Quantum dot, preparation method thereof and light-emitting device

Abstract

The invention discloses a quantum dot, a preparation method thereof and a luminescent device, and the preparation method of the quantum dot comprises the following steps: providing a monomolecular source precursor solution, and heating the monomolecular source precursor solution to obtain a sulfur-containing quantum dot core; and forming one or more shell layers on the surface of the sulfur-containing quantum dot core to obtain the quantum dot. The sulfur-containing quantum dots prepared by the method have few core defects, and the defects of the finally generated core-shell quantum dots are reduced.

Description

Technical Field

[0001] This application relates to the field of display technologies, and particularly to a method for preparing quantum dots, quantum dots obtained by the preparation method, and light-emitting devices. Background Art

[0002] In display technologies, the lifetime of quantum dots is determined by their internal structure. There are defects inside the quantum dots, which affect the lifetime of excitons and the efficiency of radiative transitions, resulting in the quenching of excitons.

[0003] Currently, quantum dots include core-shell quantum dots. The quantum dot core usually adopts the hot injection method, which involves injecting an anion precursor liquid into a high-temperature cation precursor solution. Since the contact time between the anion precursor and the cation precursor is short, a large number of defects exist in the quantum dot core, and thus the number of defects in the obtained quantum dots increases. Summary of the Invention

[0004] In view of this, this application provides a sulfur-containing quantum dot core, a preparation method thereof, quantum dots, light-emitting devices, and display devices, aiming to improve the problem of many defects in existing quantum dots.

[0005] The embodiments of this application are implemented as follows. A method for preparing quantum dots includes:

[0006] Providing a single-molecule source precursor solution, where the single-molecule source precursor solution includes a single-molecule source precursor compound, and the single-molecule source precursor compound includes a first metal ion and a first anion.

[0007] Heating the single-molecule source precursor solution to obtain a sulfur-containing quantum dot core.

[0008] Forming one or more layers of shell layers on the surface of the sulfur-containing quantum dot core to obtain quantum dots.

[0009] Among them, the first anion is selected from one or more of formula (I), formula (II), and formula (III), and the structures of formula (I), formula (II), and formula (III) are as follows:

[0010]

[0011]

[0012] Among them, R1, R2, R3, and R4 are independently selected from one of substituted or unsubstituted C1-C24 alkyl groups, C3-C10 cycloalkyl groups, aryl groups with 6 to 24 ring atoms, and heteroaryl groups with 5 to 24 ring atoms.

[0013] The substituted substituent is selected from the group consisting of deuterium, amino group, halogen, hydroxyl group, carboxyl group, nitro group, aldehyde group, cyano group, C1-C6 alkyl group, C1-C6 alkoxy group, C1-C6 alkoxycarbonyl group, and C1-C6 alkyl acyloxy group.

[0014] In some embodiments, R1, R2, R3, and R4 are independently selected from unsubstituted C1-C16 alkyl groups; and / or

[0015] The first metal ion is selected from one or more of zinc ion, cadmium ion, indium ion, lead ion, and mercury ion.

[0016] In some embodiments, the first anion includes one or more of dithiocarbamate, xanthate, and mercaptide;

[0017] Optionally, the dithiocarbamate includes one or more of dimethyldithiocarbamate, diethyldithiocarbamate, dipropyldithiocarbamate, and dibutyldithiocarbamate;

[0018] Optionally, the xanthate includes alkyl xanthate, and the alkyl xanthate includes one or more of methyl xanthate, ethyl xanthate, propyl xanthate, butyl xanthate, tetradecyl xanthate, pentadecyl xanthate, and hexadecyl xanthate;

[0019] Optionally, the mercaptide is selected from one or more of methanethiol, ethanethiol, propanethiol, and dodecanethiol.

[0020] In some embodiments, the single-molecule source precursor solution further includes a second metal ion and / or a second anion source;

[0021] Wherein, the second metal ion is selected from one or more of zinc ion, cadmium ion, indium ion, lead ion, and mercury ion; and / or

[0022] The second anion source includes one or more of a selenium source, a phosphorus source, and an antimony source;

[0023] Optionally, the selenium source includes one or more of elemental selenium, sodium selenide, and potassium selenide;

[0024] Optionally, the phosphorus source includes one or more of elemental phosphorus, trialkylphosphine, tris(trialkylsilyl)phosphine, tris(dialkylsilyl)phosphine, and tris(dialkylamino)phosphine;

[0025] Optionally, the antimony source includes one or more of elemental antimony, antimony tribromide, and antimony chloride.

[0026] In some embodiments, the solvent in the single-molecule source precursor solution includes a coordinating solvent and / or a non-coordinating solvent;

[0027] Optionally, the coordination solvent includes a fatty amine compound having 4 to 30 carbon atoms and / or an acid compound having 4 to 24 carbon atoms. The fatty amine compound includes an alkylamine and / or an alkenylamine. The acid compound includes a fatty acid, and the fatty acid includes an unsaturated fatty acid.

[0028] Preferably, the coordination solvent includes one or more of octylamine, dioctylamine, trioctylamine, oleylamine, oleic acid, linoleic acid, stearic acid, palmitic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, and heptadecenoic acid.

[0029] Optionally, the non-coordination solvent includes a hydrocarbon compound, and the hydrocarbon compound includes an alkene having 6 to 24 carbon atoms and / or an alkane having 6 to 24 carbon atoms.

[0030] Preferably, the non-coordination solvent includes one or more of dodecene, tetradecene, hexadecene, heptadecene, and octadecene.

[0031] In some embodiments, the heating step includes:

[0032] Heating at a first temperature for a first preset time to obtain sulfur-containing quantum dots;

[0033] wherein the first temperature is 200 to 280 °C, and the first preset time is 20 to 120 min.

[0034] In some embodiments, before the heating step, a preheating step is further included, and the preheating step includes:

[0035] Heating at a second temperature for a second preset time;

[0036] wherein the second temperature is 80 to 200 °C, and the second preset time is 20 to 120 min;

[0037] Optionally, before the preheating step, a pretreatment step is further included, and the pretreatment step includes: heating at a third temperature for a third preset time; wherein the third temperature is 25 to 60 °C, and the third preset time is 20 to 120 min.

[0038] Correspondingly, the present application provides a quantum dot, which is prepared by the above preparation method.

[0039] In some embodiments, the material of the sulfur-containing quantum dot core is selected from one or more of ZnS, CdS, InS, PbS, HgS, ZnCdS, ZnInS, ZnPbS, ZnHgS, CdInS, CdPbS, CdHgS, InPbS, InHgS, PbHgS, ZnSeS, CdSeS, InSeS, PbSeS, HgSeS, ZnPS, CdPS, InPS, PbPS, HgPS, ZnSbS, CdSbS, InSbS, PbSbS, HgSbS, ZnCdSeS, ZnInSeS, ZnPbSeS, ZnHgSeS, CdInSeS, CdPbSeS, CdHgSeS, InPbSeS, InHgSeS, PbHgSeS, ZnCdPS, ZnInPS, ZnPbPS, ZnHgPS, CdInPS, CdPbPS, CdHgPS, InPbPS, InHgPS, PbHgPS, ZnCdSbS, ZnInSbS, ZnPbSbS, ZnHgSbS, CdInSbS, CdPbSbS, CdHgSbS, InPbSbS, InHgSbS, PbHgSbS; and / or

[0040] The material of each shell layer is independently selected from one or more of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, SnPbSTe, GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, CuInS2, CuInSe2, AgInS2.

