WO2020224439A1 - 一种核壳量子点、其制备方法及量子点光电器件 - Google Patents

一种核壳量子点、其制备方法及量子点光电器件 Download PDF

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WO2020224439A1
WO2020224439A1 PCT/CN2020/086243 CN2020086243W WO2020224439A1 WO 2020224439 A1 WO2020224439 A1 WO 2020224439A1 CN 2020086243 W CN2020086243 W CN 2020086243W WO 2020224439 A1 WO2020224439 A1 WO 2020224439A1
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precursor
core
quantum dot
shell
cadmium
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French (fr)
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周健海
何洋
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纳晶科技股份有限公司
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
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    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/88—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing selenium, tellurium or unspecified chalcogen elements
    • C09K11/881—Chalcogenides
    • C09K11/883—Chalcogenides with zinc or cadmium

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  • the invention relates to the technical field of quantum dot materials, in particular to a core-shell quantum dot, a preparation method thereof, and a quantum dot optoelectronic device.
  • quantum dots In the past two decades, the synthetic chemistry of quantum dots has mainly focused on monodisperse control of size and morphology and how to improve the fluorescence quantum yield. But to make quantum dots as a class of excellent light-emitting and optoelectronic materials, the more important goal in synthesis is to obtain quantum dots with high environmental stability, that is, to reduce the environment as much as possible, especially the optical and electrical effects of water and oxygen on quantum dots. The influence of the nature of quantum dots has a great promotion effect on the academic and applied research of quantum dots.
  • the quantum dots For single-size nuclear quantum dots, due to the large specific surface area of the quantum dots and the dangling bonds on the surface, it will affect the optical and chemical stability of the quantum dots. Therefore, to improve the stability of the quantum dots, it is generally in the quantum dots.
  • the surface is covered with a shell material with a wider band structure to isolate the connection between the quantum dot exciton state and the environment. So far, among all the quantum dot materials, CdSe and the core-shell structure quantum dots based on it are the most widely studied. Its fluorescence range can cover the entire visible light region, and the synthesis method is mature and simple.
  • the quantum dots are generally coated with CdS or ZnS.
  • CdSe/CdS core-shell quantum dots since the difference between the conduction band of CdS and the conduction band of CdSe is very small, electrons are easily delocalized to the shell. Therefore, the environment must be stabilized. Studies have shown that The thickness of the CdS shell layer is greater than 16 layers.
  • CdSe/ZnS core-shell quantum dots Although the valence band and conduction band of ZnS and CdSe have a large difference, the lattice matching degree between the two materials is about 11%, resulting in After coating the ZnS shell layer, as the thickness of the shell layer increases, the fluorescence half-peak width becomes wider, the fluorescence quantum yield decreases, the monodispersity of the size and morphology deteriorates, and the purity of the crystal form also deteriorates. Therefore, for CdSe/ZnS core-shell quantum dots, CdZnS is often coated between the two to reduce the lattice mismatch, so as to obtain a core-shell quantum dot with a narrow fluorescence half-width.
  • the general method of coating the CdZnS shell layer is to inject the sulfur precursor into the mixture of the cadmium precursor and the zinc precursor to form a CdZnS layer, but the CdSe/CdZnS core-shell quantum dots obtained by this method are used in the subsequent
  • ZnS is continuously coated, the fluorescence half-peak width becomes wider, the efficiency is reduced, the monodispersity of the size and morphology is poor, and the water and oxygen resistance is poor.
  • the purpose of the present invention is to provide a core-shell quantum dot with high fluorescence efficiency, narrow fluorescence half-peak width, and strong water and oxygen resistance, its preparation method and quantum dot optoelectronic device.
  • a method for preparing core-shell quantum dots including the following steps:
  • step S3 the core-shell quantum dots obtained in step S2 are purified and added to the solution containing the second zinc precursor to obtain a second mixed solution;
  • the first anion precursor and the second anion precursor are each independently selected from a sulfur precursor, a selenium precursor, or a combination thereof;
  • the above preparation method also includes at least one of the following features A, B, and C:
  • step S2 after adding the first anion precursor, a first amount of the second cadmium precursor is added for reaction;
  • step S3 is further included, in which a second amount of a third cadmium precursor is added to the second mixed solution;
  • step S4 a third amount of the third cadmium precursor is added to the second mixed solution to react.
  • the ratio of the amount of the first zinc precursor to the first cadmium precursor in the first mixed solution is (5:1) to (2000:1), preferably, the first zinc precursor
  • the ratio of the amount of the substance to the first cadmium precursor is (5:1) to (200:1).
  • the ratio of the amount of the first cadmium precursor in the first mixed solution to the amount of the second cadmium precursor in the step S2 is (1:2) to (50:1).
  • the ratio of the amount of the first cadmium precursor in the first mixed solution to the amount of the third cadmium precursor in the step S4 is (1:2) to (50:1).
  • reaction temperature in step S2 is 280-310°C.
  • reaction temperature in step S4 is 240-310°C.
  • the quantum dot core is a binary quantum dot, a ternary quantum dot, a multi-element quantum dot, or a core-shell quantum dot including group II and group VI elements.
  • the size of the aforementioned quantum dot core is 3-4.5 nm.
  • a core-shell quantum dot prepared by the above-mentioned preparation method of the present invention, and the fluorescence emission wavelength of the above-mentioned core-shell quantum dot is 600-640 nm.
  • a quantum dot optoelectronic device including the core-shell quantum dot prepared by the above-mentioned preparation method of the present invention.
  • the core-shell quantum dot preparation method of the present invention supplements the addition of a small amount of cationic precursors (ie, cadmium precursors) with higher reactivity during the shell growth process, which is beneficial to reduce the defect state of the shell.
  • a small amount of cationic precursors ie, cadmium precursors
  • the core-shell quantum dots with good stability are obtained; the whole synthesis process of the core-shell quantum dots of the present invention is simple, with few influencing factors and good repeatability.
  • Figure 1 shows the fluorescence emission spectra of Example 14 and Comparative Example 1 of the present application
  • FIG. 2 shows the relationship between the aging time and the fluorescence efficiency of Example 14 and Comparative Example 1 of the present application.
  • the step of coating the CdZnS shell layer on the CdSe quantum dots is to inject the sulfur precursor into the mixed solution of the cadmium precursor and the zinc precursor for reaction.
  • the present invention provides a method for preparing core-shell quantum dots. By supplementing the cadmium precursor with higher activity during the growth of the shell layer, a shell layer with fewer defects is obtained, which is beneficial to the preparation Core-shell quantum dots with high fluorescence efficiency, narrow fluorescence half-peak width and good stability.
  • the preparation method of core-shell quantum dots of the present invention includes the following steps:
  • step S3 the core-shell quantum dots obtained in step S2 are purified and added to the solution containing the second zinc precursor to obtain a second mixed solution;
  • first anion precursor and the second anion precursor are independently selected from sulfur precursors, selenium precursors or a combination thereof;
  • the preparation method also includes at least one of the following features A, B, and C:
  • step S2 after adding the first anion precursor, a first amount of the second cadmium precursor is added for reaction;
  • Step S3' is included between steps S3 and S4, adding a second amount of the third cadmium precursor to the second mixture;
  • step S4 a third amount of the third cadmium precursor is added to the second mixed solution to react.
  • the solution containing the quantum dot core may be added to the solution containing the first cadmium precursor and the first zinc precursor to form the first mixed solution.
  • step S2 is: adding a first anion precursor to the first mixed solution for reaction, and then adding a first amount of second cadmium The precursor reacts to coat the quantum dot core with an intermediate shell.
