A ZnSe (Te) quantum dot and its preparation method, and electroluminescent device

Abstract

The invention discloses a ZnSe (Te) quantum dot, comprising a quantum dot core, wherein the quantum dot core comprises a halogen ion X doped in the quantum dot core. ‑ The quantum dot core includes a cation and an anion, and the halogen ion X ‑ Combined with the cation. The present application obtains ZnSe quantum dots with a fluorescence emission wavelength of more than 430nm and ZnSeTe quantum dots with a fluorescence emission wavelength of more than 480nm by doping halogen X in the core of ZnSe(Te) quantum dots. The quantum dots have high quantum efficiency (≥75%) and can be applied in many fields. In addition, the preparation method of the present application is simple to operate, short reaction time and high efficiency, which meets the needs of large-scale production of quantum dots.

Description

Technical Field

[0001] The invention belongs to the field of quantum dots, and in particular relates to a ZnSe (Te) quantum dot and a preparation method thereof, and an electroluminescent device. Background Art

[0002] In the prior art, the emission wavelength of common ZnSe-based quantum dots is generally less than 430nm, which limits its application in the wavelength range above 430nm. Some researchers have constructed ZnSeTe quantum dots by introducing Te elements, which can extend the emission wavelength of such quantum dots to 532nm, but the quantum yield of quantum dots obtained by this method is not high, which affects the further application of such quantum dots.

[0003] Based on the above problems, it is necessary to develop a new type of ZnSe-based quantum dots and a preparation method thereof to expand the types of current lead-free and cadmium-free quantum dots and at the same time expand the scope of use of ZnSe-based quantum dots. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a ZnSe (Te) quantum dot with an emission wavelength range of 430nm-580nm and a preparation method thereof, which has a high quantum yield and expands the application scope of ZnSe-based quantum dots in the prior art.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The first object of the present invention is to provide a ZnSe (Te) quantum dot, comprising a quantum dot core, wherein the quantum dot core comprises a halogen ion X doped in the quantum dot core. - The quantum dot core includes a cation and an anion, and the halogen ion X - Combined with the cation.

[0007] Specifically, the halogen ion is selected from F - , Cl - Br - ,I - At least one of .

[0008] Specifically, the quantum dot further includes a shell layer coated outside the quantum dot core, and the shell layer is one selected from ZnS, ZnSe, ZnSeS, ZnSe / ZnS and ZnSeS / ZnS.

[0009] Preferably, the quantum dot core is ZnSe, and the emission wavelength of the quantum dot is 430-480 nm.

[0010] Preferably, the quantum dot core is ZnSeTe, and the emission wavelength of the quantum dot is 480-580 nm.

[0011] The second object of the present invention is to provide a method for preparing ZnSe (Te) quantum dots, comprising the following steps:

[0012] S1. Obtaining the quantum dot core as described above;

[0013] S2. mixing the coordination solution of the metal halide with the quantum dot core at a first temperature to obtain a first mixed solution containing the quantum dot core;

[0014] S3. Adding a zinc precursor and a sulfur precursor to the first mixed solution, and coating the quantum dot core with a shell layer at a second temperature to obtain the quantum dot.

[0015] Specifically, the molar ratio of the quantum dot core to the coordination solution of the metal halide is 1:(1-10).

[0016] Specifically, the coordination solution of the metal halide is at least one of an amine, phosphine or carboxylic acid solution of the metal halide;

[0017] Preferably, the coordination solution of the metal halide is a trioctylphosphine or oleylamine solution of the metal halide, and the metal halide is at least one selected from zinc halide, magnesium halide, calcium halide, iron halide or manganese halide.

[0018] Specifically, in S2, the first temperature is 180-320° C., and the concentration of the coordination solution of the metal halide is (0.04-0.4) mol / L.

[0019] Specifically, the molar ratio of the zinc precursor, the sulfur precursor and the quantum dot core is (1.8-3):(1.8-3):1;

[0020] The zinc precursor is at least one selected from zinc carboxylate, zinc halide or organic zinc;

[0021] The sulfur precursor is at least one selected from an organic phosphorus complex of sulfur, a fatty amine compound of sulfur, and a long-chain olefin solution of sulfur;

[0022] The second temperature is 230-320°C.

[0023] The third object of the present invention is to provide an electroluminescent device, comprising a light-emitting layer, wherein the light-emitting layer comprises the ZnSe (Te) quantum dots as described above or the ZnSe (Te) quantum dots prepared by the preparation method as described above.