[0041] Correspondingly, the present application provides a light-emitting device, which includes an anode, a light-emitting layer, and a cathode stacked, wherein the light-emitting layer includes the above-mentioned quantum dots.

[0042] Compared with the prior art, the present application has the following advantages:

[0043] In the present application, a sulfur-containing quantum dot core is prepared by setting a single-molecule source precursor solution. Since the single-molecule precursor solution contains a first metal ion and a first anion, the first metal ion and the first anion can react slowly, so that the sulfur-containing quantum dot core has fewer defects, and finally the defects of the generated quantum dots are reduced. Description of the Drawings

[0044] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0045] Figure 1 is a flowchart of the method for preparing quantum dots provided by an embodiment of the present application;

[0046] Figure 2 is a flowchart of the preparation of the single-molecule source precursor compound provided by an embodiment of the present application;

[0047] Figure 3 is a front-emitting device diagram provided by an embodiment of the present application;

[0048] Figure 4 is an inverted-emitting device diagram provided by an embodiment of the present application;

[0049] Figure 5 is a transmission electron microscope image of the sulfur-containing quantum dot core of Example 2 provided by the present invention;

[0050] Figure 6 is a transmission electron microscope image of the sulfur-containing quantum dot core of Example 5 provided by the present invention;

[0051] Figure 7 is a transmission electron microscope image of the sulfur-containing quantum dot core of Comparative Example 1 provided by the present invention;

[0052] Figure 8 is a transmission electron microscope image of the sulfur-containing quantum dot core of Comparative Example 2 provided by the present invention.

[0053] In the figure:

[0054] 100 - light-emitting device, 10 - anode, 20 - light-emitting layer, 30 - cathode, 40 - hole functional layer, 50 - electron functional layer. Detailed Embodiments

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0056] In this application, unless otherwise specified, the orientation terms such as "upper" and "lower" generally refer to the upper and lower directions in the actual use or working state of the device, specifically the drawing direction in the attached drawings; while "inner" and "outer" refer to the outline of the device. Additionally, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are only used as labels without imposing numerical requirements or establishing an order.

[0057] In this application, "and / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Here, A and B can be singular or plural.

[0058] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one item (piece) below" or similar expressions refer to any combination of these items, including any combination of single item (piece) or plural items (pieces). For example, "at least one item (piece) among a, b, or c", or "at least one item (piece) among a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0059] The various embodiments of this application can exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub - ranges and the individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub - ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and the individual numbers within that range, such as 1, 2, 3, 4, 5, and 6, which applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0060] The technical solution of this application is as follows:

[0061] Please refer to Figure 1 , the embodiment of this application provides a method for preparing quantum dots, including:

[0062] Step S11: Provide a single - molecule - source precursor solution, the single - molecule - source precursor solution includes a single - molecule - source precursor compound, and the single - molecule - source precursor compound includes a first metal ion and a first anion.

[0063] Step S12: Heat the single-molecule source precursor solution to obtain a sulfur-containing quantum dot core.

[0064] Step S13: Form one or more shell layers on the surface of the sulfur-containing quantum dot core to obtain quantum dots.

[0065] In step S11:

[0066] Wherein, the first anion is selected from one or more of formula (I), formula (II) and formula (III), and the structures of formula (I), formula (II) and formula (III) are shown as follows:

[0067]

[0068]

[0069] Wherein, R1, R2, R3, R4 are independently selected from one of substituted or unsubstituted C1-C24 alkyl, C3-C10 cycloalkyl, aryl with 6 to 24 ring atoms, and heteroaryl with 5 to 24 ring atoms.

[0070] The substituents of the substituted ones are selected from deuterium, amino group, halogen, hydroxyl group, carboxyl group, nitro group, aldehyde group, cyano group, C1-C6 alkyl, C1-C6 alkoxy group, C1-C6 alkoxycarbonyl group, C1-C6 alkyl acyloxy group.

[0071] Preferably, R1, R2, R3, R4 are independently selected from unsubstituted C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C7 alkyl, C8 alkyl, C9 alkyl, C10 alkyl, C12 alkyl, C14 alkyl, C16 alkyl.

[0072] In some embodiments, the first metal ion is selected from one or more of zinc ion, cadmium ion, indium ion, lead ion and mercury ion.

[0073] In some embodiments, the first anion includes one or more of dithiocarbamate, xanthate and mercaptide. The dithiocarbamate includes one or more of dimethyldithiocarbamate, diethyldithiocarbamate (DDTC), dipropyldithiocarbamate and dibutyldithiocarbamate. The xanthate includes one or more of methylxanthate, ethylxanthate (ex), propylxanthate, butylxanthate, tetradecylxanthate, pentadecylxanthate and hexadecylxanthate. The mercaptide is selected from one or more of methanethiol, ethanethiol, propanethiol and dodecanethiol.

[0074] Specifically, the single-molecule precursor solution of the present application contains a first metal ion and a first anion. The first metal ion and the first anion can react slowly, thereby reducing the defects in the sulfur-containing quantum dot core and ultimately reducing the defects in the quantum dots. At the same time, the elemental molar ratio of the sulfur-containing quantum dot core is consistent with the elemental molar ratio in the single-molecule source solution.

[0075] In some embodiments, the single-molecule source precursor solution further includes a second metal ion and / or a second anion source. Wherein, the first metal ion and the second metal ion are each independently selected from one or more of zinc ions, cadmium ions, indium ions, lead ions, and mercury ions. The second anion source includes one or more of selenium, phosphorus, and antimony. Optionally, the selenium source includes one or more of elemental selenium, sodium selenide, and potassium selenide. Optionally, the phosphorus source includes one or more of elemental phosphorus, trialkylphosphine, tris(trialkylsilyl)phosphine, tris(dialkylsilyl)phosphine, and tris(dialkylamino)phosphine. Optionally, the antimony source includes one or more of elemental antimony, antimony tribromide, and antimony chloride. It should be noted that the above second metal ion and / or second anion source are provided on the basis of the above first metal ion. Here, trialkylphosphine may include triethylphosphine, tributylphosphine, tripropylphosphine, etc.

[0076] In some embodiments, the solvent in the second anion source includes one or more of trioctyl phosphate (TOP), tributyl phosphate (TBP), n-octadecane (ODE), oleylamine (OLAM), and tetramethylsilane (TMS).

[0077] In some embodiments, the second metal ion may further include a first anion, and the first anion includes one or more of acetate, nitrate, halide, phosphate, and carbonate. The halide includes one or more of fluoride ion, chloride ion, bromide ion, and iodide ion.

[0078] In some embodiments, by providing a second anion source on the basis of the first metal ion and the first anion in the present application, the types of elements can be increased, a single-molecule source precursor solution with more element types can be obtained, and then sulfur-containing quantum dot cores with more element types can be obtained, and finally quantum dots with more element types can be obtained.

[0079] In some embodiments, the first metal ion and the second metal ion may be the same and / or different. If the first metal ion and the second metal ion are the same, the ratio of the single-molecule source precursor solution can be adjusted, and then sulfur-containing quantum dot cores with different ratios can be obtained, and finally quantum dots with different ratios can be obtained. If the first metal ion and the second metal ion are different, the types of elements in the single-molecule source precursor solution can be adjusted, and then sulfur-containing quantum dot cores with different element types can be obtained, and finally quantum dots with different element types can be obtained.

[0080] In some embodiments, the solvent in the single-molecule source precursor solution includes a coordinating solvent and / or a non-coordinating solvent.