  • the reaction activity of the first cadmium precursor is higher, so the first cadmium precursor quickly participates in the reaction, and the more the middle shell layer grows outward, the solution
  • the second cadmium precursor is added one or more times to obtain the intermediate shell layer
  • the distribution of cadmium atoms is more uniform than the prior art.
  • the method of this embodiment is conducive to reducing the defect state of the middle shell layer and improving the purity of the crystal form. At the same time, it is also conducive to the continuous coating of the subsequent shell layer, so as to obtain core-shell quantum dots with high fluorescence efficiency, narrow half-peak width and good stability. .
  • the second cadmium precursor is added before the reaction of the first anion precursor is completed, and this part of the second cadmium precursor participates in the formation of the intermediate shell layer.
  • the outer side of the middle shell layer also contains a certain amount of cadmium atoms.
  • the second cadmium precursor is added after the reaction of the first anion is completed.
  • the shell layer no longer grows, it passes through a cation exchange reaction.
  • Part of the zinc atoms in the original shell is replaced by cadmium atoms, thus forming an intermediate shell with a certain amount of cadmium atoms on the outside.
  • the second cadmium precursor is not added in the prior art, so the second cadmium precursor is added.
  • the shell layer covered by an anion precursor is similar to CdS/CdZnS with a small amount of cadmium/thick ZnS, rather than a uniform CdZnS shell; in the first embodiment, by adding in the shell formation process A certain amount of the second cadmium precursor can at least partially convert the thicker ZnS outside the shell layer in the prior art into CdZnS, thereby reducing the thickness of ZnS, and making a CdZnS shell layer with better uniformity.
  • the ZnS shell layer is continuously coated outside the layer, the ZnS in the previous layer is reduced or even eliminated, so that the coating thickness of the ZnS shell layer is increased, which is beneficial to obtain a stable core-shell quantum dot.
  • feature B is included, that is, after step S3 is completed, a second amount of the third cadmium precursor is added to the second mixed solution, and then before the second anion is added.
  • the body reaction causes the core-shell quantum dot to be coated with a shell layer. Since the reactivity of the third cadmium precursor is higher than that of the second zinc precursor, it is equivalent to that during the growth of the outer shell layer, a layer with a higher lattice matching degree with the middle shell layer (substantially the same composition) is grown. This layer is beneficial to reduce the defect state between the middle shell layer and the outer shell layer.
  • the second anion precursor reacts with the second zinc precursor so that the outer shell layer continues to grow.
  • the defect state between the outer shell layer and the middle shell layer is reduced, it is conducive to the thick packing of the subsequent materials of the outer shell layer, which also improves the coating efficiency of the outer shell layer, which is beneficial to obtain high fluorescence efficiency, narrow half-value width, and good stability.
  • Core-shell quantum dots are beneficial to obtain high fluorescence efficiency, narrow half-value width, and good stability.
  • the middle shell layer is coated with the outer shell layer (that is, ZnS shell layer), no cadmium precursor is added; while in this embodiment, when the shell layer is grown, the third cadmium precursor is added first, and then the second anion precursor, the third cadmium precursor, and the second anion are added.
  • the CdZnS formed by the reaction of the precursor and the second zinc precursor is coated outside the middle shell, that is, the inner side of the outer shell is the CdZnS layer.
  • This part can be regarded as the continuation of the middle shell. The existence of this part can reduce the middle shell.
  • the second anion precursor and the second zinc precursor continue to react to form a ZnS layer.
  • the inner side of the ZnS layer is a layer with fewer defects, which makes the ZnS layer more effective.
  • the coating thickness is increased, which is beneficial to obtain the stable core-shell quantum dots.
  • feature C is included, that is, in step S4, the second anion precursor and the third amount of the third cadmium precursor are added to the second mixed solution, so that The core-shell quantum dots are coated with an upper shell layer.
  • the third cadmium precursor can be added to the solution during the addition of the second anion precursor, or it can be added to the solution after the second anion precursor is completely added.
  • the third cadmium precursor has high reactivity, and the second anion precursor preferentially reacts with the third cadmium precursor in the solution.
  • the cadmium atoms in the third cadmium precursor can enter through the cation exchange reaction.
  • the composition inside the outer shell layer is similar to that of the middle shell layer (both contain cadmium atoms), increasing
  • the lattice matching degree between the outer shell layer and the middle shell layer is improved, which is beneficial to reduce the defect states during the growth of the outer shell layer, and is also conducive to the continued growth of the outer shell layer, and improves the coating efficiency of the outer shell layer, thereby facilitating high fluorescence efficiency.
  • the middle shell layer is coated with the outer shell layer (that is, ZnS shell layer), the cadmium precursor will not be added; while in this embodiment, when the shell layer is grown, the second anion precursor is first added to react with the second zinc precursor, and the generated ZnS is coated outside the middle shell layer. During the growth of the ZnS shell layer, a third cadmium precursor is added.
  • the third cadmium precursor can enter the already grown ZnS shell layer through a cation exchange reaction, transform the ZnS layer into a CdZnS layer, and the CdZnS layer formed after the transformation It can be regarded as the continuation of the middle shell layer. The existence of this part can reduce the defect state between the middle shell layer and the outer shell layer.
  • the second anion precursor and the second zinc precursor continue to react.
  • a ZnS layer is formed, and the inner side of the ZnS layer is a layer with fewer defect states, which increases the coating thickness of the ZnS layer, thereby facilitating obtaining a stable core-shell quantum dot.
  • features A and B are included, or features A and C are included, or features B and C are included, or features A, B, and C are included.
  • step S1 only needs to mix the quantum dot core (or the solution containing the quantum dot core) with the solution containing the first cadmium precursor and the first zinc precursor to form the first mixture.
  • the solution containing the first cadmium precursor and the first zinc precursor can be added to the reaction vessel containing the quantum dot core; in step S2, “before adding the first anion to the first mixed solution
  • the "body reaction” can also be the reaction of adding the first mixed solution to the first anion precursor; in step S3, only the purified core-shell quantum dots can be mixed with the solution containing the second zinc precursor, that is, in actual operation.
  • the solution containing the second zinc precursor is added to the reaction vessel containing the purified core-shell quantum dots.
  • the ratio of the amount of the first zinc precursor to the first cadmium precursor in the first mixed solution is the ratio of the zinc element of the first zinc precursor to the cadmium element of the first cadmium precursor
  • the ratio of the amount of the substance satisfies (5:1) to (2000:1).
  • the ratio of the amount of the zinc element of the first zinc precursor to the amount of cadmium element of the first cadmium precursor is (5:1) ) To (200:1), and more preferably, the ratio of the amount of the first zinc precursor zinc element to the cadmium element of the first cadmium precursor is (5:1) to (100:1).
  • the ratio of the amount of substances of the first cadmium precursor to the second cadmium precursor is (1:2) to (50:1).
  • the ratio of the amount of substances of the first cadmium precursor to the third cadmium precursor is (1:2) to (50:1).
  • the reaction temperature in step S2 is 280-310°C
  • the reaction temperature in step S4 is 240-310°C.
  • the quantum dot core is a binary quantum dot, a ternary quantum dot, a multivariate quantum dot, or a core-shell quantum dot including group II elements and group VI elements.
  • the quantum dot core may be CdSe, CdSeS, CdZnSe, CdZnSeS, CdSe/ZnSe, CdSe/CdZnSe, CdZnSeS/ZnSe, CdSeS/ZnSe, etc.
  • the size of the quantum dot core is 3-4.5 nm.
  • the fluorescence peak position of the core-shell quantum dot can be adjusted by adjusting the ratio of the amount of the first zinc precursor to the first cadmium precursor, or adjusting the amount of the first anion precursor added.
