A method for preparing quantum dots, quantum dots and their applications

Abstract

This invention discloses a method for preparing semiconductor nanocrystalline quantum dots, the quantum dots themselves, and their applications, relating to the field of quantum dot synthesis technology. The quantum dots have a core-shell structure. The preparation method includes the preparation of a (Cu)AgInGaZnS core solution and the initial (Cu)AgInGaZnS / Ga x Preparation of S quantum dots and the final (Cu)AgInGaZnS / Ga x The preparation of S quantum dots and the preparation method of (Cu)AgInGaZnS core solution include: mixing (Cu source), Ag source, In source, Ga source, Zn source and oleylamine solution and placing them in a vacuum environment. After complete dissolution, the mixture is filled with nitrogen gas to obtain a mixed precursor solution containing (Cu)AgInGaZn. Sulfur powder is dissolved in a mixed solution of oleylamine and octyl mercaptan and injected into the mixed precursor solution. After a single heating and holding, an initial (Cu)AgInGaZnS core solution is obtained. After a single cooling of the initial (Cu)AgInGaZnS core solution, trioctylphosphine (TOP) is injected and held at that temperature. Subsequently, the solution is cooled to room temperature to obtain the (Cu)AgInGaZnS core solution. This invention studies the Ga of quantum dots. x The S-shell is thicker, resulting in high absorption capacity, high efficiency, and pure color.

Description

Technical Field

[0001] This invention relates to the field of quantum dot synthesis technology, and in particular to a method for preparing quantum dots, quantum dots and their applications. Background Technology

[0002] Environmentally friendly I-III-VI quantum dots and their derivatives are promising candidates to replace traditional Cd-based and Pb-based quantum dots due to their tunable band gaps that vary with composition, full visible light coverage, high efficiency, excellent stability, and non-toxicity. In particular, the flexible tunability of their composition is highly advantageous for precisely controlling the band structure and microstructure.

[0003] I-III-VI quantum dots are more prone to splitting into sublevels near the conduction band (CB) and valence band (VB), often leading to asymmetric PL broadening and higher defect state density. AIGS cores exhibit significant broadband emission characteristics, which stem from defect-involved recombination processes, typically seen in GaN growth. x After the S-shell is formed, it transforms into edge-emitting emission. However, even when growing Ga... x After S, they still retain a significant defect emission magnitude, and the fluorescence quantum yield (PLQY) is unsatisfactory. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a method for preparing quantum dots, quantum dots themselves, and their applications. The purpose of this invention is to synthesize (Cu)AgInGaS quantum dots with high absorption capacity, high efficiency, and pure color. The specific details are as follows:

[0005] A quantum dot comprising the following components: 0.01-0.04 mol CuCl, 0.1-0.2 mol AgNO3, 0.05-0.2 mol InCl3, 0.6-0.8 mol Ga(acac)3, 0.03-0.1 mol ZnCl2, 30.4-60.8 mol oleylamine, 1.4-1.8 g sulfur powder, 28.8-57.6 mol octyl mercaptan, 9-13.5 mol TOP, 0.1-0.3 mol Ga(DDTC)3, 0.3-0.6 mol DMTU, and 0.8-2.4 mol GaCl3.

[0006] Preferably, the quantum dot comprises a core structure and a shell structure, wherein the shell structure is Ga... x The S-shell and the core structure is (Cu)AgInGaZnS core.

[0007] Preferably, a method for preparing quantum dots includes:

[0008] Preparation of S1, (Cu)AgInGaZnS core solution;

[0009] S2, Initial (Cu)AgInGaZnS / Ga x Preparation of S quantum dots;

[0010] S3, Ultimate (Cu)AgInGaZnS / Ga x Preparation of S quantum dots.

[0011] Preferably, the preparation of the (Cu)AgInGaZnS core in S1 includes:

[0012] S101. Mix CuCl, AgNO3, InCl3, Ga(acac)3, ZnCl2 and oleylamine solution and place in a vacuum environment. After complete dissolution, fill with nitrogen gas to obtain a mixed precursor solution containing Ag, In, Ga and Zn.