[0081] The coordinating solvent includes fatty amine compounds having 4 to 30 carbon atoms and / or fatty acid compounds having 4 to 24 carbon atoms in the main chain. For example, fatty amine compounds having 9, 12, 15, 18, 21, or 24 carbon atoms; fatty acid compounds having 6, 12, 13, 14, 15, 16, 18, 20, or 22 carbon atoms in the main chain.

[0082] Among them, the amine compounds include alkylamines and / or alkenylamines, the acid compounds include fatty acids, and the fatty acids include unsaturated fatty acids. Here, the coordinating solvent includes one or more of octylamine, oleylamine (also known as OLAM), oleic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, and heptadecenoic acid.

[0083] The non-coordinating solvent includes hydrocarbon compounds.

[0084] Among them, the hydrocarbon compounds include alkenes having 6 to 24 carbon atoms in the main chain and / or alkanes having 6 to 24 carbon atoms in the main chain. For example, alkenes having 6, 8, 10, 12, 15, 18, 21, or 24 carbon atoms; alkanes having 6, 8, 10, 12, 13, 14, 15, or 16 carbon atoms in the main chain. Here, the non-coordinating solvent includes one or more of hexadecene, heptadecene, octadecene (ODE), and paraffin.

[0085] In some embodiments, when a coordinating solvent and a non-coordinating solvent are used simultaneously, the volume ratio of the coordinating solvent to the non-coordinating solvent is 1:1 to 5. For example, the volume ratio of the coordinating solvent to the non-coordinating solvent is 1:1, 1:2, 1:3, 1:4, or 1:5.

[0086] In some embodiments, before the step of heating the single-molecule source precursor solution, a water and oxygen removal step is further included, and the water and oxygen removal step includes:

[0087] Removing water and oxygen from the solvent and / or the non-coordinating solvent at a fourth temperature, then lowering the temperature to a fifth temperature, adding the single-molecule source precursor solution, and removing water and oxygen at a sixth temperature.

[0088] The fourth temperature is 100 to 150 °C, and the duration at the fourth temperature is 20 to 120 min, which is used to remove water and oxygen and / or impurities in the coordinating solvent and the non-coordinating solvent. For example, the temperature is 110 °C, 123 °C, 128 °C, 136 °C, or 142 °C. The time is 21 min, 25 min, 30 min, 37 min, or 39 min.

[0089] The fifth temperature is 25 to 60 °C, and the duration at the fifth temperature is 20 to 120 min. At the fifth temperature, it can be ensured that the single-molecule source precursor solution does not react. For example, the temperature is 26 °C, 30 °C, 36 °C, 42 °C, 55 °C. The time is 40 min, 60 min, 80 min, 100 min, 110 min.

[0090] The sixth temperature is 25 to 60 °C, and the duration at the sixth temperature is 20 to 120 min, which is used to remove water and oxygen. For example, the temperature is 26 °C, 30 °C, 36 °C, 42 °C, 55 °C. The time is 40 min, 60 min, 80 min, 100 min, 110 min.

[0091] In some embodiments, referring to Figure 2 , the method for preparing the quantum dots further includes a step of preparing a single-molecule source precursor compound, and the step of preparing the single-molecule source precursor compound includes:

[0092] S11a. Provide a sulfur-containing compound and a metal salt, wherein the sulfur-containing compound includes the first anion, and the metal salt includes the first metal ion;

[0093] S12b. Mix the sulfur-containing compound and the metal salt to obtain a single-molecule source precursor compound.

[0094] In step S11a:

[0095] Wherein, the first anion is selected from one or more of formula (I), formula (II) and formula (III), and the structures of formula (I), formula (II) and formula (III) are shown as follows:

[0096]

[0097] Wherein, R1, R2, R3, R4 are independently selected from a substituted or unsubstituted C1-C24 alkyl group, a C3-C10 cycloalkyl group, an aryl group with 6 to 24 ring atoms, and a heteroaryl group with 5 to 24 ring atoms.

[0098] The substituents of the substituted ones are selected from deuterium, amino group, halogen, hydroxyl group, carboxyl group, nitro group, aldehyde group, cyano group, C1-C6 alkyl group, C1-C6 alkoxy group, C1-C6 alkoxycarbonyl group, C1-C6 alkyl acyloxy group.

[0099] Preferably, R1, R2, R3, R4 are independently selected from an unsubstituted C1 alkyl group, C2 alkyl group, C3 alkyl group, C4 alkyl group, C5 alkyl group, C6 alkyl group, C7 alkyl group, C7 alkyl group, C8 alkyl group, C9 alkyl group, C10 alkyl group, C12 alkyl group, C14 alkyl group, C16 alkyl group.

[0100] In some embodiments, the first anion includes one or more of dithiocarbamate, xanthate, and mercaptide. The dithiocarbamate includes one or more of dimethyldithiocarbamate, diethyldithiocarbamate, dipropyldithiocarbamate, and dibutyldithiocarbamate. The xanthate includes alkyl xanthate, and the alkyl xanthate includes one or more of methyl xanthate, ethyl xanthate, propyl xanthate, butyl xanthate, tetradecyl xanthate, pentadecyl xanthate, and hexadecyl xanthate.

[0101] In some embodiments, the sulfur-containing compound includes cations, and the cations include one or more of potassium ions, sodium ions, and lithium ions.

[0102] In some embodiments, the metal salt includes one or more of acetate, nitrate, halide salt, phosphate, and carbonate. The halide salt includes one or more of fluoride salt, chloride salt, bromide salt, and iodide salt.

[0103] In some embodiments, the first metal ion includes one or more of zinc ions, cadmium ions, indium ions, lead ions, and mercury ions.

[0104] In some embodiments, the concentration of the first anion solution is 0.2 - 10 mmol / ml. The concentration of the metal salt solution is 0.1 - 20 mmol / ml. For example, the concentration of the first anion solution is 0.7 mmol / ml, 3 mmol / ml, 5 mmol / ml, 7 mmol / ml, 9 mmol / ml. The salt solution of the metal ion is 5 mmol / ml, 8 mmol / ml, 10 mmol / ml, 12 mmol / ml, 16 mmol / ml, 19 mmol / ml.

[0105] Wherein, the molar ratio of the sulfur-containing compound to the metal salt is 1 - 2:1. For example, the molar ratio is 1.2:1, 1.4:1, 1.6:1, 1.8:1, 1.9:1.

[0106] In step S11b:

[0107] In some embodiments, the mixing method can be stirring, and the mixing time can be 0.5 - 10 h. For example, the time is 3 h, 5 h, 7 h, 8 h, 9 h.

[0108] In some embodiments, the preparation step of the single-molecule source precursor compound further includes: cleaning and drying the single-molecule source precursor compound.

[0109] Optionally, the cleaning includes washing the precipitate with deionized water.

[0110] Optionally, the drying can be drying under room temperature vacuum, and the drying time can be 20 to 24 h. For example, the time can be 21 h, 22 h, 22.5 h, 23 h, 23.5 h.

[0111] In step S12:

[0112] The heating step includes: heating at a first temperature for a first preset time to obtain sulfur-containing quantum dots.

[0113] Among them, the first temperature is 200 to 280 °C, and the first preset time is 20 to 120 min. For example, the temperature can be 210 °C, 230 °C, 240 °C, 250 °C, 260 °C. The time can be 20 min, 40 min, 60 min, 80 min, 120 min, 140 min.

