Synthesis method of ternary copper indium sulfide quantum dots

Abstract

The application belongs to the technical field of semiconductor nanometer materials, and particularly relates to a synthesis method of ternary copper indium sulfide quantum dots. The synthesis method of the ternary copper indium sulfide quantum dots comprises the following steps: (1) heating and dissolving 1,3-dimethylthiourea under a vacuum state to obtain a 1,3-dimethylthiourea solution, and then removing the 1,3-dimethylthiourea solution as a sulfur precursor after standing; (2) adding copper salt and indium salt into a solvent to obtain a mixed solution, then adding the sulfur precursor dropwise, and then performing constant-temperature reaction, cooling, centrifugation and cleaning. The sulfur precursor is added dropwise into the mixed solution of the copper salt and the indium salt, and the constant-temperature reaction is performed to obtain the ternary copper indium sulfide quantum dots which are stable in crystal phase, have few defects, and are uniform in morphology and size.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor nanomaterials technology, specifically relating to a method for synthesizing ternary copper indium sulfide quantum dots. Background Technology

[0002] Quantum dots (QDs) are a special type of semiconductor nanomaterial with dimensions all below 100 nm in all three dimensions, resembling an extremely small dot. They are currently the smallest nanomaterials that can be fabricated, including silicon quantum dots, germanium quantum dots, cadmium sulfide quantum dots, cadmium selenide quantum dots, cadmium telluride quantum dots, zinc selenide quantum dots, lead sulfide quantum dots, lead selenide quantum dots, indium phosphide quantum dots, and indium arsenide quantum dots. Quantum dots possess unique properties, including high color purity (full width at half maximum (FWHM)), high photoluminescence (PL) quantum yield (QY), full visible light coverage, and excellent stability, attracting significant attention in display applications.

[0003] Compared to toxic cadmium (Cd)-based and lead halide perovskite quantum dots, ternary I-III-VI semiconductor quantum dots, such as copper indium sulfide (CIS), are considered ideal candidates for display backlights due to their non-toxicity and low cost. However, the broad emission spectrum of CIS quantum dots, originating from defect states within the band gap, and their lack of monochromaticity remain significant limiting factors for their application in high-color-purity lighting and displays. Researchers typically employ rapid implantation methods to prepare non-stoichiometric CIS quantum dots, such as Cu:In:S = 1:4:8 and Cu:In:S = 1:8:16, to achieve high luminescence performance. However, the rapid reactions and deviations from the stoichiometric ratio during nucleation can introduce more crystal defects, enhancing the donor (D) and acceptor (A) energy levels within the quantum dot band and inducing DA-enhanced luminescence and DA recombination luminescence. While these crystal defects can induce enhanced luminescence, they can also lead to the random positioning of emission centers within the quantum dot, significantly broadening the photoluminescence (PL) spectrum, resulting in current PL emission linewidths exceeding 130 nm. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned technical problems by providing a method for synthesizing narrow half-peak width and high monochromatic ternary copper indium sulfide quantum dots, which is low-cost, environmentally friendly and non-toxic, and the resulting copper indium sulfide quantum dot crystals are stable, have few defects, and are uniform in morphology and size.

[0005] The method for synthesizing ternary copper indium sulfide quantum dots in the technical solution of this invention includes the following steps:

[0006] (1) 1,3-Dimethylthiourea was dissolved by heating under vacuum to obtain a 1,3-dimethylthiourea solution, which was then removed after standing as a sulfur precursor.

[0007] (2) Add copper salt and indium salt to a solvent and heat to dissolve to obtain a mixed solution. Then add sulfur precursor dropwise, react at a constant temperature, cool, centrifuge and wash.

[0008] Preferably, the solvent for the 1,3-dimethylthiourea solution in step (1) is oleylamine.

[0009] Furthermore, the molar concentration of the 1,3-dimethylthiourea solution in step (1) is 0.2–0.6 mmol / mL.

[0010] Furthermore, the temperature at which the 1,3-dimethylthiourea solution is heated and dissolved in step (1) is 100–140 °C.

[0011] Further, in step (1), the 1,3-dimethylthiourea solution is allowed to stand for 30–60 min.