[0013] S102. Dissolve sulfur powder in a mixed solution of oleylamine and octyl mercaptan and inject it into the mixed precursor solution. After heating and holding the temperature once, the initial AIGZS core solution is obtained.

[0014] S103, after the initial (Cu)AIGZS nucleus solution is cooled once, TOP is injected and kept at that temperature, and then cooled to room temperature to obtain (Cu)AgInGaZnS nucleus solution. TOP acts to passivate the surface defects of the nucleus quantum dots, suppress nonradiative transitions, and highlight band edge emission.

[0015] Preferably, in S2, (Cu)AgInGaZnS / Ga x The preparation of S quantum dots includes:

[0016] Ga(acac)3, Ga(DDTC)3, and DMTU were dissolved in an oleylamine solution and injected into a (Cu)AgInGaZnS core solution under a nitrogen atmosphere. The solution was then heated a second time and held at that temperature to obtain the initial (Cu)AgInGaZnS / Ga x S-quantum dots.

[0017] Preferably, the mass ratio of the oleylamine solution to the octyl mercaptan mixed solution is 6.1:28.8;

[0018] The molar ratios of AgNO3, InCl3, Ga(acac)3, ZnCl2, and oleylamine solution are 0.12:0.05:0.8:0.03:61 and 0.2:0.2:0.6:0.03:61, respectively.

[0019] The mass ratio of the mixed solution of sulfur powder, oleylamine solution, and octyl mercaptan is 63.3:6.1:28.8;

[0020] The molar ratios of Ga(acac)3, Ga(DDTC)3, and DMTU are 0.3:0.1:0.3, respectively.

[0021] Preferably, the process of heating and holding the temperature in one step involves heating to 280-300℃ and holding for 5-30 minutes.

[0022] After one cooling process, the procedure involves cooling the temperature to 180-200℃, injecting the TOP, and maintaining the temperature for 10-30 minutes.

[0023] The temperature range of a nitrogen atmosphere is 80-120℃;

[0024] The specific steps for the second heating and holding process are to raise the temperature to 240 ℃ and hold it for 30-60 minutes.

[0025] Preferably, the final (Cu)AgInGaZnS / Ga in S3 x The preparation of S quantum dots includes:

[0026] S301, Inject the mixed precursor solution into the initial (Cu)AgInGaZnS / Ga at the target temperature. x S quantum dots are heated;

[0027] The mixed precursor solution is a mixed precursor solution of Ga(acac)3, Ga(DDTC)3 and DMTU dissolved in an oleylamine solution;

[0028] S302, repeating S301, yielded the final Ga. x S-shell core / shell quantum dots;

[0029] S303, inject GaCl3 oleylamine solution at the target temperature and keep it warm, then cool down to inject 4 mL TOP and keep it warm, then cool to room temperature;

[0030] In the GaCl3 oleylamine solution, the molar ratio of GaCl3 to OAm is 0.72:5.5 mmol, which promotes shell growth.

[0031] TOP (topology) can passivate quantum dot surface defects in situ, thereby improving fluorescence quantum yield (PLQY).

[0032] The volume ratio of GaCl3 oleylamine solution to TOP is 1:2.2.

[0033] The component percentages of the mixed precursor solution of Ga(acac)3, Ga(DDTC)3, and DMTU dissolved in oleylamine solution in S301 are 42.9:14.2:42.9.

[0034] The target temperature in S301 and S303 is 240-260ºC.

[0035] Inject 0.4M GaCl3-OAm solution into S303 and keep it at this temperature for 30-60 minutes;

[0036] The process of cooling down to 180-200ºC, injecting 4-6 mL of TOP, and maintaining the temperature for 10-30 minutes is as follows:

[0037] Preferably, a quantum dot fabrication and application method is used in the display field, where the quantum dots exhibit high brightness and pure color.