[0024] Compared with the prior art, the present invention has at least the following advantages:

[0025] The present invention obtains ZnSe quantum dots with a fluorescence emission wavelength of more than 430nm and ZnSeTe quantum dots with a fluorescence emission wavelength of more than 480nm by doping halogen X in the core of ZnSe(Te) quantum dots. The quantum dots have high quantum efficiency (≥75%) and can be applied in many fields. In addition, the preparation method of the present invention is simple to operate, has a short reaction time and high efficiency, and meets the needs of large-scale production of quantum dots. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Attached Figure 1 It is a comparison diagram of the fluorescence emission spectra of Example 2 and Example 3;

[0028] Attached Figure 2 It is a comparison diagram of the fluorescence emission spectra of Example 9 and Example 15. DETAILED DESCRIPTION

[0029] The following will describe the technical solution in the embodiment in detail in combination with the implementation of the present application. It should be noted that the implementation is only a partial method, not all.

[0030] As stated herein, for example, "at least one (individual)" modifies the entire list of elements when preceding or following a list of elements without modifying the individual elements of the list. If not otherwise defined, all terms (including technical and scientific terms) in the specification may be defined as those skilled in the art generally understand. The terms defined in the commonly used dictionaries should be interpreted as being consistent with their meanings in the context of the relevant art and the present disclosure, and may not be interpreted in an ideal manner or too broadly unless clearly defined. In addition, unless explicitly described to the contrary, the wording "including" and the wording "comprising" when used in this specification indicate the presence of the stated features, regions, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components, and / or their collections. Therefore, the above wording will be understood to mean including the stated elements, but not excluding any other elements.

[0031] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. The term "or" means "and / or".

[0032] It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms.

[0033] As used herein, "about" or "approximately" includes the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" may mean that the deviation from the stated value is within one or more standard deviations, or within ±10%, ±5%.

[0034] In the prior art, the emission wavelength of common ZnSe-based quantum dots is generally less than 430nm, which limits its application in the wavelength range above 430nm. Some researchers have constructed ZnSeTe quantum dots by introducing Te elements, which can extend the emission wavelength of such quantum dots to 480nm, but the quantum yield of quantum dots obtained by this method is not high, which affects the further application of such quantum dots. In order to solve the problems of the prior art, the present invention provides a quantum dot and a preparation method thereof.

[0035] The first object of the present invention is to provide a ZnSe (Te) quantum dot, comprising a quantum dot core and a shell layer coated outside the quantum dot core, wherein the quantum dot core comprises a halogen ion X doped in the quantum dot core. - The quantum dot core includes cations and anions, and the halogen ion X - Combined with cations. Specifically, halide ions X - With cation Zn 2+ The dangling bonds of the quantum dot core are passivated. The shell layer is selected from one of ZnS, ZnSe, ZnSeS, ZnSe / ZnS and ZnSeS / ZnS. The halogen ion is selected from F - , Cl - Br - ,I - At least one of the above, wherein the halogen ions in the present invention are derived from a coordination solution of a metal halide.

[0036] The quantum dots of the present application all contain ligands on their surfaces, and the presence of the ligands can keep the quantum dots stable. There are many types of ligands, and any common ligand in the prior art can be used, or an oil-soluble or water-soluble ligand can be selected as needed.

[0037] In one embodiment of the present application, the quantum dot core is ZnSe, the emission wavelength of the quantum dot is 430-480nm, and the quantum yield can be as high as 75%, which overcomes the difficulty in preparing ZnSe-based quantum dots with an emission wavelength of 430-480nm in the prior art.

[0038] In another embodiment of the present application, the quantum dot core is ZnSeTe, the emission wavelength of the quantum dot is 480-580nm, and the quantum yield is ≥75%, which solves the problem of decreased quantum yield when the wavelength is increased in the prior art.

[0039] The present application also provides a method for preparing ZnSe(Te) quantum dots, comprising the following steps:

[0040] S1. Obtain the quantum dot core as above;

[0041] S2. At a first temperature of 180-320° C., mixing the coordination solution of the metal halide with the quantum dot core to obtain a first mixed solution containing the quantum dot core; the molar ratio of the quantum dot core to the coordination solution of the metal halide is 1:(1-10); the concentration of the coordination solution of the metal halide is (0.04-0.4) mol / L;

[0042] S3. Add zinc precursor and sulfur precursor to the first mixed solution, and at a second temperature of 230-320°C, coat the quantum dot core with a shell layer to obtain quantum dots; the molar ratio of the zinc precursor, sulfur precursor and quantum dot core is (1.8-3):(1.8-3):1.

