Quantum dot preparation method

Abstract

The invention provides a preparation method of quantum dots. The preparation method comprises the following steps: S1, preparing a mixture containing an indium precursor, fatty acid, a gallium precursor and a non-coordination solvent in a container, wherein the molar ratio of a gallium element to an indium element in the mixture is greater than or equal to 5: 1; s2, when the mixture is at a first temperature, injecting a first sulfur precursor into the container, and reacting for a first time; s3, continuing to inject the silver precursor into the container, and reacting for second time; s4, injecting a second sulfur precursor into the container at a second temperature, and reacting for a third time; injecting a third sulfur precursor at a third temperature, reacting for a fourth time, and obtaining AgInGaS / GaS quantum dots after the reaction is ended; the first temperature < the second temperature < the third temperature. According to the technical scheme, the high-quality AgInGaS quaternary core is firstly formed, then the Ga2S3 shell is formed on the surface of the core, and then the transition shell layer is formed between the core and the Ga2S3 through high-temperature alloying, so that the core-shell lattice difference is reduced, and high quantum yield and narrow fluorescence half-peak width are further realized.

Description

Technical Field

[0001] The present disclosure relates to the field of quantum dot technology, and in particular to a method for preparing quantum dots. Background Art

[0002] Among all nanomaterials, semiconductor colloidal quantum dots (CQDs) have attracted widespread attention in the scientific community for their exceptional optical properties, such as high fluorescence quantum yield, wide absorption bandwidth, narrow emission peak, and excellent optical stability. Quantum dot research has become a hot topic in the fields of biomarkers and imaging, light-emitting diodes, and lasers. In particular, in displays (e.g., quantum dot televisions), CQDs offer a wider color gamut and higher color resolution, and have already found practical application. As CQD technology transitions from scientific research to practical applications, concerns are growing about the risks posed by cadmium-containing CQDs to human health and the environment. To this end, the European Union has introduced regulations requiring cadmium content in consumer electronics to be less than 100 ppm. Consequently, the development of high-performance CQDs, particularly InP-based CQDs, has become a research hotspot in both industry and academia. However, InP-based CQDs have relatively low blue light absorption, making them difficult to apply to display applications requiring high blue light absorption, such as AR / VR. Compared to InP-based CQDs, AgInGaS quaternary alloy CQDs exhibit higher blue light absorption and have garnered considerable attention in recent years. Summary of the Invention

[0003] The purpose of the present disclosure is to provide a method for preparing quantum dots to improve the optical parameters of AgInGaS / GaS quantum dots, such as quantum yield and fluorescence half-maximum width.

[0004] According to a first aspect of the present disclosure, a method for preparing quantum dots is provided, the method comprising: S1: preparing a mixture containing an indium precursor, a fatty acid, a gallium precursor, and a non-coordinating solvent in a container, wherein the molar ratio of gallium to indium in the mixture is greater than or equal to 5:1; S2: when the mixture is at a first temperature, injecting a first sulfur precursor into the container and reacting for a first time; S3: continuing to inject a silver precursor into the container and reacting for a second time; S4: at a second temperature, injecting a second sulfur precursor into the container and reacting for a third time; at a third temperature, injecting a third sulfur precursor and reacting for a fourth time, and terminating the reaction to obtain a quantum dot. to AgInGaS / GaS quantum dots; the first temperature is less than the second temperature and less than the third temperature; or, S1': preparing a mixture containing an indium precursor, a fatty amine and a gallium precursor in a container, wherein the molar ratio of gallium element to indium element in the mixture is greater than or equal to 5:1, and the indium precursor or the gallium precursor contains sulfur element; S2': when the mixture is at the first temperature, injecting a silver precursor into the container and reacting for a second time; S3': reacting at the second temperature for a third time; reacting at the third temperature for a fourth time, and obtaining AgInGaS / GaS quantum dots after the reaction is terminated; the first temperature is less than the second temperature and less than the third temperature.

