Green light-emitting core-shell quantum dot and preparation method thereof

Abstract

The invention discloses a green light-emitting core-shell quantum dot and a preparation method thereof, and relates to the technical field of quantum dots. Comprising the following steps: dissolving powdered sulfur in oleylamine to obtain a sulfur stock solution; the preparation method comprises the following steps: mixing silver acetate, indium acetate, gallium triacetylacetonate and oleylamine, degassing, heating to 100-120 DEG C, injecting a ligand and a sulfur stock solution, heating to 270-280 DEG C, reacting, purifying the obtained coarse AgInGaS2 core quantum dot, dispersing in oleylamine, adding GaCl3 and the sulfur stock solution at 115-125 DEG C, heating to 220-260 DEG C, reacting to grow an AgGaS2 shell layer, purifying, and drying to obtain the AgInGaS2 core quantum dot. The green light-emitting core-shell quantum dot with high blue light absorption coefficient (up to 6.46 * 10 < 5 > M <-1 >. Cm <-1 >), narrow-spectrum emission (the half-peak width is 32 nm), defect-free light emission, high color purity and high light-emitting efficiency (up to 94%) is obtained.

Description

Technical Field

[0001] This invention relates to the field of quantum dot technology, and in particular to a green luminescent core-shell quantum dot and its preparation method. Background Technology

[0002] In color conversion-based display technologies, quantum dot films are typically excited by blue light backlighting, making their ability to absorb blue light crucial. If the molar absorption coefficient of the quantum dots for blue light is low, blue light can easily leak out, affecting the color purity of the emitted light. To compensate for insufficient absorption, it might be necessary to increase the concentration of quantum dots, but this would shorten the distance between the quantum dots, leading to energy reabsorption loss and consequently affecting color conversion efficiency.

[0003] Currently, InP quantum dots emitting green and red light have pushed photoluminescence performance close to the theoretical limit, with photoluminescence quantum yield (PLQY) exceeding 90%. However, their absorption of blue light is insufficient, making them unsuitable for color conversion displays. To address this, researchers have developed ZnSeTe quantum dots, which exhibit high absorption of blue light, but their emission spectrum is broad, with a typical full width at half maximum (FWHM) of 40–45 nm and poor color purity, still failing to meet the requirements for high-quality displays. Group I–III–VI quantum dots have attracted widespread attention due to their high absorption coefficients and tunable optical properties. However, in terms of luminescence performance, group I–III–VI quantum dots typically have broad emission spectral lines and moderate PLQY, with poor color purity, making them unsuitable for display applications. This is mainly attributed to the high-density surface defects, vacancy defects, and donor-acceptor pair (DAP) energy levels resulting from their complex structure; the recombination process of these defect states leads to spectral broadening. To improve their luminescence performance, researchers have coated AgInS2 (AIS) quantum dots with GaS... x The shell enables near-band edge emission. Despite using GaS... x The surface passivation achieved by the shell exhibits a narrow emission spectrum (emission spectrum half-width at half-maximum of about 41 nm) in the 500–590 nm range, but traditional amorphous GaS… x The shell and the AIS core have poor lattice matching, which easily introduces defect states at the interface, leading to nonradiative recombination (such as defect luminescence). Furthermore, its emission spectrum exhibits significant defect luminescence in the longer wavelength region, manifesting as a shoulder (tail), and its intensity increases with Ga. 3+ The tail emission intensifies with increasing concentration, significantly affecting the color purity of light. Therefore, eliminating this tail emission, which leads to a decrease in color purity, is crucial for the true application of this type of quantum dot in color-conversion display technology.

[0004] Therefore, there is an urgent need to develop a new type of quantum dot with high blue light absorption coefficient, narrow spectrum emission, defect-free luminescence, high color purity, and high luminescence efficiency. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a green luminescent core-shell quantum dot and its preparation method, aiming to provide a quantum dot with high blue light absorption coefficient, narrow spectrum emission, defect-free luminescence, high color purity and high luminescence efficiency.

