Synthesis method of large-size high-light-efficiency multi-element blue quantum dots with narrow spectrum band

Abstract

The application belongs to the technical field of quantum dot synthesis, and specifically discloses a synthesis method of large-size high-light-efficiency narrow-spectrum-band multi-element blue quantum dots, which comprises the following steps: preparing a quantum dot core solution with a low doping ratio, and washing out the inner core in the quantum dot core solution; introducing inorganic fluoride ions to control the growth behavior of the quantum dot core, so that the quantum dot core grows uniformly, and the fluorescence spectrum data of the growth process are monitored; when the fluorescence spectrum data reaches an expected value, the growth of the quantum dot core is immediately stopped; and the stopped quantum dot core is coated with a protective shell of ZnSe and ZnS. The synthesis method of the large-size high-light-efficiency narrow-spectrum-band multi-element blue quantum dots can avoid non-uniform growth caused by excessively large size, reduce the Te doping ratio in the core, and reduce the spectral tailing caused by non-uniform Te doping, thereby providing a feasible path for preparing high-performance blue light electroluminescent diodes and realizing commercialization of quantum dots.

Description

Technical Field

[0001] This invention belongs to the field of quantum dot synthesis technology, specifically relating to a method for synthesizing large-size, high-efficiency, narrow-band multi-element blue quantum dots. Background Technology

[0002] Zinc selenide telluride (ZnSeTe) quantum dots can achieve photoluminescence (PL) emission covering the entire blue light spectrum by changing the tellurium (Te) doping ratio, making them one of the most promising environmentally friendly blue light quantum dot materials. However, as the Te doping ratio increases, spectral broadening inevitably occurs, severely affecting the color purity of the quantum dots. Currently, the narrowest emission peak in existing ZnSeTe quantum dot systems is 14 nm, but the emission wavelength is below 450 nm, which is insufficient for subsequent commercial applications. Meanwhile, quantum dots with wavelengths above 450 nm that meet current application requirements have a minimum half-width of 22 nm, resulting in lower color purity.

[0003] This is mainly because zinc selenide (ZnSe) has a bulk band gap of 2.7 eV, and after forming quantum dots, its emission peak is located around 420 nm, requiring Te doping to adjust the spectrum. However, as the Te ratio increases, Te becomes non-uniformly distributed within the quantum dot core, with multiple Te clusters forming Te agglomerates. This introduces a shallow energy level near the valence band top, causing the emission peak to broaden and tail. Therefore, ZnSeTe quantum dots struggle to achieve narrow-band emission within the blue light emission range (450-465 nm) required for commercial applications.

[0004] Therefore, there is a need in this field to develop a method for synthesizing large-size, high-efficiency, narrow-band multi-element blue quantum dots that can effectively solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for synthesizing large-size, high-efficiency, narrow-bandgap, multi-element blue quantum dots. This method employs a large-size, low-doping strategy, combining a large-size weakened confinement effect strategy with a tellurium (Te) doping strategy to jointly promote the spectral redshift of zinc selenide (ZnSe), synthesizing low-doped, large-size ZnSeTe quantum dots that emit blue light. This method avoids the non-uniform growth caused by excessive size while reducing the proportion of Te doping within the core, thus reducing spectral tailing caused by non-uniform Te doping. This improves the photoluminescence and electroluminescence performance of the quantum dots, providing a feasible path for the fabrication of high-performance blue photoluminescent diodes and the commercialization of quantum dots.

[0006] To achieve the above objectives, this invention provides a method for synthesizing large-size, high-efficiency, narrow-bandgap, multi-element blue quantum dots, comprising the following steps:

[0007] Step S1: Prepare a quantum dot core solution with a low doping ratio and wash out the cores from the quantum dot core solution;

[0008] Step S2: Introduce inorganic fluorine ions to ensure uniform growth of quantum dot nuclei, and monitor the fluorescence spectral data of the growth process.

[0009] Step S3: When the fluorescence spectral data reaches the expected value, immediately stop the growth of quantum dot nuclei;

[0010] Step S4: Coat the stopped quantum dot cores with a protective shell of zinc selenide and zinc sulfide to obtain narrow-band blue ZnSeTe / ZnSe / ZnS core-shell structured quantum dots with high fluorescence quantum yield.