  • the fluorescence peak position of the core-shell quantum dots can be adjusted by adjusting the addition time of the second cadmium precursor.
  • the fluorescence peak position of the core-shell quantum dots can be adjusted by adjusting the addition amount of the second anion precursor during the process of coating the outer shell layer.
  • the thickness of the middle shell layer can be adjusted by changing the added amount of the first anion precursor.
  • the sulfur precursor can be but not limited to S-ODE solution, trialkylphosphine sulfur, mercaptan;
  • the selenium precursor can be, but not limited to Se-ODE suspension, Se-ODE solution, three Alkylphosphine selenium.
  • the fluorescence emission wavelength of the core-shell quantum dot prepared by the above method of the present invention is 600-640 nm.
  • the present invention also provides a quantum dot optoelectronic device, which includes a core-shell quantum dot prepared by the core-shell quantum dot preparation method of the present invention.
  • the quantum dot optoelectronic device can be, but is not limited to, a liquid crystal display, an OLED display, a QLED display, an electro- or photo-induced lighting device, etc.
  • Se-ODE suspension Disperse selenium powder (0.0237g, 0.3mmol, 100 mesh or 200 mesh) into 3 mL of ODE, sonicate for 5 minutes to prepare 0.1 mmol/mL Se-ODE suspension Turbid liquid.
  • the preparation of other concentrations of Se-ODE suspension is similar to this, just change the amount of selenium powder. Shake well by hand before use.
  • S-TBP cardiackylphosphine
  • Synthesis of spherical CdSe quantum dots Put CdO (0.0256g, 0.2mmol), stearic acid (0.1420g, 0.5mmol) and ODE (4mL) into a 25mL three-necked flask, stir and ventilate (argon) for 10 minutes The temperature was raised to 280°C to obtain a clear solution, and the temperature was lowered to 250°C. 1mL of Se-ODE suspension with a concentration of 0.1mmol/mL was quickly injected into a three-necked flask, and the reaction temperature was controlled at 250°C.
  • Methanol:acetone:chloroform (volume ratio 1:1:1) mixed solution configuration respectively take 5mL methanol, acetone, and chloroform into a 20mL chromatography bottle.
  • CdSe quantum dot purification method take 1 ⁇ 1.5mL stock solution, put it into a 4mL vial, add 2 ⁇ 3mL methanol, acetone, chloroform mixture, heat to about 50°C, then centrifuge at 4000 rpm for 20 After taking it out, pour out the supernatant while it is hot; add 0.5 mL of toluene and perform the same precipitation and centrifugation process again. After the supernatant is poured out while it is hot, add 0.5 mL of toluene, add 3 mL of acetone, and centrifuge at room temperature for precipitation. The precipitate is dissolved in a certain amount of ODE.
  • Core-shell quantum dot purification method Take 10mL stock solution in a 50mL centrifuge tube, add 40mL acetone, heat to about 50°C, then centrifuge at a speed of 8,000 rpm for 3 minutes, then discard the supernatant and remove The substance is dissolved in a certain amount of toluene.
  • Example 2 The difference between Example 2 and Example 1 is that the amount of cadmium oleate added in step (2) is different.
  • Step (2) in Example 2 is: then quickly inject 2 mL of S-TBP solution with a concentration of 0.625 mmol/mL, react for 1 minute, inject 0.1 mL of cadmium oleate solution with a concentration of 0.2 mmol/mL, and continue the reaction for 2 minutes. The reaction was stopped and the temperature was quickly lowered. The CdSe/CdZnS obtained was purified and dissolved in 1 mL of ODE.
  • Example 3 The difference between Example 3 and Example 1 lies in the addition of sulfur precursor in step (2).
  • Step (2) in Example 3 is: then quickly inject 2 mL of S-TBP solution with a concentration of 0.5 mmol/mL, react for 1 minute, inject 0.25 mL of cadmium oleate solution with a concentration of 0.2 mmol/mL, and continue the reaction for 2 minutes. The reaction was stopped and the temperature was quickly lowered. The CdSe/CdZnS obtained was purified and dissolved in 1 mL of ODE.
  • Example 4 The difference between Example 4 and Example 1 is that the molar ratio of zinc and cadmium in step (1) is different.
  • Step (1) in Example 4 is: take 4mmol zinc acetate, 0.1mmol cadmium acetate, 4.4g oleic acid and 15mL ODE into a 100mL three-necked flask, blow in inert gas for 30 minutes at 200°C, and then inject The purified CdSe quantum dot solution with the first exciton absorption peak at 570nm and absorbance at 50 is raised to 300°C.
  • Example 5 The difference between Example 5 and Example 1 is that the amount of sulfur precursor added in step (4) is different.
  • Step (4) in Example 5 is: then add 5 mL of S-TBP solution with a concentration of 0.5 mmol/mL at a rate of 25 mL/h, and stop the reaction after the addition is complete.
  • Example 6 The difference between Example 6 and Example 1 is that the reaction temperature after adding the quantum dot core solution in step (1) is different.
  • Step (1) in Example 6 is: take 4mmol zinc acetate, 0.2mmol cadmium acetate, 4.4g oleic acid and 15mL ODE into a 100mL three-necked flask, at 200 °C, inert gas exhaust for 30 minutes, and then inject The purified CdSe quantum dot solution with the first exciton absorption peak at 570nm and absorbance at 50 is raised to 280°C.
  • Example 7 The difference between Example 7 and Example 1 is that the reaction temperature after adding the core-shell quantum dots in step (3) is different.
  • Step (3) in Example 7 is: Weigh basic zinc carbonate (0.66g, 1.2mmol), 2.8g oleic acid, 10mL ODE into a 100mL three-necked flask, exhaust with inert gas for 10 minutes, and raise the temperature to At 280°C, a clear solution is obtained, and then the purified CdSe/CdZnS core-shell quantum dot solution is injected, and the temperature is reduced to 260°C.
  • Example 8 The difference between Example 8 and Example 1 is that the time of adding the cadmium precursor in step (2) is different.
  • Step (2) in Example 8 is: then quickly inject 2 mL of S-TBP solution with a concentration of 0.625 mmol/mL, react for 2 minutes, inject 0.25 mL of cadmium oleate solution with a concentration of 0.2 mmol/mL, and continue the reaction for 1 minute. The reaction was stopped and the temperature was quickly lowered. The CdSe/CdZnS obtained was purified and dissolved in 1 mL of ODE.
  • Example 9 The difference between Example 9 and Example 1 is that the time of adding the cadmium precursor in step (2) is different.
  • Step (2) in Example 9 is: then quickly inject 2mL of S-TBP solution with a concentration of 0.625mmol/mL, stop the reaction after 3 minutes of reaction, quickly cool to 200°C, and inject 0.25mL of oil with a concentration of 0.2mmol/mL Acid cadmium solution, continue to react for 1 minute, cool to room temperature to purify the prepared CdSe/CdZnS and dissolve it in 1 mL of ODE.
  • Example 10 The difference between Example 10 and Example 1 is that cadmium precursor is also added in step (4).
  • Step (4) in Example 10 is: then add 5 mL of S-TBP solution with a concentration of 0.4 mmol/mL at a rate of 25 mL/h, and when the dripping is halfway, inject 0.25 mL of oleic acid with a concentration of 0.2 mmol/mL After the cadmium solution is dripped, stop the reaction.
  • Example 12 The difference between Example 12 and Example 1 is that the molar ratio of zinc and cadmium in step (1) is different.