[0006] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing green luminescent core-shell quantum dots, comprising the following steps: S1. Dissolve sulfur powder in oleylamine to prepare sulfur stock solution; S2. Silver acetate, indium acetate, gallium triacetylacetonate and oleylamine are mixed, then degassed and heated to 100~120℃. Ligands and sulfur stock solution are injected, and then the temperature is raised to 270~280℃ to react and obtain crude AgInGaS2 (AIGS) quantum dots. S3. After purifying the crude AIGS core quantum dots, disperse them in oleylamine, add GaCl3 and sulfur stock solution at 115~125℃, and heat to 220~260℃ to grow AgGaS2 (AGS) shell. After purifying the obtained crude core-shell quantum dots, green luminescent core-shell quantum dots (i.e. AIGS / AGS core-shell quantum dots) are obtained.

[0007] Optionally, purifying the crude AIGS core quantum dots specifically includes: Step A1: Dilute the crude AIGS quantum dots with a first organic solvent, then centrifuge to obtain the supernatant; Step A2: Repeat step A2 several times, dilute the obtained supernatant with the first organic solvent, add the precipitant, and centrifuge.

[0008] Optionally, the first organic solvent includes at least one of n-hexane and toluene; the precipitant is ethanol, a mixture of ethanol and acetone, or a mixture of ethanol and methanol. Optionally, when the precipitant is a mixture of ethanol and acetone, the volume ratio of ethanol to acetone is 5:1; when the precipitant is a mixture of ethanol and methanol, the volume ratio of ethanol to methanol is 5:1.

[0009] Optionally, the ratio of silver acetate, indium acetate, gallium triacetylacetonate and oleylamine is 0.2 mmol : 0.3 mmol : 0.6 mmol : 10 mL.

[0010] Optionally, the ligand includes at least one of 1-octylthiol, 1-dodecylthiol, and 1-hexylthiol.

[0011] Optionally, when the concentration of sulfur in the sulfur stock solution is 1 M, in step S3, the ratio of silver acetate, ligand and sulfur stock solution is 0.2 mmol : (1-2) mL : (1~3) mL.

[0012] Optionally, in step S3, the ratio of purified AgInGaS2 quantum dots, GaCl3, and sulfur in the sulfur stock solution is 150 µmol : (2~3.2) mmol : (0.5~2) mmol.

[0013] Optionally, the purification of the obtained crude core-shell quantum dots specifically includes: Step B1: Dilute the coarse core-shell quantum dots with a first organic solvent, then centrifuge to obtain the supernatant; Step B2: Repeat step B2 several times, dilute the obtained supernatant with the first organic solvent, add the precipitant, and centrifuge.

[0014] In a second aspect, the present invention provides a green luminescent core-shell quantum dot, wherein it is prepared by the preparation method of the present invention as described above. Beneficial Effects: This invention, through the selection of precursors and control of reaction conditions, initially adds only cationic precursors and uses oleylamine as a solvent for degassing to limit early nucleation. After the precursors are fully and uniformly dissolved, ligands and sulfur stock solutions are injected, and the temperature is raised to the target growth temperature to promote rapid nucleation and growth of quantum dots, thus preparing AIGS core quantum dots. Then, an AGS shell is grown through ion exchange. In this process, GaCl3 is used as a precursor, which not only provides Ga ions for shell formation but also releases chloride ions that effectively passivate the surface of the AIGS / AGS core-shell quantum dots. Finally, green luminescent AIGS / AGS core-shell quantum dots with a high blue light absorption coefficient (up to 6.46 × 10⁻⁶) are obtained. 5 M -1 ·cm -1 It features narrow-spectrum emission (half-width at half maximum of 32 nm), high brightness, defect-free luminescence, high color purity, and high luminous efficiency (up to 94%). Attached Figure Description

[0015] Figure 1 A schematic diagram of the fabrication process for green luminescent AIGS / AGS core-shell quantum dots.

[0016] Figure 2 A schematic diagram of the structure of green luminescent AIGS / AGS core-shell quantum dots.

[0017] Figure 3 This is a schematic diagram of the preparation of green luminescent AIGS / AGS in Example 1.

[0018] Figure 4 The images show the HRTEM and XRD results of different quantum dots in Example 1, where (a) is the HRTEM result of AIGS core quantum dot, (b) is the HRTEM result of AIGS / AGS core-shell quantum dot at low magnification, (c) is the HRTEM result of AIGS / AGS core-shell quantum dot at high magnification, and (d) is the XRD result of AIGS core quantum dot and AIGS / AGS core-shell quantum dot.