[0114] In this application, reacting at 200 to 280 °C for 10 to 180 min can ripen the first metal ion, the second metal ion, the second anion source, and the first anion, thereby controlling the crystal morphology and quality. At the same time, at this temperature and time, the first metal ion, the second metal ion, the second anion source, and the first anion can be further slowly released.

[0115] In some embodiments, before the heating step, a preheating step is further included, and the preheating step includes: heating at a second temperature for a second preset time.

[0116] Among them, the second temperature is 80 to 200 °C, and the second preset time is 20 to 120 min, which is used to slowly release the first metal ion, the second metal ion, the second anion source, and the first anion. For example, the temperature can be 85 °C, 100 °C, 120 °C, 140 °C, 160 °C. The time is 40 min, 60 min, 80 min, 100 min, 110 min.

[0117] In some embodiments, slowly releasing the first metal ion, the second metal ion, the second anion source, and the first anion at 80 to 200 °C can effectively reduce lattice defects, and can also ensure regular morphology, providing a guarantee for obtaining quantum dots with high fluorescence quantum yield. At the same time, it can also ensure that the proportion of sulfur-containing quantum dots is consistent with the set first metal ion, second metal ion, second anion source, and first anion.

[0118] Specifically, the slow release of the first metal ion, the second metal ion, the second anion source, and the first anion at 80-200 °C can avoid rapid temperature changes during crystal growth, thereby reducing defects such as cracks and dislocations in the crystal. At the same time, the slow release of the first metal ion, the second metal ion, the second anion source, and the first anion at 80-200 °C can also promote the improvement of the crystallinity and order of the crystal, making the internal structure of the crystal more stable and the morphology more regular, so that the quantum dots have better fluorescence properties. In addition, the slow release of the first metal ion, the second metal ion, the second anion source, and the first anion at 80-200 °C can also ensure that the elemental molar ratio of the sulfur-containing quantum dot core is consistent with the set elemental molar ratio of the first metal ion, the second metal ion, the second anion source, and the first anion. This consistency can ensure that the sulfur-containing quantum dot core has higher chemical stability and optical properties, providing better guarantee for practical applications.

[0119] In some embodiments, before the step of preheating, a pretreatment step is further included, and the pretreatment step includes: heating at a third temperature for a third preset time.

[0120] Wherein, the third temperature is 25-60 °C, and the third preset time is 20-120 min, which is used to remove water and oxygen. For example, the temperature is 26 °C, 30 °C, 36 °C, 42 °C, 55 °C. The time is 40 min, 60 min, 80 min, 100 min, 110 min.

[0121] In step S13:

[0122] In some embodiments, the number of shell layers is 1-5 layers. For example, the number of shell layers can be 1 layer, 2 layers, 3 layers, 4 layers, 5 layers.

[0123] In some embodiments, the materials of each shell layer are independently selected from one or more of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, SnPbSTe, GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, CuInS2, and AgInS2.

[0124] The application embodiments further provide a quantum dot, which is prepared by the above preparation method and includes a sulfur-containing quantum dot core and at least one shell layer coated on the outer surface of the sulfur-containing quantum dot core.

[0125] In some embodiments, the material of the sulfur-containing quantum dot core is selected from one or more of ZnS, CdS, InS, PbS, HgS, ZnCdS, ZnInS, ZnPbS, ZnHgS, CdInS, CdPbS, CdHgS, InPbS, InHgS, PbHgS, ZnSeS, CdSeS, InSeS, PbSeS, HgSeS, ZnPS, CdPS, InPS, PbPS, HgPS, ZnSbS, CdSbS, InSbS, PbSbS, HgSbS, ZnCdSeS, ZnInSeS, ZnPbSeS, ZnHgSeS, CdInSeS, CdPbSeS, CdHgSeS, InPbSeS, InHgSeS, PbHgSeS, ZnCdPS, ZnInPS, ZnPbPS, ZnHgPS, CdInPS, CdPbPS, CdHgPS, InPbPS, InHgPS, PbHgPS, ZnCdSbS, ZnInSbS, ZnPbSbS, ZnHgSbS, CdInSbS, CdPbSbS, CdHgSbS, InPbSbS, InHgSbS, PbHgSbS.

[0126] In some embodiments, the sulfur-containing quantum dot core can serve as a luminescent core. For example, the luminescent core emits red light or blue light. Among them, the wavelength range of the red light is 620 - 640 nm, and the wavelength range of the blue light is 460 - 480 nm. For example, the wavelength of the red light is 625 nm, 627 nm, 630 nm, 635 nm, 637 nm. The wavelength range of the blue light is 465 nm, 467 nm, 470 nm, 475 nm, 477 nm.

[0127] In some embodiments, the material of each shell layer is independently selected from one or more of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, SnPbSTe, GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, CuInS2, CuInSe2, AgInS2.

[0128] Please refer to Figure 3 and Figure 4 , this application provides a light-emitting device 100, and the light-emitting device 100 includes an anode 10, a light-emitting layer 20, and a cathode 30 which are stacked, wherein the light-emitting layer 20 includes the above-mentioned quantum dots.

[0129] The materials of the anode 10 and the cathode 30 are independently selected from one or more of indium-doped tin oxide, fluorine-doped tin oxide, antimony-doped tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, indium-doped zinc oxide, magnesium-doped zinc oxide, aluminum-doped magnesium oxide, AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, Ag, Al, Cu, Mo, Au, Pt, Si, Ca, Mg, and Ba.

[0130] The light-emitting device 100 further includes a hole functional layer 40, and the functional layer includes a hole transport layer and / or a hole injection layer. When the hole functional layer 40 includes the hole transport layer and the hole injection layer, the hole injection layer is disposed between the light-emitting layer and the anode, and the hole transport layer is disposed between the light-emitting layer and the hole injection layer.

[0131] The material of the hole transport layer may also be a material known in the art for hole transport layers, and may include, for example, but not limited to, 4,4'-N,N'-dicarbazolyl-biphenyl (CBP), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4”-diamine (α-NPD), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD), poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (Poly-TPD), N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-spiro(spiro-TPD), N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine (DNTPD), 4,4',4'-tris(N-carbazolyl)-triphenylamine (TCTA), 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine (m-MTDATA), poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))] (TFB), poly(N-vinylcarbazole) (PVK) and its derivatives, N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4-4'-diamine (NPB), spiro-NPB, poly(phenylene vinylene) (PPV), poly[2-methoxy-5-(2-ethylhexoxy)-1,4-phenylene vinylene] (MEH-PPV), poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MOMO-PPV), 2,2',7,7'-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-omeTAD), 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline] (TAPC), 1,3-bis(carbazol-9-yl)benzene (MCP), polyaniline, polypyrrole, poly(p-phenylene vinylene), aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, PEDOT:PSS and its derivatives, polymethacrylate and its derivatives, poly(9,9-octylfluorene) and its derivatives, poly(spirofluorene) and its derivatives, doped graphene, undoped graphene, C60, doped or undoped NiO, doped or undoped MoO3, doped or undoped WO3, doped or undoped V2O5, doped or undoped p-type gallium nitride, doped or undoped CrO3, doped or undoped CuO, one or more of them.

