Chiral perovskite quantum dot, preparation method thereof and application of chiral perovskite quantum dot in spin light-emitting diode

Abstract

The invention discloses a chiral perovskite quantum dot, a preparation method thereof and application of the chiral perovskite quantum dot in a spin light-emitting diode, and relates to the field of semiconductor materials. The preparation method comprises the steps that perovskite quantum dots are cleaned and then added into a solvent to form a redispersion solution, the solvent is at least one of methylbenzene, chloroform and normal hexane, the redispersion solution and a chiral ligand are mixed and subjected to ultrasonic treatment, then supernate is collected through centrifugation, and the chiral perovskite quantum dots are obtained. According to the invention, perovskite quantum dots are dispersed in a solvent with low polarity, ultrasound is introduced to assist ligand exchange, energy and vibration provided by ultrasound enhance the ligand exchange efficiency, surface defects of PQDs are passivated, and the chiral PQDs with strong CD and CPL signals are prepared. The LED device using the chiral PQDs shows excellent circular polarization electroluminescent performance and relatively good external quantum efficiency, and has extremely high application potential.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials, and more particularly to a chiral perovskite quantum dot, its preparation method, and its application in spin light-emitting diodes. Background Technology

[0002] Perovskite quantum dots (PQDs) are a novel type of nanoscale semiconductor material used in the fabrication of light-emitting diodes (LEDs). When chiral organic molecules are attached to their surface, they are called chiral perovskite quantum dots, which are the light-emitting materials for spin LEDs. Currently, the main steps for preparing chiral PQDs via ligand exchange are as follows: first, chiral PQDs are prepared using a binary hot-injection method; then, the cleaned PQD solution is mixed with a methyl acetate solution containing a certain amount of chiral molecular salt, such as R- / S-MBA:Br; ligand exchange is performed by shaking; and impurities are removed by centrifugation to obtain the final product.

[0003] The aforementioned ligand exchange method addresses the issue of reduced chiral properties of PQDs caused by the cleaning process by exchanging chiral ligands onto the PQDs surface after cleaning. However, current chiral ligand exchange techniques primarily employ chemically assisted methods, resulting in limited ligand exchange efficiency, weak adsorption capacity of chiral ligands, and easy desorption from the PQDs surface, leading to defects and weak chiral luminescence in the prepared spin LEDs. Furthermore, ligand exchange methods have poor applicability; different methods or solutions are required to facilitate ligand exchange for different PQDs and chiral ligands. Summary of the Invention

[0004] This invention provides a chiral perovskite quantum dot, its preparation method, and its application in spin light-emitting diodes. By using ultrasound to promote ligand exchange, chiral PQDs with strong chirality and fewer defects can be prepared. It not only has high ligand exchange efficiency, but also has universal applicability to different perovskite quantum dots and chiral ligands.

[0005] To address the aforementioned technical problems, one objective of this invention is to provide a method for preparing chiral perovskite quantum dots, comprising the following steps: After washing the perovskite quantum dots, they are added to a solvent to form a redispersible solution. The solvent is at least one of toluene, chloroform, and n-hexane. The redispersible solution is mixed with a chiral ligand and subjected to ultrasonic treatment. The supernatant is then collected by centrifugation to obtain chiral perovskite quantum dots.

[0006] This application disperses cleaned perovskite quantum dots in a low-polarity solvent such as toluene or chloroform. In this case, the perovskite quantum dots are stable in the solvent and will not decompose, and are uniformly dispersed. Subsequently, ultrasonic treatment is used to assist in promoting ligand exchange and improve the ligand exchange efficiency, so that chiral organic molecules attach to the surface of the perovskite quantum dots, thereby preparing chiral PQDs with strong CD and CPL signals. These PQDs not only have strong chirality and fewer surface defects, but can also be adapted to different perovskite quantum dots and chiral ligands, exhibiting high versatility and suitability for industrial applications.

[0007] In some embodiments, the perovskite quantum dots have the general structural formula CsPbX. a X is at least one of Br, Cl, and I, and a is 1-3.

[0008] In some embodiments, the perovskite quantum dots include CsPbBr3 PQDs and CsPbCl. 1.5 Br 1.5 At least one of PQDs and CsPbI3PQDs. The perovskite quantum dots used in this application have high crystal structure stability and are not easily decomposed during ultrasonic-assisted ligand exchange, thus maintaining crystal structure stability.