[0019] Figure 5 The images show the absorption and PL spectra of the AIGS core quantum dots and AIGS / AGS core-shell quantum dots in Example 1. Detailed Implementation

[0020] This invention provides a green luminescent core-shell quantum dot and its preparation method. 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 only for explaining the invention and are not intended to limit the invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0022] If the embodiments of the present invention involve descriptions such as "first" or "second", such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0023] Although coating the surface of quantum dots with an inorganic shell can effectively passivate surface dangling bonds and reduce defects, the inventors discovered that AIGS quantum dots (groups I–III–VI quantum dots) still exhibit defect luminescence. The tail emission primarily originates from radiative recombination of charge carriers in defect states such as donor-acceptor pair (DAP) levels and lattice vacancies / substitutions. The generation of these defects is closely related to their diverse composition, particularly the variation in Ga content within the AIGS core, which significantly affects the intensity of defect emission. This phenomenon stems from the different chemical behaviors of Ag, In, Ga, and S ions during the reaction. According to the hard-soft-acid-base (HSAB) theory, Ag and In are soft acids, Ga is a hard acid, and S is a soft base. Following the principle of "like attracts like," in the early stages of the reaction, Ag and In tend to combine with S to form AIS, while Ga is typically introduced later, through diffusion or substitution of In. Inhomogeneous Ga doping induces defect luminescence. Therefore, precise control of the Ga doping process is crucial for obtaining homogeneous AIGS core quantum dots. Previous synthesis strategies mainly employ a single-pot method to grow AIGS core quantum dots, where AIGS nucleation primarily occurs during the degassing stage, while Ga doping occurs in a subsequent stage, making reaction kinetics difficult to control. Consequently, the synthesized AIGS core quantum dots and their core / shell structured quantum dots generally exhibit strong defect luminescence. Based on this, this invention provides a method for preparing green luminescent core-shell quantum dots, wherein, as... Figure 1 As shown, it includes the following steps: S1. Dissolve sulfur powder in oleylamine to prepare sulfur stock solution; S2. Silver acetate, indium acetate, gallium triacetylacetonate, and oleylamine are mixed, then degassed and heated to 100-120°C (e.g., 100°C, 105°C, 110°C, 115°C, or 120°C, etc.), ligands and sulfur stock solution are injected, and then the temperature is raised to 270-280°C (e.g., 270°C, 272°C, 275°C, 278°C, or 280°C, etc.) to react and obtain crude AIGS quantum dots; S3. After purifying the crude AIGS core quantum dots, disperse them in oleylamine, add GaCl3 and sulfur stock solution at 115~125℃ (e.g., 115℃, 118℃, 120℃, 122℃ or 125℃, etc.), and heat to 220~260℃ to grow an AGS shell. After purifying the obtained crude core-shell quantum dots, green luminescent AIGS / AGS core-shell quantum dots are obtained.

[0024] This embodiment provides a novel method for synthesizing high-efficiency core-shell quantum dots, employing a low-cost organic precursor and synthesizing green luminescent quantum dots via hot-injection technology. In the initial stage (low-temperature degassing step), only a cationic precursor is added, and oleylamine is used as a solvent for degassing to limit early nucleation. After the precursor is fully and uniformly dissolved, ligands (e.g., 1-dodecylthiol or 1-octylthiol) and a sulfur stock solution (i.e., sulfur powder as a sulfur source) are injected to prevent premature sulfur reaction. The temperature is then raised to the target growth temperature to promote rapid nucleation and growth of the AIGS quantum dots. After synthesis, the AIGS quantum dots are purified for AGS shell preparation. The AGS shell growth employs a cation exchange (CE) mechanism, where In ions on the surface of the AIGS quantum dots are replaced with Ga ions to form the AGS shell. GaCl3 is used as a precursor in this process, providing Ga ions for shell formation, and the released chloride ions effectively passivate the surface of the AIGS / AGS core-shell quantum dots, further improving the PLQY of the core-shell quantum dots.

[0025] This invention achieves high-quality growth of core-shell quantum dots under controllable reaction kinetics. By selecting appropriate precursors and controlling reaction conditions, the prepared AIGS core quantum dots, after being coated with an AGS shell, exhibit extremely high PLQY (up to 94%), narrow-band emission characteristics (32 nm FWHM), defect-free luminescence, and a higher molar absorptivity for blue light (6.46 × 10⁻⁶). 5 M -1 ·cm -1 With its excellent blue light absorption capability, AIGS / AGS core-shell quantum dots are very suitable as a high-efficiency color conversion material for use in next-generation display technologies, and have broad application prospects in color conversion displays.