[0005] Optionally, the first time is 1-10 minutes; the second time is 5-10 minutes; preferably, the third time is 5-30 minutes; more preferably, the fourth time is 5-30 minutes.

[0006] Optionally, the first temperature is 100-150°C, the second temperature is 150-220°C; and the third temperature is 250-300°C.

[0007] Optionally, S1 includes: mixing an indium precursor, a fatty acid, a gallium precursor and a non-coordinating solvent in a container, heating until dissolved, and obtaining a mixture; the indium precursor is a fatty acid indium or the gallium precursor is a fatty acid gallium; preferably, the fatty acid is oleic acid or a saturated fatty acid containing 8-18 carbon atoms.

[0008] Optionally, the first, second and third sulfur precursors are selected from one or more of thio-1-octadecene, trialkylphosphinesulfide, sulfur-fatty amine, thiourea and mercaptan.

[0009] Optionally, the indium precursor is selected from one or more of fatty acid indium with 2-18 carbon atoms, indium halide-fatty amine mixed solution, halogenated indium bis(diethyldithiocarbamate), or indium diethyldithiocarbamate.

[0010] Optionally, the gallium precursor is selected from one or more of gallium aliphatic acid with 2-18 carbon atoms, gallium acetylacetonate-fatty amine, gallium halide-fatty amine solution, gallium halide bis(diethyldithiocarbamate), or gallium diethyldithiocarbamate.

[0011] Optionally, the fatty amine is selected from oleylamine or a saturated fatty amine containing 8 to 18 carbon atoms.

[0012] Optionally, the fluorescence half-peak width of the quantum dots is less than 40 nm, and the fluorescence quantum yield is greater than or equal to 70%.

[0013] Optionally, the silver precursor is selected from one or more of fatty acid silver with a carbon number of 2-18, a fatty acid silver-fatty amine mixed solution, and a silver halide-fatty amine mixed solution.

[0014] Optionally, the molar ratio between the silver element and the indium element in the silver precursor is (3:1)-(1:3).

[0015] By applying the above technical solution, a high-quality AgInGaS quaternary core is first formed, and then a Ga2S3 shell is formed on the core surface. Subsequently, a transition shell is formed between the core and Ga2S3 through high-temperature alloying, thereby reducing the core-shell lattice difference and achieving high quantum yield and narrow fluorescence half-width. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are intended to explain the present disclosure and do not constitute an improper limitation of the present disclosure. In the accompanying drawings:

[0017] Figure 1 This is the UV-visible absorption spectrum of Example 1 of the present disclosure.

[0018] Figure 2 is the fluorescence emission spectrum of Example 1 of the present disclosure. DETAILED DESCRIPTION

[0019] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0020] It should be noted that the terms "first", "second" etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged in appropriate circumstances, so that the embodiments of the present application described herein. In addition, the terms "comprise" and "have" and their any distortion are intended to cover non-exclusive inclusions, for example, the process, method, system, product or equipment comprising a series of steps or units need not be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or equipment. Below "optional" material includes that this material may or may not exist.

[0021] The inventors believe that the traditional method for synthesizing AgInGaS quaternary alloy quantum dots is to inject an S precursor into Ag, In, and Ga precursors at a certain temperature. This will cause the composition of the AgInGaS quaternary alloy quantum dots to be non-uniform, and nanoparticles such as Ag2S and AgInS2 to coexist. In addition, the fluorescence quantum yield of the AgInGaS alloy quantum dots themselves is low, and the usual method is to coat the surface of the core quantum dots with a Ga2S3 shell. The traditional coating method is to synthesize the AgInGaS quantum dots, purify them, add them to the gallium precursor, and then increase the temperature, inject a sulfur precursor, and coat the shell. However, due to the large lattice mismatch between Ga2S3 and the core, internal defects will be caused, resulting in a low fluorescence quantum yield of the core-shell quantum dots.