  • the step (1) in Example 12 is: take 4mmol zinc acetate, 0.3mmol cadmium acetate, 4.4g oleic acid and 15mL ODE into a 100mL three-necked flask, blow in inert gas for 30 minutes at 200°C, and then inject The purified CdSe quantum dot solution with the first exciton absorption peak at 570nm and absorbance at 50 is raised to 300°C.
  • Figure 1 shows the fluorescence spectra of Example 14 of the present application and Comparative Example 1. Compared with Comparative Example 1, the fluorescence peak position of Example 14 has a red shift, indicating that the preparation method of the present application before adding the second cadmium The cadmium content in the middle shell layer behind the body increases.
  • Figure 2 shows the relationship curve between the aging time and the fluorescence efficiency of Example 14 of the present application and Comparative Example 1.
  • the quantum dots prepared in Comparative Example 1 have a rapid decline in fluorescence efficiency after a short aging process. After the aging time of 250 hours, the fluorescence efficiency dropped to the same level as that of Example 14 after 1000 hours of aging, indicating that the quantum dots obtained by the preparation method of this application have good aging stability.
  • the general quantum dot film must meet the requirements of basic applications, and the efficiency must be above 85% after 1000 hours of aging.
  • the quantum dots obtained by the preparation method of Comparative Example 1 cannot meet the above requirements and cannot be well applied to the quantum dot film, but the quantum dots obtained by the preparation method of the present application have achieved this breakthrough.
  • Table 1 lists the fluorescence peak position, half-width, and fluorescence efficiency of each example and comparative example.
  • the method for detecting the fluorescence efficiency of quantum dots is: using a 450nm blue LED lamp as the backlight spectrum, using an integrating sphere to test the blue backlight spectrum and the spectrum through the quantum dot composite material, and using the integrated area of the spectrum to calculate the luminous efficiency of the quantum dot .
  • Quantum dot fluorescence efficiency (quantum dot emission peak area)/(blue backlight peak area-unabsorbed blue peak area through quantum dot composite)*100%.
  • Example 4 618 25 88
  • Example 5 625 27 89
  • Example 6 26 90
  • Example 7 622 twenty four 92
  • Example 8 623 25
  • Example 9 623 26 91
  • Example 10 624 25
  • Example 11 623 25
  • Example 12 626 27 88
  • Example 13 624 25
  • Example 14 622 26 91 Comparative example 1 620 26 87
  • the core-shell quantum dots prepared in each of the examples and comparative examples were used to prepare quantum dot films, and the aging stability of the quantum dot films was tested (aging conditions, 85°C/95 % Humidity), the test results are shown in Table 2.

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Abstract

本发明公开了一种核壳量子点、其制备方法及量子点光电器件。核壳量子点的制备方法包括以下步骤：S1，将量子点核加入含有第一镉前体以及第一锌前体的溶液中，形成第一混合液；S2，向第一混合液中加入第一阴离子前体反应，在量子点核外包覆上中间壳层；S3，将提纯核壳量子点加入含有第二锌前体的溶液中，得到第二混合液；S4，向第二混合液中加入第二阴离子前体反应，在核壳量子点外包覆上外壳层；制备方法还包括以下特征A、B、C中的至少一种特征：A，在步骤S2中，在加入第一阴离子前体后再加入第一定量的第二镉前体反应；B，步骤S3与S4之间还包括步骤S3'，向第二混合液中加入第二定量的第三镉前体；C，在步骤S4中，向第二混合液中加入第三定量的第三镉前体反应。