[0043] In the present application, by limiting the molar ratio of the quantum dot core to the coordination solution of the metal halide, the coordination solution of the metal halide reacts fully with the quantum dot core, so that the halogen ions are doped into the quantum dot core and / or the surface, thereby passivating the metal cations and preventing them from being oxidized. When there is too much coordination solution of the metal halide, the solution will emit white light and the quantum yield will be low; when there is too little coordination solution of the metal halide, the halogen ions will not be enough to participate in the reaction, and the requirements of the present invention cannot be met.

[0044] The coordination solution of the metal halide is at least one of an amine, phosphine or carboxylic acid solution of the metal halide; preferably, the coordination solution of the metal halide is a trioctylphosphine or oleylamine solution of the metal halide, and the metal halide is at least one selected from zinc halide, magnesium halide, calcium halide, iron halide or manganese halide.

[0045] The zinc precursor is at least one selected from zinc carboxylate, zinc halide or organic zinc; preferably, the zinc precursor is at least one selected from zinc powder, zinc oxide, zinc chloride, zinc oxalate, zinc acetate, zinc carbonate, zinc stearate, zinc acetylacetonate, diethyl zinc, zinc undecylenate, zinc tetradecanoate and zinc oleate.

[0046] The sulfur precursor is at least one selected from the group consisting of sulfur organic phosphorus complexes, sulfur fatty amine compounds, and sulfur long-chain olefin solutions. Preferably, the sulfur precursor is at least one selected from the group consisting of sulfur powder, sulfur tetradecene solution, sulfur pentadecene solution, sulfur hexadecene solution, sulfur heptadecene solution, sulfur octadecene solution, sulfur n-octylamine solution, sulfur tri-n-octylamine solution, trioctylphosphine sulfur, tributylphosphine sulfur, 1-octanethiol, 1-dodecanethiol, a mixture of 1-octanethiol and tri-n-octylamine, and a mixture of 1-octanethiol and tributylphosphine.

[0047] The wavelength can be increased by doping Te in ZnSe quantum dots, and the mass percentage of doped Te in the present application is not greater than 5%. The present application dopes halogen X in the core of ZnSe (Te) quantum dots, and can obtain ZnSe quantum dots with a fluorescence emission wavelength of more than 430nm and ZnSeTe quantum dots with a fluorescence emission wavelength of more than 480nm, while the quantum efficiency of the quantum dots is not reduced, and the application range of ZnSe (Te) quantum dots can be expanded.

[0048] In the present application, the quantum dot core ZnSe or ZnSeTe can be prepared by any known method or can be commercially obtained. The preparation process of the quantum dot is carried out under an inert gas atmosphere. In some preferred embodiments of the present invention, the inert gas is at least one of nitrogen, argon, etc.

[0049] In some preferred embodiments of the present invention, the method for preparing quantum dots further comprises the steps of precipitating and purifying the prepared quantum dots using a purifying agent. These steps are well-known methods in the art and will not be described in detail here.

[0050] The third object of the present invention is to provide an electroluminescent device, comprising a light-emitting layer, wherein the light-emitting layer comprises the above ZnSe (Te) quantum dots or the ZnSe (Te) quantum dots prepared by the above preparation method.

[0051] An electroluminescent device comprises a light-emitting layer, wherein the light-emitting layer comprises the above ZnSe(Te) quantum dots or the ZnSe(Te) quantum dots prepared by the above preparation method. The light-emitting layer and the electroluminescent device can be prepared by methods known in the art.

[0052] The present application will be described in detail below with reference to specific embodiments.

[0053] Example 1

[0054] This embodiment provides a method for preparing ZnSe / ZnS quantum dots, and the specific steps are as follows:

[0055] S1. Obtain quantum dot core ZnSe;

[0056] S2. At a first temperature of 240 ° C, 2.5mmol 0.1M ZnCl2 TOP solution was mixed with 0.5mmol quantum dot cores and reacted for 30min to obtain a first mixed solution containing quantum dot cores;

[0057] S3. Add 1 mmol zinc stearate and 1 mmol n-dodecyl mercaptan to the first mixed solution, and at a second temperature of 240° C., coat the quantum dot core with a shell layer, purify, and obtain quantum dot ZnSe / ZnS with chlorine doped in the quantum dot core.

[0058] The quantum dots ZnSe / ZnS prepared above are used to prepare the electroluminescent device ITO / PEDOT / TFB / QD / ZnMgO / Al. The preparation method adopts the conventional method in the prior art, which will not be repeated here.