[0011] Preferably, step S1 specifically involves:

[0012] Step S11: Prepare selenium nucleation precursor solution and tellurium nucleation precursor solution;

[0013] Step S12: Take zinc acetate, add oleic acid, oleylamine and 1-octadecene, mix well, and vacuum at 100-150℃ for 40-120 minutes to obtain solution A;

[0014] Step S13: Heat solution A to 260-320℃ under a nitrogen atmosphere, and inject selenium nucleation precursor solution and tellurium nucleation precursor solution at a ratio of 1mL:0.02mL. The amount of selenium nucleation precursor solution added is 0.5-2mL, and the amount of tellurium nucleation precursor solution added is 0.01-0.04mL. React at 260-320℃ for 40-100 minutes to obtain ZnSeTe quantum dot core solution.

[0015] Step S14: Take the ZnSeTe quantum dot core solution, add hexane and ethanol solution in sequence, centrifuge and disperse the precipitate in hexane; repeat step S14 2-3 times to obtain the washed quantum dot cores.

[0016] Preferably, in step S11, the preparation of the selenium nucleation precursor solution specifically involves dissolving selenium powder in diphenylphosphine under a nitrogen atmosphere, controlling the ratio between the two to make the concentration of the selenium nucleation precursor solution 1-2 mmol / mL, thus obtaining the selenium nucleation precursor solution.

[0017] The specific method for preparing the tellurium nucleation precursor solution is as follows: under a nitrogen atmosphere, tellurium powder is dissolved in tri-n-octylphosphine, and the ratio of the two is controlled so that the concentration of the tellurium nucleation precursor solution is 0.05-0.1 mmol / mL, thus obtaining the tellurium nucleation precursor solution.

[0018] Preferably, in step S12, the addition ratio of zinc acetate, oleic acid, oleylamine and 1-octadecene is 2 mmol: 2 mL: 1 mL: 10 mL;

[0019] In step S14, the addition ratio of ZnSeTe quantum dot core solution, n-hexane, and 99.9% ethanol solution is 2mL:1mL:2mL.

[0020] Preferably, step S2 specifically involves:

[0021] Step S21: Prepare tellurium growth precursor solution, selenium growth precursor solution, and zinc oleate solution;

[0022] Step S22: Take octadecene, add the washed quantum dot cores, and add inorganic fluoride salt. After vacuuming at 120°C for 30 minutes, raise the temperature to 310°C.

[0023] Inject the selenium growth precursor solution at a rate of 0.5-2 mL / h using a micro-injection pump, and the tellurium growth precursor solution at a rate of 0.1-0.4 mL / h. At the same time, add 3-5 mL of zinc oleate solution every half hour to ensure uniform growth of ZnSeTe quantum dot nuclei.

[0024] Step S23: Monitor the fluorescence spectrum data of the ZnSeTe quantum dot core growth process. Stop adding the precursor solution after it reaches the required wavelength and wait for further coating layer.

[0025] Preferably, in step S21, the preparation of the selenium growth precursor solution specifically involves dissolving selenium powder in tri-n-phosphine under a nitrogen atmosphere, controlling the ratio between the two to make the concentration of the selenium growth precursor solution 1-2 mmol / mL, thereby obtaining the selenium growth precursor solution.

[0026] The preparation of the tellurium growth precursor solution involves dissolving selenium powder in tri-n-phosphine under a nitrogen atmosphere, controlling the ratio between the two to achieve a tellurium growth precursor solution concentration of 0.05-0.1 mmol / mL.

[0027] The specific steps for preparing zinc oleate solution are as follows: zinc acetate is placed in a flask, and tri-n-octylamine and oleic acid are added. The ratio of zinc acetate, tri-n-octylamine and oleic acid is 2 mL:1 mL:1 mL. After mixing evenly, the mixture is heated to 100-150℃ and vacuumed for 40-120 minutes. Then, it is kept warm under a nitrogen atmosphere to obtain the zinc oleate solution.