[0022] Based on the above analysis, the present application proposes a method for preparing quantum dots, S1: preparing a mixture of an indium precursor, a fatty acid, a gallium precursor and a non-coordinating solvent in a container, the molar ratio of gallium element to indium element in the mixture is greater than or equal to 5:1; S2: when the mixture is at a first temperature, injecting a first sulfur precursor into the container and reacting for a first time; S3: continuing to inject a silver precursor into the container and reacting for a second time; S4: injecting a second sulfur precursor into the container at a second temperature and reacting for a third time; at a third temperature, injecting a third sulfur precursor and reacting for a fourth time, and obtaining AgInGaS / GaS quantum dots after the reaction is terminated; the first temperature < the second temperature < the third temperature; or, S1': preparing a mixture of an indium precursor, a fatty amine, and a gallium precursor in a container, the molar ratio of gallium element to indium element in the mixture is greater than or equal to 5:1, and the indium precursor and / or the gallium precursor contains sulfur element. S2': when the mixture is at a first temperature, injecting a silver precursor into the container and reacting for a second time; S3': at a second temperature, reacting for a third time; at the third temperature, reacting for a fourth time, and obtaining AgInGaS / GaS quantum dots after the reaction is terminated; the first temperature < the second temperature < the third temperature.

[0023] In the S1-S4 schemes, to avoid the formation of byproduct nanoparticles such as Ag2S and AgInS2, an Ag precursor is injected into nanoparticles formed by the elements In, Ga, and S (primarily indium sulfide nanoparticles). Through cation exchange, AgInGaS alloy quantum dots are ultimately formed. Furthermore, due to the large lattice mismatch between Ga2S3 and the AgInGaS core, internal defects result, resulting in low fluorescence quantum yields in the resulting core-shell quantum dots. The traditional solution to this problem is to add a transition shell. In the present application, considering that the gallium precursor has the lowest activity and a higher temperature is required to form the Ga2S3 shell, the amount of Ga precursor in the initial stage of the reaction is greater than that of the In precursor. After the sulfur precursor is added (or the Ga precursor itself contains the S element and no additional addition is required), due to the high activity of the In precursor and the large amount of Ga precursor (so even if Ga2S3 particles are formed, they will dissolve quickly due to their small size), it is speculated that indium sulfide nanoparticles are formed first, and then the Ag precursor is added. Due to cation exchange between In and Ag, AgInS2 is formed. Subsequently, the S precursor is continuously added to cover the Ga2S3 shell. By increasing the temperature and continuously alloying, the In element and the Ag element continuously diffuse outward and gradually transition to the Ga2S3 shell. A transition shell is naturally formed in the middle, and finally the AgInGaS / Ga2S3 core-shell structure (also written as AgInGaS / GaS in this application) is realized, thereby reducing internal defects and achieving high quantum yield and narrow fluorescence half-width of quantum dots. Similarly, the sulfur-containing indium precursor decomposes to form In2S3 at the first temperature, while the sulfur-containing gallium precursor decomposes to form Ga2S3 at the second temperature. In the S1'-S3' scheme, the high quantum yield and narrow fluorescence half-width of AgInGaS / Ga2S3 quantum dots can also be achieved.

[0024] In short, S1-S2 is to form In2S3, avoiding the direct addition of silver precursors to form Ag nanoparticles. S3 forms AgInS2, and S4 is to coat Ga2S3 and form an intermediate transition shell. This is to achieve more uniform size and composition of subsequent quantum dots (alloying) and to prevent the decomposition of Ag2S or AgInS2 formed in the previous steps to form Ag nanoparticles.

[0025] It should be noted that the above-mentioned injection at a certain temperature does not refer to the temperature of the added substance, but refers to the temperature of the contents in the container before the addition.

[0026] In some embodiments, the second time is greater than or equal to the first time. In some embodiments, the first time is 1-10 minutes. In some embodiments, the second time is 5-10 minutes. In some embodiments, the third time is 5-30 minutes. In some embodiments, the non-coordinating solvent is a solvent common in the art, such as 1-octadecene, alkanes, vaseline, etc.

