleic acid (OA), 1.8 mL of oleylamine (OAm), and 5 mL of octadecene (ODE) to the three-necked flask. Evacuate the three-necked flask for 30 min to remove water, oxygen, and other components from the apparatus. Then, fill the three-necked flask with inert gas and heat the reaction solution to 160 °C with continuous stirring. Quickly inject 0.4 mL of cesium oleate (Cs-OA) precursor into the mixed precursor. After reacting for about 5 s, continuously cool the reaction apparatus with an ice-water bath. When the solution temperature drops to 80 °C, quickly inject 0.25 mL of octanoyl chloride (which can be diluted with 5 mL of auxiliary reagent) at once for passivation. After the reaction solution cools to room temperature, the CsPbI3 perovskite quantum dot stock solution is obtained. After a series of subsequent purification processes, CsPbI3 perovskite quantum dots were obtained for testing and application.

[0061] Figure 1 This describes the reaction mechanism of acyl chloride passivation of surface defects in red perovskite quantum dots in Example 1. The perovskite quantum dots in this example exhibit excellent optical properties, significantly improved photostability, and achieve fluorescence emission in the pure red light band (peak position at 630-650 nm). Figure 2 The images show the UV-Vis absorption and fluorescence emission spectra of the passivated CsPbI3 quantum dots in this embodiment. The passivated quantum dots achieved pure red light emission. Figure 3 This is a comparison of the fluorescence quantum yield and fluorescence lifetime of the CsPbI3 quantum dot solution before and after passivation in this embodiment. The fluorescence quantum dot yield of the perovskite quantum dots after passivation is close to 100%, and the non-radiative recombination channel is significantly suppressed, which can be fitted by a single exponent. Figure 4 The image shows a comparison of the fluorescence quantum yield and fluorescence lifetime of the CsPbI3 quantum dot film before and after passivation in this embodiment. The quantum dot film can be prepared by solution spin coating. The fluorescence quantum yield of the perovskite quantum dot film after passivation is significantly improved, and the fluorescence lifetime is twice that before passivation. Figure 5 The image shows a comparison of the variable excitation fluorescence quantum yield of CsPbI3 quantum dot films before and after passivation. The quantum yield of the perovskite quantum dot film after passivation does not change much under different excitation intensities of laser light, indicating that its surface defects are significantly reduced and its photostability is improved. Figure 6The conductivity test results of CsPbI3 quantum dot films before and after passivation are shown. The conductivity of the passivated quantum dot film is significantly improved due to the reduction of long-chain ligands on the surface. The fluorescence quantum yield of CsPbI3 quantum dot solutions before and after passivation at different temperatures is also presented. The fluorescence quantum yield of the unpassivated quantum dot solution is 90%, indicating the presence of a certain amount of defects on its surface. Implantation of acyl chloride at a moderate temperature (100-140℃) allows for sufficient reaction with organic acids and amines, passivating the surface defects of the quantum dots and achieving a fluorescence quantum yield close to 100%. Implantation of acyl chloride at lower temperatures (below 100℃) results in insufficient reactivity and only partial passivation of the quantum dot surface defects.

[0062] Example 2

[0063] Preparation of CsPbI3 quantum dots and passivation with hexanoyl chloride: Weigh 88 mg PbI2 and 244 mg ZnI2 and add them to a 25 mL three-necked flask. Add 1.75 mL of oleic acid (OA), 1.8 mL of oleylamine (OAm), and 5 mL of octadecene (ODE) to the three-necked flask. Evacuate the three-necked flask for 30 min to remove water, oxygen, and other components from the apparatus. Then, fill the three-necked flask with inert gas and heat the reaction solution to 160 °C with continuous stirring. Quickly inject 0.4 mL of cesium oleate (Cs-OA) precursor into the mixed precursor. After reacting for about 5 s, continuously cool the reaction apparatus with an ice-water bath. When the solution temperature drops to 120-140 °C, quickly inject 0.2 mL of hexanoyl chloride (which can be diluted with 5 mL of auxiliary reagent) for passivation. After the reaction solution cools to room temperature, the passivated red CsPbI3 perovskite quantum dot stock solution is obtained. After a series of subsequent purification processes, CsPbI3 perovskite quantum dots for testing and application were obtained. In this embodiment, hexanoyl chloride was used instead of octanoyl chloride in Example 1 for passivation treatment. To achieve the same effect, the molar amounts of hexanoyl chloride and octanoyl chloride need to be adjusted to be consistent. Other types of acyl chlorides can be passivated in the same way.