[0028] Preferably, in step S22, the addition ratio of octadecene, the washed quantum dot core, and inorganic fluoride is 10-15 mL: 5-6 mL: 0.5-2 mmol;

[0029] Among them, the inorganic fluoride salt is one of ZnF2, NH4F, LiF, and KF.

[0030] Preferably, step S4 specifically involves:

[0031] Step S41: Prepare selenium-coated precursor solution, sulfur-coated precursor solution, and zinc oleate solution;

[0032] Step S42: Maintain the ZnSeTe quantum dot core solution at 260-320℃, and inject the selenium-coated precursor solution at a rate of 1-3 mL / h using a micro-injection pump. At the same time, add 3-5 mL of zinc oleate solution every half hour to coat the zinc selenide layer.

[0033] Step S43: Subsequently, the same amount of injection pump is used to inject the sulfur-coated precursor solution at a rate of 1-3 mL / h. 3-5 mL of zinc oleate solution is added every half hour to coat the zinc sulfide layer, resulting in a quantum dot reaction solution with zinc selenide and zinc sulfide double shell coating.

[0034] Step S44: Cool the reaction solution to room temperature and purify it 2-3 times using n-hexane and ethanol to obtain narrow-band blue ZnSeTe / ZnSe / ZnS core-shell quantum dots with high fluorescence quantum yield.

[0035] Preferably, in step S41, the preparation of the selenium-coated precursor solution specifically involves dissolving selenium powder in tri-n-phosphine under a nitrogen atmosphere, controlling the ratio between the two to make the concentration of the selenium-coated precursor solution 1-2 mmol / mL, thereby obtaining the selenium-coated precursor solution.

[0036] The preparation of the sulfur-coated precursor solution involves dissolving sulfur powder in tri-n-phosphine under a nitrogen atmosphere, controlling the ratio of the two to make the concentration of the sulfur-coated precursor solution 1-2 mmol / mL, and obtaining the sulfur-coated precursor solution.

[0037] The specific steps for preparing zinc oleate solution are as follows: zinc acetate is placed in a flask, and tri-n-octylamine and oleic acid are added. The ratio of zinc acetate, tri-n-octylamine and oleic acid is 2 mL:1 mL:1 mL. After mixing evenly, the mixture is heated to 100-150℃ and vacuumed for 40-120 minutes. Then, it is kept warm under a nitrogen atmosphere to obtain the zinc oleate solution.

[0038] The present invention employs the above-mentioned method for synthesizing large-size, high-efficiency, narrow-band multi-element blue quantum dots, with the following beneficial effects:

[0039] (1) The ZnSeTe quantum dots synthesized by the large-size low-doping strategy of the present invention can achieve an ultra-narrow emission peak width (14-16nm) in the blue light range (450-465nm) that meets the display application requirements, compared with ZnSeTe quantum dots obtained by other systems, which greatly improves the color purity of ZnSeTe as a light-emitting material.

[0040] (2) The quantum dots synthesized in this invention have a large size and high crystal quality. Compared with other ZnSeTe systems, their storage stability and photo-induced stability are significantly improved. At the same time, the maximum external quantum efficiency, maximum brightness, operating lifetime, and efficiency roll-off of the deep blue photoelectric device all reach the optimal values ​​of this system. Using them to prepare electroluminescent diodes, breakthroughs can be achieved in the performance of cadmium-free deep blue quantum dot electroluminescent diodes in terms of efficiency, brightness, lifetime, low efficiency roll-off, and color purity.

[0041] (3) Compared with the commonly used ZnSeTe synthesis system with high fluorescence quantum yield, this invention does not use highly dangerous hydrofluoric acid (HF) and diethylzinc (ZnEt2), making the synthesis method safer and more reliable; and the blue quantum dots synthesized by this invention are lead-free and cadmium-free, making them ideal environmentally friendly display materials.

