Quantum dot purifying method, purifying agent, application of purifying agent, quantum dot and light-emitting device

Abstract

The invention discloses a quantum dot purifying method, a purifying agent, application of the purifying agent, a quantum dot and a light-emitting device. According to the quantum dot purification method, fatty alcohol with the main chain carbon atom number being 12-18 is added into a quantum dot stock solution, and the fatty alcohol with the main chain carbon atom number being 12-18 can react with a cation precursor dissolved in a solvent of the quantum dot stock solution and can also react with a cation precursor ligand attached to the surface of a quantum dot; the method comprises the following steps: adding a cationic precursor into a reaction kettle to generate a substance which is easy to clean and remove, thereby removing the cationic precursor, obtaining the quantum dot which is relatively high in purity and does not contain the cationic precursor, and further obtaining the purified quantum dot which is relatively good in luminescent property, stability and conductivity.

Description

Technical Field

[0001] The present application relates to the technical field of luminescent materials, and in particular to a quantum dot purification method, a purifying agent and application thereof, quantum dots and a luminescent device. Background Art

[0002] Quantum dots refer to semiconductor nanocrystals whose particle size is smaller than the Bohr radius of their material. The particle size is generally between 1 and 10 nm. Since electrons and holes are quantum confined, the continuous energy band structure becomes a discrete energy level structure with molecular characteristics, which can emit fluorescence after being excited. Therefore, quantum dots of different sizes can be excited simultaneously with a single wavelength light source. Changing the particle size of quantum dots can adjust its emission wavelength and Stokes shift, and the fluorescence spectrum is narrow and symmetrical, so that various quantum dots with different fluorescence spectral characteristics can be prepared. Quantum dots have the advantages of adjustable emission spectrum with particle size and composition, high fluorescence quantum yield, narrow emission spectrum, wide excitation spectrum, and good optical stability. They have excellent application prospects in many fields such as field effect transistors, light-emitting diodes, photoresistors, solar cells, biological characterization, and photoelectric sensors.

[0003] In recent years, with the development of quantum dot synthesis technology, quantum dot materials with high fluorescence quantum yield and good stability have been obtained through reasonable structural design and ligand selection. Applying the quantum dot materials to devices can also obtain device performance with high external quantum efficiency.

[0004] The purity of quantum dots is a key factor affecting their performance. However, the purity of existing quantum dots is not high enough and needs to be further improved. Summary of the invention

[0005] In view of this, the present application provides a quantum dot purification method, aiming to improve the problem of insufficient purity of existing quantum dots.

[0006] The embodiment of the present application is implemented as follows: a method for purifying quantum dots comprises the following steps:

[0007] Providing a quantum dot stock solution, wherein the quantum dot stock solution includes a cationic precursor;

[0008] Adding a purifying agent to the quantum dot stock solution, reacting, and obtaining a reaction solution, wherein the purifying agent comprises a fatty alcohol having a main chain carbon number of 12 to 18;

[0009] The reaction solution is washed to obtain purified quantum dots.

[0010] Optionally, in some embodiments of the present application, the quantum dot stock solution comes from a quantum dot solution prepared by a solution method;

[0011] And / or, the fatty alcohol having 12 to 18 carbon atoms in the main chain includes dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, dodecanediol, tridecandiol, tetradecandiol, pentadecandiol, hexadecandiol, heptadecandiol, and octadecandiol. Preferably, the fatty alcohol having 12 to 18 carbon atoms in the main chain is selected from tetradecanol.

[0012] Optionally, in some embodiments of the present application, the adding of a purifying agent to the quantum dot stock solution comprises: adding a first extractant and a first precipitant to the quantum dot stock solution, centrifuging and separating, dissolving the solid in a first non-polar solvent, and then adding a purifying agent to the solution system;

[0013] And / or, the ratio of the volume of the purifying agent to the volume of the quantum dot stock solution is (0.02-2):1.

[0014] Optionally, in some embodiments of the present application, the cleaning of the reaction solution comprises: adding a precipitant to the reaction solution, and then centrifuging and separating; or

[0015] The cleaning of the reaction liquid comprises: adding a second extractant and a second precipitant to the reaction liquid, centrifuging and separating, dissolving the solid in a second non-polar solvent, and then adding a third precipitant, precipitating, centrifuging and separating.