[0027] In some embodiments, the amount ratio of the second sulfur precursor in S4 to the first sulfur precursor in S1 is 5:1-1:5.

[0028] In some embodiments, in S4 , the amount ratio of the second sulfur precursor to the third sulfur precursor is 1:1-1:10.

[0029] In some embodiments, the amount ratio of the gallium precursor in S1 to the first sulfur precursor in S2 is 5:1-20:1.

[0030] In some embodiments, the mixture in S1' may further comprise a non-coordinating solvent.

[0031] In some embodiments, the temperature increase in S3' can be linear, for example, the second temperature is a temperature in a gradually increasing interval, the third temperature is a temperature in a gradually increasing interval, and the reaction time is calculated starting from the temperature increase. Alternatively, the temperature increase in S3' can be multi-stage, for example, the second temperature and the third temperature are both constant temperatures, and then the reaction time is calculated after the constant temperature is reached. In some embodiments, when the second temperature and the third temperature in S3' are both constant temperatures, a fourth temperature for a fifth time, a fifth temperature for a sixth time, and so on can be introduced, that is, the number of steps in the temperature curve can be greater than 2.

[0032] In some embodiments, S1 includes: mixing an indium precursor, a fatty acid, a gallium precursor, and a non-coordinating solvent in a container, heating until dissolved, and obtaining the mixture; the aforementioned indium precursor is a fatty acid indium or the gallium precursor is a fatty acid gallium. In some embodiments, the number of C atoms in the fatty acid indium or the fatty acid gallium is 2-18. In some embodiments, the process of heating to dissolve further includes exhausting. In some embodiments, the molar ratio of the amount of fatty acid to (the sum of the amount of the indium precursor In element and the gallium precursor Ga element) is greater than 3:1.

[0033] In some embodiments, the fatty acid is oleic acid or a saturated fatty acid containing 8-18 carbon atoms. The fluorescence peak position of the quantum dots can be controlled by adjusting the C chain length of the fatty acid.

[0034] In some embodiments, the first, second, and third sulfur precursors are selected from one or more of 1-octadecene thiosulfide, trialkylphosphine thiosulfide, sulfur-fatty amine, thiourea, and mercaptan. "1-octadecene thiosulfide" and "sulfur-fatty amine" refer to dispersions of sulfur in 1-octadecene and fatty amine, respectively. In some embodiments, the second sulfur precursor is the same as the third sulfur precursor and is different from the first sulfur precursor.

[0035] In some embodiments, the indium precursor is selected from one or more of an indium fatty acid with 2-18 carbon atoms, an indium halide-oleylamine mixed solution, an indium halogenated bis(diethyldithiocarbamate) (e.g., InCl(DDTC)2), or an indium diethyldithiocarbamate. The fluorescence peak position of the quantum dots is regulated by adjusting the carbon chain length of the indium fatty acid. "Indium halide-oleylamine" refers to a dispersion of indium halide in oleylamine. "Gallium halide-oleylamine" and "GaIlium acetylacetonate-oleylamine" are explained below for reference.

[0036] In some embodiments, the gallium precursor is selected from one or more of a gallium fatty acid with 2-18 carbon atoms, a gallium acetylacetonate-oleylamine solution, a gallium halide-oleylamine mixed solution, a gallium halide bis(diethyldithiocarbamate) (e.g., GaCl(DDTC)2), or gallium diethyldithiocarbamate. The fluorescence peak position of the quantum dots can be controlled by adjusting the carbon chain length of the gallium fatty acid.

[0037] In some embodiments, the first reaction temperature is 100-150° C. In some embodiments, the second reaction temperature is 150-220° C. In some embodiments, the third reaction temperature is 250-300° C. In some embodiments, the second reaction temperature and the third reaction temperature are both greater than or equal to 200° C.

