Quantum dot and purification method thereof, luminescent device and display device

Abstract

The invention discloses a quantum dot and a purification method thereof, a light-emitting device and a display device.The purification method comprises the steps that a to-be-purified quantum dot solution and an ion trapping agent are provided, the to-be-purified quantum dot solution contains the to-be-purified quantum dot, and the ion trapping agent comprises carbon quantum dots with the surfaces connected with ligands; the ligand has a coordination group; mixing the to-be-purified quantum dot solution and the ion trapping agent for reaction to obtain a mixed solution; and separating the mixed solution to obtain the purified quantum dots. According to the method, the carbon quantum dots containing the coordination groups on the surfaces are added into the to-be-purified quantum dot solution, the carbon quantum dots interact with free cations in the solvent to form the adduct, then the adduct is removed, impurity luminescence generated by combination of the free cations with acetic acid, oleic acid and oleylamine ligands is reduced, the luminous efficiency of the quantum dots is improved, and the service life of the quantum dots is prolonged.

Description

Technical Field

[0001] The present application relates to the field of display technologies, and in particular, to a purification method for quantum dots, quantum dots obtained by the purification method, a light-emitting device including the quantum dots, and a display device including the light-emitting device. Background Art

[0002] Quantum dots refer to semiconductor nanocrystals with a particle size smaller than the Bohr radius of their material. The particle size is generally in the range of 1-10 nm. Due to the quantum confinement of electrons and holes, the continuous energy band structure becomes a discrete energy level structure with molecular characteristics and can emit fluorescence when excited. Therefore, quantum dots of different sizes can be simultaneously excited by a light source with a single wavelength. By changing the particle size of the quantum dots, their emission wavelength and Stokes shift can be adjusted. The fluorescence spectrum is narrow and symmetric, and thus quantum dots with various different fluorescence spectrum characteristics can be prepared. Due to their quantum size effect, quantum confinement effect, surface effect, etc., quantum dots have unique optical, electrical, and magnetic properties and have broad application prospects in fields such as light-emitting diodes, solar cells, biological characterization, and photoelectric sensors.

[0003] Quantum dots usually need to be purified before use. However, the purity of the quantum dots obtained by existing quantum dot purification methods is not high enough and needs to be further improved. Summary of the Invention

[0004] In view of this, the present application provides a purification method for quantum dots.

[0005] The embodiments of the present application are implemented as follows:

[0006] In a first aspect, a purification method for quantum dots includes the following steps:

[0007] Provide a quantum dot solution to be purified and an ion capturer. The quantum dot solution to be purified contains quantum dots to be purified, and the ion capturer includes carbon quantum dots with ligands connected to the surface. The ligand has a coordination group;

[0008] Mix and react the quantum dot solution to be purified and the ion capturer to obtain a mixture;

[0009] Separate the mixture to obtain purified quantum dots.

[0010] Optionally, the mass ratio of the carbon quantum dots to the quantum dots to be purified is (0.01-0.03):1; and / or,

[0011] The volume ratio of the ion capturer to the quantum dot solution to be purified is 1:(1-10).

[0012] Optionally, the temperature of the mixing reaction is 20 to 30 °C, and the time of the mixing reaction is 3 to 6 h; and / or,

[0013] the particle size of the quantum dots to be purified is 2 to 10 nm; and / or,

[0014] the particle size of the carbon quantum dots is 2 to 20 nm.

[0015] Optionally, the quantum dot solution to be purified further includes cations, and the cations include one or more of zinc ions, cadmium ions, lead ions, silver ions, indium ions, mercury ions, gallium ions, and copper ions; and / or,

[0016] The structural formula of the ligand is *-L-R, where * is the connection site, L is the linking group, and R is the coordination group;

[0017] L is independently selected from one or more of a single bond, C1-C8 alkylene, C2-C8 alkenylene, and C2-C8 alkynylene; R is independently selected from one or more of a hydroxyl group, a carboxyl group, an aldehyde group, a C1-C4 carbonyl alkyl group, an amino group, and an amide group; and / or,

[0018] The number of the coordination groups is more than 30.

[0019] Optionally, in the ligand, L is selected from a single bond; and / or

[0020] The quantum dot solution to be purified includes a first solvent, and the first solvent includes one or more of n-pentane, n-hexane, cyclopentane, cyclohexane, cyclohexadiene, cyclobenzadiene, and petroleum ether; and / or,

[0021] The ion capturer includes a carbon quantum dot solution, and the carbon quantum dot solution includes carbon quantum dots and a second solvent, and the second solvent includes one or more of methanol, ethanol, isopropanol, butanol, and DMSO; and / or,

[0022] The mass concentration of the quantum dot solution to be purified is 30 mg / mL to 50 mg / mL; and / or,

[0023] The concentration of the carbon quantum dot solution is 0.1 mg / mL to 80 mg / mL.

[0024] Optionally, separating the mixture includes:

[0025] Washing the mixture with a first cleaning agent to obtain a first precipitate;

[0026] Wash the first precipitate with a second cleaning agent, and collect the precipitate to obtain purified quantum dots; wherein, the first cleaning solvent includes a C1-C4 alcohol solvent, and the C1-C4 alcohol solvent is selected from one or more of methanol, ethanol, isopropanol, and butanol; and / or,

[0027] The second cleaning solvent includes an ester solvent, and the ester solvent includes one or more of ethyl acetate, butyl acetate, ethyl butyrate, and methyl acetate.

[0028] Optionally, the quantum dot light material in the quantum dot solution to be purified is selected from at least one of single-structure quantum dots and core-shell structure quantum dot materials; the materials of the single-structure quantum dots, the core materials of the core-shell structure quantum dots, and the shell materials of the core-shell structure quantum dots are each independently selected from at least one of II-VI group compounds, IV-VI group compounds, III-V group compounds, and I-III-VI group compounds. The shell layer of the core-shell structure quantum dots includes one or more layers; the II-VI group compounds are selected from at least one 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, and HgZnSTe; the IV-VI group compounds are selected from at least one of SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, and SnPbSTe; the III-V group compounds are selected from at least one of 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, and InAlPSb; the I-III-VI group compounds are selected from at least one of CuInS2, CuInSe2, and AgInS2.

[0029] In a second aspect, the present application provides a quantum dot, which is prepared by the purification method of the quantum dot as described above.