[0016] Optionally, in some embodiments of the present application, the first extractant and the second extractant independently include one or more of a hydrocarbon solvent and an ester solvent. Optionally, the hydrocarbon solvent includes C6-C 10 One or more of alkanes, benzene, toluene and xylene, the ester solvent comprises R1COOR2, wherein R1 and R2 are independently selected from C1-C5 alkyl groups;

[0017] And / or, the precipitant, the first precipitant, the second precipitant and the third precipitant each independently include a polar solvent, and optionally, the polar solvent includes one or more of methanol, ethanol, acetone and isopropanol;

[0018] And / or, the first non-polar solvent and the second non-polar solvent independently include chloroform, toluene, chlorobenzene, C6-C 14 One or more of alkanes, decahydronaphthalene, and octadecene.

[0019] Optionally, in some embodiments of the present application, the volume ratio of the precipitant to the reaction solution is (1-1.5):1; and / or

[0020] The volume ratio of the first precipitant to the quantum dot stock solution is in the range of (0.5-1.5):1; and / or

[0021] The mass ratio of the second precipitant to the reaction solution is in the range of (0.5-1.5):1; and / or

[0022] The volume ratio of the third precipitant to the second non-polar solvent is (0.3-0.6):1; and / or

[0023] The volume ratio of the first extractant to the quantum dot stock solution is in the range of (1.2-2):1; and / or

[0024] The volume ratio of the second extractant to the reaction solution is (1.2-2):1.

[0025] Optionally, in some embodiments of the present application, before adding the purification agent to the quantum dot stock solution, the method further includes: adding thiol to the quantum dot stock solution; or

[0026] When adding a purifying agent to the quantum dot stock solution, the method further includes: adding thiol to the quantum dot stock solution; or

[0027] After obtaining the reaction liquid and before cleaning the reaction liquid, the method further includes: adding thiol to the reaction liquid.

[0028] Optionally, in some embodiments of the present application, the thiol includes an alkylthiol, and the alkylthiol includes one or more of hexylthiol, n-octylthiol, isooctylthiol, dodecanethiol, and tetradecanethiol;

[0029] And / or, the mass ratio of the thiol to the quantum dots in the quantum dot stock solution is (1.2-2.5):1.

[0030] Optionally, in some embodiments of the present application, before adding thiol to the quantum dot stock solution or adding thiol to the reaction solution, the step further includes: cooling the temperature of the quantum dot stock solution or the reaction solution to 230-260°C.

[0031] Optionally, in some embodiments of the present application, the cationic precursor includes one or more of a zinc ion precursor, a cadmium ion precursor, a lead ion precursor, a silver ion precursor, an indium ion precursor, a mercury ion precursor, a gallium ion precursor, and a copper ion precursor.

[0032] Optionally, in some embodiments of the present application, the zinc ion precursor includes one or more of zinc oleate, zinc stearate, zinc palmitate, and zinc myristate;

[0033] And / or, the cadmium ion precursor includes one or more of cadmium oleate, cadmium stearate, cadmium palmitate, and cadmium myristate;

[0034] And / or, the lead ion precursor includes one or more of lead oleate, lead stearate, lead palmitate, and lead tetradecanoate;

[0035] And / or, the silver ion precursor includes one or more of silver oleate, silver stearate, silver palmitate, and silver myristate;

[0036] And / or, the indium ion precursor includes one or more of indium oleate, indium stearate, indium palmitate, and indium tetradecanoate;

[0037] And / or, the mercury ion precursor includes one or more of mercury oleate, mercury stearate, mercury palmitate, and mercury tetradecanoate;

[0038] And / or, the gallium ion precursor includes one or more of gallium oleate, gallium stearate, gallium palmitate, and gallium tetradecanoate;

[0039] And / or, the cadmium ion precursor includes one or more of cadmium oleate, cadmium stearate, cadmium palmitate, and cadmium myristate.