[0026] Step S1, which involves dissolving sulfur powder in oleylamine to obtain a sulfur stock solution, specifically includes: Sulfur is added to oleylamine at 100°C and stirred for 30 minutes to obtain a sulfur stock solution (the concentration of which can be 1 M, i.e., 10 ml / L).

[0027] In step S2, the selection of the precursor is crucial. The present invention uses the aforementioned precursor, which allows the reaction temperature to reach 270-280°C, thus obtaining highly crystalline AIGS quantum dots. Simultaneously, a sulfur stock solution is injected into the Ag, In, and Ga precursor mixture to prevent premature S reaction.

[0028] In step S3, such as Figure 2As shown, GaCl3 was added to the purified AIGS quantum dot solution to perform ion exchange and form a transition shell (i.e., there is a transition layer between the AIGS quantum dots and the AGS layer), which reduced defects caused by lattice mismatch at the interface.

[0029] The preparation method provided by this invention achieves a smooth transition from AIGS to AGS at the interface between the AIGS core and the AGS shell (e.g., Figure 2 (See the schematic diagram shown), thereby preparing AIGS / AGS quantum dots with defect-free photoluminescence emission. In some embodiments, the ratio of silver acetate, indium acetate, gallium triacetylacetonate, and oleylamine is 0.2 mmol : 0.3 mmol : 0.6 mmol : 10 mL.

[0030] In some embodiments, the ligand includes at least one of 1-octylthiol, 1-dodecylthiol, and 1-hexylthiol.

[0031] In some embodiments, when the sulfur concentration in the sulfur stock solution is 1 M, in step S3, the ratio of silver acetate, ligand and sulfur stock solution is 0.2 mmol : (1-2) mL : (1~3) mL, for example, it can be 0.2 mmol : 1 mL : 1 mL, 0.2 mmol : 1 mL : 3 mL, 0.2 mmol : 2 mL : 1 mL or 0.2 mmol : 2 mL : 3 mL, etc.

[0032] In some embodiments, purifying the crude AIGS nuclear quantum dots specifically includes: Step A1: Dilute the crude AIGS quantum dots with a first organic solvent, then centrifuge to obtain the supernatant; Step A2: Repeat step A2 several times (e.g., twice), dilute the obtained supernatant with the first organic solvent, add the precipitant, and centrifuge.

[0033] In step A1, in some embodiments, the first organic solvent includes at least one of n-hexane and toluene; the precipitant is ethanol, a mixture of ethanol and acetone, or a mixture of ethanol and methanol.

[0034] In some specific embodiments, when the precipitant is a mixture of ethanol and acetone, the volume ratio of ethanol to acetone is 5:1; when the precipitant is a mixture of ethanol and methanol, the volume ratio of ethanol to methanol is 5:1.

[0035] In step S3, in some embodiments, the ratio of purified AIGS quantum dots, GaCl3, and sulfur in the sulfur stock solution is 150 µmol: (2~3.2) mmol: (0.5~2) mmol.

[0036] In some embodiments, the purification of the obtained crude core-shell quantum dots specifically includes: Step B1: Dilute the coarse core-shell quantum dots with a first organic solvent (see above for the specific selection), then centrifuge to obtain the supernatant; Step B2: Repeat step B2 several times (e.g., twice), dilute the obtained supernatant with the first organic solvent, then add a precipitant (see above for specific selection), and centrifuge.

[0037] This invention also provides a green luminescent core-shell quantum dot, which is prepared using the preparation method described above. The present invention will be further described below through specific embodiments.

[0038] Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.

[0039] Example 1 This embodiment provides a method for preparing AIGS / AGS core-shell quantum dots, such as... Figure 3 As shown, it includes the following steps: (1) Preparation of sulfur stock solution: At 100°C, sulfur powder is dissolved in oleylamine (OLA) and stirred vigorously for 30 minutes to prepare a sulfur stock solution with a sulfur concentration of 1 M for later use.

[0040] (2) Synthesis of crude AIGS quantum dots: 0.2 mmol silver acetate (Ag(oAc)), 0.3 mmol indium acetate (In(oAc)3), and 0.6 mmol gallium triacetylacetonate (Ga(acac)3) were added to a three-necked flask, followed by 10 mL oleylamine (OLA) as a solvent. A magnetic stir bar was added, and stirring was started. The reaction system was degassed and heated under vacuum, with nitrogen purging repeated times. When the temperature reached 120°C, 1 mL of 1-octylthiol was rapidly injected, followed immediately by 1 mL of a pre-prepared sulfur stock solution. The temperature was then rapidly increased to 280°C and held for 5 minutes to promote the growth of AIGS quantum dots. After the reaction was completed, the flask was immediately placed in a water bath to cool and terminate the reaction, yielding crude AIGS quantum dots.