[0030] In a third aspect, the present application provides a light-emitting device, comprising an anode, a light-emitting layer, and a cathode, wherein the light-emitting layer comprises quantum dots prepared by the preparation method as described above or the quantum dots as described above.

[0031] Optionally, the light-emitting device further comprises a first carrier functional layer disposed between the anode and the light-emitting layer; and / or

[0032] the light-emitting device further comprises a second carrier functional layer disposed between the cathode and the light-emitting layer; and / or

[0033] the first carrier functional layer comprises a hole injection layer and / or a hole transport layer; and / or,

[0034] the second carrier functional layer comprises an electron injection layer and / or an electron transport layer.

[0035] Optionally, the anode and the cathode are independently selected from a metal electrode, a carbon material electrode, a metal oxide electrode, or a composite electrode. The material of the metal electrode is selected from at least one of Ag, Al, Mg, Au, Cu, Mo, Yb, Ca, and Ba. The material of the carbon material electrode is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fiber. The material of the metal oxide electrode is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO. The composite electrode is selected from at least one of 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, and ZnS / Al / ZnS; and / or,

[0036] The materials of the hole transport layer and the hole injection layer are independently selected from at least one of TFB, CuPc, PVK, Poly-TPD, DNTPD, TCATA, TCCA, CBP, TPD, NPB, NPD, PEDOT:PSS, TAPC, MCC, F4-TCNQ, HATCN, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, polyaniline, transition metal oxides, transition metal sulfides, transition metal stannides, doped graphene, undoped graphene, and C60; and / or,

[0037] The materials of the electron transport layer and / or the electron injection layer include inorganic materials and / or organic materials. The inorganic materials are selected from doped or undoped metal oxides, and the metal oxides include one or more of zinc oxide, barium oxide, aluminum oxide, nickel oxide, titanium oxide, tin oxide, tantalum oxide, zirconium oxide, nickel oxide, lithium titanium oxide, aluminum zinc oxide, manganese zinc oxide, tin zinc oxide, lithium zinc oxide, indium tin oxide, cadmium sulfide, zinc sulfide, molybdenum sulfide, tungsten sulfide, copper sulfide, zinc stannide, indium phosphide, gallium phosphide, copper indium sulfide, copper gallium sulfide, and barium titanate. The doping elements include one or more of aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, and gadolinium. The organic materials are selected from one or more of quinoxaline compounds, imidazole compounds, triazine compounds, fluorene-containing compounds, and hydroxyquinoline compounds.

[0038] In a fourth aspect, the present application provides a display device, which includes the above-mentioned light-emitting device. Description of the Drawings

[0039] In order 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 following drawings are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0040] Figure 1 It is a schematic flowchart of a method for purifying quantum dots provided by an embodiment of the present application;

[0041] Figure 2 It is a schematic flowchart of a method for manufacturing a light-emitting device provided by an embodiment of the present application;

[0042] Figure 3 It is a schematic structural diagram of a light-emitting device provided by an embodiment of the present application;

[0043] Figure 4 It is a schematic structural diagram of a light-emitting device provided by an embodiment of the present application;

[0044] Figure 5 It is a schematic structural diagram of a light-emitting device provided by an embodiment of the present application;

[0045] Figure 6 It is a schematic structural diagram of a light-emitting device provided by an embodiment of the present application.

[0046] Reference Numerals:

[0047] 100 - Light-emitting device; 101 - Substrate; 10 - Anode; 20 - First carrier functional layer; 21 - Hole injection layer; 22 - Hole transport layer; 23 - Electron injection layer, 24 - Electron transport layer; 30 - Light-emitting layer; 50 - Second carrier functional layer; 40 - Cathode. Detailed implementation

[0048] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the 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 implementation manners described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0049] In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, specifically the drawing direction in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. In addition, in the description of the present application, the term "including" means "including but not limited to". The terms first, second, third, etc. are only used as labels without imposing a numerical requirement or establishing an order.

[0050] In the present application, "and / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural.

[0051] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one kind", "at least one of the following items (pieces)" 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 of a, b, or c", or, "at least one of 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.

[0052] The various embodiments of the present application may 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 the present application; therefore, it should be considered that the description of the range has specifically disclosed all possible sub-ranges and the individual values within the range. For example, it should be considered that the description of the range 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 the 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.

[0053] The technical solution of the present application is as follows:

[0054] In a first aspect, please refer to Figure 1 , an embodiment of the present application provides a method for purifying quantum dots, including the following steps:

[0055] Step S11: Provide a quantum dot solution to be purified and an ion capturer. The quantum dot solution to be purified contains quantum dots to be purified, and the ion capturer includes carbon quantum dots with ligands connected to the surface, and the ligand has a coordination group;

[0056] Step S12: Mix and react the quantum dot solution to be purified and the ion capturer to obtain a mixture;

[0057] Step S13: Separate the mixture to obtain purified quantum dots.

[0058] Precursors containing metal elements such as cadmium and zinc elements are usually used in the synthesis process of quantum dot materials. After synthesis, the synthesized quantum dots are washed with solvents of different polarities to remove residual Cd 2+ (cadmium ions) and Zn 2+ (zinc ions), but there will still be trace amounts of Cd 2+ and Zn 2+ on the washed quantum dots. These residual metal ion impurities will cause defects on the surface of the quantum dots, and the combination of metal ions with the ligands of the quantum dots (such as acetic acid, oleic acid, oleylamine, etc.) will emit light in the form of impurities, which will lead to a decrease in the performance of the quantum dots, such as fluorescence efficiency.

[0059] The purification method of quantum dots described in this application performs purification treatment by adding carbon quantum dots with coordination groups attached to their surfaces to the quantum dot solution to be purified. On the one hand, the coordination groups on the surface of the carbon quantum dots interact with the free metal ions in the quantum dot solution to be purified to form an adduct, reducing the free cations in the core-shell structure quantum dots. On the other hand, the carbon quantum dots combined with the coordination groups react with the free cations in the solution and are quenched, which are easily removed, without generating impurity luminescence and without affecting the defects on the surface of the quantum dots, thereby achieving the purpose of improving the luminescence efficiency and lifespan of the quantum dots.