Description

一种核壳量子点、其制备方法及量子点光电器件 技术领域
本发明涉及量子点材料技术领域，尤其涉及一种核壳量子点、其制备方法及量子点光电器件。
背景技术
在过去的二十多年里，量子点合成化学主要集中在尺寸形貌的单分散控制以及如何提高荧光量子产率上。但是要使量子点作为一类优异的发光和光电材料，在合成上更重要的目标是得到环境稳定性高的量子点，即尽可能的降低环境尤其水和氧气对于量子点的光学、电学等性质的影响，这对于量子点的学术以及应用研究具有极大的推动作用。
对于单一尺寸的核量子点来说，由于量子点的比表面积大，以及表面的悬挂键等会影响量子点的光学与化学稳定性，因此要提高量子点的稳定性，一般都是在量子点表面包覆能带结构更宽的壳层材料，隔绝量子点激子态与环境之间的联系。到目前为止，在所有的量子点材料中，CdSe以及以其为基础的核壳结构量子点是研究的最为广泛的，其荧光范围可以覆盖整个可见光区域，而且合成方法上成熟、简单。对于以CdSe为基础的核壳结构量子点，一般都是在量子点的外延包覆CdS或ZnS。对于CdSe/CdS核壳结构量子点，由于CdS的能带的导带和CdSe的导带之间的差值很小，电子容易离域到壳层，因此要使得其环境稳定好，研究表明，CdS的壳层厚度要大于16层。而对于CdSe/ZnS核壳量子点，尽管ZnS的价带和导带与CdSe的价带和导带差值很大，但是由于两种材料之间的晶格匹配度大约为11％，从而导致在包覆ZnS壳层后，随着壳层厚度的增加，荧光半峰宽变宽，荧光量子产率降低，尺寸形貌的单分散性变差，晶型的纯度也 变差。所以对于CdSe/ZnS核壳量子点，往往是在两者之间包覆CdZnS，降低晶格不匹配度，从而得到荧光半峰宽较窄的核壳结构量子点。
目前，一般包覆CdZnS壳层的方法是将硫前体注入到镉前体与锌前体的混合液中，从而形成CdZnS层，但是用这种方法得到的CdSe/CdZnS核壳量子点在后续继续包覆ZnS时，荧光半峰宽变宽，效率降低，尺寸形貌的单分散性较差，而且抗水氧能力很差。
发明内容
为了克服现有技术的不足，本发明的目的在于提供一种荧光效率高、荧光半峰宽窄、抗水氧能力强的核壳量子点、其制备方法及量子点光电器件。
根据本发明的一个方面，提供一种核壳量子点的制备方法，包括以下步骤：
S1，将量子点核加入含有第一镉前体以及第一锌前体的溶液中，形成第一混合液；
S2，向上述第一混合液中加入第一阴离子前体反应，使得在上述量子点核外包覆上中间壳层；
S3，将上述步骤S2中得到的核壳量子点提纯后加入含有第二锌前体的溶液中，得到第二混合液；
S4，向上述第二混合液中加入第二阴离子前体反应，使得在上述核壳量子点外包覆上外壳层；
其中，上述第一阴离子前体以及上述第二阴离子前体分别独立地选自硫前体、硒前体或其组合；
上述制备方法还包括以下特征A、B、C中的至少一种特征：
A，在上述步骤S2中，在加入上述第一阴离子前体后再加入第一定量的第二镉前体反应；
B，上述步骤S3与上述步骤S4之间还包括步骤S3’，向上述第二混合液中加入第二定量的第三镉前体；
C，在上述步骤S4中，向上述第二混合液中加入第三定量的第三镉前体反应。
进一步地，上述第一混合液中的上述第一锌前体与上述第一镉前体的物质的量之比为(5:1)～(2000:1)，优选地，上述第一锌前体与上述第一镉前体的物质的量之比为(5:1)～(200:1)。
进一步地，上述第一混合液中的上述第一镉前体与上述步骤S2中的上述第二镉前体的物质的量之比为(1:2)～(50:1)。
进一步地，上述第一混合液中的上述第一镉前体与上述步骤S4中的上述第三镉前体的物质的量之比为(1:2)～(50:1)。
进一步地，上述步骤S2的反应温度为280～310℃。
进一步地，上述步骤S4的反应温度为240～310℃。
进一步地，上述步骤S1中，上述量子点核为包括II族和VI族元素的二元量子点、三元量子点、多元量子点或核壳量子点。
进一步地，上述量子点核的尺寸为3～4.5nm。
根据本发明的另一个方面，提供一种由本发明的上述制备方法制备得到的核壳量子点，上述核壳量子点的荧光发射波长为600～640nm。
根据本发明的另一个方面，提供一种量子点光电器件，包括由本发明的上述制备方法制备得到的核壳量子点。
相比现有技术，本发明的核壳量子点制备方法在壳层生长的过程中，补充添加少量反应活性较高的阳离子前体(也即镉前体)，有利于降低壳层的缺陷态，获得稳定性好的核壳量子点；本发明的核壳量子点的整个合成过程简单，影响 因素少，重复性好。
附图说明
图1示出了本申请的实施例14与对比例1的荧光发射谱图；
图2示出了本申请的实施例14与对比例1的老化时间和荧光效率关系曲线。
具体实施方式
下面，结合具体实施方式，对本发明做进一步描述，需要说明的是，在不相冲突的前提下，以下描述的各实施例之间或各技术特征之间可以任意组合形成新的实施例。
需要说明的是，本申请的说明书和权利要求书中的术语“第一”、“第二”等是用于区别类似的对象，而不必用于描述特定的顺序或先后次序。应该理解这样使用的数据在适当情况下可以互换，以便这里描述的本申请的实施例。此外，术语“包括”和“具有”以及他们的任何变形，意图在于覆盖不排他的包含，例如，包含了一系列步骤或单元的过程、方法、系统、产品或设备不必限于清楚地列出的那些步骤或单元，而是可包括没有清楚地列出的或对于这些过程、方法、产品或设备固有的其它步骤或单元。
现有技术中，在CdSe量子点外包覆CdZnS壳层的步骤是将硫前体注入到镉前体与锌前体的混合液中进行反应。发明人发现，由于镉前体的反应活性高于锌前体的反应活性，CdZnS壳层越往外镉原子的含量越少，现有技术包覆的CdZnS壳层相当于CdS/含有少量镉的CdZnS/较厚的ZnS，这就导致了CdZnS壳层的外侧有较厚ZnS，使得CdZnS壳层的缺陷态增多，晶型纯度变差，后续再在CdZnS壳层外包覆ZnS壳层时，ZnS壳层的包覆效率低，获得的核壳量子点荧光半峰宽变窄，荧光效率降低，抗水氧能力差。为解决这一问题，本发明 提供一种核壳量子点的制备方法，通过在壳层的生长过程中补加活性较高的镉前体，获得缺陷态较少的壳层，有利于制得荧光效率高、荧光半峰宽窄、稳定性好的核壳量子点。
本发明的核壳量子点的制备方法包括以下步骤：
S1，将量子点核加入含有第一镉前体以及第一锌前体的溶液中，形成第一混合液；
S2，向第一混合液中加入第一阴离子前体反应，使得在量子点核外包覆上中间壳层；
S3，将步骤S2中得到的核壳量子点提纯后加入含有第二锌前体的溶液中，得到第二混合液；
S4，向第二混合液中加入第二阴离子前体反应，使得在核壳量子点外包覆上外壳层；
其中，第一阴离子前体以及第二阴离子前体分别独立地选自硫前体、硒前体或其组合；
制备方法还包括以下特征A、B、C中的至少一种特征：
A，在步骤S2中，在加入第一阴离子前体后再加入第一定量的第二镉前体反应；
B，步骤S3与S4之间还包括步骤S3’，向第二混合液中加入第二定量的第三镉前体；
C，步骤S4中，向第二混合液中加入第三定量的第三镉前体反应。
在上述步骤S1中，可以将含有量子点核的溶液加入含有第一镉前体以及第一锌前体的溶液中，以形成上述第一混合液。
在核壳量子点制备方法的第一个实施例中，包括特征A，也即步骤S2为： 向第一混合液中加入第一阴离子前体反应，然后再加入第一定量的第二镉前体反应，使得在量子点核外包覆上中间壳层。第一阴离子前体与第一镉前体以及第一锌前体反应时，第一镉前体的反应活性较高，因此第一镉前体快速参与反应，中间壳层越往外生长，溶液中的第一镉前体的含量越少，为了使获得的中间壳层相对均匀，本实施例在中间壳层的形成过程中，一次或多次添加第二镉前体，从而得到的中间壳层中镉原子的分布相比现有技术更加均匀。本实施例的方法有利于降低中间壳层的缺陷态，提高晶型纯度，同时也有利于后续外壳层的继续包覆，从而获得荧光效率高、半峰宽窄、稳定性好的核壳量子点。