[0041] (3) Purification of crude AIGS quantum dots to obtain AIGS quantum dots: The 18 mL of crude AIGS quantum dots obtained in the previous step was diluted with 7 mL of n-hexane and centrifuged at 12000 rpm for 3 minutes to remove unreacted precursors and large particulate byproducts. This process was repeated twice to ensure complete removal of impurities. The resulting supernatant was diluted again with n-hexane and aliquoted into two 50 mL centrifuge tubes, 20 mL in each tube. 25 mL of ethanol was added to each tube to precipitate the quantum dots, and the tubes were centrifuged again at 9000 rpm for 3 minutes to complete the purification and obtain AIGS quantum dots.

[0042] (4) Synthesis of crude AIGS / AGS core-shell quantum dots: 150 µmol of purified AIGS core quantum dots were dispersed in 10 mL of oleylamine. The mixture was stirred and degassed at 120°C for 30 minutes. Then, 2.7 mmol of GaCl3 and 1.5 mL of sulfur stock solution (containing 1.5 mmol of S, i.e., a Ga to S molar ratio of 1.8:1) were added to the reaction system. The mixture was heated to 240°C and maintained for 2 hours to promote the growth of the AGS shell. After the reaction was completed, the mixture was rapidly cooled to obtain crude AIGS / AGS core-shell quantum dots.

[0043] (5) Purification of crude AIGS / AGS core-shell quantum dots to obtain AIGS / AGS core-shell quantum dots: ~12 mL of the obtained crude AIGS / AGS core-shell quantum dots were diluted with 10 mL of n-hexane and centrifuged at 12000 rpm for 3 minutes to remove unreacted precursors and large particulate byproducts. This process was repeated twice to ensure complete removal of impurities. The resulting supernatant was diluted again with 18 mL of n-hexane and aliquoted into two 50 mL centrifuge tubes, 20 mL in each tube. 20 mL of ethanol was added to each tube to precipitate the quantum dots, and the tubes were purified by centrifugation at 9000 rpm for 3 minutes to obtain AIGS / AGS core-shell quantum dots.

[0044] High-resolution transmission electron microscopy (HRTEM) image of AIGS nuclear quantum dots as shown below Figure 4 As shown in (a), the successful synthesis of AIGS core quantum dots is demonstrated; the HRTEM image of AIGS / AGS core-shell quantum dots is shown in Figure (a). Figure 4 As shown in (b) and (c), the results indicate that the particle size of AIGS / AGS core-shell quantum dots is slightly larger than that of AIGS core quantum dots, indicating that the shell coating was successful. In addition, the interplanar spacing of (112) is approximately 0.32 nm.

[0045] X-ray diffraction (XRD) results of AIGS / AGS core-shell quantum dots and AIGS core quantum dots are shown in the figure. Figure 4As shown in (d), the formation of the AGS shell is further confirmed: compared with the XRD results of the AIGS core quantum dots, the AIGS / AGS core-shell quantum dots show the characteristics of the AGS crystal phase, and its crystal structure is between AgInS2 and AGS.

[0046] Absorption and fluorescence (PL) spectra of AIGS core quantum dots and AIGS / AGS core-shell quantum dots are shown in the figure. Figure 5 As shown, the emission peak of AIGS core quantum dots is relatively broad, the weak PL peak appearing in the green band represents band-edge emission signals, and the strong tail emission comes from defect state recombination. In contrast, the emission peak of AIGS / AGS core-shell quantum dots is significantly enhanced and becomes narrower and sharper, due to the enhanced band-edge recombination emission, while defect-related tail emission is completely suppressed (i.e., defect-free luminescence), and the emission peak is located at a wavelength of 533 nm, emitting green light.

[0047] The full width at half maximum (FWHM) of the PL peak of AIGS / AGS core-shell quantum dots was measured to be 32 nm, and the absolute PL quantum efficiency (PLQY) was 90%. Its molar absorption coefficient (ε) at 450 nm was also measured. 450 The nanometer (nm) is 6.46 × 10 5 M -1 ·cm -1 This is far higher than that of green-emitting InP quantum dots (2.88 × 10⁻⁶). 4 M -1 ·cm -1 It exhibits excellent light absorption capabilities and application potential.