[0042] (4) In this invention, quantum dot cores with a low Te doping ratio are first synthesized and then washed out using ethanol and n-hexane. The quantum dot cores are dispersed in a suitable solvent, and inorganic fluorine ions are introduced to regulate the growth behavior of the quantum dot cores. Subsequently, Te and Se precursors are added to ensure uniform growth, while the growth process is monitored. When the spectrum reaches the expected value, the core growth is immediately stopped, and the cores are coated with ZnSe and ZnS protective shells to obtain narrow-band blue ZnSeTe / ZnSe / ZnS core-shell structured quantum dots with high fluorescence quantum yield.

[0043] (5) In the process of nucleus growth, to address the stacking faults and stacking issues in the quantum dot lattice caused by excessively long growth times, this invention further introduces fluoride ions to replace the oleic acid ligands on the quantum dot surface. By utilizing the selective adsorption of fluoride ions on specific crystal planes of the quantum dot core, the original long-chain organic ligands with significant steric hindrance on the surface are removed, achieving rapid and uniform growth of the quantum dot core and obtaining high-quality, large-size quantum dot cores. During the growth process, the full width at half maximum (FWHM) of the core remains consistently narrow (~17 nm). Finally, a shell coating is applied to obtain ZnSeTe / ZnSe / ZnS core-shell structured quantum dots with nearly 100% fluorescence quantum dot yield.

[0044] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0045] Figure 1 This is a schematic diagram illustrating the synthesis of narrow-band blue ZnSeTe / ZnSe / ZnS core-shell quantum dots using a low-doping strategy in an embodiment of the method for synthesizing large-size, high-efficiency, narrow-band multi-element blue quantum dots according to the present invention.

[0046] Figure 2The images show the quantum dot spectra at each stage of an embodiment of the synthesis method for large-size, high-efficiency, narrow-band multi-element blue quantum dots according to the present invention; where a represents small size, b represents large size, and c represents shell coating.

[0047] Figure 3 This is an example of a method for synthesizing large-size, high-efficiency, narrow-bandgap multi-element blue quantum dots according to the present invention. The quantum dot core spectra are shown at various stages during the ZnSeTe quantum dot core growth process. Wherein, a represents 0h of core growth, b represents 0.5h of core growth, c represents 1.0h of core growth, d represents 1.5h of core growth, e represents 2.0h of core growth, f represents 3.0h of core growth, g represents 4.0h of core growth, and h represents 5.0h of core growth.

[0048] Figure 4 This is an example of a method for synthesizing large-size, high-efficiency, narrow-bandgap multi-element blue quantum dots according to the present invention. The images show transmission electron microscopy (TEM) images of the quantum dot nuclei at various stages of the ZnSeTe quantum dot nucleus growth process. Specifically, a is the TEM image after 0.5 h of nucleus growth, b is the TEM image after 1.0 h of nucleus growth, c is the TEM image after 1.5 h of nucleus growth, d is the TEM image after 2.0 h of nucleus growth, e is the particle size distribution after 0.5 h of nucleus growth, f is the particle size distribution after 1.0 h of nucleus growth, g is the particle size distribution after 1.5 h of nucleus growth, and h is the particle size distribution after 2.0 h of nucleus growth.

[0049] Figure 5 This invention provides an example of a method for synthesizing large-size, high-efficiency, narrow-bandgap multi-element blue quantum dots. The comparison of HRTEM values ​​of the ZnSeTe quantum dot nuclei during growth with and without fluoride ions is shown. In this example, a represents growth without fluoride ions, b represents growth with fluoride ions, c represents lattice stacking faults without fluoride ions, and d represents growth without lattice stacking faults after adding fluoride ions.

[0050] Figure 6 The figures shown are performance test diagrams of a deep blue quantum dot electroluminescent device in an experimental example of a method for synthesizing large-size, high-efficiency, narrow-band multi-element blue quantum dots according to the present invention; wherein, a is the relationship between the brightness of the electroluminescent device and voltage and the current density and voltage, b is the relationship between the external quantum efficiency of the device and brightness, c is the device lifetime test diagram, and d is the electroluminescence spectrum of the device. Detailed Implementation

[0051] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[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] like Figure 1As shown, a method for synthesizing large-size, high-efficiency, narrow-band multi-element blue quantum dots includes the following steps:

[0054] Step S1: Prepare a quantum dot core solution with a low doping ratio and wash out the cores from the quantum dot core solution.