[0060] In some embodiments, the mass ratio of the carbon quantum dots to the quantum dots to be purified is (0.01 - 0.03):1. For example, the mass ratio of the carbon quantum dots to the quantum dots to be purified can be 0.01:1, 0.015:1, 0.02:1, 0.025:1, 0.03:1, and values within the range between any two of the above-listed values, etc. Controlling the mass ratio of the carbon quantum dots to the quantum dots to be purified within this range can obtain a better purification effect. Controlling the mass ratio of the carbon quantum dots to the quantum dots to be purified within this range can fully remove the free cations in the quantum dot solution, and at the same time, at this mass ratio, it can avoid the carbon quantum dots and the quantum dots to be purified from interacting with each other and aggregating, thereby ensuring the purification effect.

[0061] Furthermore, the volume ratio of the ion capturer to the quantum dot solution to be purified is 1:(1 - 10). For example, the volume ratio of the ion capturer to the quantum dot solution to be purified can be 1:2, 1:5, 1:7, 1:9, and values within the range between any two of the above-listed values, etc. Controlling the volume ratio of the ion capturer to the quantum dot solution to be purified within this range can fully remove the free cations in the quantum dot solution, and at the same time, at this volume ratio, it can avoid the carbon quantum dots and the quantum dots to be purified from interacting with each other and aggregating, thereby ensuring the purification effect.

[0062] In some embodiments, the temperature for the mixed reaction of the quantum dot solution to be purified and the ion capturer is 20 - 30 °C. For example, the temperature of the mixed reaction can be 22 °C, 24 °C, 25 °C, 27 °C, 28 °C, 29 °C, and values within the range between any two of the above-listed values, etc.

[0063] The time for the mixed reaction of the quantum dot solution to be purified and the ion capturer is 3 - 6 h. For example, the time for the mixed reaction is 3 h, 4 h, 5 h, 6 h, and values within the range between any two of the above-listed values, etc.

[0064] In some embodiments, the particle size of the quantum dots to be purified is 2 to 10 nm. For example, the particle size of the quantum dots to be purified can be 2 nm, 3 nm, 5 nm, 7 nm, 9 nm, and values within the range between any two of the above-listed values, etc.

[0065] In some embodiments, the particle size of the carbon quantum dots is 2 to 20 nm. For example, the particle size of the carbon quantum dots can be 2 nm, 5 nm, 9 nm, 12 nm, 15 nm, 18 nm, and values within the range between any two of the above-listed values, etc.

[0066] In step S11:

[0067] The quantum dots to be purified are quantum dot solutions prepared by a known solution method, that is, quantum dot solutions prepared by mixing a cationic precursor solution and an anionic solution. The quantum dot stock solution contains quantum dots, a first solvent, and cations.

[0068] It can be understood that the cations are the cations remaining in the quantum dot stock solution that did not participate in the reaction during the preparation of the quantum dots. The cations include cations dissolved in the first solvent and / or cations attached to the quantum dots. The cations attached to the quantum dots include cations attached to the surface of the quantum dots as ligands and / or cations adsorbed on the ligands on the surface of the quantum dots.

[0069] The quantum dot solution to be purified also contains cations, which are cation sources known in the art for preparing quantum dots. For example, the cations can include, but are not limited to, one or more of zinc ions, cadmium ions, lead ions, silver ions, indium ions, mercury ions, gallium ions, and copper ions.

[0070] The source of zinc ions in the solution can be, but is not limited to, one or more of zinc oleate, zinc stearate, zinc palmitate, and zinc myristate.

[0071] The source of cadmium ions in the solution can be, but is not limited to, one or more of cadmium oleate, cadmium stearate, cadmium palmitate, and cadmium myristate.

[0072] The source of lead ions in the solution can be, but is not limited to, one or more of lead oleate, lead stearate, lead palmitate, and lead myristate.

[0073] The source of silver ions in the solution can be, but is not limited to, one or more of silver oleate, silver stearate, silver palmitate, and silver myristate.

[0074] The source of indium ions in the solution can be, but is not limited to, one or more of indium oleate, indium stearate, indium palmitate, and indium myristate.

[0075] The source of mercury ions in the solution can be, but is not limited to, one or more of mercury oleate, mercury stearate, mercury palmitate, and mercury myristate.

[0076] The source of gallium ions in the solution can be, but is not limited to, one or more of gallium oleate, gallium stearate, gallium palmitate, and gallium myristate.

[0077] The source of cadmium ions in the solution can be, but is not limited to, one or more of cadmium oleate, cadmium stearate, cadmium palmitate, and cadmium myristate.

[0078] The structural formula of the ligand is *-L-R, where * is the connection site, L is the linking group, and R is the coordination group. L is independently selected from one or more of a single bond, C1-C8 alkylene, C2-C8 alkenylene, and C2-C8 alkynylene; R is independently selected from one or more of a hydroxyl group (*-OH), a carboxyl group (*-COOH), an aldehyde group (*-(C=O)H), a C1-C4 carbonyl alkyl group (*-(C=O)-R'), an amino group (*-NH2), and an amide group (*-(C=O)-NH2).

[0079] It can be understood that "*" is the connection site connected to the surface of the carbon quantum dots. The C1-C8 alkylene, C2-C8 alkenylene, and C2-C8 alkynylene can be straight-chain alkylene, alkenylene, and alkynylene. For example, they can also be branched-chain alkylene, alkenylene, and alkynylene, and can also be alkylene, cycloalkenylene, and alkynylene.

[0080] It can be understood that "alkylene" refers to the group derived by removing two hydrogens from an alkane, that is, the group derived by removing one more hydrogen from an "alkyl" group; "alkenylene" refers to the group derived by removing two hydrogens from an alkene, that is, the group derived by removing one more hydrogen from an "alkenyl" group; "alkynylene" refers to the group derived by removing two hydrogens from an alkyne, that is, the group derived by removing one more hydrogen from an "alkynyl" group.

[0081] In a specific embodiment, when the coordination group on the carbon quantum dots is a carbonyl alkyl group (*-(C=O)-R'), R' is a C1-C4 alkane, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, etc.

[0082] The number of coordination groups is more than 30, for example, 30-50.

[0083] The coordination groups are connected to the surface of the carbon quantum dots. By controlling the type and quantity of the coordination groups within the above ranges, free cations in the quantum dot solution can be fully removed. Meanwhile, within the range of type and quantity, agglomeration of the carbon quantum dots due to excessive interaction with the quantum dots to be purified can be avoided, thus ensuring the purification effect.