[0009] In some embodiments, the chiral ligand is at least one selected from R-(+)-α-methylbenzylamine, S-(-)-α-methylbenzylamine, (R)-2-aminooctane, (S)-2-aminooctane, (R)-2-aminooctanoic acid, and (S)-2-aminooctanoic acid. The chiral ligands used in this application exhibit good compatibility with the solvent, forming a homogeneous solution. Furthermore, after ultrasonic treatment-assisted ligand exchange, chiral organic molecules can adhere to the surface of the PQDs, thereby causing the prepared chiral PQDs to exhibit larger CD and CPL signals.

[0010] In some embodiments, the concentration of perovskite quantum dots in the redispersible solution is 10-20 mg / mL.

[0011] In some embodiments, the volume ratio of the redispersible solution to the chiral ligand is 100:(1-6).

[0012] In some embodiments, the volume ratio of the redispersible solution to the chiral ligand is any one of 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, or a range between any two.

[0013] By controlling the volume ratio of the redispersed solution and the chiral ligand within the above-mentioned range, the CD and CPL signal intensity of the chiral PQDs can be increased, thereby improving the chiral ability. The preferred volume ratio is 100:1. If the volume ratio is too small, the CD and CPL signals will gradually weaken, and the chiral ability will decrease.

[0014] In some implementations, the ultrasonic power of the ultrasonic treatment is 200-800 W.

[0015] In some implementations, the ultrasonic power of the ultrasonic treatment is any one or a range between any two of 200 W, 300 W, 400 W, 500 W, 600 W, 700 W, and 800 W.

[0016] This application controls the power of ultrasound-assisted ligand exchange within the above-mentioned range, preferably at 400 W. If the ultrasound power is too low, it will not effectively promote ligand exchange, resulting in low CD and CPL signal intensity and poor chiral ability of chiral PQDs.

[0017] In some implementations, the ultrasonic treatment time is 3-9 minutes.

[0018] In some implementations, the ultrasonic treatment time is any one of 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, or a range between any two.

[0019] This application controls the time of ultrasound-assisted ligand exchange within the above-mentioned range, and preferably within 5 minutes. If the ultrasound time is too short, the ligand exchange efficiency will be low and the CD and CPL signal strength of chiral PQDs will be low. If the ultrasound time is too long, the process time will be increased.

[0020] In some implementations, the centrifugation speed is 2000-4000 rpm and the centrifugation time is 3-20 min.

[0021] In some implementations, the centrifugal speed is any one of 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, 4000 rpm, or a range between any two.

[0022] In some implementations, the centrifugation time is any one or a range between any two of the following: 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, and 20 min.

[0023] To address the aforementioned technical problems, a second objective of this invention is to provide a method for preparing chiral perovskite quantum dots using the aforementioned chiral perovskite quantum dot preparation method.

[0024] To address the aforementioned technical problems, a third objective of this invention is to provide an application of the chiral perovskite quantum dots in spin light-emitting diodes.

[0025] The chiral perovskite quantum dots prepared in this application not only possess extremely strong chirality but also have few surface defects. When applied to spin-emitting diodes (SLEDs), they exhibit high brightness and peak external quantum efficiency (PEE), and also possess circularly polarized electroluminescence properties, achieving high EQE and high g-efficiency. EL The EL intensity of the LED did not show any decay over a period of 220 minutes, demonstrating the potential of chiral PQDs in spin LED applications.

[0026] Compared with the prior art, the present invention has the following beneficial effects: 1. In this application, perovskite quantum dots are dispersed in toluene or chloroform solvents with low polarity. Ultrasound is introduced as an auxiliary means for PQD ligand exchange. The energy and vibration provided by ultrasound enhance the efficiency of ligand exchange and successfully passivate the surface defects of PQDs. Chiral PQDs with strong CD and CPL signals are prepared, and the LED devices made from the treated PQDs exhibit excellent circularly polarized electroluminescence performance and good external quantum efficiency.