[0132] The material of the hole injection layer can be a material known in the art for hole injection layers, and can be selected from, but not limited to, one or more of 2,3,6,7,10,11 - hexacyano - 1,4,5,8,9,12 - hexaazatriphenylene (HAT - CN), PEDOT, PEDOT:PSS, derivatives of PEDOT:PSS doped with s - MoO3 (PEDOT:PSS:s - MoO3), 4,4',4' - tris(N - 3 - methylphenyl - N - phenylamino) triphenylamine (m - MTDATA), tetracyanoquinodimethane (F4 - TCQN), copper phthalocyanine, nickel oxide, molybdenum oxide, tungsten oxide, vanadium oxide, molybdenum sulfide, tungsten sulfide, and copper oxide.

[0133] The light - emitting device 100 further includes an electron - functional layer 50 disposed between the light - emitting layer 20 and the cathode 30, and the electron - functional layer 50 includes one or more of an electron injection layer and an electron transport layer.

[0134] The material of the electron transport layer is a material known in the art for electron transport layers, and can be selected from, but not limited to, one or more of inorganic electron transport materials and organic electron transport materials. The inorganic electron transport materials include, but are not limited to, one or more of doped metal oxide particles, undoped metal oxide particles, ceramic semiconductor materials, IIB - VIA group semiconductor materials, IIIA - VA group semiconductor materials, and IB - IIIA - VIA group semiconductor materials. The metal oxides in the undoped metal oxide particles include, but are not limited to, one or more of ZnO, TiO2, SnO2, ZrO2, Ta2O5. The metal oxides in the doped metal oxides include, but are not limited to, one or more of ZnO, TiO2, SnO2, ZrO2, Ta2O5, Al2O3, and the doping elements in the doped metal oxides include, but are not limited to, one or more of Al, Mg, Li, Mn, Y, La, Cu, Ni, Zr, Ce, In, Ga, Sn. By way of example, the doped metal oxides can be aluminum - doped zinc oxide (AZO), lithium - doped zinc oxide (LZO), magnesium - doped zinc oxide (MZO), tin - doped zinc oxide (Sn - ZnO), etc. The ceramic semiconductor materials include, but are not limited to, barium titanate. The IIB - VIA group semiconductor materials include, but are not limited to, one or more of ZnS, ZnSe, CdS. The IIIA - VA group semiconductor materials include, but are not limited to, one or more of InP, GaP. The IB - IIIA - VIA group semiconductor materials include, but are not limited to, one or more of CuInS, CuGaS. The organic electron transport materials include one or more of quinoxaline compounds, imidazole compounds, triazine compounds, fluorene - containing compounds, and hydroxyquinoline compounds.

[0135] It can be understood that, in addition to the above-mentioned functional layers, the light-emitting device 100 may further be provided with some functional layers that are commonly used in light-emitting devices and are helpful for improving the performance of the light-emitting device, such as an electron blocking layer, a hole blocking layer, and / or an interface modification layer, etc.

[0136] It can be understood that the materials and thicknesses of the respective layers of the light-emitting device 100 can be correspondingly set and adjusted according to the light-emitting requirements of the light-emitting device 100.

[0137] The light-emitting device 100 further includes a substrate (not shown in the figure). The substrate can be a rigid substrate or a flexible substrate. The rigid substrate can be a ceramic material or various glass materials, etc. The flexible substrate can be a substrate formed of materials such as polyimide film (PI) and its derivatives, polyethylene naphthalate (PEN), phosphoenolpyruvate (PEP), or polyphenylene ether resin.

[0138] It can be understood that, referring to Figure 3 and Figure 4 , the light-emitting device 100 can be a normal light-emitting device or an inverted light-emitting device. When the light-emitting device 100 is a normal light-emitting device, the substrate is bonded to the side of the anode away from the light-emitting layer 20. When the light-emitting device 100 is an inverted light-emitting device, the substrate is bonded to the side of the cathode away from the light-emitting layer 20.

[0139] In some embodiments, the preparation method of the light-emitting layer 20 can adopt conventional techniques in the art, such as chemical methods or physical methods. Among them, the chemical methods include chemical vapor deposition method, sequential ionic layer adsorption and reaction method, anodic oxidation method, electrolytic deposition method, coprecipitation method. The physical methods include physical coating method and solution method. Among them, the physical coating method includes: thermal evaporation coating method, electron beam evaporation coating method, magnetron sputtering method, multi-arc ion plating method, physical vapor deposition method, atomic layer deposition method, pulsed laser deposition method, etc.; the solution method can be spin coating method, printing method, inkjet printing method, blade coating method, printing method, dip coating method, immersion method, spraying method, roll coating method, casting method, slot die coating method, and bar coating method, etc.

[0140] In some embodiments, the thickness of the anode 10 is 80-120 nm.

[0141] In some embodiments, the thickness of the cathode 30 can be 50-150 nm.

[0142] In some embodiments, the thickness of the light-emitting layer 20 can be 10-100 nm, for example, 15 nm, 40 nm, 50 nm, 60 nm, 80 nm, 90 nm.

[0143] In some embodiments, the thickness of the electron functional layer 50 can be 15-40 nm.

[0144] In some embodiments, the thickness of the hole functional layer 40 may be 20 to 90 nm. The thickness of the hole injection layer may be 10 to 40 nm, and the hole transport layer may be 10 to 50 nm.

[0145] An embodiment of the present application provides a display device, which may be any electronic product with a display function. The electronic product includes but is not limited to a smart phone, a tablet computer, a laptop computer, a digital camera, a digital video camera, a smart wearable device, a smart weighing electronic scale, a vehicle-mounted display, a television, or an e-book reader. Among them, the smart wearable device may be, for example, a smart bracelet, a smart watch, a virtual reality (VR) helmet, etc.

[0146] The present application will be specifically described below through specific embodiments. The following embodiments are only partial embodiments of the present application and do not limit the present application.

[0147] Embodiment 1

[0148] This embodiment provides a quantum dot. The quantum dot core is CdS, and the quantum dot shell material is CdZnS / ZnS. Among them, the molar ratio of Cd:S in the quantum dot core is 1:4. The preparation method is as follows.

[0149] Under the condition of vigorous stirring, 20 mmol of sodium diethyldithiocarbamate (NaDDTC) is dissolved in 60 ml of aqueous solution, and 10 mmol of Cd(Ac)2·2H2O is dissolved in 100 ml of aqueous solution.

[0150] The sodium diethyldithiocarbamate aqueous solution is gradually dropped into the Cd(AC)2·2H2O aqueous solution, and mixed for 2 h to obtain white Cd(DDTC)2.

[0151] Cd(DDTC)2 is washed with deionized water for 3 times and dried in a vacuum drying oven at room temperature for 24 h.

[0152] 10 ml of oleylamine (OLAM) and 20 ml of octadecene (ODE) are placed in a 100 ml three-necked flask. First, water and oxygen are removed at 100 °C for 30 min, then cooled to 25 °C, and 1 mmol of Cd(DDTC)2 is added. The temperature is raised to 60 °C for 30 min to remove water and oxygen, and a single-molecule source precursor with a Cd:S molar ratio of 1:4 is obtained.

[0153] The single-molecule source precursor with a Cd:S molar ratio of 1:4 is deaerated at 25 °C for 30 min, heated to 150 °C and reacted for 60 min, and then heated to 250 °C and reacted for 80 min to obtain a sulfur-containing quantum dot core of CdS.

[0154] Epitaxial growth of a CdZnS / ZnS shell on a sulfur-containing quantum dot core of CdS.