[0084] In some embodiments, the quantum dot solution to be purified includes a first solvent, and the first solvent includes one or more of n-pentane, n-hexane, cyclopentane, cyclohexane, cyclohexadiene, cyclobenzadiene, and petroleum ether.

[0085] The ion capturer includes a second solvent, and the second solvent includes one or more of methanol, ethanol, isopropanol, butanol, and DMSO.

[0086] The carbon quantum dots are a carbon quantum dot solution, and the mass concentration of the carbon quantum dot solution is 0.1 mg / mL to 80 mg / mL.

[0087] In some embodiments, the mass concentration of the quantum dot solution to be purified is 30 mg / mL to 50 mg / mL. For example, the mass concentration of the quantum dot solution to be purified can be 30 mg / mL, 35 mg / mL, 40 mg / mL, 45 mg / mL, 50 mg / mL, and values within the range between any two of the above-listed values, etc. By controlling the quantum dot solution to be purified within this mass concentration range, free cations in the quantum dot solution to be purified can be fully removed. Meanwhile, within this mass concentration range, agglomeration of the carbon quantum dots and the quantum dots to be purified due to interaction can be avoided, thus ensuring the purification effect.

[0088] In this embodiment, separating the mixture includes:

[0089] Washing the mixture with a first cleaning agent to obtain a first precipitate. Washing the first precipitate with a second cleaning agent, and collecting the precipitate to obtain purified quantum dots.

[0090] Among them, the first cleaning solvent includes C1-C4 alcohol solvents, and the C1-C4 alcohol solvents are selected from one or more of methanol, ethanol, isopropanol, and butanol.

[0091] The second cleaning solvent includes an ester solvent, and the ester solvent includes one or more of ethyl acetate, butyl acetate, ethyl butyrate, and methyl acetate.

[0092] Washing the mixed solution twice with the first cleaning solvent and the second cleaning solvent can remove the carbon quantum dots and reaction by-products therein, and improve the purity of the finally obtained quantum dots.

[0093] In some embodiments, the quantum dot material in the quantum dot solution to be purified may be selected from, but not limited to, one or more of single-structure quantum dots and core-shell structure quantum dots.

[0094] The quantum dots may include, but are not limited to, one or more of single-structure quantum dots and core-shell structure quantum dots.

[0095] The materials of the single-structure quantum dots, the core materials of the core-shell structure quantum dots, and the shell materials of the core-shell structure quantum dots may be independently selected from, but not limited to, one or more of II-VI group compounds, IV-VI group compounds, III-V group compounds, and I-III-VI group compounds. The shell of the core-shell structure quantum dots includes one or more layers. The II-VI group compounds may include, but are not limited to, 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, and HgZnSTe. The IV-VI group compounds may include, but are not limited to, one or more of SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, and SnPbSTe. The III-V group compounds may include, but are not limited to, one or more of 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, and InAlPSb. The I-III-VI group compounds may include, but are not limited to, one or more of CuInS2, CuInSe2, and AgInS2.

[0096] It is understandable that the materials of the core and the shell of the quantum dots with a core-shell structure can be the same or different. In at least one embodiment, the materials of the core and the shell of the quantum dots with a core-shell structure are different.

[0097] As an example, the quantum dots with a core-shell structure may include, but are not limited to, one or more of CdSe / ZnSe, CdTe / ZnSe, CdZnSe / ZnSe, ZnSe / ZnS, ZnSeTe / ZnS, CdSe / ZnS, CdSe / CdSeS / CdS, InP / ZnSeS / ZnS, CdZnSe / ZnSe / ZnS, CdSeS / ZnSeS / ZnS, CdSe / ZnSe / ZnSCdZnTe / ZnSe, CdSe / CdZnSe / ZnSe, CdSe / CdZnSeS / ZnS, CdTe / CdZnTe / ZnSe, CdTe / CdZnSe / ZnSe, and InP / ZnSe / ZnS.

[0098] In some embodiments, the method further includes the steps of:

[0099] Testing the initial fluorescence quantum yield of the quantum dot solution to be purified;

[0100] Dissolving the purified quantum dots in a hydrocarbon-based solvent and testing the fluorescence quantum yield of the quantum dots after purification; wherein the hydrocarbon-based solvent can be selected from one or more of n-hexane, heptane, and n-octane.

[0101] In some embodiments, in step S12:

[0102] The synthesis steps of the carbon quantum dot solution include:

[0103] Adding a compound containing a coordination group to a solvent containing a carbon source and allowing it to stand at room temperature to obtain a mixture;

[0104] Adding an acid solution to the mixture to adjust the pH to 6.5 - 7.5;

[0105] Drying to obtain a mixture containing carbon quantum dots and by-products, separating and purifying the mixture containing carbon quantum dots and by-products to obtain a carbon quantum dot powder with a coordination group on the surface;

[0106] Dissolving the carbon quantum dot powder with a coordination group on the surface in a non-polar solvent to obtain a carbon quantum dot solution.

[0107] It is understandable that the compound containing a coordination group is used to provide groups such as hydroxyl, carboxyl, carbonyl, amino, and amide groups, and the solution containing a carbon source is used to provide the materials for forming carbon quantum dots.

[0108] In some embodiments, the compound containing a coordination group includes one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, acetic acid, acetic acid, citric acid, benzaldehyde, acetophenone, acetaldehyde, aniline, and dimethylformamide.

[0109] The solvent containing a carbon source includes one or more of formic acid, acetic acid, methanol, ethanol, ethylene glycol, propanol, acetone, amino acids, and dimethylformamide.

[0110] The acid solution includes one or more of sulfuric acid, nitric acid, hydrochloric acid, sulfurous acid, phosphoric acid, acetic acid, carbonic acid, hydrosulfuric acid, etc.

[0111] The non-polar solvent includes one or more of toluene, chlorobenzene, n-hexane, n-octane, decalin, tridecane, and octadecene.

[0112] The addition ratio of the compound containing a coordination group: the solvent containing a carbon source: the acid solution is (6-12):(30-60):1.

[0113] The drying temperature is 80-120 °C.

[0114] It can be understood that the present application does not limit the specific type of the carbon quantum dot solution, as long as the carbon quantum dots containing a coordination group after synthesis can be used in the technical solution of the present application.