[0027] 2. The ultrasound-assisted ligand exchange method of this application has a wide range of applications and can be applied to a variety of different PQDs and a variety of chiral ligands. It has high versatility and is suitable for industrial applications. Attached Figure Description

[0028] Figure 1 A schematic diagram (A) of the preparation method of chiral perovskite quantum dots using chemically assisted ligand exchange and a CD spectrum (B) of the chiral perovskite quantum dots. Figure 2 This is a schematic diagram of a method for preparing chiral perovskite quantum dots according to an embodiment of this application, and shows the CD, CPL, and g values ​​of different chiral perovskite quantum dots. abs and g lum Results (Note: Figure A - Schematic diagram of the preparation method of chiral perovskite quantum dots in the examples; B - CPL spectra of chiral perovskite quantum dots in Comparative Examples 1-2; C - CD spectra of Examples 1-2 and Comparative Examples 3-4; D - CPL spectra of Examples 1-2 and Comparative Examples 3-4; E - g of Examples 1-2 and Comparative Examples 3-4) abs and g lum Results; g of F-Examples 3-6abs and g lum Results; g of G-Examples 7-10 abs and g lum Results; g of H-Examples 11-15 abs and g lum result); Figure 3 The images provided are HRTEM images before and after processing of chiral PQDs in Embodiment 1 of this application, and XPS, FTIR, and [other images] of different chiral PQDs. 1 HNMR spectra (Note: A - HRTEM image of chiral PQDs in Comparative Example 5; B - HRTEM image of chiral PQDs prepared in Example 1; C - XPS images of chiral PQDs in Comparative Example 5, Example 1, and Comparative Example 3; D - FTIR images of chiral PQDs in Comparative Example 5, Example 1, and Comparative Example 3; E - C=O and COO in the FTIR image) - The peak area ratio; G-Comparative Example 5 chiral PQDs and Example 1 and Comparative Example 3 chiral PQDs. 1 HNMR spectrum; H- 1 The oleic acid / oleylamine peak and R-MBA characteristic peak in the HNMR spectrum; ligand exchange efficiency of chiral PQDs in Comparative Example 5 and chiral PQDs in Example 1 and Comparative Example 3). Figure 4 The following are the XRD, PL, PLQY, TRPL, FTIR, SOLC, and C-ω characteristic curves of the chiral PQDs in Example 1 and Comparative Example 3 of this application (Note: A - XRD results of chiral PQDs in Example 1 and Comparative Example 3; B - PL and PLQY results of chiral PQDs in Example 1 and Comparative Example 3; C - TRPL results of chiral PQDs in Example 1 and Comparative Example 3; D - FTIR results of chiral PQDs in Example 1 and Comparative Example 3; E - XRD-SCLC results of chiral PQDs in Example 1 and Comparative Example 3; F - C-ω characteristic curve results of chiral PQDs in Example 1 and Comparative Example 3; G - Defect state density of chiral PQDs in Example 1 and Comparative Example 3). Figure 5CD and CPL spectra of chiral PQDs were prepared for Examples 16-23 and Comparative Examples 6-7 of this application (Note: A - CD spectra of chiral PQDs in Examples 16-17; B - CD spectra of chiral PQDs in Examples 18-19; C - CPL spectra of chiral PQDs in Examples 16-17; D - CPL spectra of chiral PQDs in Examples 18-19; E - CD spectra of chiral PQDs in Examples 20-21). F - CD spectrum of chiral PQDs in Examples 22-23; G - CPL spectrum of chiral PQDs in Examples 20-21; H - CPL spectrum of chiral PQDs in Examples 22-23; I - Properties of MAPbI3 before and after ultrasound in Comparative Example 6; J - Properties of CsPbBr3 before and after ultrasound in Example 1; K - CD spectrum of chiral PQDs in Comparative Examples 6-7; L - CPL spectrum of chiral PQDs in Comparative Examples 6-7 Figure 6 Performance verification test results for spin LEDs fabricated from chiral PQDs in Examples 1-2 of this application (Note: EL spectra of AR-LED and S-LED; JLV characteristic curves of BR-LED and S-LED; EQE characteristic curves of CR-LED and S-LED; left- and right-handed polarization electroluminescence intensity of DR-LED; left- and right-handed polarization electroluminescence intensity of ES-LED; g-values ​​of FR-LED and S-LED). EL ; EQE and g of GR-LED and S-LED EL Statistics; stability test results of HR-LED; T50 characteristic curve of IR-LED). Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0031] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0032] As used in this article: In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0033] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0034] In the description of this invention, it should be understood that the terms "upper", "lower", "left", "right", "top", "bottom", etc., indicating orientation or positional relationship are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0035] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of the composite sheet with a pre-formed sintering layer on its surface, its preparation method, and its application, is provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention. Unless otherwise specified, the raw materials used in the following embodiments and comparative examples are all commercially available, and the same raw materials were used in parallel experiments.