[0155] Example 2

[0156] This example is basically the same as Example 1, except that the quantum dot core in this example is CdZnS, and the molar ratio of Cd:Zn:S is 3:1:4;

[0157] Under the condition of vigorous stirring, 20 mmol of sodium diethyldithiocarbamate was dissolved in 60 ml of aqueous solution, and 10 mmol of Zn(Ac)2·2H2O was dissolved in 100 ml of aqueous solution;

[0158] The aqueous solution of sodium diethyldithiocarbamate was added dropwise to the aqueous solution of Zn(AC)2·2H2O, and mixed for 2 h to obtain white Zn(DDTC)2;

[0159] The Zn(DDTC)2 was washed with deionized water for 3 times and dried in a vacuum drying oven at room temperature for 24 h;

[0160] 10 ml of oleylamine and 20 ml of octadecene were placed in a 100 ml three-necked flask. First, water and oxygen were removed at 100 °C for 30 min, then cooled to 25 °C, 5 mmol of Zn(DDTC)2 and 15 mmol of Cd(Ac)2 were added, and the temperature was raised to 60 °C for 30 min to remove water and oxygen, obtaining a single-molecule source precursor with a Cd:S molar ratio of 1:4;

[0161] The single-molecule source precursor with a Cd:Zn:S molar ratio of 3:1:4 was deaerated at 25 °C for 30 min, heated to 150 °C and reacted for 60 min, and then heated to 250 °C and reacted for 80 min to obtain a sulfur-containing quantum dot core of CdZnS.

[0162] Example 3

[0163] This example is basically the same as Example 1, except that the quantum dot core in this example is ZnSeS, and the molar ratio of Zn:Se:S is 5:3:20;

[0164] Under the condition of vigorous stirring, 20 mmol of sodium diethyldithiocarbamate was dissolved in 60 ml of aqueous solution, and 10 mmol of Zn(Ac)2·2H2O was dissolved in 100 ml of aqueous solution;

[0165] The aqueous solution of sodium diethyldithiocarbamate was added dropwise to the aqueous solution of Zn(AC)2·2H2O, and mixed for 2 h to obtain white Zn(DDTC)2;

[0166] The Zn(DDTC)2 was washed with deionized water for 3 times and dried in a vacuum drying oven at room temperature for 24 h;

[0167] Put 10 ml of oleylamine and 20 ml of octadecene into a 100 ml three-necked flask. First, remove water and oxygen at 100 °C for 30 min, then cool to 25 °C, add 5 mmol of Zn(DDTC)₂ and 3 mmol of Se / TOP, and heat to 60 °C for 30 min to remove water and oxygen, obtaining a single-source precursor with a molar ratio of Zn:Se:S of 5:3:20;

[0168] Keep the single-source precursor with a molar ratio of Zn:Se:S of 5:3:20 at 25 °C for 30 min to remove water and oxygen, heat to 150 °C and react for 60 min, then heat to 250 °C and react for 80 min to obtain a sulfur-containing quantum dot core of ZnSeS.

[0169] Example 4

[0170] This example is basically the same as Example 1, except that the quantum dot core in this example is CdZnSeS, and the molar ratio of Cd:Zn:Se:S is 1:5:1:20;

[0171] Under the condition of vigorous stirring, dissolve 20 mmol of sodium diethyldithiocarbamate in 60 ml of aqueous solution, and dissolve 10 mmol of Zn(Ac)₂·2H₂O in 100 ml of aqueous solution;

[0172] Dropwise add the aqueous solution of sodium diethyldithiocarbamate into the aqueous solution of Zn(AC)₂·2H₂O and mix for 2 h to obtain white Zn(DDTC)₂;

[0173] Wash the precipitate of Zn(DDTC)₂ with deionized water 3 times and dry it in a vacuum drying oven at room temperature for 24 h;

[0174] Then provide Cd(Ac)₂·2H₂O and Se / TOP;

[0175] Put 10 ml of oleylamine and 20 ml of octadecene into a 100 ml three-necked flask. First, remove water and oxygen at 100 °C for 30 min, then cool to 25 °C, add 1 mmol of Cd(Ac)₂·2H₂O, 5 mmol of Zn(DDTC)₂ and 1 mmol of Se / TOP, and heat to 60 °C for 30 min to remove water and oxygen, obtaining a single-source precursor with a molar ratio of Cd:Zn:Se:S of 1:5:1:20;

[0176] Keep the single-source precursor with a molar ratio of Cd:Zn:Se:S of 1:5:1:20 at 25 °C for 30 min to remove water and oxygen, heat to 150 °C and react for 60 min, then heat to 250 °C and react for 80 min to obtain a sulfur-containing quantum dot core of CdZnSeS.

[0177] Example 5

[0178] This example is basically the same as Example 1, except that in this example, the quantum dot core is CdZnSeS, and the molar ratio of Cd:Zn:Se:S is 1:1:1:1;

[0179] Cd(DDTC)2 was washed with deionized water to precipitate 3 times, dried in a vacuum drying oven at room temperature for 24 h, and then Zn(Ac)2·2H2O and Se / TOP were provided.

[0180] 10 ml of oleylamine and 20 ml of octadecene were placed in a 100 ml three-necked flask. First, water and oxygen were removed at 100 °C for 30 min, then the temperature was lowered to 25 °C, and 1 mmol of Cd(DDTC)2, 3 mmol of Cd(Ac)2·2H2O, 4 mmol of Zn(Ac)2·2H2O, and 4 mmol of Se / TOP were added. The temperature was raised to 60 °C and water and oxygen were removed for 30 min to obtain a single-molecule source precursor with a molar ratio of Cd:Zn:Se:S of 1:1:1:1;

[0181] The single-molecule source precursor with a molar ratio of Cd:Zn:Se:S of 1:1:1:1 was dewatered and deoxygenated at 25 °C for 30 min, the temperature was raised to 150 °C, and the reaction was carried out for 60 min to release cations and anions. Finally, the temperature was raised to 250 °C and the reaction was carried out for 80 min to obtain a sulfur-containing quantum dot core of CdZnSeS.

[0182] Example 6

[0183] This example is basically the same as Example 1, except that in this example, potassium ethyl xanthate was used to replace sodium diethyldithiocarbamate in Example 1 to obtain Cd(ex)2.

[0184] Example 7

[0185] This example is basically the same as Example 1, except that in this example, 80 °C was used to replace 150 °C in Example 1.

[0186] Example 8

[0187] This example is basically the same as Example 1, except that in this example, 200 °C was used to replace 150 °C in Example 1.

[0188] Example 9

[0189] This example is basically the same as Example 5, except that in this example, 80 °C was used to replace 150 °C in Example 1.

[0190] Example 10

[0191] This example is basically the same as Example 5, except that in this example, 200 °C is used to replace 150 °C in Example 1.

[0192] Comparative Example 1

[0193] Mix 0.1 mmol of cadmium oxide, 0.2 mmol of zinc acetate, 1 mL of oleic acid, and 10 mL of octadecene in a vacuum environment at 120 °C for 30 min;

[0194] Under an argon atmosphere, heat up to 280 °C, inject a mixed solution of 0.1 mmol of Se / TOP and 0.2 mmol of S / TOP, and ripen for 20 min to obtain a sulfur-containing quantum dot core of ZnCdSeS;

[0195] Epitaxially grow a CdZnS / ZnS shell layer on the sulfur-containing quantum dot core of ZnCdSeS.

[0196] Comparative Example 2

[0197] Mix 0.4 mmol of cadmium oxide, 0.4 mmol of zinc acetate, 1 mL of oleic acid, and 10 mL of octadecene in a vacuum environment at 120 °C for 30 min;

[0198] Under an argon atmosphere, heat up to 280 °C, inject a n-octylphosphine solution mixed with 0.4 mmol of Se and 0.4 mmol of S, and ripen for 20 min to obtain a sulfur-containing quantum dot core of ZnCdSeS;

[0199] Epitaxially grow a CdZnS / ZnS shell layer on the sulfur-containing quantum dot core of ZnCdSeS.