[0012] Preferably, step (1) involves removing the solution under a nitrogen atmosphere.

[0013] Furthermore, in step (2), the copper salt is one or more of copper acetate, basic copper carbonate, cuprous chloride, and cuprous iodide, preferably cuprous iodide.

[0014] Furthermore, in step (2), the indium salt is one or more of indium chloride, indium sulfate, and indium acetate, preferably indium acetate.

[0015] Furthermore, in step (2), the molar ratio of copper ions to indium ions in the copper salt and indium salt is 1.0:0.8 to 8.0.

[0016] Preferably, the solvent in step (2) is n-dodecyl mercaptan.

[0017] Preferably, step (2) involves heating and dissolving the substance under a nitrogen atmosphere.

[0018] Furthermore, the heating and melting temperature in step (2) is 160–180°C.

[0019] Furthermore, the molar concentrations of copper ions and indium ions in the mixed solution of step (2) are both 0.03 to 0.08 mmol / ml.

[0020] Furthermore, in step (2), the sulfur precursor is added at a rate of 2 to 16 mL / h.

[0021] Furthermore, in step (2), the volume of the sulfur precursor is 0.1 to 0.8 times the volume of the mixed solution.

[0022] Furthermore, in step (2), the isothermal reaction temperature is 160–180 °C and the time is 30–80 min.

[0023] As a preferred option, in step (2), the centrifugation and washing are performed by first centrifuging at 6000-10000 rpm for 3-8 minutes, dispersing the solid precipitate in toluene, adding excess methanol to precipitate it again, and then centrifuging at 6000-10000 rpm for 3-8 minutes, so that the final solid precipitate is dispersed in toluene.

[0024] The present invention also provides a ternary copper indium sulfide quantum dot, which is prepared by the above-described synthesis method of ternary copper indium sulfide quantum dots.

[0025] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0026] (1) By slowly adding a sulfur precursor, mainly composed of 1,3-dimethylthiourea solution, to a mixed solution of copper salt and indium salt, and reacting at a constant temperature, ternary copper indium sulfide quantum dots were obtained.

[0027] (2) 1,3-Dimethylthiourea slowly releases sulfur ions during the synthesis of ternary copper indium sulfide quantum dots, thereby regulating the reaction kinetics. The resulting copper indium sulfide quantum dot crystals are stable, have few defects, and have uniform morphology and size.

[0028] (3) The luminescence of the obtained copper indium sulfide quantum dots has a narrow half-width and high monochromaticity;

[0029] (4) The method for synthesizing copper indium sulfide quantum dots uses low-cost raw materials and is environmentally friendly. Attached Figure Description

[0030] Figure 1 TEM images of ternary copper indium sulfide quantum dots obtained in the examples: a-Example 1, b-Example 4, c-Example 5;

[0031] Figure 2 The XRD patterns of the ternary copper indium sulfide quantum dots obtained in Examples 1 and 4-6 are shown.

[0032] Figure 3 The graph shows the variation of the ternary copper indium sulfide quantum dots (FWHM) obtained in Examples 1 and 4-6 with the feed ratio. Detailed Implementation

[0033] The technical solution of the present invention will be further described and illustrated below with reference to specific embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of helping to understand the present invention and are not intended to limit the specific scope of the present invention. Furthermore, the accompanying drawings used herein are merely for better illustrating the content disclosed in the present invention and do not limit the scope of protection. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used in the art, and the methods used in the embodiments are all conventional methods in the art.

[0034] Example 1

[0035] The method for synthesizing ternary copper indium sulfide quantum dots in this embodiment is characterized by including the following steps:

[0036] (1) Add 8 mmol of 1,3-dimethylthiourea and 20 mL of oleylamine to a three-necked flask at a concentration of 0.4 mmol / mL. Heat at 120 °C under vacuum until 1,3-dimethylthiourea is completely dissolved. After standing for 30 min, remove the sulfur precursor under a nitrogen atmosphere.