一些情况下，在核壳量子点制备方法的第一个实施例中，至少部分第二镉前体在第一阴离子前体反应完之前加入，这部分第二镉前体参与到中间壳层的生长过程中，使得中间壳层的外侧也含有一定量的镉原子。
另一些情况下，在核壳量子点制备方法的第一个实施例中，至少部分第二镉前体在第一阴离子反应完之后加入，此时壳层虽然不再生长，但是通过阳离子交换反应，原壳层中的部分锌原子被镉原子替换，从而形成外侧含有一定量的镉原子的中间壳层。
以第一阴离子前体、第二阴离子前体均为硫前体为例，进一步说明第一个实施例与现有技术的区别：在现有技术中不添加第二镉前体，因此加入第一阴离子前体后包覆的壳层类似于CdS/含有少量镉的CdZnS/较厚的ZnS，而非均匀的CdZnS壳层；在第一个实施例中，通过在壳层的形成过程中加入一定量的第二镉前体，可以将现有技术中壳层外侧较厚的ZnS至少部分地转化为CdZnS，从而减少ZnS的厚度，制得均匀程度更好的CdZnS壳层，后续在CdZnS壳层外继续包覆ZnS壳层时，由于前一层的ZnS减少甚至被消除，使得ZnS壳层的可包覆厚度增加，从而有利于获得稳定性好的核壳量子点。
在核壳量子点制备方法的第二个实施例中，包括特征B，也即步骤S3完成后，向第二混合液中加入第二定量的第三镉前体，然后再加入第二阴离子前体反应，使得在核壳量子点外包覆上外壳层。由于第三镉前体的反应活性比第二锌前体的反应活性高，相当于外壳层生长过程中，首先生长了与中间壳层晶格匹配度较高的层(组分基本相同)，该层有利于减少中间壳层与外壳层之间的缺陷态，第三镉前体反应完后，第二阴离子前体与第二锌前体反应使得外壳层继续生长。由于外壳层与中间壳层之间的缺陷态减少，有利于外壳层后续材料的厚包，也即提高了外壳层的包覆效率，从而有利于获得荧光效率高、半峰宽窄、稳定性好的核壳量子点。
以第一阴离子前体、第二阴离子前体为硫前体为例，进一步说明第二个实施例与现有技术的区别：现有技术中，在中间壳层外包覆外壳层(也即ZnS壳层)时，不会再加入镉前体；而本实施例在外壳层生长时，先加入第三镉前体，然后再加入第二阴离子前体，第三镉前体、第二阴离子前体以及第二锌前体反应生成的CdZnS包覆在中间壳层外，也即外壳层的内侧为CdZnS层，这一部分可以看做是中间壳层的延续，这一部分的存在可以减少中间壳层外侧的缺陷态，第三镉前体反应完后，第二阴离子前体与第二锌前体继续反应生成ZnS层，ZnS层的内侧为缺陷态较少的层，这使得ZnS层的可包覆厚度增加，从而利于获得稳定性好的核壳量子点。
在核壳量子点制备方法的第三个实施例中，包括特征C，也即步骤S4中，向第二混合液中加入第二阴离子前体以及第三定量的第三镉前体，使得在核壳量子点外包覆上外壳层。值得一提的是，第三镉前体可以是在第二阴离子前体加入的过程中加入到溶液中，也可是在第二阴离子前体完全加入后，再加入到溶液中的。一方面，第三镉前体的反应活性高，第二阴离子前体优先与溶液中 的第三镉前体反应，另一方面，第三镉前体中的镉原子可以通过阳离子交换反应进入到已经生长的外壳层(也即由第二阴离子前体与第二锌前体反应生成的壳层)中，从而使得外壳层内侧的组成与中间壳层的组成相近(均含有镉原子)，增加了外壳层与中间壳层的晶格匹配度，进而有利于减少外壳层生长过程中的缺陷态，也有利于外壳层的继续生长，提高外壳层的包覆效率，从而有利于获得荧光效率高、半峰宽窄、稳定性好的核壳量子点。
以第一阴离子前体、第二阴离子前体为硫前体为例，进一步说明第三个实施例与现有技术的区别：现有技术中，在中间壳层外包覆外壳层(也即ZnS壳层)时，不会再加入镉前体；而本实施例在外壳层生长时，先加入第二阴离子前体与第二锌前体反应，生成的ZnS包覆在中间壳层外，在ZnS壳层生长的过程中，加入第三镉前体，第三镉前体可以通过阳离子交换反应进入到已经生长的ZnS壳层中，将ZnS层转变为CdZnS层，转变后形成的CdZnS层可以看做是中间壳层的延续，这一部分的存在可以减少中间壳层与外壳层之间的缺陷态，第三镉前体反应完后，第二阴离子前体与第二锌前体继续反应生成ZnS层，ZnS层的内侧为缺陷态较少的层，这使得ZnS层的可包覆厚度增加，从而利于获得稳定性好的核壳量子点。
在核壳量子点制备方法的其他实施例中，包括特征A以及B，或者包括特征A以及C，或者包括特征B以及C，或者包括特征A、B以及C。
需要说明的是，在以上各实施例中，步骤S1只要将量子点核(或含有量子点核的溶液)与含有第一镉前体以及第一锌前体的溶液混合即可形成第一混合液，即在实际操作时可以将含有第一镉前体以及第一锌前体的溶液加入到装有量子点核的反应容器中；步骤S2中“向第一混合液中加入第一阴离子前体反应”也可以是向第一阴离子前体中加入第一混合液反应；步骤S3只要将提纯后的核 壳量子点与含有第二锌前体的溶液混合即可，即在实际操作时可以将含有第二锌前体的溶液加入到装有提纯后的核壳量子点的反应容器中。
在一些实施例中，第一混合液中的第一锌前体与第一镉前体的物质的量之比，即为第一锌前体的锌元素与第一镉前体的镉元素的物质的量之比，满足(5:1)～(2000:1)，优选地，第一锌前体的锌元素与第一镉前体的镉元素的物质的量之比为(5:1)～(200:1)，更优选地，第一锌前体锌元素与第一镉前体的镉元素的物质的量之比为(5:1)～(100:1)。
在一些实施例中，第一镉前体与第二镉前体的物质的量之比为(1:2)～(50:1)。
在一些实施例中，第一镉前体与第三镉前体的物质的量之比为(1:2)～(50:1)。
在一些实施例中，步骤S2的反应温度为280～310℃，步骤S4的反应温度为240～310℃。
本发明的实施例中，量子点核为包括II族元素和VI族元素的二元量子点、三元量子点、多元量子点或核壳量子点。例如，量子点核可以是CdSe、CdSeS、CdZnSe、CdZnSeS、CdSe/ZnSe、CdSe/CdZnSe、CdZnSeS/ZnSe、CdSeS/ZnSe等。
在一些实施例中，量子点核的尺寸为3～4.5nm。
本发明的实施例中，可以通过调整第一锌前体与第一镉前体的物质的量之比，或者调整加入的第一阴离子前体的量，来调节核壳量子点荧光峰位。
本发明的实施例中，可以在包覆中间壳层的过程中，通过调节第二镉前体的加入时间来调节核壳量子点的荧光峰位。
本发明的实施例中，可以在包覆外壳层的过程中，通过调节第二阴离子前 体的加入量来调节核壳量子点的荧光峰位。
本发明的实施例中，可以通过改变第一阴离子前体的加入量，来调节中间壳层的厚度。
本发明的实施例中，硫前体可以是但不限于S-ODE溶液、三烷基膦硫、硫醇；硒前体可以是但不限于Se-ODE悬浊液、Se-ODE溶液、三烷基膦硒。
本发明的上述方法制备的核壳量子点的荧光发射波长为600～640nm。
本发明还提供一种量子点光电器件，该量子点光电器件包括由本发明的核壳量子点制备方法制得的核壳量子点。量子点光电器件可以是但不限于液晶显示器、OLED显示器、QLED显示器、电致或光致照明器件等。
0.1mmol/mL Se-ODE悬浊液的配制：将硒粉(0.0237g，0.3mmol，100目或200目)分散到3mL的ODE中，超声5分钟配制成0.1mmol/mL的Se-ODE悬浊液。其他浓度的Se-ODE悬浊液的配制与此类似，只需改变硒粉的量即可。使用前用手摇匀。
2mmol/mL S-TBP(三烷基膦)溶液的配制：称取0.64g S，将其置于20mL带胶塞的玻璃瓶中密封，用惰性气体置换出其中空气，注入10mL的TBP，将此混合物反复振荡超声直至S充分溶解。其他浓度的配制只需改变S的量即可。
0.2mmol/mL油酸镉溶液的配制：称取0.2560g氧化镉(CdO)，5mmol油酸，10mL ODE于三颈烧瓶中，通入惰性气体排气10分钟，升高温度至280℃，得到澄清溶液，停止反应待用。