[0048] Example 2 This embodiment provides a method for preparing AIGS / AGS core-shell quantum dots, including the following steps: (1) Preparation of sulfur stock solution: At 100 °C, sulfur powder is dissolved in oleylamine (OLA) and stirred vigorously for 30 minutes to prepare a sulfur stock solution with a sulfur concentration of 1 M for later use.

[0049] (2) Synthesis of crude AIGS quantum dots: 0.2 mmol silver acetate (Ag(oAc)), 0.3 mmol indium acetate (In(oAc)3), and 0.6 mmol gallium triacetylacetonate (Ga(acac)3) were added to a three-necked flask, followed by 10 mL of oleylamine (OLA) as a solvent. A magnetic stir bar was added, and stirring was started. The reaction system was degassed and heated under vacuum, with nitrogen purging repeated times. When the temperature reached 110°C, 2 mL of 1-octylthiol was rapidly injected, followed immediately by 3 mL of a pre-prepared sulfur stock solution. The temperature was then rapidly increased to 275°C and held for 4 minutes to promote the growth of AIGS quantum dots. After the reaction was completed, the flask was immediately placed in a water bath to cool and terminate the reaction, yielding crude AIGS quantum dots.

[0050] (3) Purification of crude AIGS nuclear quantum dots to obtain AIGS nuclear quantum dots: same as in Example 1.

[0051] (4) Synthesis of crude AIGS / AGS core-shell quantum dots: 150 µmol of purified AIGS core quantum dots were dispersed in 10 mL of oleylamine, stirred, and degassed at 120°C for 30 min. Subsequently, 3.2 mmol of GaCl3 and 0.5 mL of sulfur stock solution (containing 0.5 mmol of S, i.e., the molar ratio of Ga to S was 3.2:0.5) were added to the reaction system, heated to 240°C, and maintained for 2 hours to promote the growth of the AGS shell. After the reaction was completed, the mixture was rapidly cooled to obtain crude AIGS / AGS core-shell quantum dots.

[0052] (5) Purification of crude AIGS / AGS core-shell quantum dots to obtain AIGS / AGS core-shell quantum dots: same as in Example 1.

[0053] Example 3 This embodiment provides a method for preparing AIGS / AGS core-shell quantum dots, including the following steps: (1) Preparation of sulfur stock solution: At 100°C, sulfur powder is dissolved in oleylamine (OLA) and stirred vigorously for 30 minutes to prepare a sulfur stock solution with a sulfur concentration of 1 M for later use.

[0054] (2) Synthesis of crude AIGS quantum dots: 0.2 mmol silver acetate (Ag(oAc)), 0.3 mmol indium acetate (In(oAc)3), and 0.6 mmol gallium triacetylacetonate (Ga(acac)3) were added to a three-necked flask, followed by 10 mL of oleylamine (OLA) as a solvent. A magnetic stir bar was added, and stirring was started. The reaction system was degassed and heated under vacuum, with nitrogen gas purging repeatedly. When the temperature reached 100°C, 1.5 mL of 1-octylthiol was rapidly injected, followed immediately by 3 mL of a pre-prepared sulfur stock solution. The temperature was then rapidly increased to 270°C and held for 3 minutes to promote the growth of AIGS quantum dots. After the reaction was completed, the flask was immediately placed in a water bath to cool and terminate the reaction, yielding crude AIGS quantum dots.

[0055] (3) Purification of crude AIGS nuclear quantum dots to obtain AIGS nuclear quantum dots: same as in Example 1.

[0056] (4) Synthesis of crude AIGS / AGS core-shell quantum dots: 150 µmol of purified AIGS core quantum dots were dispersed in 10 mL of oleylamine, stirred, and degassed at 120°C for 30 min. Then, 2 mmol of GaCl3 and 2 mL of sulfur stock solution (containing 2 mmol of S) were added to the reaction system, heated to 240°C, and maintained for 2 hours to promote the growth of the AGS shell. After the reaction was completed, the mixture was rapidly cooled to obtain crude AIGS / AGS core-shell quantum dots.