[0064] The UV-Vis absorption spectra in the examples were obtained using an Agilent Cary 5000 UV-Vis-IR absorption spectrometer; fluorescence spectra and fluorescence lifetimes were obtained using a Zolix OmniFluo 990LSP transient / steady-state fluorescence spectrometer, with a xenon lamp as the light source for fluorescence spectroscopy and a 375nm laser paired with a time-correlated single-photon counter as the light source for fluorescence lifetime testing; fluorescence quantum dot yields were obtained using an Edinburgh FLS920 integrating sphere, with a xenon lamp as the light source. Fluorescence quantum yield testing was performed in nitrogen atmosphere, while all other tests were performed in air.

[0065] In summary, this invention provides a method for passivating surface defects in red-light perovskite quantum dots. By adding acyl chloride during the cooling process of high-temperature quantum dot synthesis, the dynamic equilibrium of organic ligands in the reaction system is altered, reducing the number of long-chain organic ligands on the quantum dot surface. Furthermore, chlorine atoms are introduced to fill iodine atom vacancies on the surface, achieving passivation of surface defects simultaneously with quantum dot synthesis. The red-light perovskite quantum dots obtained through this method exhibit significantly reduced surface defects, superior optical properties and photostability, and avoid complex post-processing ligand exchange. This method is of great significance for promoting the development and application of perovskite quantum dots in semiconductor devices such as light-emitting diodes and solar cells.

Claims

1. A method for passivating surface defects in red perovskite quantum dots, characterized in that, Includes the following steps: A monovalent cation precursor is provided, the monovalent cation precursor being composed of at least one monovalent cation selected from cesium (Cs), rubidium (Rb), formamidinium (FA), methylammonium (MA), and aminoformamidinium (GA) and an acid; A mixed precursor containing an iodine source, a lead source, an organic acid, and an organic amine is provided; The monovalent cation precursor is added to the mixed precursor for reaction at a temperature of 150-190°C. During the cooling process after the reaction, an acyl chloride is added at a temperature range of 100-140℃ to achieve passivation, wherein the acyl chloride is octanoyl chloride or hexanoyl chloride.

2. The method for passivating surface defects of red perovskite quantum dots according to claim 1, characterized in that, The monovalent cation precursor includes one or more of cesium carbonate (Cs2CO3), cesium formate (CsHCOO), cesium acetate (CsAc), rubidium carbonate (Rb2CO3), rubidium formate (RbHCOO), rubidium acetate (RbAc), formamidine formate (FAHCOO), formamidine acetate (FA-Ac), methylamine formate (MAHCOO), guanidine carbonate (GA2CO3), and guanidine acetate (GA-Ac).

3. The method for passivating surface defects of red perovskite quantum dots according to claim 1, characterized in that, The iodine source in the mixed precursor includes one or more of hydrogen iodide (HI), potassium iodide (KI), magnesium iodide (MgI2), lead iodide (PbI2), zinc iodide (ZnI2), manganese iodide (MnI2), strontium iodide (SrI2), tin iodide (SnI2), zirconium iodide (ZrI4), and cobalt iodide (CoI2).

4. The method for passivating surface defects of red perovskite quantum dots according to claim 1, characterized in that, The lead sources in the mixed precursors include lead iodide (PbI2), lead acetate (Pb(Ac)2), lead oleate (Pb(OA)2), and lead stearate ([CH3(CH2)2]). 16 One or more of COO]2Pb.

5. The method for passivating surface defects of red perovskite quantum dots according to claim 1, characterized in that, In the mixed precursor, the volume ratio of organic acid to organic amine is 1:1-1.

5.

6. The method for passivating surface defects of red perovskite quantum dots according to claim 1, characterized in that, The monovalent cation precursor is added to the mixed precursor to form a reaction solution, and the volume ratio of the added acyl chloride to the reaction solution should be less than 1:

10.

7. The method for passivating surface defects of red perovskite quantum dots according to claim 1, characterized in that, The acyl chloride can be dispersed in an auxiliary reagent, which includes one or more of benzene-based and alkane-based reagents.

8. The method for passivating surface defects of red perovskite quantum dots according to claim 1, characterized in that, The wavelength range of the red light is 620-760 nm.

9. The method for passivating surface defects of red perovskite quantum dots according to claim 6, characterized in that, The ratio of the amount of added acyl chloride to the volume of the reaction solution is 1:20-200.

Images