球形CdSe量子点的合成：将CdO(0.0256g，0.2mmol)、硬脂酸(0.1420g，0.5mmol)和ODE(4mL)放入25mL的三颈烧瓶中，搅拌通气(氩气)10分钟后，升温至280℃，得到澄清溶液，降温至250℃，将1mL浓度为0.1mmol/mL的Se-ODE 悬浊液快速注入到三颈烧瓶中，将反应温度控制在250℃，反应7分钟后，每隔2-3分钟，快速注入0.05mL浓度为0.1mmol/mL的Se-ODE悬浊液，直到量子点的尺寸达到目标尺寸，立即停止加热。在反应过程中，取一定量的反应溶液注入到含有1～2mL甲苯的石英比色皿中，进行紫外可见吸收光谱和荧光光谱的测量，分别制备第一激子吸收峰570nm的CdSe量子点(平均尺寸为3.7nm)以及第一激子吸收峰550nm的CdSe量子点(平均尺寸为3.3nm)。
甲醇：丙酮：氯仿(体积比1:1:1)混合溶液的配置：分别取5mL甲醇、丙酮、氯仿放入20mL的色谱瓶中。
CdSe量子点提纯方法：取1～1.5mL原液，放入容积为4mL的小瓶中，加入2～3mL甲醇、丙酮、氯仿混合液，加热至约50℃，然后以4000转/分钟的速度离心20秒，取出后趁热倒掉上清液；再加入0.5mL甲苯，再次进行同样的沉淀离心过程，趁热倒掉上清液后，加入0.5mL甲苯，加入3mL丙酮，常温离心沉淀，最后将沉淀物溶于一定量的ODE中。
核壳结构量子点提纯方法：取10mL原液于50mL离心管，加入40mL丙酮，加热至约50℃，然后以8000转/分钟的速度高速离心沉淀3分钟，取出后倒掉上清液，将沉淀物溶于一定量的甲苯中。
【实施例1】
中间壳层的包覆：
(1)取4mmol醋酸锌、0.2mmol醋酸镉、4.4g油酸以及15mL ODE加入100mL三颈烧瓶中，在200℃下，通入惰性气体排气30分钟，然后注入提纯好的第一激子吸收峰为570nm、吸光度为50的CdSe量子点溶液，升高温度至300℃；
(2)然后快速注入2mL浓度为0.625mmol/mL的S-TBP溶液，反应1分钟，注入0.25mL浓度为0.2mmol/mL的油酸镉溶液，继续反应2分钟，停止反应迅速降温， 提纯制得的CdSe/CdZnS并溶于1mL的ODE中。
外壳层的包覆：
(3)称取碱式碳酸锌(0.66g，1.2mmol)、2.8g油酸、10mL ODE加入100mL三颈烧瓶中，用惰性气体排气10分钟，升高温度至280℃，得到澄清溶液，然后注入提纯好的CdSe/CdZnS核壳量子点溶液，升高温度至300℃；
(4)然后以25mL/h的速度滴加5mL浓度为0.4mmol/mL的S-TBP溶液，滴加结束后，停止反应。
【实施例2】
实施例2与实施例1的不同之处在于步骤(2)中油酸镉的添加量不同。
实施例2中步骤(2)为：然后快速注入2mL浓度为0.625mmol/mL的S-TBP溶液，反应1分钟，注入0.1mL浓度为0.2mmol/mL的油酸镉溶液，继续反应2分钟，停止反应迅速降温，提纯制得的CdSe/CdZnS并溶于1mL的ODE中。
【实施例3】
实施例3与实施例1的不同之处在于步骤(2)中硫前体的加入量不同。
实施例3中步骤(2)为：然后快速注入2mL浓度为0.5mmol/mL的S-TBP溶液，反应1分钟，注入0.25mL浓度为0.2mmol/mL的油酸镉溶液，继续反应2分钟，停止反应迅速降温，提纯制得的CdSe/CdZnS并溶于1mL的ODE中。
【实施例4】
实施例4与实施例1的不同之处在于步骤(1)中的锌镉摩尔比不同。
实施例4中步骤(1)为：取4mmol醋酸锌、0.1mmol醋酸镉、4.4g油酸以及15mL ODE加入100mL三颈烧瓶中，在200℃下，通入惰性气体排气30分钟，然后注入提纯好的第一激子吸收峰为570nm、吸光度为50的CdSe量子点溶液，升高温度至300℃。
【实施例5】
实施例5与实施例1的不同之处在于步骤(4)中硫前体的加入量不同。
实施例5中步骤(4)为：然后以25mL/h的速度滴加5mL浓度为0.5mmol/mL的S-TBP溶液，滴加结束后，停止反应。
【实施例6】
实施例6与实施例1的不同之处在于步骤(1)中加入量子点核溶液后的反应温度不同。
实施例6中步骤(1)为：取4mmol醋酸锌、0.2mmol醋酸镉、4.4g油酸以及15mL ODE加入100mL三颈烧瓶中，在200℃下，通入惰性气体排气30分钟，然后注入提纯好的第一激子吸收峰为570nm、吸光度为50的CdSe量子点溶液，升高温度至280℃。
【实施例7】
实施例7与实施例1的不同之处在于步骤(3)中加入核壳量子点后的反应温度不同。
实施例7中步骤(3)为：称取碱式碳酸锌(0.66g，1.2mmol)、2.8g油酸、10mL ODE加入100mL三颈烧瓶中，用惰性气体排气10分钟，升高温度至280℃，得到澄清溶液，然后注入提纯好的CdSe/CdZnS核壳量子点溶液，降低温度至260℃。
【实施例8】
实施例8与实施例1的不同之处在于步骤(2)中镉前体的加入时间不同。
实施例8中步骤(2)为：然后快速注入2mL浓度为0.625mmol/mL的S-TBP溶液，反应2分钟，注入0.25mL浓度为0.2mmol/mL的油酸镉溶液，继续反应1分钟，停止反应迅速降温，提纯制得的CdSe/CdZnS并溶于1mL的ODE中。
【实施例9】
实施例9与实施例1的不同之处在于步骤(2)中镉前体的加入时间不同。
实施例9中步骤(2)为：然后快速注入2mL浓度为0.625mmol/mL的S-TBP溶液，反应3分钟后停止反应，迅速降温至200℃，注入0.25mL浓度为0.2mmol/mL的油酸镉溶液，继续反应1分钟，降温至室温提纯制得的CdSe/CdZnS并溶于1mL的ODE中。
【实施例10】
实施例10与实施例1的不同之处在于步骤(4)中还加入镉前体。
实施例10中步骤(4)为：然后以25mL/h的速度滴加5mL浓度为0.4mmol/mL的S-TBP溶液，滴加到一半时，注入0.25mL浓度为0.2mmol/mL的油酸镉溶液，滴加结束后，停止反应。
【实施例11】
中间壳层的包覆：
(1)取4mmol醋酸锌、0.2mmol醋酸镉、4.4g油酸以及15mL ODE加入100mL三颈烧瓶中，在200℃下，通入惰性气体排气30分钟，然后注入提纯好的第一激子吸收峰为570nm、吸光度为50的CdSe量子点溶液，升高温度至300℃；
(2)然后快速注入2mL浓度为0.625mmol/mL的S-TBP溶液，反应3分钟，停止反应迅速降温，提纯制得的CdSe/CdZnS并溶于1mL的ODE中。
外壳层的包覆：
(3)称取碱式碳酸锌(0.66g，1.2mmol)、2.8g油酸、10mL ODE加入100mL三颈烧瓶中，用惰性气体排气10分钟，升高温度至280℃，得到澄清溶液，然后注入提纯好的CdSe/CdZnS核壳量子点溶液，升高温度至300℃；
(4)然后以25mL/h的速度滴加5mL浓度为0.4mmol/mL的S-TBP溶液， 滴加到一半时，注入0.25mL浓度为0.2mmol/mL的油酸镉溶液，滴加结束后，停止反应。
【实施例12】
实施例12与实施例1的不同之处在于步骤(1)中的锌镉摩尔比不同。
实施例12中步骤(1)为：取4mmol醋酸锌、0.3mmol醋酸镉、4.4g油酸以及15mL ODE加入100mL三颈烧瓶中，在200℃下，通入惰性气体排气30分钟，然后注入提纯好的第一激子吸收峰为570nm、吸光度为50的CdSe量子点溶液，升高温度至300℃。
【实施例13】
中间壳层的包覆：
(1)取4mmol醋酸锌、0.6mmol醋酸镉、4.4g油酸以及15mL ODE加入100mL三颈烧瓶中，在200℃下，通入惰性气体排气30分钟，然后注入提纯好的第一激子吸收峰为550nm、吸光度为50的CdSe量子点溶液，升高温度至300℃；