[0055] First, a low-doped ZnSeTe core was synthesized, and then Se and Te precursors were added to further promote uniform growth of the core, resulting in large-sized, low-doped ZnSeTe quantum dots that meet the required spectrum. The quantum dot cores were then washed out using ethanol and n-hexane.

[0056] Step S2: Introduce inorganic fluorine ions to ensure uniform growth of quantum dot nuclei, and monitor the fluorescence spectral data of the growth process.

[0057] Step S3: When the fluorescence spectral data reaches the expected value, immediately stop the quantum dot nucleus growth.

[0058] By utilizing the large-size weakened confinement effect to reduce the Te doping in ZnSeTe quantum dots, Te can be uniformly distributed within the core, reducing spectral tailing and achieving an ultra-narrow emission peak width (14-16nm) in the blue light range (450-465nm) that meets the requirements of display applications.

[0059] Step S4: Coat the stopped-growing quantum dot core with a protective shell of zinc selenide (ZnSe) and zinc sulfide (ZnS) to obtain narrow-band blue ZnSeTe / ZnSe / ZnS core-shell structured quantum dots with high fluorescence quantum yield.

[0060] The spectrum can be adjusted between 450-465 nm by adjusting the Te doping ratio in the initial ZnSeTe core, the Te to Se precursor ratio during subsequent growth, the size of the nucleus, and the thickness of the subsequent ZnSe and ZnS layers.

[0061] Example

[0062] A method for synthesizing narrowband blue ZnSeTe / ZnSe / ZnS core-shell structured quantum dots includes the following steps:

[0063] Step S1: Preparation of selenium nucleation precursor solution: Dissolve 2 mmol of selenium powder in 2 mL of diphenylphosphine under a nitrogen atmosphere to obtain the selenium nucleation precursor solution.

[0064] Preparation of tellurium nucleation precursor solution: Dissolve 1 mmol of tellurium powder in 20 mL of tri-n-octylphosphine under a nitrogen atmosphere to obtain the tellurium nucleation precursor solution.

[0065] Take 2 mmol of zinc acetate, add 2 mL of oleic acid, 1 mL of oleylamine, and 10 mL of 1-octadecene, and evacuate at 120 °C for 1 hour. Then, heat to 310 °C under a nitrogen atmosphere. Add 1 mL of selenium nucleation precursor solution and 0.02 mL of tellurium nucleation precursor solution, and react at this temperature for 1 hour to obtain a ZnSeTe quantum dot nucleus solution. Figure 2 As shown in 'a'.

[0066] Quantum dot core elution: Take 20 mL of ZnSeTe quantum dot core solution, add 10 mL of n-hexane, then add 20 mL of ethanol solution. Centrifuge and disperse the precipitate in n-hexane. Repeat the above washing operation 2-3 times to obtain the eluted quantum dot cores.

[0067] Step S2: Preparation of selenium growth precursor solution: Dissolve 5 mmol of selenium powder in 5 mL of tri-n-phosphine under a nitrogen atmosphere to obtain selenium growth precursor solution.

[0068] Preparation of tellurium growth precursor solution: 1 mmol of tellurium powder was dissolved in 20 mL of tri-n-octylphosphine under a nitrogen atmosphere to obtain the tellurium growth precursor solution.

[0069] Preparation of zinc oleate solution: Take 20 mL of zinc acetate in a flask, add 10 mL of tri-n-octylamine and 10 mL of oleic acid, mix well, vacuum at 120 °C for 1 hour, and then keep warm under a nitrogen atmosphere to obtain zinc oleate solution.

[0070] Take 15 mL of octadecene (ODE), add 6 mL of the eluted quantum dot cores, and add 2 mmol of an inorganic fluoride salt (ZnF2, NH4F, LiF, or KF). After vacuuming at 120 °C for 30 min, raise the temperature to 310 °C.