[0036] Example 1 A method for preparing chiral perovskite quantum dots includes the following steps: The perovskite quantum dots (CsPbBr3PQDs) were washed with three times their volume of methyl acetate. They were then added to toluene to form a redispersible solution with a concentration of 15 mg / mL. One mL of the redispersible solution was added to a transparent glass bottle, followed by 10 μL of a chiral ligand, R-(+)-α-methylbenzylamine (R-MBA). The solution was then sonicated for 5 min (US) using a cell disruptor probe at 400 W to promote ligand exchange. The sonicated solution was then centrifuged at 3000 rpm for 5 min to remove large PQDs particles and other impurities. The supernatant was collected to obtain chiral perovskite quantum dots, sample name: R-chiral w / US PQDs.

[0037] Example 2 A method for preparing chiral perovskite quantum dots includes the following steps: The perovskite quantum dots (CsPbBr3PQDs) were washed with three times the volume of methyl acetate. The resulting solution was then added to toluene to form a redispersible solution with a concentration of 15 mg / mL. One mL of this redispersible solution was added to a transparent glass bottle, followed by 10 μL of the chiral ligand S-(-)-α-methylbenzylamine (S-MBA). The solution was then sonicated for 5 min (US) using a cell disruptor probe at 400 W to promote ligand exchange. The sonicated solution was then centrifuged at 3000 rpm for 5 min to remove large PQDs particles and other impurities. The supernatant was collected to obtain chiral perovskite quantum dots, named S-chiral w / US PQDs.

[0038] Examples 3-6 A method for preparing chiral perovskite quantum dots differs from Example 1 in that the ultrasonic treatment power is different, as shown in Table 1 below.

[0039] Examples 7-10 A method for preparing chiral perovskite quantum dots differs from Example 1 in that the ultrasonic treatment time is different, as shown in Table 1 below.

[0040] Examples 11-15 A method for preparing chiral perovskite quantum dots differs from Example 1 in that the volume of the chiral ligand is different, as shown in Table 1 below.

[0041] Example 16 A method for preparing chiral perovskite quantum dots, differing from Example 1 in that the perovskite quantum dots are CsPbCl. 1.5 Br 1.5 .

[0042] Example 17 A method for preparing chiral perovskite quantum dots, differing from Example 2 in that the perovskite quantum dots are CsPbCl. 1.5 Br 1.5 .

[0043] Example 18 A method for preparing chiral perovskite quantum dots, which differs from Example 1 in that the perovskite quantum dots are CsPbI3.

[0044] Example 19 A method for preparing chiral perovskite quantum dots, which differs from Example 2 in that the perovskite quantum dots are CsPbI3.

[0045] Example 20 A method for preparing chiral perovskite quantum dots differs from Example 1 in that the chiral ligand is (R)-2-aminooctane, abbreviated as R-OcAm.

[0046] Example 21 A method for preparing chiral perovskite quantum dots differs from Example 1 in that the chiral ligand is (S)-2-aminooctane, abbreviated as S-OcAm.

[0047] Example 22 A method for preparing chiral perovskite quantum dots differs from Example 1 in that the chiral ligand is (R)-2-aminooctanoic acid, abbreviated as R-AOA.

[0048] Example 23 A method for preparing chiral perovskite quantum dots differs from Example 1 in that the chiral ligand is (S)-2-aminooctanoic acid, abbreviated as S-AOA.