[0115] As an example, the synthesis process of the carbon quantum dot solution is as follows:

[0116] Add 8 g of sodium hydroxide to 50 mL of acetone, stir magnetically for 1 h, and then let it stand at room temperature for 120 h.

[0117] After standing, slowly add 1 mol / L hydrochloric acid dropwise to the above mixture to adjust the pH of the mixture to 7;

[0118] Dry the above solution at 80 °C to obtain a mixture of carbon quantum dots and sodium chloride, wash the mixture with ethanol and dry it, and repeat the washing and drying steps 3 times to obtain carbon quantum dot powder;

[0119] Dissolve the carbon quantum dot powder in DMF to prepare a 0.2 mg / mL carbon quantum dot solution.

[0120] Furthermore, the concentration range of the carbon quantum dot solution may not be fixed. Setting it to 0.2 mg / mL in the following examples is only for convenience of calculation, and the concentration of the carbon quantum dot solution can also be other values. Second, the present application also provides a quantum dot prepared by the purification method of the quantum dot described above.

[0121] In a third aspect, a light-emitting device is provided, including an anode, a light-emitting layer, and a cathode; wherein, the light-emitting layer includes quantum dots prepared by the purification method of the quantum dots described in the first aspect above or the quantum dots described in the second aspect above.

[0122] The materials of the cathode and the anode can be any kind known in the art. The materials of the anode and the cathode can be, for example, one or more of metals, carbon materials, and metal oxides. The metal can be, for example, one or more of Ag, Al, Mg, Au, Cu, Mo, Yb, Ca, and Ba; the carbon material can be, for example, one or more of graphite, carbon nanotubes, graphene, and carbon fibers; the metal oxide can be a doped or undoped metal oxide, including one or several of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), magnesium-doped zinc oxide (MZO), and aluminum-doped magnesium oxide (AMO). In addition, the anode and the cathode can also include a composite electrode in which a metal is sandwiched between doped or undoped transparent metal oxides. The composite electrode can be, for example, 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, etc.

[0123] In some embodiments, the light-emitting device further includes a first carrier functional layer disposed between the anode and the light-emitting layer.

[0124] The first carrier functional layer includes a hole injection layer and / or a hole transport layer. It can be understood that when the first carrier functional layer only includes the hole injection layer or the hole transport layer, the hole injection layer or the hole transport layer is disposed on the anode. When the first carrier functional layer includes a hole injection layer and a hole transport layer, the hole injection layer is disposed on the anode, and the hole transport layer is disposed on the hole injection layer.

[0125] It can be understood that the material of the hole transport layer can be selected from organic materials with hole transport ability, including but not limited to TFB, CuPc, PVK, Poly-TPD, DNTPD, TCATA, TCCA, CBP, TPD, NPB, NPD, PEDOT:PSS, TAPC, MCC, F4-TCNQ, HATCN, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, polyaniline, transition metal oxides, transition metal sulfides, transition metal stannides, doped graphene, undoped graphene, and at least one of C60. The material of the hole injection layer is a material known in the art for hole injection layers, including but not limited to TFB, CuPc, PVK, Poly-TPD, DNTPD, TCATA, TCCA, CBP, TPD, NPB, NPD, PEDOT:PSS, TAPC, MCC, F4-TCNQ, HATCN, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, polyaniline, transition metal oxides, transition metal sulfides, transition metal stannides, doped graphene, undoped graphene, and at least one of C60.

[0126] In some embodiments, the light-emitting device further includes a second carrier functional layer disposed between the cathode and the light-emitting layer.

[0127] The second carrier functional layer includes an electron injection layer and / or an electron transport layer. It can be understood that when the second carrier functional layer only includes an electron injection layer or an electron transport layer, the electron injection layer or the electron transport layer is disposed on the quantum dot light-emitting layer. When the second carrier functional layer includes an electron injection layer and an electron transport layer, the electron injection layer is disposed on the quantum dot light-emitting layer, and the electron transport layer is disposed on the electron injection layer.

[0128] It can be understood that the materials of the electron transport layer and / or the electron injection layer include inorganic materials and / or organic materials. The inorganic materials are selected from doped or undoped metal oxides, and the metal oxides include one or more of zinc oxide, barium oxide, aluminum oxide, nickel oxide, titanium oxide, tin oxide, tantalum oxide, zirconium oxide, nickel oxide, lithium titanium oxide, aluminum zinc oxide, manganese zinc oxide, tin zinc oxide, lithium zinc oxide, indium tin oxide, cadmium sulfide, zinc sulfide, molybdenum sulfide, tungsten sulfide, copper sulfide, zinc stannide, indium phosphide, gallium phosphide, copper indium sulfide, copper gallium sulfide, barium titanate. The doped elements include one or more of aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, gadolinium. The organic materials are selected from one or more of quinoxaline compounds, imidazole compounds, triazine compounds, fluorene-containing compounds, hydroxyquinoline compounds. In some embodiments, the thickness of the anode is 20 - 200 nm; the thickness of the hole injection layer is 20 - 200 nm; the thickness of the hole transport layer is 30 - 180 nm; the total thickness of the quantum dot light-emitting layer is 30 - 180 nm. The thickness of the electron transport layer is 10 - 180 nm; the thickness of the cathode is 40 - 190 nm.

[0129] As an example, the thickness of the anode can be 20 nm, 40 nm, 50 nm, 60 nm, 70 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, etc.

[0130] As an example, the thickness of the hole injection layer can be 20 nm, 40 nm, 50 nm, 60 nm, 70 nm, 90 nm, 110 nm, 130 nm, 150 nm, 190 nm, 200 nm, etc.

[0131] As an example, the thickness of the hole transport layer can be 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 90 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, etc.

[0132] As an example, the thickness of the quantum dot light-emitting layer can be 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 900 nm, 110 nm, 130 nm, 160 nm, 180 nm, etc.

[0133] As an example, the thickness of the electron transport layer can be 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 90 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, etc.

[0134] As an example, the thickness of the cathode can be 40 nm, 50 nm, 60 nm, 70 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm, 190 nm, etc.

[0135] In some embodiments, in order to accelerate the forward aging of the device, the freshly prepared device is usually heat-treated at 60 - 150 °C for 1 min - 48 h.