[0037] (2) Add 0.4 mmol of cuprous iodide and 0.4 mmol of indium acetate to 10 mL of n-dodecyl mercaptan and heat at 180 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, use a syringe pump to dropwise inject 2 mL of sulfur precursor at a rate of 4 mL / h. After reacting at 180 °C for 30 min, cool and centrifuge at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Add excess methanol to precipitate it again, and then centrifuge at 8000 rpm for 5 min. The final solid precipitate is dispersed in toluene.

[0038] Example 2

[0039] The method for synthesizing ternary copper indium sulfide quantum dots in this embodiment is characterized by including the following steps:

[0040] (1) Add 6 mmol of 1,3-dimethylthiourea and 20 mL of oleylamine to a three-necked flask at a concentration of 0.3 mmol / mL. Heat at 125 °C under vacuum until 1,3-dimethylthiourea is completely dissolved. After standing for 30 min, remove the sulfur precursor under a nitrogen atmosphere.

[0041] (2) Add 0.4 mmol of cuprous iodide and 0.4 mmol of indium acetate to 12 mL of n-dodecyl mercaptan and heat at 170 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, inject 2 mL of sulfur precursor dropwise at a rate of 6 mL / h using a syringe pump. After reacting at 160 °C for 30 min, cool and centrifuge at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Add excess methanol to precipitate it again, and then centrifuge at 8000 rpm for 5 min. The final solid precipitate is dispersed in toluene.

[0042] Example 3

[0043] The method for synthesizing ternary copper indium sulfide quantum dots in this embodiment is characterized by including the following steps:

[0044] (1) Add 10 mmol of 1,3-dimethylthiourea and 20 mL of oleylamine to a three-necked flask at a concentration of 0.5 mmol / mL. Heat at 130 °C under vacuum until 1,3-dimethylthiourea is completely dissolved. After standing for 40 min, remove the sulfur precursor under a nitrogen atmosphere.

[0045] (2) Add 0.4 mmol of cuprous iodide and 0.4 mmol of indium acetate to 8 mL of n-dodecyl mercaptan. Heat at 160 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, use a syringe pump to dropwise inject 2 mL of sulfur precursor at a rate of 8 mL / h. React at 170 °C for 30 min and then cool. Centrifuge at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Add excess methanol to precipitate it again. Centrifuge at 8000 rpm for 5 min. The final solid precipitate is dispersed in toluene.

[0046] Example 4

[0047] The difference between this embodiment and Example 1 is only in step (2): 0.48 mmol cuprous iodide and 0.40 mmol indium acetate are added to 10 mL of n-dodecyl mercaptan and heated to 180 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, 2 mL of sulfur precursor is injected dropwise at a rate of 4 mL / h using a syringe pump. After reacting at a constant temperature of 180 °C for 30 min, the mixture is cooled and centrifuged at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Excess methanol is added to precipitate the solid precipitate again, and then the mixture is centrifuged at 8000 rpm for 5 min. The final solid precipitate is dispersed in toluene.

[0048] Example 5

[0049] The difference between this embodiment and Example 1 is only in step (2): 0.4 mmol of cuprous iodide and 0.8 mmol of indium acetate are added to 10 mL of n-dodecyl mercaptan and heated at 180 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, 4 mL of sulfur precursor is injected dropwise at a rate of 4 mL / h using a syringe pump. After reacting at a constant temperature of 180 °C for 30 min, the mixture is cooled and centrifuged at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Excess methanol is added to precipitate the solid precipitate again, and then the mixture is centrifuged at 8000 rpm for 5 min. The final solid precipitate is dispersed in toluene.

[0050] Example 6

[0051] The difference between this embodiment and Example 1 is only in step (2): 0.4 mmol of cuprous iodide and 1.6 mmol of indium acetate are added to 10 mL of n-dodecyl mercaptan and heated at 180 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, 8 mL of sulfur precursor is injected dropwise at a rate of 4 mL / h using a syringe pump. After reacting at a constant temperature of 180 °C for 30 min, the mixture is cooled and centrifuged at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Excess methanol is added to precipitate the solid precipitate again, and then the mixture is centrifuged at 8000 rpm for 5 min. Finally, the resulting solid precipitate is dispersed in toluene.