[0049] Table 1 - Process settings for the preparation method of chiral perovskite quantum dots in Example 3-23 Comparative Example 1 A method for preparing chiral perovskite quantum dots includes the following steps: (1) Methylamine hydrochloride, lead chloride and potassium bromide are dissolved in dimethylformamide, and (R)-2-aminooctane and oleic acid are added as ligands to form a mixed solution, wherein the molar ratio of methylamine hydrochloride, lead chloride and potassium bromide is 4:5:40, the volume ratio of (R)-2-aminooctane, oleic acid and dimethylformamide is 1:25:550, and the concentration of lead ions in the solution is 0.0174 mol / L; (2) Place this mixed solution in an ultrasonic cleaner and sonicate for 2.5 hours to obtain a precursor solution. Then add toluene to the above precursor solution. The volume ratio of the precursor solution to the toluene solution is 1:50. The precursor solution can be observed to change from pale yellow to clear green with the naked eye, which is the chiral perovskite quantum dot solution.

[0050] Comparative Example 2 A method for preparing chiral perovskite quantum dots includes the following steps: (1) Methylamine hydrochloride, lead chloride and potassium bromide are dissolved in dimethylformamide, and (R)-2-aminooctane and oleic acid are added as ligands to form a mixed solution, wherein the molar ratio of methylamine hydrochloride, lead chloride and potassium bromide is 4:5:40, the volume ratio of (S)-2-aminooctane, oleic acid and dimethylformamide is 1:25:550, and the concentration of lead ions in the solution is 0.0174 mol / L; (2) Place this mixed solution in an ultrasonic cleaner and sonicate for 2.5 hours to obtain a precursor solution. Then add toluene to the above precursor solution. The volume ratio of the precursor solution to the toluene solution is 1:50. The precursor solution can be observed to change from pale yellow to clear green with the naked eye. This is the chiral perovskite quantum dot solution.

[0051] Comparative Example 3 A method for preparing chiral perovskite quantum dots includes the following steps: CsPbBr3PQDs were washed with three volumes of methyl acetate and then added to toluene to form a redispersible solution with a concentration of 15 mg / mL. 1 mL of the redispersible solution was added to a transparent glass bottle, followed by 10 μL of the chiral ligand R-(+)-α-methylbenzylamine (R-MBA). The mixture was stirred in air at 2000 rpm for 5 min to promote ligand exchange. Subsequently, it was centrifuged at low speed to remove large PQDs particles and other impurities. The supernatant was collected to obtain chiral perovskite quantum dots, and the sample name was R-chiral w / o USPQDs.

[0052] Comparative Example 4 A method for preparing chiral perovskite quantum dots includes the following steps: CsPbBr3PQDs were washed with three volumes of methyl acetate and then added to toluene to form a redispersible solution with a concentration of 15 mg / mL. 1 mL of the redispersible solution was added to a transparent glass bottle, followed by 10 μL of the chiral ligand S-(-)-α-methylbenzylamine (S-MBA). The mixture was stirred in air at 2000 rpm for 5 min to promote ligand exchange. Subsequently, the mixture was centrifuged at low speed to remove large PQDs particles and other impurities. The supernatant was collected to obtain chiral perovskite quantum dots, and the sample name was S-chiral w / oUS PQDs.

[0053] Comparative Example 5 A method for preparing achiral perovskite quantum dots includes the following steps: cleaning CsPbBr3PQDs to prepare achiral perovskite quantum dots, abbreviated as Achiral.

[0054] Comparative Example 6 A method for preparing chiral perovskite quantum dots, which differs from Example 1 in that the perovskite quantum dots are MAPbI3, which are formed into a pale yellow emulsion after ultrasonic treatment.

[0055] Comparative Example 7 A method for preparing chiral perovskite quantum dots differs from Example 1 in that the chiral ligand is (R)-1-(1-naphthyl)ethylamine, abbreviated as R-NEA.

[0056] Comparative Example 8 A method for preparing chiral perovskite quantum dots differs from Example 1 in that the chiral ligand is (S)-1-(1-naphthyl)ethylamine, abbreviated as S-NEA.

[0057] Performance testing like Figure 1 As shown in Figure A, when preparing chiral PQDs via ligand exchange using this chemically assisted method, taking chiral CsPbBr3PQDs as an example, the preparation process and ligand exchange process exhibit low exchange efficiency and poor stability of the chiral ligands anchored in the PQDs. The efficiency of chiral ligand exchange can be reflected by the circular dichroism and circularly polarized luminescence of the PQDs, such as... Figure 1 As shown in Figure B, the chiral PQDs exhibit weak circular dichroism.