[0071] The selenium growth precursor solution was injected at a rate of 1 mL / h using a micro-injection pump, and the tellurium growth precursor solution was injected at a rate of 0.2 mL / h. At the same time, 4 mL of zinc oleate solution was added every half hour to ensure uniform growth of ZnSeTe quantum dot nuclei.

[0072] The fluorescence spectrum data of the ZnSeTe quantum dot core growth process were monitored. Once the desired wavelength was reached, the addition of the precursor solution was stopped, and the process was allowed to proceed with further coating. Figures 3-4 As shown.

[0073] Step S3: When the fluorescence spectral data reaches the expected value, immediately stop the quantum dot nucleus growth, such as... Figure 2 As shown in b in the figure.

[0074] Step S4: Prepare selenium-coated precursor solution: Dissolve 5 mmol of selenium powder in 5 mL of tri-n-octylphosphine under a nitrogen atmosphere to obtain a selenium-coated precursor solution.

[0075] Preparation of sulfur-coated precursor solution: 5 mmol of sulfur powder was dissolved in 5 mL of tri-n-octylphosphine under a nitrogen atmosphere to obtain sulfur-coated precursor solution.

[0076] Preparation of zinc oleate solution: Take 30 mL of zinc acetate in a flask, add 15 mL of tri-n-octylamine and 15 mL of oleic acid, vacuum at 120 °C for 1 hour, and then keep warm under a nitrogen atmosphere to obtain zinc oleate solution.

[0077] The ZnSeTe quantum dot core solution was maintained at 310°C. A selenium-coated precursor solution was injected at a rate of 1.5 mL / h using a micro-injection pump, with 4 mL of zinc oleate solution added every half hour to coat the zinc selenide layer. Subsequently, a sulfur-coated precursor solution was injected at the same rate of 1.5 mL / h using a micro-injection pump, with 4 mL of zinc oleate solution added every half hour to coat the zinc sulfide layer, yielding the reaction solution.

[0078] The reaction solution was cooled to room temperature and purified 2-3 times using n-hexane and ethanol to obtain large-size, low-doped, narrow-band blue ZnSeTe / ZnSe / ZnS core-shell quantum dots with a photofluorescent emission wavelength range of 450-465 nm, a full width at half maximum (FWHM) of 14-16 nm, and a photofluorescent quantum dot yield greater than 95%. Figure 2 As shown in c in the figure.

[0079] Comparative Example

[0080] The difference between this comparative example and the embodiment is that no inorganic fluoride salt (ZnF2, NH4F, LiF or KF) is added in step S2 of the comparative example.

[0081] like Figure 5 As shown, in the examples, the quantum dot cores with added fluoride ions showed no lattice stacking faults, indicating high crystal quality, which is beneficial for improving photoluminescence and electroluminescence performance. In contrast, the quantum dot cores without fluoride ions in the comparative examples showed lattice stacking faults, indicating poor quantum dot crystal quality and internal lattice defects. These defects lead to a decrease in subsequent photoluminescence and electroluminescence performance.

[0082] Experimental Example

[0083] Fabrication of a quantum dot electroluminescent diode device:

[0084] In the examples, narrow-band blue ZnSeTe / ZnSe / ZnS core-shell quantum dots were used as the luminescent layer, and ITO was used as the anode material. Further spin-coating was performed with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), a hole transport layer (poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-n-butyl)phenyl)-diphenylamine)] (TFB), polyvinylcarbazole (PVK)), the luminescent layer, and an electron transport layer (zinc oxide nanoparticles (ZnO) or magnesium-doped zinc oxide nanoparticles (ZnMgO)). Finally, a certain thickness of aluminum was deposited using a vacuum coating machine to construct the quantum dots.

[0085] like Figure 6 As shown, the deep blue (CIE-y≤0.046) electroluminescent diode device fabricated with quantum dots in this experimental example achieves a maximum external quantum efficiency of 21.3% and a maximum luminance of 56000 cd / m². -2 Device lifespan LT95@1000cdm -2 It reaches 6.1 hours, and can operate at 5000-50000 cd m -2 It exhibits extremely low efficiency roll-off within the range.