[0136] The methods for forming the anode, hole injection layer, hole transport layer, quantum dot light-emitting layer, electron transport layer, electron injection layer, and cathode can be achieved by conventional techniques in the art, such as chemical methods or physical methods. Among them, chemical methods include chemical vapor deposition, sequential ionic layer adsorption and reaction, anodic oxidation, electrodeposition, and coprecipitation. Physical methods include physical coating methods and solution methods. Among them, physical coating methods include: thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion coating, physical vapor deposition, atomic layer deposition, pulsed laser deposition, etc.; solution methods can be spin coating, printing, inkjet printing, blade coating, printing, dip coating, immersion, spraying, roll coating, casting, slot die coating, and bar coating, etc.

[0137] It can be understood that when the light-emitting device 100 further includes functional layers that are commonly used in light-emitting devices and help improve the performance of the light-emitting device, such as an electron blocking layer, a hole blocking layer, an interface modification layer, etc., the method for preparing the light-emitting device 100 may further include steps of preparing the above functional layers by conventional techniques in the art.

[0138] It can be understood that the materials of the respective layers of the light-emitting device 100 can be adjusted according to the light-emitting requirements of the light-emitting device.

[0139] Please refer to Figure 3 , in some embodiments, the light-emitting device 100 includes a substrate 101, an anode 10, a first carrier functional layer 20, a light-emitting layer 30, a second carrier functional layer 50, and a cathode 40 stacked in sequence. The first carrier functional layer 20 is a hole injection layer or a hole transport layer, and the second carrier functional layer 50 is an electron injection layer or an electron transport layer.

[0140] Please refer to Figure 4 , in some embodiments, the light-emitting device 100 includes a substrate 101, an anode 10, a first carrier functional layer 20, a light-emitting layer 30, and a cathode 40 stacked in sequence. The first carrier functional layer 20 includes a hole injection layer 21 and a hole transport layer 22 stacked in sequence on the anode 10.

[0141] Please refer to Figure 5, in some embodiments, the light-emitting device 100 includes a substrate 101, an anode 10, a first carrier functional layer 20, a light-emitting layer 30, and a cathode 40 stacked in sequence. The first carrier functional layer 20 includes an electron injection layer 23 and an electron transport layer 24 stacked in sequence on the anode 10.

[0142] Please refer to Figure 6 , in some embodiments, the light-emitting device 100 includes a substrate 101, an anode 10, a first carrier functional layer 20, a light-emitting layer 30, a second carrier functional layer 50, and a cathode 40 stacked in sequence. The first carrier functional layer 20 is a hole injection layer 21 and a hole transport layer 22 stacked in sequence on the anode 10, and the second carrier functional layer 50 is an electron transport layer 24 and an electron injection layer 23 stacked in sequence on the light-emitting layer 30.

[0143] The substrate 101, anode 10, first carrier functional layer 20, light-emitting layer 30, cathode 40, and second carrier functional layer 50 are as described above and will not be elaborated here.

[0144] In some embodiments, please refer to Figure 2 , a method for manufacturing a light-emitting device, includes the following steps:

[0145] S21: Provide a substrate, and form an anode on the substrate;

[0146] S22: Form a first carrier functional layer on the anode;

[0147] S23: Form a quantum dot light-emitting layer on the first carrier functional layer, wherein the quantum dot light-emitting layer is formed by quantum dots obtained by the quantum dot purification method described above;

[0148] S24: Form a second carrier functional layer on the quantum dot layer;

[0149] S25: Form a cathode on the second carrier functional layer.

[0150] Fourthly, the present application further provides a display device, and the display device includes the light-emitting device.

[0151] The display device can be any electronic product with a display function, and the electronic product includes but is not limited to a smart phone, a tablet computer, a notebook 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 can be, for example, a smart bracelet, a smart watch, a virtual reality (VR) helmet, etc.

[0152] 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.

[0153] Example 1

[0154] CdSe is provided as a quantum dot solution to be purified. Among them, the initial fluorescence quantum yield of the CdSe quantum dot solution is 50%, and the concentration is 30 mg / mL.

[0155] Take 7.5 mL of a 0.2 mg / mL carbon quantum dot solution and add it to 10 mL of the CdSe quantum dot solution. Start magnetic stirring at room temperature for 5 h to obtain a mixture of carbon quantum dots and CdSe quantum dots; among them, the coordination group of the ligand on the carbon quantum dots is a hydroxyl group.

[0156] Wash the mixture of carbon quantum dots and CdSe quantum dots with ethanol, stir at a speed of 5000 r / min for 2 minutes, pour out the supernatant, then add ethyl acetate, stir at a speed of 5000 r / min for 2 minutes, pour out the supernatant, and dry the precipitate at 80 °C to obtain the purified CdSe quantum dot powder.

[0157] Dissolve the CdSe quantum dot powder in n-octane to obtain a solution with a concentration of 0.1 mg / mL, and test its fluorescence quantum yield to be 60%. The fluorescence quantum yield of the CdSe quantum dots before and after purification has increased by 10%.

[0158] Example 2

[0159] This example is basically the same as Example 1, except that the volume of the carbon quantum dot solution added in this example is 15 mL.

[0160] Example 3

[0161] This example is basically the same as Example 1, except that the volume of the carbon quantum dot solution added in this example is 30 mL.

[0162] Example 4

[0163] This example is basically the same as Example 1, except that the volume of the carbon quantum dot solution added in this example is 45 mL.

[0164] Example 5

[0165] This example is basically the same as Example 1, except that the volume of the carbon quantum dot solution added in this example is 30 mL and the CdSe quantum dot solution is replaced with a CdSe / ZnSe core-shell quantum dot solution, and the coordination group of the ligand on the carbon quantum dots is a carbonyl group.

[0166] Example 6

[0167] This example is basically the same as Example 1, except that the volume of the carbon quantum dot solution added in this example is 30 mL, the CdSe quantum dot solution is replaced with a CdSe / CdZnSe / ZnSe core-shell quantum dot solution, and the coordination group of the ligand on the carbon quantum dot is an amino group.

[0168] Example 7

[0169] This example is basically the same as Example 1, except that the volume of the carbon quantum dot solution added in this example is 30 mL, the CdSe quantum dot solution is replaced with a CdTe / CdZnTe / ZnSe core-shell quantum dot solution, and the coordination groups of the ligand on the carbon quantum dot are a hydroxyl group and a carboxyl group.