[0058] like Figure 2 As shown in Figure B, in Comparative Examples 1-2, PQDs were dissolved and decomposed using a highly polar solution, dimethylformamide, followed by the addition of chiral ligands for ligand exchange. Perovskite was then precipitated using toluene to form quantum dots. The chiral PQDs prepared using this method exhibited weak CPL activity. In Examples 1-2 of this application, PQDs were dissolved using a low-polarity solution, toluene, and then ultrasonic-assisted ligand exchange was used. The circular dichroism (CD) and circularly polarized light luminescence (CPL) spectra of the prepared chiral PQDs are shown below. Figure 2 The strong signals in B and C are shown in the circular dichroism (CD) and circularly polarized light luminescence (CPL) spectra of chiral PQDs detected without ultrasound assistance in Comparative Examples 3-4 are as follows: Figure 2 The weak chiral signals of C and D are shown. This indicates that the CD and CPL properties of chiral PQDs prepared by ultrasound-assisted ligand exchange are greatly enhanced. The calculated g, used to express the strength of CD and CPL abilities, is further supported. abs and g lum like Figure 2 As shown in Figure E, the CD and CPL capabilities of the chiral PQDs in Examples 1-2 are stronger than those in Comparative Examples 3-4.

[0059] Figure 2 The figures in Table F show the statistical g values ​​of chiral PQDs prepared under different ultrasonic powers in Examples 1-2 and 3-6, respectively.abs and g lum The results showed that chiral PQDs prepared with ultrasonic power of 400-800 W had strong chirality. Figure 2 The figures in G represent the statistical results of chiral PQDs prepared under different ultrasound durations in Examples 1-2 and 7-10, respectively. abs and g lum The results showed that the chiral PQDs prepared by sonication for 3-9 minutes had strong chiral ability. Figure 2 The figures in H represent the statistical g values ​​of chiral PQDs prepared under different chiral ligand volumes in Examples 1-2 and 11-15, respectively. abs and g lum The results demonstrate that highly chiral PQDs can be prepared under optimal conditions of 10-40 μL of chiral ligands.

[0060] like Figure 3 Figures A and B show the high-resolution transmission electron microscopy (HRTEM) results of the chiral PQDs in Example 1 and the chiral PQDs in Comparative Example 5, respectively. Figure 3 In Figure C, the X-ray diffraction (XRD) spectra of chiral PQDs prepared with ultrasound assistance in Example 1, chiral PQDs without ultrasound treatment in Comparative Example 3, and chiral PQDs without ultrasound treatment in Comparative Example 5 are shown. HRTEM and XRD indicate that the morphology and cubic crystal structure of the PQDs in Example 1 did not change before and after treatment.

[0061] like Figure 3 As shown in Figure C, in the XPS of Example 1, -NH 2 and -NH 3+ The peak area is larger than that in Comparative Example 5. For example... Figure 3 As shown in Figure D, the peak of C=C (derived from chiral molecules) appears in the Fourier transform infrared (FTIR) spectrum of Example 1, and as shown in Figure D... Figure 3 As shown in Figure E, the FTIR spectrum of Example 1 shows C=O (derived from free oleic acid, used to determine the amount of oleic acid desorbed from the PQDs surface) and COO. - The peak area ratio (derived from oleic acid adsorbed on the surface of PQDs) is larger than that of Comparative Example 5, such as... Figure 3 As shown in Figure E, the C=C and CH in the FTIR spectrum of Example 1 x The peak area ratio (derived from the original oleic acid and oleylamine ligands) is increased compared to Comparative Example 5. For example... Figure 3 As shown in Figures G and H, the 1H NMR peaks of the chiral PQDs in Example 1 show shifts and changes in peak area compared to Comparative Example 5. The XPS, FTIR, and 1H NMR peak results all collectively demonstrate that the chiral ligands in Example 1 were successfully attached to the surface of the PQDs with ultrasonic assistance. Furthermore, as... Figure 3As shown in Figure I, it is demonstrated that the ultrasound-assisted ligand exchange method in Example 1 has a higher exchange efficiency than the ultrasound-free method in Comparative Example 3.