[0038] In summary, the quantum dot preparation method, quantum dots, and their applications of this invention, compared to traditional technologies, demonstrate that the passivation of core surface defects based on in-situ trioctylphosphine (TOP) treatment is highly effective, resulting in significant suppression of edge tail emission. Furthermore, thanks to Ga… x S-shell heteroepitaxial growth effectively passivates the surface, AgInGaZnS / Ga x S quantum dots exhibit bright, sharp emission (80% quantum yield and 33 nm FW-50 for green light; 68% quantum yield and 24 nm FW-50 for blue light) and completely suppressed defect emission. Furthermore, this invention adds Cu to AgInGaZnS quantum dots to obtain CuAgInGaZnS alloy quantum dots with high entropy characteristics. After growing a GaS shell, red (630 nm) quantum dots with a PL QY of 96% and a FW-50 of 60 nm are obtained.

[0039] The technical method of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0040] Figure 1 The above are the absorption and photoluminescence spectra of AIGZS and AIGZS / GS for sample ID 1 of this invention. Figure 1 (a) shows the absorption spectra of AIGZS and AIGZS / GS. Figure 1 (b) in the figure is the photoluminescence spectrum of AIGZS and AIGZS / GS;

[0041] Figure 2 These are TEM images of AIGZS and AIGZS / GS of sample ID 1 of this invention. Figure 2 (a) in the text refers to the AIGZS core. Figure 2 (b) in the text refers to the basic AIGZS / GS. Figure 2 (c) in the text refers to the final AIGZS / GS.

[0042] Figure 3The above are the absorption and photoluminescence spectra of AIGZS and AIGZS / GS for sample ID 2 of this invention. Figure 3 (a) shows the absorption spectra of AIGZS and AIGZS / GS. Figure 3 (b) in the figure is the photoluminescence spectrum of AIGZS and AIGZS / GS;

[0043] Figure 4 These are TEM images of AIGZS and AIGZS / GS of sample ID 2 of this invention. Figure 4 (a) in the text refers to the AIGZS core. Figure 4 (b) in the text refers to the basic AIGZS / GS. Figure 4 (c) in the text represents the intermediate AIGZS / GS. Figure 4 (d) in the text refers to the final AIGZS / GS.

[0044] Figure 5 The images show the photoluminescence spectra of the AIGZS cores of samples IDs 1, 2, and 3 before and after TOP treatment. Figure 5 (a) in the text represents sample ID 1. Figure 5 (b) in the image represents sample ID 2. Figure 5 (c) in the text represents sample ID 3;

[0045] Figure 6 This is the final AIGZS / GS absorption and photoluminescence spectrum of sample ID 3 of this invention. Figure 6 (a) in the diagram is the absorption spectrum. Figure 6 (b) in the image is the photoluminescence spectrum;

[0046] Figure 7 The images show the absorption and photoluminescence spectra of CAIGZS and CAIGZS / GS for sample ID 4 of this invention. Figure 7 (a) shows the absorption spectra of CAIGZS and CAIGZS / GS. Figure 1 (b) in the figure is the photoluminescence spectrum of CAIGZS and CAIGZS / GS;

[0047] Figure 8 This is a high-resolution TEM image of the CAIGZS core of sample ID 4 of this invention. Detailed Implementation

[0048] The technical method of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the present invention.

[0049] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0050] Techniques, systems, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the instruction manual.

[0051] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0052] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0053] This invention provides a method for preparing quantum dots, quantum dots and their applications, including a core-shell structure for the quantum dots, and the preparation method comprising the preparation of a (Cu)AgInGaZnS core solution, and initial (Cu)AgInGaZnS / Ga x Preparation of S quantum dots and the final (Cu)AgInGaZnS / Ga x The preparation of S quantum dots and the preparation method of (Cu)AgInGaZnS core solution include: mixing (Cu source), Ag source, In source, Ga source, Zn source (e.g., CuCl, AgNO3; InCl3; Ga(acac)3, ZnCl2) and oleylamine solution and placing them in a vacuum environment. After complete dissolution, the mixture is filled with nitrogen gas to obtain a mixed precursor solution containing (Cu)AgInGaZn. Sulfur powder is dissolved in a mixed solution of oleylamine and octyl mercaptan and injected into the mixed precursor solution. After a single heating and holding, an initial (Cu)AgInGaZnS core solution is obtained. After a single cooling of the initial (Cu)AgInGaZnS core solution, trioctylphosphine (TOP) is injected and held at that temperature. Subsequently, the solution is cooled to room temperature to obtain the (Cu)AgInGaZnS core solution. This invention studies the Ga of quantum dots. x The S-shell is thicker, resulting in synthesis of high absorption capacity, high efficiency, and pure color. Specific embodiments are as follows:

[0054] Example 1

[0055] Preparation of AgInGaZnS core solution

[0056] Sample ID 1 was prepared using the following typical synthesis of AgInGaZnS core: 0.12 mmol 0.006 M AgNO3, 0.05 mmol 0.0025 M InCl3, 0.8 mmol 0.04 M Ga(acac)3, 0.03 mmol 0.0015 M ZnCl2 and 20 mL oleylamine solution were mixed and placed in a 100 mL three-necked flask for degassing and vacuuming. After the powder was completely dissolved, the flask was filled with nitrogen.

[0057] Dissolve 1.6 mmol of sulfur powder in a mixed solution of 2 mL of oleylamine and 5 mL of octyl mercaptan and load it into an airtight syringe. Then heat the solution to 280 °C and keep it at that temperature for 30 minutes. Remove the heating mantle and allow the solution to cool to 180 °C.

[0058] Inject 4 mL of TOP and keep for 20 min, then cool to room temperature.

[0059] Samples ID 2 and 3 were also synthesized using this method, with the only difference being the ratio of In source to Ga source. Sample ID 2 used 0.2 mmol / L InCl3 (0.01 M) and 0.6 mmol / L Ga(acac)3 (0.03 M), while sample ID 3 used 0.3 mmol / L InCl3 (0.015 M) and 0.3 mmol / L Ga(acac)3 (0.015 M). The optical properties of the AgInGaZnS core are summarized in Table 1.

[0060] Table 1

[0061]

[0062] Example 2

[0063] AgInGaZnS / Ga x Preparation of S:

[0064] 0.3 mmol Ga(acac)3 gallium acetylacetonate, 0.1 mmol Ga(DDTC)3 gallium diethyldithiocarbamate and 0.3 mmol DMTU N,N-dimethylthiourea were dissolved in 10 mL of oleylamine solution and injected into the sample 1, 2 and 3 nuclei solutions under nitrogen atmosphere at 90 °C. The temperature was then raised to 240 °C and held for 30 min.

[0065] To obtain a thicker Ga x For the S shell, a mixed precursor solution of 0.3 mmol Ga(acac)3, 0.1 mmol Ga(DDTC)3 and 0.3 mmol DMTU dissolved in 2 mL oleylamine solution was injected at 260 °C for 30 minutes.

[0066] Repeat the above steps to obtain Ga grown three times. x S-shell core / shell quantum dots. Then, 2 mL of 0.4 M GaCl3 oleylamine solution was injected at 260°C and held for 30 min. Finally, the temperature was lowered to 180°C, 4 mL of TOP was injected and held for 20 min, followed by cooling to room temperature. AgInGaZnS / Ga x The optical properties of S material are summarized in Table 2.

[0067] Table 2

[0068]

[0069] Example 3

[0070] In-situ surface treatment with trioctylphosphine (TOP) and gallium chloride promote shell growth

[0071] The surface modification of AgInGaZnS nuclei was achieved by directly adding a trioctylphosphine solution to the quantum dot stock solution and maintaining it at 180ºC for 10-30 minutes. This treatment resulted in a significant enhancement of band-edge emission of the nuclei, such as... Figure 5 As shown. The role of gallium chloride is to promote Ga... x The S-shell continues to grow, as evidenced by the continuously narrowing half-width at half-maximum, ultimately resulting in an average diameter of approximately 10 nm for the AIGZS / GS core / shell quantum dots.