[0086] Therefore, this invention employs the aforementioned method for synthesizing large-size, high-efficiency, narrow-bandgap, multi-element blue quantum dots. It utilizes a large-size, low-doping strategy, combining a large-size weakening confinement effect strategy with a tellurium doping strategy to jointly promote the spectral redshift of zinc selenide, synthesizing low-doped, large-size blue-emitting ZnSeTe quantum dots. This method avoids the non-uniform growth caused by excessive size while reducing the tellurium doping ratio within the core, thus minimizing spectral tailing caused by non-uniform tellurium doping. Furthermore, fluorine ions are introduced during the core growth process to regulate the quantum dot nucleus growth behavior, improving the crystallinity of the quantum dots and obtaining blue core-shell quantum dots with both high-efficiency photoluminescence and electroluminescence properties.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions 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 solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for synthesizing large-size, high-efficiency, narrow-bandgap, multi-element blue quantum dots, characterized in that, Includes the following steps: Step S1: Prepare a quantum dot core solution with a low doping ratio and wash out the cores from the quantum dot core solution; Step S11: Prepare selenium nucleation precursor solution and tellurium nucleation precursor solution; Step S12: Take zinc acetate, add oleic acid, oleylamine and 1-octadecene, mix well, and vacuum at 100-150℃ for 40-120 minutes to obtain solution A; Step S13: Heat solution A to 260-320℃ under a nitrogen atmosphere, and inject selenium nucleation precursor solution and tellurium nucleation precursor solution at a ratio of 1mL:0.02mL. The amount of selenium nucleation precursor solution added is 0.5-2mL, and the amount of tellurium nucleation precursor solution added is 0.01-0.04mL. React at 260-320℃ for 40-100 minutes to obtain ZnSeTe quantum dot core solution. Step S14: Take the ZnSeTe quantum dot core solution, add n-hexane and 99.9% ethanol solution in sequence, centrifuge, and disperse the precipitate in n-hexane; repeat step S14 2-3 times to obtain the washed quantum dot cores; Step S2: Introduce inorganic fluorine ions to ensure uniform growth of quantum dot nuclei, and monitor the fluorescence spectral data of the growth process. Step S21: Prepare tellurium growth precursor solution, selenium growth precursor solution, and zinc oleate solution; Step S22: Take octadecene, add the washed quantum dot cores, and add an inorganic fluoride salt. After vacuuming at 120°C for 30 minutes, raise the temperature to 310°C. The inorganic fluoride salt is one of ZnF2, NH4F, LiF, and KF. Inject the selenium growth precursor solution at a rate of 0.5-2 mL / h using a micro-injection pump, and the tellurium growth precursor solution at a rate of 0.1-0.4 mL / h. At the same time, add 3-5 mL of zinc oleate solution every half hour to ensure uniform growth of ZnSeTe quantum dot nuclei. Step S23: Monitor the fluorescence spectrum data of the ZnSeTe quantum dot core growth process, and stop adding the precursor solution after it reaches the required wavelength, and wait for further coating shell; Step S3: When the fluorescence spectral data reaches the expected value, immediately stop the growth of quantum dot nuclei; Step S4: Coat the stopped quantum dot cores with a protective shell of zinc selenide and zinc sulfide to obtain narrow-band blue ZnSeTe / ZnSe / ZnS core-shell structured quantum dots with high fluorescence quantum yield.

2. The method for synthesizing large-size, high-efficiency, narrow-bandgap, multi-element blue quantum dots according to claim 1, characterized in that: In step S11, the preparation of the selenium nucleation precursor solution specifically involves dissolving selenium powder in diphenylphosphine under a nitrogen atmosphere, controlling the ratio between the two to make the concentration of the selenium nucleation precursor solution 1-2 mmol / mL, thus obtaining the selenium nucleation precursor solution. The specific method for preparing the tellurium nucleation precursor solution is as follows: under a nitrogen atmosphere, tellurium powder is dissolved in tri-n-octylphosphine, and the ratio of the two is controlled so that the concentration of the tellurium nucleation precursor solution is 0.05-0.1 mmol / mL, thus obtaining the tellurium nucleation precursor solution.