[0059] The quantum dot core ZnSe prepared in Example 1 was cleaned and the Cl content in the quantum dots was measured using the GB / T 34672-2017 method to be 1004.8 ppm.

[0060] Example 2

[0061] This embodiment provides a method for preparing ZnSe / ZnS quantum dots, which is basically the same as that of Embodiment 1, except that, in step S2, 0.5 mmol of 0.1 M ZnCl2 TOP solution is added.

[0062] Example 3

[0063] This embodiment provides a method for preparing ZnSe / ZnS quantum dots, which is basically the same as that of Embodiment 1, except that in step S2, 5 mmol of 0.1 M ZnCl2 TOP solution is added.

[0064] Example 4

[0065] This embodiment provides a method for preparing ZnSe / ZnS quantum dots, which is basically the same as that of Embodiment 1, except that in step S2, the coordination solution of the metal halide is a TOP solution of ZnBr2, so as to obtain quantum dots ZnSe / ZnS with bromine doped in the quantum dot core.

[0066] Example 5

[0067] This embodiment provides a method for preparing ZnSe / ZnS quantum dots, which is basically the same as that of Embodiment 1, except that in step S2, the coordination solution of the metal halide is a TOP solution of ZnI2, so as to obtain quantum dots ZnSe / ZnS with iodine doped in the quantum dot core.

[0068] Example 6

[0069] This embodiment provides a method for preparing ZnSe / ZnS quantum dots, which is basically the same as that of Embodiment 1, except that in step S2, the coordination solution of the metal halide is a 2.5 mmol 0.4 M ZnCl2 oleylamine solution.

[0070] Example 7

[0071] This embodiment provides a method for preparing ZnSe / ZnS quantum dots, which is basically the same as that of Embodiment 1, except that in step S2, the coordination solution of the metal halide is a 2.5 mmol 0.4 M ZnCl2 TOP solution.

[0072] Example 8

[0073] This embodiment provides a method for preparing ZnSe / ZnS quantum dots, which is basically the same as that of Embodiment 1, except that in step S2, the coordination solution of the metal halide is a 2.5 mmol 0.04 M ZnCl2 TOP solution.

[0074] Example 9

[0075] This embodiment provides a method for preparing ZnSeTe / ZnS quantum dots, and the specific steps are as follows:

[0076] S1. obtaining a quantum dot core ZnSeTe, wherein the mass percentage of Te doped in the quantum dot core is 3%;

[0077] S2. At a first temperature of 200 ° C, 3.5mmol 0.1M ZnCl2 TOP solution was mixed with 0.5mmol quantum dot cores and reacted for 30min to obtain a first mixed solution containing quantum dot cores;

[0078] S3. Add 1 mmol zinc stearate and 1 mmol n-dodecyl mercaptan to the first mixed solution, and at a second temperature of 240° C., coat the quantum dot core with a shell layer, purify, and obtain quantum dot ZnSeTe / ZnS with chlorine doped in the quantum dot core.

[0079] The quantum dots ZnSeTe / ZnS prepared above are used to prepare the electroluminescent device ITO / PEDOT / TFB / QD / ZnMgO / Al. The preparation method adopts the conventional method in the prior art, which will not be repeated here.

[0080] Example 10

[0081] This embodiment provides a method for preparing ZnSeTe / ZnS quantum dots, which is basically the same as that of Embodiment 9, except that, in step S2, the reaction is carried out at a first temperature of 180°C.

[0082] Embodiment 11

[0083] This embodiment provides a method for preparing ZnSeTe / ZnS quantum dots, which is basically the same as that of Embodiment 9, except that, in step S2, the reaction is carried out at a first temperature of 320°C.

[0084] Example 12

[0085] This embodiment provides a method for preparing ZnSeTe / ZnS quantum dots, which is basically the same as that of Embodiment 9, except that a TOP solution of 3.5 mmol 0.1 M MgCl2 is selected as the coordination solution of the metal halide.

[0086] Example 13

[0087] This embodiment provides a method for preparing ZnSeTe / ZnS quantum dots, which is basically the same as that of Embodiment 9, except that in step S2, 0.05 mmol of 0.1 M ZnCl2 TOP solution is added.

[0088] Embodiment 14

[0089] This embodiment provides a method for preparing ZnSeTe / ZnS quantum dots, which is basically the same as that of Embodiment 9, except that in step S2, 0.5 mmol of 0.1 M ZnCl2 TOP solution is added.