[0038] In some embodiments, the fatty amine used in the above reaction or the fatty amine used for dispersion in the precursor is selected from oleylamine or a saturated fatty amine containing 8-18 carbon atoms. The fatty amine can react with the metal salt in the precursor to form a complex, thereby increasing the activity of the precursor and promoting the reaction.

[0039] In some embodiments, in the reaction with gallium diethyldithiocarbamate Ga(DDTC)3 or indium diethyldithiocarbamate In(DDTC)3 as precursor, aliphatic amine can promote the formation of DDTC. - decomposition.

[0040] In some embodiments, the quantum dot has a fluorescence half-width less than 40 nm and a fluorescence quantum yield greater than or equal to 70%. In some embodiments, the quantum dot has a fluorescence half-width greater than or equal to 30 nm. In some embodiments, the quantum dot has a fluorescence quantum yield less than or equal to 99%. In some embodiments, the quantum dot has a fluorescence quantum yield of 70-80%. In some embodiments, the quantum dot has a fluorescence peak position of 500-600 nm. In some embodiments, the quantum dot has a fluorescence peak position of 520-540 nm.

[0041] In some embodiments, the silver precursor is selected from one or more of fatty acid silver having 2-18 carbon atoms, the aforementioned fatty acid silver-fatty amine mixed solution, and silver halide-fatty amine mixed solution.

[0042] Changing the ratio of silver to indium can adjust the fluorescence peak position. In some embodiments, the molar ratio of the silver element in the fatty acid silver to the indium element in the indium precursor is (3:1)-(1:3).

[0043] Hereinafter, the embodiments are described in more detail with reference to specific examples. However, they are illustrative examples of the present disclosure, and the present disclosure is not limited thereto.

[0044] Example 1

[0045] Weigh 0.4 mmol of indium chloride, 0.1 mmol of In(DDTC)3, 2.5 mmol of Ga(DDTC)3, and 40 mL of oleylamine into a 250 mL three-necked flask, raise the temperature to 130°C, inject 0.5 mmol of silver acetate-oleylamine solution (0.5 mmol of silver acetate dissolved in 2 mL of oleylamine), react for 10 min, raise the temperature to 200°C and react for 20 min, then raise the temperature to 280°C and react for 30 min, then stop the reaction.

[0046] Example 2

[0047] Weigh 0.5 mmol indium acetate, 2.5 mmol gallium acetylacetonate, 15 mmol oleic acid, and 40 g ODE into a 250 mL three-necked flask, raise the temperature to 180°C, exhaust for 30 min, cool to 130°C, inject 0.5 mmol S-oleylamine solution, react for 5 min, inject 0.5 mmol silver acetate-oleylamine solution (0.5 mmol silver acetate is dissolved in 2 mL oleylamine), react for 10 min, raise the temperature to 200°C, inject 0.5 mL 2 mmol / mL S-TOP solution, react for 20 min, raise the temperature to 280°C, inject 0.5 mL 2 mmol / mL S-TOP solution, react for 30 min, and stop the reaction.

[0048] Example 3

[0049] Weigh 0.5mmol indium acetate, 5mmol gallium acetylacetonate, 20mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0050] Example 4

[0051] Weigh 0.5mmol indium chloride, 5mmol gallium acetylacetonate, and 40mL oleylamine in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL2mmol / mL S-TOP solution, react for 20min, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0052] Example 5

[0053] Weigh 0.5mmol indium chloride, 5mmol gallium acetylacetonate, 10mmol oleic acid, 10mL oleylamine, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, raise the temperature to 280℃, inject 0.5mL2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0054] Example 6

[0055] Weigh 0.5mmol indium acetate, 5mmol gallium acetate, 20mmol oleic acid, and 40g ODE into a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0056] Example 7

[0057] Weigh 0.5mmol indium acetate, 5mmol gallium acetate, 20mmol oleic acid, and 40g ODE into a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 1mmol silver acetate-oleylamine solution (1mmol silver acetate is dissolved in 4mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL2mmol / mL S-TOP solution, react for 20min, raise the temperature to 280℃, inject 0.5mL2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0058] Example 8