(2)然后快速注入2mL浓度为1.25mmol/mL的S-TBP溶液，反应1分钟，注入0.25mL浓度为0.2mmol/mL的油酸镉溶液，继续反应2分钟，停止反应迅速降温，提纯制得的CdSe/CdZnS并溶于1mL的ODE中。
外壳层的包覆：
(3)称取碱式碳酸锌(0.66g，1.2mmol)、2.8g油酸、10mL ODE加入100mL三颈烧瓶中，用惰性气体排气10分钟，升高温度至280℃，得到澄清溶液，然后注入提纯好的CdSe/CdZnS核壳量子点溶液，升高温度至300℃；
(4)然后以25mL/h的速度滴加5mL浓度为0.4mmol/mL的S-TBP溶液，滴加结束后，停止反应。
【实施例14】
中间壳层的包覆：
(1)取4mmol醋酸锌、0.3mmol醋酸镉、4.4g油酸以及15mL ODE加入100mL三颈烧瓶中，在200℃下，通入惰性气体排气30分钟，然后注入提纯好的第一激子吸收峰为550nm、吸光度为50的CdSe量子点溶液，升高温度至300℃；
(2)然后快速注入2mL浓度为0.625mmol/mL的S-TBP溶液，反应1分钟，注入3mL浓度为0.2mmol/mL的油酸镉溶液，继续反应2分钟，停止反应迅速降温，提纯制得的CdSe/CdZnS并溶于1mL的ODE中。
外壳层的包覆：
(3)称取碱式碳酸锌(0.66g，1.2mmol)、2.8g油酸、10mL ODE加入100mL三颈烧瓶中，用惰性气体排气10分钟，升高温度至280℃，得到澄清溶液，然后注入提纯好的CdSe/CdZnS核壳量子点溶液，升高温度至300℃；
(4)然后以25mL/h的速度滴加5mL浓度为0.4mmol/mL的S-TBP溶液，滴加结束后，停止反应。
【对比例1】
(1)取4mmol醋酸锌、0.3mmol醋酸镉、4.4g油酸以及15mL ODE加入100mL三颈烧瓶中，在200℃下，通入惰性气体排气30分钟，然后注入提纯好的第一激子吸收峰为550nm、吸光度为50的CdSe量子点溶液，升高温度至300℃；
(2)然后快速注入2mL浓度为0.625mmol/mL的S-TBP溶液，反应3分钟，停止反应迅速降温，提纯制得的CdSe/CdZnS并溶于1mL的ODE中；
(3)称取碱式碳酸锌(0.66g，1.2mmol)、2.8g油酸、10mL ODE加入100mL三颈烧瓶中，用惰性气体排气10分钟，升高温度至280℃，得到澄清溶液，然后注入提纯好的CdSe/CdZnS核壳量子点溶液，升高温度至300℃；
(4)然后以25mL/h的速度滴加5mL浓度为0.4mmol/mL的S-TBP溶液， 滴加结束后，停止反应。
图1示出了本申请的实施例14与对比例1的荧光谱图，相比对比例1，实施例14的荧光峰位置发生了红移，表明本申请的制备方法中加入第二镉前体后中间壳层的镉含量增加。
图2示出了本申请的实施例14与对比例1的老化时间和荧光效率关系曲线，从图中可以看到，对比例1制备的量子点经过短时间的老化过程荧光效率下降速度很快，在老化时间250小时左右荧光效率就下降到了与实施例14经过1000小时老化一样的水平，表明本申请的制备方法得到的量子点的老化稳定性好。本领域技术人员所公知的是，一般量子点膜要满足基本应用的要求，老化1000小时要达到效率85％以上。显然对比例1的制备方法得到的量子点不能满足上述要求，无法很好地应用于量子点膜中，但是本申请的制备方法得到的量子点则实现了这个突破。
表1列出了各实施例以及对比例的荧光峰位置、半峰宽、荧光效率。其中量子点荧光效率的检测方法为：利用450nm蓝色LED灯作为背光光谱，利用积分球分别测试蓝色背光光谱和透过量子点复合材料的光谱，利用谱图的积分面积计算量子点发光效率。量子点荧光效率＝(量子点发射峰面积)/(蓝色背光峰面积-透过量子点复合物未被吸收的蓝色峰面积)*100％。
表1
  荧光峰位置(nm) 半峰宽(nm) 荧光效率(％)
实施例1 623 24 91
实施例2 621 26 90
实施例3 620 25 91
实施例4 618 25 88
实施例5 625 27 89
实施例6 622 26 90
实施例7 622 24 92
实施例8 623 25 92
实施例9 623 26 91
实施例10 624 25 90
实施例11 623 25 89
实施例12 626 27 88
实施例13 624 25 90
实施例14 622 26 91
对比例1 620 26 87
为了进一步检测本发明核壳量子点的稳定性，分别用各实施例以及对比例制得的核壳量子点制备量子点膜，对量子点膜进行老化稳定性检测(老化条件，85℃/95％湿度)，测试结果见表2。
表2
Figure PCTCN2020086243-appb-000001
Figure PCTCN2020086243-appb-000002
上述实施方式仅为本发明的优选实施方式，不能以此来限定本发明保护的范围，本领域的技术人员在本发明的基础上所做的任何非实质性的变化及替换均属于本发明所要求保护的范围。

Claims (10)

  1. 一种核壳量子点的制备方法，其特征在于，包括以下步骤：
    S1，将量子点核加入含有第一镉前体以及第一锌前体的溶液中，形成第一混合液；
    S2，向所述第一混合液中加入第一阴离子前体反应，使得在所述量子点核外包覆上中间壳层；
    S3，将所述步骤S2中得到的核壳量子点提纯后加入含有第二锌前体的溶液中，得到第二混合液；
    S4，向所述第二混合液中加入第二阴离子前体反应，使得在所述核壳量子点外包覆上外壳层；
    其中，所述第一阴离子前体以及所述第二阴离子前体分别独立地选自硫前体、硒前体或其组合；
    所述制备方法还包括以下特征A、B、C中的至少一种特征：
    A，在所述步骤S2中，在加入所述第一阴离子前体后再加入第一定量的第二镉前体反应；
    B，所述步骤S3与所述步骤S4之间还包括步骤S3’，向所述第二混合液中加入第二定量的第三镉前体；
    C，在所述步骤S4中，向所述第二混合液中加入第三定量的第三镉前体反应。
  2. 根据权利要求1所述的核壳量子点的制备方法，其特征在于，所述第一混合液中的所述第一锌前体与所述第一镉前体的物质的量之比为(5:1)～ (2000:1)，优选地，所述第一锌前体与所述第一镉前体的物质的量之比为(5:1)～(200:1)。
  3. 根据权利要求1所述的核壳量子点的制备方法，其特征在于，所述第一混合液中的所述第一镉前体与所述步骤S2中的所述第二镉前体的物质的量之比为(1:2)～(50:1)。
  4. 根据权利要求1所述的核壳量子点的制备方法，其特征在于，所述第一混合液中的所述第一镉前体与所述步骤S4中的所述第三镉前体的物质的量之比为(1:2)～(50:1)。
  5. 根据权利要求1-4任一所述的核壳量子点的制备方法，其特征在于，所述步骤S2的反应温度为280～310℃。
  6. 根据权利要求1-4任一所述的核壳量子点的制备方法，其特征在于，所述步骤S4的反应温度为240～310℃。
  7. 根据权利要求1-4任一所述的核壳量子点的制备方法，其特征在于，所述步骤S1中，所述量子点核为包括II族和VI族元素的二元量子点、三元量子点、多元量子点或核壳量子点。
  8. 根据权利要求1-4任一所述的核壳量子点的制备方法，其特征在于，所述量子点核的尺寸为3～4.5nm。
  9. 一种核壳量子点，其特征在于，由权利要求1-8任一所述的核壳量子点的制备方法制得，所述核壳量子点的荧光发射波长为600～640nm。
  10. 一种量子点光电器件，其特征在于，所述量子点光电器件包括由权利要求1-8任一所述的核壳量子点的制备方法制备而成的量子点。
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