[0090] Embodiment 15

[0091] This embodiment provides a method for preparing ZnSeTe / ZnS quantum dots, which is basically the same as that of Embodiment 9, except that in step S2, 5 mmol of 0.1 M ZnCl2 TOP solution is added.

[0092] Example 16

[0093] This embodiment provides a method for preparing ZnSeTe / ZnS quantum dots, which is basically the same as that of Embodiment 9, except that in step S1, a quantum dot core ZnSeTe is obtained, wherein the mass percentage of Te doped in the quantum dot core is 1%.

[0094] Comparative Example 1.

[0095] This comparative example provides a method for preparing ZnSe / ZnS quantum dots, and the specific steps are as follows: obtaining a quantum dot core ZnSe; adding 1mmol zinc stearate and 1mmol n-dodecyl mercaptan to 0.5mmol quantum dot core ZnSe, coating the quantum dot body with a shell layer at a second temperature of 240°C, and purifying to obtain quantum dot ZnSe / ZnS.

[0096] Comparative Example 2.

[0097] This comparative example provides a method for preparing ZnSeTe / ZnS quantum dots, and the specific steps are as follows: obtaining 0.5 mmol quantum dot core ZnSeTe; adding 1 mmol zinc stearate and 1 mmol n-dodecyl mercaptan to the quantum dot core ZnSeTe, coating the quantum dot body with a shell layer at a second temperature of 240°C, and purifying to obtain quantum dot ZnSeTe / ZnS.

[0098] The ZnSe(Te) quantum dots (QD) obtained in Examples 1-16 and Comparative Examples 1-2 were respectively prepared into electroluminescent devices ITO / PEDOT / TFB / QD / ZnMgO / Al, and their fluorescence spectra and fluorescence quantum yields were tested.

[0099] The specific test results are shown in the following table:

[0100]

[0101]

[0102] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A quantum dot, comprising a quantum dot core, characterized in that: The quantum dot core is ZnSe, and the emission wavelength of the quantum dot is 430-480nm; or the quantum dot core is ZnSeTe, and the emission wavelength of the quantum dot is 480-580nm; the quantum dot core also includes a halogen ion X doped in the quantum dot core. - , the halogen ion X - Combined with the zinc ions, the halide ions are derived from a coordination solution of a metal halide.

2. The quantum dot according to claim 1, characterized in that: The quantum dot further includes a shell layer coated outside the quantum dot core, and the shell layer is one selected from ZnS, ZnSe, ZnSeS, ZnSe / ZnS and ZnSeS / ZnS.

3. A method for preparing quantum dots, characterized in that: The steps include: S1. Obtaining a ZnSe or ZnSeTe quantum dot core as claimed in any one of claims 1-2; S2. At a first temperature, the metal halide coordination solution is mixed with the ZnSe or ZnSeTe quantum dot core to obtain a first mixed solution containing a quantum dot core; S3. Adding a zinc precursor and a sulfur precursor to the first mixed solution, and coating the quantum dot core with a shell layer at a second temperature to obtain the quantum dot.

4. The method for preparing quantum dots according to claim 3, characterized in that: The feeding molar ratio of the ZnSe or ZnSeTe quantum dot core to the coordination solution of the metal halide is 1:(0.1-10).

5. The method for preparing quantum dots according to claim 3, characterized in that: The coordination solution of the metal halide is at least one of an amine, a phosphine or a carboxylic acid solution of the metal halide.

6. The method for preparing quantum dots according to claim 5, characterized in that: The coordination solution of the metal halide is trioctylphosphine or oleylamine solution of the metal halide, and the metal halide is at least one selected from zinc halide, magnesium halide, calcium halide, iron halide or manganese halide.

7. The method for preparing quantum dots according to claim 3, characterized in that: In S2, the first temperature is 180-320°C, and the concentration of the coordination solution of the metal halide is (0.04-0.4) mol / L.

8. The method for preparing quantum dots according to claim 3, characterized in that: The molar ratio of the zinc precursor, the sulfur precursor and the quantum dot core is (1.8-3):(1.8-3):1; The zinc precursor is at least one selected from zinc carboxylate, zinc halide or organic zinc; The sulfur precursor is at least one selected from an organic phosphorus complex of sulfur, a fatty amine compound of sulfur, and a long-chain olefin solution of sulfur; The second temperature is 230-320°C.

9. An electroluminescent device comprising a light-emitting layer, characterized in that: The light-emitting layer comprises the quantum dots described in any one of claims 1-2 or the quantum dots prepared by the preparation method described in any one of claims 3-8.

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