[0059] Weigh 0.5mmol indium chloride, 5mmol gallium acetylacetonate, 10mmol oleic acid, 20g octadecylamine, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, raise the temperature to 280℃, inject 0.5mL2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0060] Example 9

[0061] Weigh 0.5mmol indium acetate, 2.5mmol gallium acetate, 2.5mmol Ga(DDTC)3, 10mmol oleic acid, 20g ODE, and 20mL oleylamine in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 1mmol silver acetate-oleylamine solution (1mmol silver acetate is dissolved in 4mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0062] Example 10

[0063] Weigh 0.4mmol indium acetate, 0.1mmol In(DDTC)3, 2.5mmol gallium acetate, 2.5mmol Ga(DDTC)3, 10mmol oleic acid, 20g ODE, and 20mL oleylamine in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 1mmol silver acetate-oleylamine solution (1mmol silver acetate is dissolved in 4mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL2mmol / mL S-TOP solution, react for 20min, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0064] Example 11

[0065] Weigh 0.5mmol indium acetate, 5mmol gallium acetylacetonate, 20mmol stearic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0066] Example 12

[0067] Weigh 0.5 mmol indium acetate, 5 mmol gallium acetylacetonate, 20 mmol oleic acid, and 40 g ODE in a 250 mL three-necked flask, raise the temperature to 180 ° C, exhaust for 30 min, cool to 130 ° C, inject 0.5 mmol S-ODE solution, react for 5 min, inject 0.5 mmol silver acetate-oleylamine solution (0.5 mmol silver acetate is dissolved in 2 mL oleylamine), react for 10 min, raise the temperature to 200 ° C, inject 0.5 mL 2 mmol / mL S-TOP solution, react for 20 min, raise the temperature to 280 ° C, inject 0.5 mL 2 mmol / mL S-TOP solution, react for 30 min, and stop the reaction.

[0068] Example 13

[0069] Weigh 0.5 mmol indium acetate, 5 mmol gallium acetylacetonate, 20 mmol oleic acid, and 40 g ODE in a 250 mL three-necked flask, raise the temperature to 180°C, exhaust for 30 min, cool to 130°C, inject 0.5 mmol S-oleylamine solution, react for 5 min, inject 0.5 mmol silver acetate-oleylamine solution (0.5 mmol silver acetate dissolved in 2 mL oleylamine), react for 10 min, raise the temperature to 200°C, inject 0.5 mL 2 mmol / mL S-TOP solution, react for 20 min, raise the temperature to 280°C, inject 1 mL dodecylmercaptan, react for 30 min, and stop the reaction.

[0070] Comparative Example 1

[0071] Take 0.5mmol silver acetate, 0.4mmol indium chloride, 0.1mmol In(DDTC)3, 0.6mmol Ga(DDTC)3, and 40mL oleylamine, and place them in a 100mL three-necked flask. Raise the temperature to 200℃, react for 20min, cool, purify with acetone and methanol, and dissolve in 5mL octane.

[0072] Weigh 0.2 mmol Ga(DDTC)3, 0.4 mmL gallium chloride, and 20 mL oleylamine into a 100 mL three-necked flask, raise the temperature to 180°C, add core quantum dots, introduce nitrogen to remove octane, raise the temperature to 280°C, react for 30 minutes, and stop the reaction.

[0073] Comparative Example 2

[0074] Weigh 0.5mmol indium acetate, 1.5mmol gallium acetylacetonate, 10mmol oleic acid, and 40g ODE into a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.25mL 2mmol / mL S-TOP solution, react for 20min, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0075] The quantum dot product obtained above was added with ethanol for precipitation, separated and purified, and dispersed in toluene solvent for integrating sphere testing. Table 1 shows the optical properties of the embodiment and the comparative example.