[0052] Example 7

[0053] The difference between this embodiment and Example 1 is only in step (2): 0.6 mmol of cuprous iodide and 0.4 mmol of indium acetate are added to 10 mL of n-dodecyl mercaptan and heated to 180 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, 2 mL of sulfur precursor is injected dropwise at a rate of 4 mL / h using a syringe pump. After reacting at a constant temperature of 180 °C for 30 min, the mixture is cooled and centrifuged at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Excess methanol is added to precipitate the solid precipitate again, and then the mixture is centrifuged at 8000 rpm for 5 min. The final solid precipitate is dispersed in toluene.

[0054] Example 8

[0055] The difference between this embodiment and Example 1 is only in step (2): 0.4 mmol of cuprous iodide and 3.6 mmol of indium acetate are added to 10 mL of n-dodecyl mercaptan and heated at 180 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, 2 mL of sulfur precursor is injected dropwise at a rate of 4 mL / h using a syringe pump. After reacting at a constant temperature of 180 °C for 30 min, the mixture is cooled and centrifuged at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Excess methanol is added to precipitate the solid precipitate again, and then the mixture is centrifuged at 8000 rpm for 5 min. Finally, the resulting solid precipitate is dispersed in toluene.

[0056] Example 9

[0057] The difference between this embodiment and Example 1 is only in step (2): 0.4 mmol of cuprous iodide and 0.4 mmol of indium acetate are added to 10 mL of n-dodecyl mercaptan and heated to 180 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, 1.5 mL of sulfur precursor is injected dropwise at a rate of 4 mL / h using a syringe pump. After reacting at a constant temperature of 180 °C for 30 min, the mixture is cooled and centrifuged at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Excess methanol is added to precipitate the solid precipitate again, and then the mixture is centrifuged at 8000 rpm for 5 min. Finally, the resulting solid precipitate is dispersed in toluene.

[0058] Example 10

[0059] The difference between this embodiment and Example 1 is only in step (2): 0.4 mmol of cuprous iodide and 0.4 mmol of indium acetate are added to 10 mL of n-dodecyl mercaptan and heated at 180 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, 18 mL of sulfur precursor is injected dropwise at a rate of 4 mL / h using a syringe pump. After reacting at a constant temperature of 180 °C for 30 min, the mixture is cooled and centrifuged at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Excess methanol is added to precipitate the precipitate again, and then the mixture is centrifuged at 8000 rpm for 5 min. Finally, the resulting solid precipitate is dispersed in toluene.

[0060] Example 11

[0061] The difference between this embodiment and Example 1 is only in step (2): 0.4 mmol of cuprous iodide and 0.4 mmol of indium acetate are added to 10 mL of n-dodecyl mercaptan and heated to 180 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, 2 mL of sulfur precursor is injected dropwise at a rate of 1 mL / h using a syringe pump. After reacting at a constant temperature of 180 °C for 30 min, the mixture is cooled and centrifuged at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Excess methanol is added to precipitate the solid precipitate again, and then the mixture is centrifuged at 8000 rpm for 5 min. Finally, the resulting solid precipitate is dispersed in toluene.

[0062] Example 12

[0063] The difference between this embodiment and Example 1 is only in step (2): 0.4 mmol of cuprous iodide and 0.4 mmol of indium acetate are added to 10 mL of n-dodecyl mercaptan and heated to 180 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, 2 mL of sulfur precursor is injected dropwise at a rate of 18 mL / h using a syringe pump. After reacting at a constant temperature of 180 °C for 30 min, the mixture is cooled and centrifuged at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Excess methanol is added to precipitate the solid precipitate again, and then the mixture is centrifuged at 8000 rpm for 5 min. The final solid precipitate is dispersed in toluene.

[0064] Figure 1 It can be seen that the ternary copper indium sulfide quantum dots obtained in Examples 1 and 4-5 have a uniform size distribution, with a size of 1-3 nm; Figure 2 It can be seen that the obtained copper indium sulfide CIS quantum dots have good crystallinity; Figure 3 It can be seen that the obtained ternary copper indium sulfide quantum dots have low PLQY (photoluminescence quantum yield) and FWHM, indicating that they have fewer internal defects and defect emission is suppressed.