[0062] like Figure 4 As shown in Figure A, during X-ray diffraction (XRD) characterization, the chiral PQDs of Example 1, after ultrasonic treatment, exhibited narrower diffraction peaks compared to those of Comparative Example 3 (untreated). The results indicate that chiral ligands can potentially passivate excessive surface defects caused by weakly bonded oleic acid and oleylamine ligands on PQDs, thereby improving crystal quality and suppressing nonradiative carrier recombination. Therefore, carrier dynamics closely related to nonradiative carrier loss were investigated using photoluminescence quantum yield (PLQY) and time-resolved photoluminescence (TRPL) measurements.

[0063] like Figure 4 As shown in Figure B, the chiral PQDs solution based on Example 1, which underwent ultrasonic treatment, exhibited a high PLQY of 94%, while the PLQY based on the untreated chiral PQDs solution of Comparative Example 3 showed 86%. This indicates that nonradiative carrier recombination in the former chiral PQDs was suppressed. Figure 4 As shown in Figure C, the carrier lifetime revealed by TRPL measurements exhibits a similar trend, with the ultrasonically treated chiral PQDs of Example 1 showing an enhanced carrier lifetime of 5.62 ns compared to 4.33 ns for the untreated chiral PQDs in Comparative Example 3. Figure 4 The space charge limiting current (SCLC) tests shown in Figures D and E demonstrate that the chiral PQDs device in Comparative Example 3, without ultrasonic treatment, exhibits a trap fill limiting voltage of 1.64 V. TFL ), and the corresponding trap density (n trap The value is calculated to be 1.2 × 10¹⁸ cm. -3 ; while the V of the device of the chiral PQDs subjected to ultrasonic treatment in Example 1 TFL Reduced to 0.96 V, n trap Reduced to 7.0 × 10¹⁷ cm -3 .like Figure 4 As shown in Figure F, the capacitance-frequency (C-ω) spectra of the devices of the two chiral PQDs in Example 1 and Comparative Example 3 show that the device of the unultrasonicated chiral PQD in Comparative Example 3 has a higher capacitance, which is related to the presence of a higher density of traps that capture charge carriers. Figure 4As shown in G, the defect state density (Nt) as a function of the defect state energy (Eω) can be further converted using C-ω spectral data. Compared with the unultrasonicated device based on chiral PQDs in Comparative Example 3, the defect state density of the ultrasonically treated device in Example 1 is significantly reduced by nearly an order of magnitude, indicating that surface defect passivation leads to the suppression of deep-level defects.

[0064] like Figure 5 As shown in A, B, C, and D, quantum dots with different emission bands, such as CsPbBr in the blue-green emission band of Examples 16-17. 1.5 Cl 1.5 PQDs and CsPbI3PQDs in the red emission band of Examples 18-19 successfully exhibited CD and CPL signals after ultrasound-assisted ligand exchange, indicating that the ultrasound-assisted ligand exchange method of this application can be applied to a variety of perovskite quantum dots.

[0065] In addition, other types of chiral ligands besides aromatics (R / S-MBA) were studied based on chiral CsPbBr3PQDs, including alkanes (R / S-OcAm) in Examples 20-21 and amino acids (R / S-AOA) in Examples 22-23, and as... Figure 5 As shown in Figures E, F, G, and H, CD and CPL signals can be detected in chiral CsPbBr3PQDs with different types of chiral ligands, demonstrating the broad applicability of the ultrasound-assisted ligand exchange method of this application. Although this method has relatively wide applicability, it still has limitations. For quantum dots with unstable crystal structures, ultrasound may destroy their structure, such as the MAPbI3PQDs in Comparative Example 6. Figure 5 As shown in Figure I, it decomposes after ultrasonic treatment, forming a pale yellow milky liquid, as... Figure 5 As shown in Figure J, the CsPbBr3PQDs in Example 1 did not undergo significant changes after sonication, and the solution remained clear and transparent. Furthermore, for ligands with poor solution miscibility, such as the (R)-1-(1-naphthyl)ethylamine chiral ligands of Comparative Example 7 and Comparative Example 8, such as... Figure 5 As shown in K and L, PQDs did not exhibit large CD and CPL signals after ultrasound-assisted ligand exchange.