[0076] Table 1

[0077]

[0078]

[0079] It can be seen from Table 1 that the embodiment is superior to the comparative example in terms of fluorescence half-peak width and fluorescence quantum dot yield.

[0080] The foregoing description is merely a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present disclosure shall be included within the scope of protection of the present disclosure.

Claims

1. A method for preparing quantum dots, characterized in that: The preparation method comprises: S1: preparing a mixture containing an indium precursor, a fatty acid, a gallium precursor, and a non-coordinating solvent in a container, wherein the molar ratio of gallium element to indium element in the mixture is greater than or equal to 5:1; S2: When the mixture is at a first temperature, injecting a first sulfur precursor into the container and reacting for a first time; S3: Continue injecting the silver precursor into the container and react for a second time; S4: injecting a second sulfur precursor into the container at the second temperature and reacting for a third time; injecting a third sulfur precursor at the third temperature and reacting for a fourth time, and obtaining AgInGaS / GaS quantum dots after the reaction is terminated; the first temperature < the second temperature < the third temperature; or S1′: preparing a mixture containing an indium precursor, an aliphatic amine, and a gallium precursor in a container, wherein the molar ratio of gallium to indium in the mixture is greater than or equal to 5:1, and the indium precursor and / or the gallium precursor contains sulfur; S2': when the mixture is at the first temperature, injecting a silver precursor into the container and reacting for a second time; S3': reacting at the second temperature for a third time; reacting at the third temperature for a fourth time, and obtaining AgInGaS / GaS quantum dots after the reaction is terminated; the first temperature < the second temperature < the third temperature.

2. The method for preparing quantum dots according to claim 1, wherein: The first time is 1-10 minutes; the second time is 5-10 minutes, preferably, the third time is 5-30 minutes; more preferably, the fourth time is 5-30 minutes.

3. The method for preparing quantum dots according to claim 1, wherein: The first temperature is 100-150°C, the second temperature is 150-220°C; and the third temperature is 250-300°C.

4. The method for preparing quantum dots according to claim 1, wherein: The S1 comprises: mixing the indium precursor, the fatty acid, the gallium precursor and the non-coordinating solvent in the container, heating until dissolved, to obtain the mixture; the indium precursor is fatty acid indium or the gallium precursor is fatty acid gallium; preferably, the fatty acid is oleic acid or a saturated fatty acid containing 8-18 carbon atoms.

5. The method for preparing quantum dots according to claim 1, wherein: The first, second and third sulfur precursors are selected from one or more of thio-1-octadecene, trialkylphosphine sulfide, sulfur-fatty amine, thiourea and mercaptan.

6. The method for preparing quantum dots according to claim 1, wherein: The indium precursor is selected from one or more of fatty acid indium with 2-18 carbon atoms, indium halide-fatty amine mixed solution, halogenated indium bis(diethyldithiocarbamate), or indium diethyldithiocarbamate.

7. The method for preparing quantum dots according to claim 1, wherein: The gallium precursor is selected from one or more of gallium aliphatic acid with 2-18 carbon atoms, gallium acetylacetonate-fatty amine, gallium halide-fatty amine solution, gallium halide bis(diethyldithiocarbamate), or gallium diethyldithiocarbamate.

8. The method for preparing quantum dots according to claim 1, 5, 6 or 7, wherein: The fatty amine is selected from oleylamine or a saturated fatty amine containing 8 to 18 carbon atoms.

9. The method for preparing quantum dots according to claim 1, wherein: The fluorescence half-peak width of the quantum dots is less than 40 nm, and the fluorescence quantum yield is greater than or equal to 70%.

10. The method for preparing quantum dots according to claim 1, wherein: The silver precursor is selected from one or more of fatty acid silver with 2-18 carbon atoms, the fatty acid silver-fatty amine mixed solution and the silver halide-fatty amine mixed solution.

11. The method for preparing quantum dots according to claim 1, wherein: The molar ratio between the silver element of the silver precursor and the indium element is (3:1)-(1:3).

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