[0072] Example 4

[0073] CuAgInGaZnS core and its CuAgInGaZnS / Ga x Preparation of S

[0074] Sample ID 4 was prepared using the following synthesis: 0.02 mmol (0.001 M) CuCl, 0.1 mmol (0.005 M) AgNO3, 0.2 mmol (0.01 M) InCl3, 0.8 mmol (0.04 M) Ga(acac)3, 0.06 mmol (0.003 M) ZnCl2, and 20 mL of oleylamine solution were mixed. The remaining nucleation conditions were exactly the same as for samples ID 1, 2, and 3, and Ga was grown... x The S-shell is also completely identical to that of samples ID1, 2, and 3. (CuAgInGaZnS / Ga) x The optical properties of S material are summarized in Table 3. The elemental contents of all CuAgInGaZnS cores, as monitored by energy-dispersive X-ray spectroscopy (EDS), are summarized in Table 4.

[0075] Table 3

[0076]

[0077] Table 4

[0078]

[0079] like Figure 1 As shown, TOP-based in-situ processing is highly effective in passivating core surface defects, leading to dominant tail emission and significant suppression of edge tail emission. Simultaneously, thanks to Ga... x Effective surface passivation from the S-shell heteroepitaxial growth resulted in bright, sharp emission (PL QY of 68%, FWHM of approximately 24 nm) and completely suppressed tail emission in sample ID 1 AIGZS / GS core / shell QDs at 480 nm. Furthermore, this invention demonstrated the effects of TEM on different Ga... x The morphology of the core-shell quantum dots was observed based on the number of growth cycles of S.

[0080] like Figure 2 As shown, the particles of sample ID 1 have good uniformity and monodispersity, and the corresponding particle sizes are 7.4, 8.0, and 10.4 nm, respectively.

[0081] like Figure 3 As shown, TOP in-situ passivation defects and Ga x The continuous growth of the S-shell enhances the photodynamic density (PL), quantum hysteresis (QY), and reduces the full width at half maximum (FWHM) of the green AIGZS / GS core-shell quantum dots. The final sample ID 2 AIGZS / GS core-shell quantum dots achieved 80% PL, QY, and FWHM at 530 nm, respectively. Figure 4 As shown, the particles of sample ID 2 have good uniformity and monodispersity, and the corresponding particle sizes are 7.3, 8.4, 9.2, and 10.3 nm, respectively.

[0082] like Figure 5 As shown, the AIGZS cores of samples ID 1, 2, and 3 exhibited significantly enhanced edge emission after TOP in-situ treatment of surface defects.

[0083] like Figure 6 As shown, the PL QY and FWHM of sample ID 3 AIGZS / GS core-shell quantum dots at 540 nm are 90% and 33 nm, respectively.

[0084] like Figure 7 As shown, the PL QY and FWHM of sample ID 4 CAIGZS / GS core-shell quantum dots at 630 nm are 96% and 60 nm, respectively. Figure 8 As shown, the particles of sample ID 4 have good uniformity and monodispersity, and the corresponding particle size is 13.5 nm.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical methods of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical methods of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical methods to deviate from the spirit and scope of the technical methods of the present invention.

Claims

1. A quantum dot, characterized in that, The raw materials include the following components: 0.01-0.04 mol CuCl, 0.1-0.2 mol AgNO3, 0.05-0.2 mol InCl3, 0.6-0.8 mol Ga(acac)3, 0.03-0.1 mol ZnCl2, 30.4-60.8 mol oleylamine, 1.4-1.8 g sulfur powder, 28.8-57.6 mol octyl mercaptan, 9-13.5 mol TOP, 0.1-0.3 mol Ga(DDTC)3, 0.3-0.6 mol DMTU, and 0.8-2.4 mol GaCl3; The quantum dot comprises a core structure and a shell structure, wherein the shell structure is Ga. x The S-shell and the core structure is a CuAgInGaZnS core.