[0057] (5) Purification of crude AIGS / AGS core-shell quantum dots to obtain AIGS / AGS core-shell quantum dots: same as in Example 1.

[0058] Measurements showed that the AIGS / AGS core-shell quantum dots prepared in Examples 2 and 3 had similar properties to the AIGS / AGS core-shell quantum dot matrix prepared in Example 1, including high blue light absorption coefficient, narrow spectrum emission, defect-free luminescence, high color purity, and high luminous efficiency (PLQY of AIGS / AGS core-shell quantum dots in Example 2 was 69%; PLQY of AIGS / AGS core-shell quantum dots in Example 3 was 78%).

[0059] In summary, this invention provides a green luminescent core-shell quantum dot and its preparation method. By selecting the precursor and controlling the reaction conditions, this invention initially adds only a cationic precursor and uses oleylamine as a solvent for degassing to limit early nucleation. After the precursor is fully and uniformly dissolved, ligands and a sulfur stock solution are injected. Heating to the target growth temperature promotes rapid nucleation and growth of the quantum dots, resulting in AIGS core quantum dots. Then, an AGS shell is grown through ion exchange. In this process, GaCl3 is used as a precursor, which not only provides Ga ions for shell formation but also releases chloride ions that effectively passivate the surface of the AIGS / AGS core-shell quantum dots. Finally, green luminescent AIGS / AGS core-shell quantum dots are prepared, exhibiting high blue light absorption coefficient, narrow-spectrum emission, high brightness, defect-free luminescence, high color purity, and high luminous efficiency.

[0060] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing green luminescent core-shell quantum dots, characterized in that, Includes the following steps: S1. Dissolve sulfur powder in oleylamine to obtain sulfur stock solution; S2. Silver acetate, indium acetate, gallium triacetylacetonate and oleylamine are mixed, then degassed and heated to 100~120℃, ligands and sulfur stock solution are injected, and then the temperature is raised to 270~280℃ to react and obtain crude AgInGaS2 core quantum dots. S3. After purifying the crude AgInGaS2 core quantum dots, disperse them in oleylamine, add GaCl3 and sulfur stock solution at 115~125℃, heat to 220~260℃ to grow AgGaS2 shell, and purify the obtained crude core-shell quantum dots to obtain green luminescent core-shell quantum dots.

2. The preparation method according to claim 1, characterized in that, The purification of the crude AgInGaS2 nuclear quantum dots specifically includes: Step A1: Dilute the crude AgInGaS2 quantum dots with a first organic solvent, then centrifuge to obtain the supernatant; Step A2: Repeat step A2 several times, dilute the obtained supernatant with the first organic solvent, add the precipitant, and centrifuge.

3. The preparation method according to claim 2, characterized in that, The first organic solvent includes at least one of n-hexane and toluene; the precipitant is ethanol, a mixture of ethanol and acetone, or a mixture of ethanol and methanol.

4. The preparation method according to claim 3, characterized in that, When the precipitant is a mixture of ethanol and acetone, the volume ratio of ethanol to acetone is 5:1; when the precipitant is a mixture of ethanol and methanol, the volume ratio of ethanol to methanol is 5:

1.

5. The preparation method according to claim 1, characterized in that, The ratio of silver acetate, indium acetate, gallium triacetylacetonate, and oleylamine is 0.2 mmol : 0.3 mmol : 0.6 mmol : 10 mL.

6. The preparation method according to claim 1, characterized in that, The ligand includes at least one of 1-octylthiol, 1-dodecylthiol, and 1-hexylthiol.

7. The preparation method according to claim 1, characterized in that, When the sulfur concentration in the sulfur stock solution is 1 M, in step S3, the ratio of silver acetate, ligand and sulfur stock solution is 0.2 mmol : (1-2) mL : (1~3) mL.

8. The preparation method according to claim 1, characterized in that, In step S3, the ratio of purified AgInGaS2 quantum dots, GaCl3 and sulfur in the sulfur stock solution is 150 µmol : (2~3.2) mmol : (0.5~2) mmol.

9. The preparation method according to any one of claims 2-4, characterized in that, The purification of the obtained crude core-shell quantum dots specifically includes: Step B1: Dilute the coarse core-shell quantum dots with a first organic solvent, then centrifuge to obtain the supernatant; Step B2: Repeat step B2 several times, dilute the obtained supernatant with the first organic solvent, add the precipitant, and centrifuge.

10. A green luminescent core-shell quantum dot, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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