[0200] Comparative Example 3

[0201] Mix 0.2 mmol of cadmium oxide, 0.4 mmol of zinc acetate, 1 mL of oleic acid, and 10 mL of octadecene in a vacuum environment at 120 °C for 30 min;

[0202] Under an argon atmosphere, heat up to 280 °C, inject a n-octylphosphine solution mixed with 0.4 mmol of S, and ripen for 20 min to obtain a sulfur-containing quantum dot core of ZnCdS;

[0203] Epitaxially grow a CdZnS / ZnS shell layer on the sulfur-containing quantum dot core of ZnCdS.

[0204] Application Example 1

[0205] Provide an ITO anode substrate, where the thickness of the ITO anode is 100 nm;

[0206] Spin-coat PEDOT:PSS on the ITO anode substrate to form a hole injection layer with a thickness of 25 nm;

[0207] Spin-coat TFB on the hole injection layer to form a hole transport layer with a thickness of 20 nm;

[0208] Spin-coat the quantum dots of Example 1 on the hole transport layer to form a light-emitting layer with a thickness of 30 nm;

[0209] Spin-coat zinc oxide on the light-emitting layer to form an electron transport layer with a thickness of 40 nm;

[0210] Evaporate Ag on the electron transport layer to form a cathode with a thickness of 80 nm;

[0211] Encapsulate to obtain a light-emitting device, namely a quantum dot light-emitting diode.

[0212] Apply Examples 2 - 10

[0213] Examples 2 - 10 are basically the same as Example 1, except that in Examples 2 - 10, the quantum dots of Example 1 are respectively replaced by the quantum dots of Examples 2 - 10.

[0214] Apply Comparative Examples 1 - 3

[0215] Comparative Examples 1 - 3 are basically the same as Example 1 of the light-emitting device, except that in Comparative Examples 1 - 3, the quantum dots of Example 1 are respectively replaced by the quantum dots of Comparative Examples 1 - 3.

[0216] Quantum dot light-emitting device testing

[0217] Test the full width at half maximum (FWHM), fluorescence emission wavelength (PL), fluorescence quantum yield (PLQY), external quantum efficiency (EQE), and lifetime (T95@1000 nit) of the light emitted by the light-emitting diodes of Examples 1 - 10 and Comparative Examples 1 - 3.

[0218] The full width at half maximum (FWHM) of the electroluminescent device is obtained by testing and calculating with a Keithley 2400 high-precision digital source meter, an OceanOptic USB2000+ spectrometer, and an LS-160 luminance meter.

[0219] The fluorescence emission wavelength (PL) is obtained by testing and calculating with an F-7000 fluorescence spectrophotometer.

[0220] The fluorescence quantum yield (PLQY) is tested using a steady-state fluorescence spectrometer from Edinburgh Instruments, with the instrument model being FS5 and the accessory for measuring the fluorescence quantum yield being SC-30.

[0221] The test method for the external quantum efficiency (EQE) is as follows:

[0222] The ratio of the number of electron-hole pairs injected into the quantum dots to the number of emitted photons, in %, is an important parameter for measuring the quality of an electroluminescent device and can be obtained by measuring with an EQE optical test instrument. The specific calculation formula is as follows:

[0223]

[0224] Among them, ηe is the optical output coupling efficiency, ηr is the ratio of the number of recombined carriers to the number of injected carriers, χ is the ratio of the number of excitons generating photons to the total number of excitons, K R is the radiation process rate, K NR is the non-radiation process rate.

[0225] Test conditions: Conducted at room temperature, with an air humidity of 30 - 60%.

[0226] The test method for the lifetime T95@1000nit is as follows:

[0227] When the device is driven by a constant current or voltage, the time required for the brightness to decrease to a certain proportion of the maximum brightness. The time when the brightness drops to 95% of the maximum brightness is defined as T95, and this lifetime is the measured lifetime. To shorten the test cycle, the device lifetime test is usually carried out by accelerating the device aging at high brightness, and the lifetime at high brightness is obtained by fitting with an extended exponential decay brightness decay fitting formula. For example, the lifetime at 1000nit is denoted as T95@1000nit. The specific calculation formula is as follows:

[0228]

[0229] Among them, T95 L is the lifetime at low brightness, T95 H is the measured lifetime at high brightness, L H is the device accelerated to the maximum brightness, L L is 1000nit, and A is the acceleration factor.

[0230] Table 1

[0231]

[0232]

[0233] It can be seen from Table 1 that:

[0234] It can be seen from Application Examples 1 to 3 and Application Comparative Example 3 that the fluorescence emission wavelengths of the sulfur-containing quantum dot cores in Application Examples 1 to 3 and Application Comparative Example 3 are all within the wavelength range of blue light. Within the wavelength range of blue light, the fluorescence quantum yield, external quantum efficiency, and lifetime of the light-emitting devices in Application Examples 1 to 3 are higher than those of the fluorescence quantum yield, external quantum efficiency, and lifetime in Application Comparative Example 3. This is because in Application Examples 1 to 3, by using a single-molecule source precursor, the obtained sulfur-containing quantum nuclei have fewer defects, which in turn reduces the defects of the generated core-shell quantum dots, and finally improves the fluorescence quantum yield, external quantum efficiency, and lifetime of the light-emitting devices.

[0235] It can be seen from Application Examples 4 to 10 and Application Comparative Examples 1 to 2 that the fluorescence emission wavelengths of the sulfur-containing quantum dot cores in Application Examples 1 to 3 and Application Comparative Example 3 are all within the wavelength range of red light. Within the wavelength range of red light, the fluorescence quantum yield, external quantum efficiency, and lifetime of the light-emitting devices in Examples 4 to 10 are higher than those of the fluorescence quantum yield, external quantum efficiency, and lifetime in Application Comparative Examples 1 to 2. This is because in Application Examples 4 to 10, by using a single-molecule source precursor, the obtained sulfur-containing quantum nuclei have fewer defects, which in turn reduces the defects of the generated core-shell quantum dots, and finally improves the fluorescence quantum yield, external quantum efficiency, and lifetime of the light-emitting devices.

[0236] It can be seen from Application Examples 7 to 8 and Application Comparative Example 3 that during the heating of the single-molecule source in Application Examples 7 to 8, by slowly releasing cations and anions at 80 to 200 °C, lattice defects can be reduced and the morphology can be ensured to be regular. At the same time, the sulfur-containing quantum nuclei have fewer defects, which in turn reduces the defects of the generated core-shell quantum dots, and finally improves the fluorescence quantum yield, external quantum efficiency, and lifetime of the light-emitting devices. In Application Comparative Example 3, the release of cations and anions is too fast, resulting in an increase in the defects of the sulfur-containing quantum dot cores, and finally shortening the lifetime of the light-emitting devices.

[0237] It can be seen from Application Examples 9 to 10 and Application Comparative Examples 1 to 2 that during the heating of the single-molecule source in Application Examples 9 to 10, by slowly releasing cations and anions at 80 to 200 °C, lattice defects can be reduced and the morphology can be ensured to be regular. At the same time, the sulfur-containing quantum nuclei have fewer defects, which in turn reduces the defects of the generated core-shell quantum dots, and finally improves the fluorescence quantum yield, external quantum efficiency, and lifetime of the light-emitting devices. In Application Comparative Examples 1 to 2, the release of cations and anions is too fast, resulting in an increase in the defects of the sulfur-containing quantum dot cores, and finally shortening the lifetime of the light-emitting devices.