[0065] The ternary copper indium sulfide quantum dots obtained in Examples 1-6 of this invention have stable crystal phases, few defects, uniform morphology and size, and exhibit narrow full width at half maximum (FWHM) and high monochromaticity. The ternary CuInS2 quantum dots obtained in Example 7 have a high copper content and a low indium content, resulting in excess Cu-induced defects within the quantum dots. This not only leads to luminescence quenching but also causes random positioning of the luminescence center, resulting in low photoluminescence intensity and a wide FWHM. The ternary CuInS2 quantum dots obtained in Example 8 have a low copper content and a high indium content, resulting in more Cu vacancies within the quantum dots, which increases the FWHM of photoluminescence. The ternary CuInS2 quantum dots obtained in Example 9... The low sulfur content in the quantum dots leads to the introduction of S vacancies, which broadens the full width at half maximum (FWHM). However, insufficient anions result in incomplete reactions and wasted resources. The ternary CuInS2 quantum dots obtained in Example 10 have a high sulfur content. In Example 11, the sulfur precursor was added at a low rate, which allowed the quantum dots to exist at high temperatures for a long time, causing excessive growth and aggregation, resulting in inconsistent sizes and ultimately low PLQY and a wide FWHM. In Example 12, the sulfur precursor was added at a high rate, which caused the quantum dots to crystallize faster. However, this crystallization process introduced more interstitial defects, resulting in lower crystallinity and lower quality of the quantum dots.

[0066] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the spirit of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A method for synthesizing ternary copper indium sulfide quantum dots, characterized in that, Includes the following steps: (1) 1,3-Dimethylthiourea was dissolved by heating under vacuum to obtain a 1,3-dimethylthiourea solution, which was then removed after standing as a sulfur precursor. (2) Add copper salt and indium salt to solvent and heat to dissolve to obtain a mixed solution. Then add sulfur precursor dropwise, react at constant temperature, cool, centrifuge and wash. In step (1), the solvent for the 1,3-dimethylthiourea solution is oleylamine; the molar concentration of the 1,3-dimethylthiourea solution is 0.2~0.6 mmol / mL; the temperature for heating and dissolving 1,3-dimethylthiourea is 100~140℃; and the standing time is 30~60 min. In step (2), the molar ratio of copper ions to indium ions in the copper salt and indium salt is 1.0:(0.8~8.0); the solvent is n-dodecyl mercaptan; the solution is dissolved under nitrogen atmosphere; the temperature for dissolution is 160~180℃; the molar concentration of copper ions in the mixed solution is 0.03~0.08mmol / mL, and the molar concentration of indium ions in the mixed solution is 0.03~0.08mmol / mL; the volume of the sulfur precursor is 0.1~0.8 times the volume of the mixed solution; the rate of sulfur precursor addition is 2~16mL / h; the temperature of the isothermal reaction is 160~180℃, and the time is 30~80min. The resulting copper indium sulfide quantum dots exhibit narrow half-width at half-maximum and high monochromaticity.

2. The method for synthesizing ternary copper indium sulfide quantum dots according to claim 1, characterized in that, Includes the following steps: (1) Add 8 mmol of 1,3-dimethylthiourea and 20 mL of oleylamine to a three-necked flask at a concentration of 0.4 mmol / mL. Heat at 120 °C under vacuum until 1,3-dimethylthiourea is completely dissolved. After standing for 30 min, remove the sulfur precursor under a nitrogen atmosphere. (2) Add 0.4 mmol of cuprous iodide and 0.4 mmol of indium acetate to 10 mL of n-dodecyl mercaptan and heat at 180 °C under a nitrogen atmosphere to dissolve and obtain a mixed solution. Then, use a syringe pump to dropwise inject 2 mL of sulfur precursor at a rate of 4 mL / h. After reacting at 180 °C for 30 min, cool and centrifuge at 8000 rpm for 5 min. The resulting solid precipitate is dispersed in toluene. Add excess methanol to precipitate it again, and then centrifuge at 8000 rpm for 5 min. The final solid precipitate is dispersed in toluene.

3. A ternary copper indium sulfide quantum dot, characterized in that, The ternary copper indium sulfide quantum dots were prepared by the synthesis method described in claim 1.

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