[0066] As a performance verification, spin LEDs with an ITO / poly-SAM / chiral PQDs / PO-T2T / TPBi / LiF / Al structure were successfully fabricated using chiral CsPbBr3PQDs from Examples 1-2. PQDs with R-MBA and S-MBA deposited on their surfaces were referred to as R-LEDs and S-LEDs, respectively. Figure 6As shown in Figure A, green light emission with a center wavelength of approximately 517 nm can be identified from the electroluminescence (EL) spectra of R-LED and S-LED devices. Furthermore, as... Figure 6 As shown in Figure B, a turn-on voltage of approximately 2.1V and a maximum current density-luminosity-voltage (JLV) of over 28,000 cdm can be extracted from the current density-luminosity-voltage (JLV) characteristic curves of the two types of devices. -2 Maximum brightness (R-LED: 28630 cdm) -2 S-LED: 32864 cdm -2 This is higher than that of existing perovskite spin LEDs in the current literature. For example... Figure 6 As shown in Figure C, the best R-LED and S-LED devices exhibit peak external quantum efficiency (EQE) values ​​of 16.8% and 16.0%, respectively, both of which are the highest among existing perovskite spin LEDs. Figure 6 As shown in Figures D and E, the left- and right-hand circularly polarized electroluminescence (σ) of R-LED and S-LED are... + and σ − The differences indicate that LEDs fabricated based on chiral PQDs possess circularly polarized electroluminescence (CPEL) properties. For example... Figure 6 As shown in Figure F, g of R-LED and S-LED EL The values ​​(used to express the strength of the CP-EL capability of spin LEDs) are 0.285 and 0.251 (full width at half maximum) in the 510 to 525 nm range, respectively, which also surpasses the state-of-the-art perovskite spin LEDs. For example... Figure 6 As shown in Figure G, compared with existing perovskite spin LEDs, the R-LED and S-LED devices of this application simultaneously achieve high EQE and high g. EL The values ​​demonstrate the potential of spin LEDs based on chiral PQD. For example... Figure 6 The graph shown in H represents the change in electroluminescence brightness over time, with the luminescence intensity at 100 cd·m. -2 Under these conditions, no attenuation of the EL light intensity of the R-LED was observed over a period of 220 minutes, such as... Figure 6 As shown in Figure I, the final estimate is 100 cd·m -2 Under these conditions, the time (T50) for the EL light intensity of the R-LED to decay to half of its maximum value is approximately 19.8 hours.

[0067] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for preparing chiral perovskite quantum dots, characterized in that, Includes the following steps: After washing the perovskite quantum dots, they are added to a solvent to form a redispersible solution. The solvent is at least one of toluene, chloroform, and n-hexane. The redispersible solution is mixed with a chiral ligand and subjected to ultrasonic treatment. The supernatant is then collected by centrifugation to obtain chiral perovskite quantum dots.

2. The method for preparing chiral perovskite quantum dots as described in claim 1, characterized in that, The general structural formula of the perovskite quantum dots is CsPbX. a X is at least one of Br, Cl, and I, and a is 1-3.

3. The method for preparing chiral perovskite quantum dots as described in claim 2, characterized in that, The perovskite quantum dots include CsPbBr3PQDs and CsPbCl. 1.5 Br 1.5 At least one of PQDs and CsPbI3PQDs.

4. The method for preparing chiral perovskite quantum dots as described in claim 1, characterized in that, The chiral ligand is at least one of R-(+)-O-methylbenzylamine, S-(-)-O-methylbenzylamine, (R)-2-aminooctane, (S)-2-aminooctane, (R)-2-aminooctanoic acid, and (S)-2-aminooctanoic acid.

5. The method for preparing chiral perovskite quantum dots as described in claim 1, characterized in that, The concentration of perovskite quantum dots in the redispersible solution is 10-20 mg / mL; And / or, the volume ratio of the redispersed solution to the chiral ligand is 100:(1-6).

6. The method for preparing chiral perovskite quantum dots as described in claim 1, characterized in that, The ultrasonic power for ultrasonic treatment is 200-800 W.

7. The method for preparing chiral perovskite quantum dots as described in claim 1, characterized in that, The ultrasonic treatment time is 3-9 minutes.

8. The method for preparing chiral perovskite quantum dots as described in claim 1, characterized in that, Centrifugation speed is 2000-4000 rpm, centrifugation time is 3-20 min.

9. A chiral perovskite quantum dot prepared using the method for preparing chiral perovskite quantum dots as described in any one of claims 1-8.

10. An application of the chiral perovskite quantum dot as described in claim 9 in a spin light-emitting diode.

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