[0170] Example 8

[0171] A CdZnSe quantum dot solution is provided, where the initial fluorescence quantum yield of the CdZnSe quantum dot solution is 55% and the concentration is 40 mg / mL.

[0172] Take 10 mL of a 0.2 mg / mL carbon quantum dot solution and add it to 10 mL of the CdZnSe quantum dot solution, and start magnetic stirring at room temperature for 4.5 h to obtain a mixture of carbon quantum dots and CdZnSe quantum dots; among them, the coordination group of the ligand on the carbon quantum dot is a carboxyl group;

[0173] Wash the mixture of carbon quantum dots and CdZnSe quantum dots with ethanol, stir at a speed of 5000 r / min for 2 minutes, pour out the supernatant, then add ethyl acetate, stir at a speed of 5000 r / min for 2 minutes, pour out the supernatant, and dry the precipitate at 80 °C to obtain purified CdSe quantum dot powder;

[0174] Dissolve the CdZnSe quantum dot powder in n-octane to obtain a solution with a concentration of 0.1 mg / mL, and test its fluorescence quantum yield to be 66%. The fluorescence quantum yield of CdSe quantum dots before and after purification has increased by 11%.

[0175] Example 9

[0176] This example is basically the same as Example 9, except that the volume of the carbon quantum dot solution in this example is 20 mL.

[0177] Example 10

[0178] This example is basically the same as Example 9, except that the volume of the carbon quantum dot solution in this example is 40 mL.

[0179] Example 11

[0180] This example is basically the same as Example 9, except that the volume of the carbon quantum dot solution in this example is 60 mL.

[0181] Example 12

[0182] Provide a CdZnSeS quantum dot solution, wherein the initial fluorescence quantum yield of the CdZnSeS quantum dot solution is 58%, and the concentration is 50 mg / mL.

[0183] Take 12.5 mL of a 0.2 mg / mL carbon quantum dot solution and add it to 10 mL of the CdZnSeS quantum dot solution. Start magnetic stirring at room temperature for 4 h to obtain a mixture of carbon quantum dots and CdZnSeS quantum dots; among them, the coordination group of the ligand on the carbon quantum dots is a carboxyl group.

[0184] Wash the mixture of carbon quantum dots and CdZnSeS quantum dots with ethanol, stir at a speed of 5000 r / min for 2 minutes, pour out the supernatant, then add ethyl acetate, stir at a speed of 5000 r / min for 2 minutes, pour out the supernatant, and dry the precipitate at 80 °C to obtain the purified CdZnSeS quantum dot powder.

[0185] Dissolve the CdZnSeS quantum dot powder in n-octane to obtain a solution with a concentration of 0.1 mg / mL, and test its fluorescence quantum yield to be 70%. The fluorescence quantum yield of the CdZnSeS quantum dots before and after purification has increased by 12%.

[0186] Example 13

[0187] This example is basically the same as Example 14, except that the volume of the carbon quantum dot solution in this example is 25 mL.

[0188] Example 14

[0189] This example is basically the same as Example 14, except that the volume of the carbon quantum dot solution in this example is 50 mL.

[0190] Example 15

[0191] This example is basically the same as Example 14, except that the volume of the carbon quantum dot solution in this example is 75 mL.

[0192] Comparative Example 1

[0193] This example is basically the same as Example 1, except that the volume of the added carbon quantum dot solution in this example is 52.5 mL.

[0194] Comparative Example 2

[0195] This example is basically the same as Example 8, except that the volume of the carbon quantum dot solution in this example is 70 mL.

[0196] Comparative Example 3

[0197] This example is basically the same as Example 12, except that the volume of the carbon quantum dot solution in this example is 87.5 mL.

[0198] Comparative Example 4

[0199] This comparative example is basically the same as Example 1, except that no carbon quantum dot solution is added in this comparative example.

[0200] Comparative Example 5

[0201] This comparative example is basically the same as Example 8, except that no carbon quantum dot solution is added in this comparative example.

[0202] Comparative Example 6

[0203] This comparative example is basically the same as Example 12, except that no carbon quantum dot solution is added in this comparative example.

[0204] The fluorescence quantum yields of Examples 1 to 15 and Comparative Examples 1 to 6 were tested using an Edinburgh FS5 fluorescence spectrometer, and the test results were recorded in Table 1. Among them, the test method is as follows:

[0205] The absolute fluorescence yield of the quantum dot solution was measured using an integrating sphere of an Edinburgh FS5 steady-state fluorescence spectrometer. n-Octane was used as the blank solution, and the quantum dot n-octane solution with a concentration of 0.1 mg / mL was tested. After the test, the fluorescence yield of the quantum dots was calculated.

[0206] Table 1:

[0207]

[0208]

[0209] As can be seen from Table 1:

[0210] Compared with the quantum dots of Comparative Examples 1-6, the purified quantum dots of Examples 2-4, 9-10, and 13-15 have a relatively large increase in fluorescence yield, and the increase in fluorescence yield exceeds 30%. This indicates that adding a carbon quantum dot solution with a coordination group on the surface to the quantum dot solution with residual cation precursors, the coordination groups on the carbon quantum dots interact with the free cations to form an adduct and are removed; reducing the impurity luminescence generated by the binding of free cations to the ligands of the quantum dots (such as acetic acid, oleic acid, oleylamine, etc.), and improving the luminescence efficiency of the quantum dots.

[0211] As can be seen from Examples 1-4 and Comparative Examples 1 and 4, Examples 8-11 and Comparative Examples 2 and 5, and Examples 12-15 and Comparative Examples 3 and 6, when the mass ratio of carbon quantum dots to the quantum dots to be purified is controlled within the range of 0.01-0.03:1, there is a good improvement in fluorescence yield. It shows that when the mass ratio of carbon quantum dots to the quantum dots to be purified is within this range, the free cations in the quantum dot solution can be sufficiently removed, the fluorescence yield of the quantum dots can be improved, and at the same time, at this mass ratio, the interaction and aggregation between carbon quantum dots and the quantum dots to be purified can be avoided, thus ensuring the purification effect.

[0212] Referring to Examples 3, 5-7, 10, and 14, different types of quantum dots all have a good improvement in fluorescence yield after purification.