2. A method for preparing quantum dots as described in claim 1, characterized in that, include: Preparation of S1, CuAgInGaZnS core solution; S2, Initial CuAgInGaZnS / Ga x Preparation of S quantum dots; S3, Ultimate CuAgInGaZnS / Ga x Preparation of S quantum dots; The preparation of CuAgInGaZnS cores in S1 includes: S101. Mix CuCl, AgNO3, InCl3, Ga(acac)3, ZnCl2 and oleylamine solution and place in a vacuum environment. After complete dissolution, fill with nitrogen gas to obtain a mixed precursor solution containing CuAgInGaZn. S102. Dissolve sulfur powder in a mixed solution of oleylamine and octyl mercaptan and inject it into the mixed precursor solution. After heating and holding the temperature once, the initial CuAIGZS core solution is obtained. S103, after the initial CuAIGZS core solution was cooled once, was injected into TOP and kept at that temperature, and then cooled to room temperature to obtain CuAgInGaZnS core solution; S2 CuAgInGaZnS / Ga x The preparation of S quantum dots includes: Ga(acac)3, Ga(DDTC)3, and DMTU were dissolved in an oleylamine solution and injected into a CuAgInGaZnS core solution under a nitrogen atmosphere. The solution was then heated a second time and held at that temperature to obtain the initial CuAgInGaZnS / Ga core. x S-quantum dots; Ultimate CuAgInGaZnS / Ga in S3 x The preparation of S quantum dots includes: S301, Inject the mixed precursor solution into the initial CuAgInGaZnS / Ga at the target temperature. x S quantum dots are heated; The mixed precursor solution is a mixed precursor solution of Ga(acac)3, Ga(DDTC)3 and DMTU dissolved in an oleylamine solution; S302, repeating S301, yielded the final Ga. x S-shell core / shell quantum dots; S303, inject GaCl3 oleylamine solution at the target temperature and keep it warm, then cool down to inject trioctylphosphine TOP and keep it warm, then cool to room temperature.

3. The method for preparing quantum dots according to claim 2, characterized in that, The mass ratio of the oleylamine solution and the octyl mercaptan mixed solution was 6.1:28.8; The molar ratios of AgNO3, InCl3, Ga(acac)3, ZnCl2, and oleylamine solution are 0.12:0.05:0.8:0.03:61 and 0.2:0.2:0.6:0.03:61, respectively. The mass ratio of the mixed solution of sulfur powder, oleylamine solution, and octyl mercaptan is 63.3:6.1:28.8; The molar ratios of Ga(acac)3, Ga(DDTC)3, and DMTU are 0.3:0.1:0.3, respectively.

4. The method for preparing quantum dots according to claim 3, characterized in that, The process of heating and holding the temperature involves heating to 280-300℃ and holding for 5-30 minutes. After one cooling process, the procedure for injecting trioctylphosphine TOP and holding the temperature is as follows: cool down to 180-200℃, inject TOP, and hold for 10-30 minutes. The temperature range of a nitrogen atmosphere is 80-120℃; The specific steps for the second heating and holding process are to raise the temperature to 240-260℃ and hold it for 30-60 minutes.

5. The method for preparing quantum dots according to claim 4, characterized in that, In S3, the component percentages of the mixed precursor solution of Ga(acac)3, Ga(DDTC)3, and DMTU dissolved in oleylamine solution are 42.9:14.2:42.

9. The molar ratio of GaCl3 to oleylamine in the GaCl3-oleylamine solution is 0.72:5.5; The volume ratio of GaCl3 oleylamine solution to TOP is 1:2.

2.

6. The method for preparing quantum dots according to claim 5, characterized in that, The target temperature in S301 and S303 is 240-260℃; Inject 0.4M GaCl3 oleylamine solution into S303 and keep it at this temperature for 30-60 minutes; The procedure involves cooling the solution to 180-200 ºC, injecting 4-6 mL of TOP, and maintaining the temperature for 10-30 minutes.

7. An application of quantum dots as described in claim 1 in display devices and the field of QLED.

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