3. The method for synthesizing large-size, high-efficiency, narrow-bandgap, multi-element blue quantum dots according to claim 1, characterized in that: In step S12, the addition ratio of zinc acetate, oleic acid, oleylamine and 1-octadecene is 2 mmol: 2 mL: 1 mL: 10 mL; In step S14, the addition ratio of ZnSeTe quantum dot core solution, n-hexane, and ethanol solution is 2mL:1mL:2mL.

4. The method for synthesizing large-size, high-efficiency, narrow-bandgap, multi-element blue quantum dots according to claim 1, characterized in that: In step S21, the preparation of the selenium growth precursor solution specifically involves dissolving selenium powder in tri-n-octylphosphine under a nitrogen atmosphere, controlling the ratio between the two to make the concentration of the selenium growth precursor solution 1-2 mmol / mL, and obtaining the selenium growth precursor solution. The preparation of the tellurium growth precursor solution involves dissolving tellurium powder in tri-n-octylphosphine under a nitrogen atmosphere, controlling the ratio of the two to achieve a tellurium growth precursor solution concentration of 0.05-0.1 mmol / mL. The specific steps for preparing zinc oleate solution are as follows: zinc acetate is placed in a flask, and tri-n-octylamine and oleic acid are added. The ratio of zinc acetate, tri-n-octylamine and oleic acid is 2 mL:1 mL:1 mL. After mixing evenly, the mixture is heated to 100-150℃ and vacuumed for 40-120 minutes. Then, it is kept warm under a nitrogen atmosphere to obtain the zinc oleate solution.

5. The method for synthesizing large-size, high-efficiency, narrow-bandgap, multi-element blue quantum dots according to claim 1, characterized in that: In step S22, the addition ratio of octadecene, the washed quantum dot core, and inorganic fluoride is 10-15 mL: 5-6 mL: 0.5-2 mmol.

6. The method for synthesizing large-size, high-efficiency, narrow-bandgap, multi-element blue quantum dots according to claim 1, characterized in that: Step S4 specifically involves, Step S41: Prepare selenium-coated precursor solution, sulfur-coated precursor solution, and zinc oleate solution; Step S42: Maintain the ZnSeTe quantum dot core solution at 260-320℃, and inject the selenium-coated precursor solution at a rate of 1-3 mL / h using a micro-injection pump. At the same time, add 3-5 mL of zinc oleate solution every half hour to coat the zinc selenide layer. Step S43: Subsequently, the sulfur-coated precursor solution is injected at a rate of 1-3 mL / h using a micro-injection pump. 3-5 mL of zinc oleate solution is added every half hour to coat the zinc sulfide layer, resulting in a quantum dot reaction solution with zinc selenide and zinc sulfide double shell coating. Step S44: Cool the reaction solution to room temperature and purify it 2-3 times using n-hexane and ethanol to obtain narrow-band blue ZnSeTe / ZnSe / ZnS core-shell quantum dots with high fluorescence quantum yield.

7. The method for synthesizing large-size, high-efficiency, narrow-bandgap, multi-element blue quantum dots according to claim 6, characterized in that: In step S41, the preparation of the selenium-coated precursor solution specifically involves dissolving selenium powder in tri-n-octylphosphine under a nitrogen atmosphere, controlling the ratio between the two to make the concentration of the selenium-coated precursor solution 1-2 mmol / mL, and obtaining the selenium-coated precursor solution. The preparation of the sulfur-coated precursor solution involves dissolving sulfur powder in tri-n-octylphosphine under a nitrogen atmosphere, controlling the ratio between the two to make the concentration of the sulfur-coated precursor solution 1-2 mmol / mL, thus obtaining the sulfur-coated precursor solution. The specific steps for preparing zinc oleate solution are as follows: zinc acetate is placed in a flask, and tri-n-octylamine and oleic acid are added. The ratio of zinc acetate, tri-n-octylamine and oleic acid is 2 mL:1 mL:1 mL. After mixing evenly, the mixture is heated to 100-150℃ and vacuumed for 40-120 minutes. Then, it is kept warm under a nitrogen atmosphere to obtain the zinc oleate solution.

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