[0238] Please refer to Figures 5 to 8 , Figure 5 which is the transmission electron microscopy (TEM) image of the sulfur-containing quantum dot core of Example 2 provided by the present invention, Figure 6 and is the TEM image of the sulfur-containing quantum dot core of Example 5 provided by the invention, Figure 7TEM image of the sulfur-containing quantum dot core of Comparative Example 1 Figure 8 TEM image of the sulfur-containing quantum dot core of Comparative Example 2. As can be seen from the figure, the morphologies of the sulfur-containing quantum dots prepared in Example 2 and Example 5 are more regular, while those of Comparative Example 1 and Comparative Example 2 are irregular. Compared with Comparative Examples 1-2, the structure inside the crystal of the sulfur-containing quantum dots prepared from the single molecular source precursor solution is more stable, and at the same time, the obtained sulfur-containing quantum dot core has fewer defects.

[0239] The quantum dots, their preparation methods, and light-emitting devices provided in the embodiments of the present application have been introduced in detail above. Specific examples are used herein to elaborate on the principles and implementation manners of the present application. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A method for preparing quantum dots, characterized in that, Comprising: Providing a single-molecule source precursor solution, the single-molecule source precursor solution comprising a single-molecule source precursor compound, the single-molecule source precursor compound comprising a first metal ion and a first anion, Heating the single-molecule source precursor solution to obtain a sulfur-containing quantum dot core; Forming one or more layers of shell on the surface of the sulfur-containing quantum dot core to obtain a quantum dot; Wherein, the first anion is selected from one or more of formula (Ⅰ), formula (Ⅱ) and formula (III), and the structures of formula (Ⅰ), formula (Ⅱ) and formula (III) are shown as follows: Wherein, R1, R2, R3, R4 are independently selected from one of substituted or unsubstituted C1-C24 alkyl, C3-C10 cycloalkyl, aryl with 6 to 24 ring atoms, and heteroaryl with 5 to 24 ring atoms, The substituents of the substituted ones are selected from deuterium, amino group, halogen, hydroxyl group, carboxyl group, nitro group, aldehyde group, cyano group, C1-C6 alkyl, C1-C6 alkoxy group, C1-C6 alkoxycarbonyl group, C1-C6 alkyl acyloxy group.

2. The method for preparing quantum dots according to claim 1, characterized in that, The R1, R2, R3, R4 are independently selected from unsubstituted C1-C16 alkyl; and / or The first metal ion is selected from one or more of zinc ion, cadmium ion, indium ion, lead ion and mercury ion.

3. The method for preparing quantum dots according to claim 2, characterized in that, The first anion comprises one or more of dithiocarbamate, xanthate and thiolate; Optionally, the dithiocarbamate comprises one or more of dimethyldithiocarbamate, diethyldithiocarbamate, dipropyldithiocarbamate and dibutyldithiocarbamate; Optionally, the xanthate comprises alkyl xanthate, and the alkyl xanthate comprises one or more of methyl xanthate, ethyl xanthate, propyl xanthate, butyl xanthate, tetradecyl xanthate, pentadecyl xanthate and hexadecyl xanthate; Optionally, the thiolate is selected from one or more of methanethiol, ethanethiol, propanethiol and dodecanethiol.

4. The method for preparing quantum dots according to claim 1, characterized in that, The single-molecule source precursor solution further comprises a second metal ion and / or a second anion source; Wherein, the second metal ion is selected from one or more of zinc ion, cadmium ion, indium ion, lead ion and mercury ion; and / or The second anion source comprises one or more of selenium source, phosphorus source and antimony source; Optionally, the selenium source comprises one or more of elemental selenium, sodium selenide and potassium selenide; Optionally, the phosphorus source comprises one or more of elemental phosphorus, trialkylphosphine, tris(trialkylsilyl)phosphine, tris(dialkylsilyl)phosphine and tris(dialkylamino)phosphine; Optionally, the antimony source comprises one or more of elemental antimony, antimony tribromide and antimony chloride.

5. The method for preparing quantum dots according to claim 1, characterized in that, The solvent in the single-molecule source precursor solution comprises a coordination solvent and / or a non-coordination solvent; Optionally, the coordination solvent comprises a fatty amine compound with 4 to 30 carbon atoms and / or an acid compound with 4 to 24 carbon atoms, the fatty amine compound comprises an alkylamine and / or an alkenylamine, the acid compound comprises a fatty acid, and the fatty acid comprises an unsaturated acid; Preferably, the coordinating solvent includes one or more of octylamine, dioctylamine, trioctylamine, oleylamine, oleic acid, linoleic acid, stearic acid, palmitic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, and heptadecenoic acid; Optionally, the non-coordinating solvent includes hydrocarbon compounds, and the hydrocarbon compounds include olefins having 6 to 24 carbon atoms and / or alkanes having 6 to 24 carbon atoms; Preferably, the non-coordinating solvent includes one or more of dodecene, tetradecene, hexadecene, heptadecene, and octadecene.

6. The method for preparing quantum dots according to claim 1, characterized in that, The heating step includes: Heating at a first temperature for a first preset time to obtain sulfur-containing quantum dots; Wherein, the first temperature is 200 to 280 °C, and the first preset time is 20 to 120 min.

7. The method for preparing quantum dots according to claim 6, characterized in that, Before the heating step, there is also a preheating step, and the preheating step includes: Heating at a second temperature for a second preset time; Wherein, the second temperature is 80 to 200 °C, and the second preset time is 20 to 120 min; Optionally, before the preheating step, there is also a pretreatment step, and the pretreatment step includes: heating at a third temperature for a third preset time; wherein, the third temperature is 25 to 60 °C, and the third preset time is 20 to 120 min.

8. A quantum dot, characterized in that, The quantum dots are prepared by the preparation method according to any one of claims 1 to 7.

9. The quantum dot according to claim 8, characterized in that, The material of the sulfur-containing quantum dot core is selected from one or more of ZnS, CdS, InS, PbS, HgS, ZnCdS, ZnInS, ZnPbS, ZnHgS, CdInS, CdPbS, CdHgS, InPbS, InHgS, PbHgS, ZnSeS, CdSeS, InSeS, PbSeS, HgSeS, ZnPS, CdPS, InPS, PbPS, HgPS, ZnSbS, CdSbS, InSbS, PbSbS, HgSbS, ZnCdSeS, ZnInSeS, ZnPbSeS, ZnHgSeS, CdInSeS, CdPbSeS, CdHgSeS, InPbSeS, InHgSeS, PbHgSeS, ZnCdPS, ZnInPS, ZnPbPS, ZnHgPS, CdInPS, CdPbPS, CdHgPS, InPbPS, InHgPS, PbHgPS, ZnCdSbS, ZnInSbS, ZnPbSbS, ZnHgSbS, CdInSbS, CdPbSbS, CdHgSbS, InPbSbS, InHgSbS, PbHgSbS; and / or The material of each shell layer is independently selected from one or more of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, SnPbSTe, GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, CuInS2, CuInSe2, AgInS2.

10. A light-emitting device, characterized in that, The light-emitting device includes an anode, a light-emitting layer, and a cathode which are stacked, wherein the light-emitting layer includes the quantum dots according to any one of claims 8 to 9.

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