[0213] The quantum dots, their purification methods, light-emitting devices, and display devices provided by the embodiments of the present application have been introduced in detail above. Specific examples are used in this article 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 purification method for quantum dots, characterized in that, It includes the following steps: Providing a quantum dot solution to be purified and an ion capturer, wherein the quantum dot solution to be purified contains quantum dots to be purified, and the ion capturer includes carbon quantum dots with ligands connected to the surface, and the ligands have coordination groups; Mixing and reacting the quantum dot solution to be purified and the ion capturer to obtain a mixture; Separating the mixture to obtain purified quantum dots.

2. The purification method according to claim 1, wherein, The mass ratio of the carbon quantum dots to the quantum dots to be purified is (0.01 - 0.03):1; and / or, The volume ratio of the ion capturer to the quantum dot solution to be purified is 1:(1 - 10).

3. The purification method according to claim 1, characterized in that, The temperature of the mixing reaction is 20 - 30 °C, and the time of the mixing reaction is 3 - 6 h; and / or, The particle size of the quantum dots to be purified is 2 - 10 nm; and / or, The particle size of the carbon quantum dots is 2 - 20 nm.

4. The purification method according to any one of claims 1 to 3, characterized in that, The quantum dot solution to be purified further includes cations, and the cations include one or more of zinc ions, cadmium ions, lead ions, silver ions, indium ions, mercury ions, gallium ions, and copper ions; and / or, The structural formula of the ligand is *-L-R, where * is the connection site, L is the linking group, and R is the coordination group; L is independently selected from one or more of a single bond, C1 - C8 alkylene, C2 - C8 alkenylene, and C2 - C8 alkynylene; R is independently selected from one or more of a hydroxyl group, a carboxyl group, an aldehyde group, a C1 - C4 carbonyl alkyl group, an amino group, and an amide group; and / or, The number of the coordination groups is more than 30.

5. The purification method according to claim 4, wherein, In the ligand, L is selected from a single bond; and / or The quantum dot solution to be purified includes a first solvent, and the first solvent includes one or more of n-pentane, n-hexane, cyclopentane, cyclohexane, cyclohexadiene, cyclobenzadiene, and petroleum ether; and / or, The ion capturer includes a carbon quantum dot solution, and the carbon quantum dot solution includes carbon quantum dots and a second solvent, and the second solvent includes one or more of methanol, ethanol, isopropanol, butanol, and DMSO; and / or, The mass concentration of the quantum dot solution to be purified is 30 mg / mL - 50 mg / mL; and / or, The concentration of the carbon quantum dot solution is 0.1 mg / mL - 80 mg / mL.

6. The purification method according to any one of claims 1 - 3, wherein, The separating of the mixture includes: cleaning the mixture with a first cleaning solvent to obtain a first precipitate; Cleaning the first precipitate with a second cleaning solvent, and collecting the precipitate to obtain purified quantum dots; wherein the first cleaning solvent includes C1 - C4 alcohol solvents, and the C1 - C4 alcohol solvents are selected from one or more of methanol, ethanol, isopropanol, and butanol; and / or The second cleaning solvent includes ester solvents, and the ester solvents include one or more of ethyl acetate, butyl acetate, ethyl butyrate, and methyl acetate.

7. The purification method according to claim 1, characterized in that, The quantum dot light materials in the quantum dot solution to be purified are selected from at least one of single-structure quantum dots and core-shell structure quantum dot materials; the materials of the single-structure quantum dots, the core materials of the core-shell structure quantum dots, and the shell materials of the core-shell structure quantum dots are each independently selected from at least one of II-VI group compounds, IV-VI group compounds, III-V group compounds, and I-III-VI group compounds. The shell layer of the core-shell structure quantum dots includes one or more layers; the II-VI group compounds are selected from at least one 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, and HgZnSTe; the IV-VI group compounds are selected from at least one of SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, and SnPbSTe; the III-V group compounds are selected from at least one of 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, and InAlPSb; the I-III-VI group compounds are selected from at least one of CuInS2, CuInSe2, and AgInS2.

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

9. A light-emitting device, characterized in that, It includes an anode, a light-emitting layer, and a cathode. The light-emitting layer includes the quantum dots obtained by the purification method according to any one of claims 1 to 7 or the quantum dots according to claim 8.

10. The light-emitting device according to claim 9, wherein, The light-emitting device further includes a first carrier functional layer disposed between the anode and the light-emitting layer; and / or The light-emitting device further includes a second carrier functional layer disposed between the cathode and the light-emitting layer; and / or The first carrier functional layer includes a hole injection layer and / or a hole transport layer; and / or, The second carrier functional layer includes an electron injection layer and / or an electron transport layer.

11. The light-emitting device according to claim 10, wherein, The anode and the cathode are independently selected from a metal electrode, a carbon material electrode, a metal oxide electrode, or a composite electrode. The material of the metal electrode is selected from at least one of Ag, Al, Mg, Au, Cu, Mo, Yb, Ca, and Ba. The material of the carbon material electrode is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fiber. The material of the metal oxide electrode is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO. The composite electrode is selected from at least one of 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, and ZnS / Al / ZnS; and / or, the materials of the hole transport layer and the hole injection layer are independently selected from at least one of TFB, CuPc, PVK, Poly-TPD, DNTPD, TCATA, TCCA, CBP, TPD, NPB, NPD, PEDOT:PSS, TAPC, MCC, F4-TCNQ, HATCN, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, polyaniline, transition metal oxides, transition metal sulfides, transition metal stannides, doped graphene, undoped graphene, and C60; and / or, The material of the electron transport layer and / or the electron injection layer includes an inorganic material and / or an organic material. The inorganic material is selected from doped or undoped metal oxides. The metal oxides include one or more of zinc oxide, barium oxide, aluminum oxide, nickel oxide, titanium oxide, tin oxide, tantalum oxide, zirconium oxide, nickel oxide, lithium titanium oxide, aluminum zinc oxide, manganese zinc oxide, tin zinc oxide, lithium zinc oxide, indium tin oxide, cadmium sulfide, zinc sulfide, molybdenum sulfide, tungsten sulfide, copper sulfide, zinc tin, indium phosphide, gallium phosphide, copper indium sulfide, copper gallium sulfide, and barium titanate. The doped elements include one or more of aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, and gadolinium. The organic material is selected from one or more of quinoxaline compounds, imidazole compounds, triazine compounds, fluorene-containing compounds, and hydroxyquinoline compounds.

12. A display device, characterized in that, The display device includes the light-emitting device according to any one of claims 9 to 11.

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