[0040] Optionally, in some embodiments of the present application, the quantum dots include one or more of single structure quantum dots and core-shell structure quantum dots, wherein the material of the single structure quantum dots, the core material of the core-shell structure quantum dots and the shell material of the core-shell structure quantum dots can respectively include one or more of II-VI group compounds, IV-VI group compounds, III-V group compounds and I-III-VI group compounds, and the II-VI group compounds include 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, and the IV-VI group compound includes SnS, SnSe, SnTe, One or more of PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, SnPbSTe, the III-V group compound includes GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, Al One or more of NSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs and InAlPSb, and the I-III-VI group compound includes one or more of CuInS2, CuInSe2 and AgInS2;

[0041] And / or, the mass concentration of quantum dots in the quantum dot stock solution is 30 to 50 mg / mL.

[0042] Correspondingly, an embodiment of the present application also provides a purifying agent for purifying quantum dots, wherein the purifying agent includes a fatty alcohol having a main chain carbon atom number of 12 to 18.

[0043] Optionally, in some embodiments of the present application, the fatty alcohol having 12 to 18 carbon atoms in the main chain includes dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, dodecanediol, tridecandiol, tetradecandiol, pentadecandiol, hexadecandiol, heptadecandiol, and octadecandiol. Preferably, the fatty alcohol having 12 to 18 carbon atoms in the main chain is selected from tetradecanol.

[0044] Correspondingly, an embodiment of the present application also provides an application of the above-mentioned purifying agent in the purification of quantum dots.

[0045] Correspondingly, an embodiment of the present application further provides a quantum dot, which is purified by the quantum dot purification method described above.

[0046] Correspondingly, an embodiment of the present application further provides a light-emitting device, comprising a stacked anode, a light-emitting layer and a cathode, wherein the light-emitting layer comprises the above-mentioned quantum dots.

[0047] Optionally, in some embodiments of the present application, the anode and the cathode independently include a doped metal oxide particle electrode, a composite electrode, a graphene electrode, a carbon nanotube electrode, a metal element electrode or an alloy electrode, the material of the doped metal oxide particle electrode includes 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 and aluminum-doped magnesium oxide, the composite electrode includes one or more 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 or ZnS / Al / ZnS, and the material of the metal element electrode includes one or more of Ag, Al, Cu, Mo, Au, Pt, Ca, Mg and Ba; and / or

[0048] The light-emitting device further comprises a hole transport layer and / or a hole injection layer located between the anode and the light-emitting layer, wherein the material of the hole transport layer comprises 4,4'-N,N'-dicarbazolyl-biphenyl, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4"-diamine, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine, poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine), N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-spiro, N,N'-di(4-(N,N'-diphenyl)-1,1'-biphenyl-4,4"-diamine. phenyl-amino)phenyl)-N,N'-diphenylbenzidine, 4,4',4'-tri(N-carbazolyl)-triphenylamine, 4,4',4'-tri(N-3-methylphenyl-N-phenylamino)triphenylamine, poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))], poly(N-vinylcarbazole) and its derivatives, N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4-4'-diamine, spiro NPB, poly(phenylene vinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene], poly[2-methoxy-5-(3',7'-dimethyloctyloxy) -1,4-phenylene vinylene], 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene, 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline], 1,3-bis(carbazol-9-yl)benzene, polyaniline, polypyrrole, poly(p-phenylene vinylene), aromatic tertiary amine, polynuclear aromatic tertiary amine, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compound, 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 N iO, 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, and the material of the hole injection layer includes one or more of 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, PEDOT, PEDOT:PSS, PEDOT:PSS doped with s-MoO3 derivatives, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, tetracyanoquinodimethane, copper phthalocyanine, nickel oxide, molybdenum oxide, tungsten oxide, vanadium oxide, molybdenum sulfide, tungsten sulfide and copper oxide; and / or

[0049] The light-emitting device further comprises an electron transport layer between the light-emitting layer and the cathode, wherein the material of the electron transport layer comprises one or more of an inorganic electron transport material and an organic electron transport material, wherein the inorganic electron transport material comprises but is not limited to one or more of doped metal oxide particles, undoped metal oxide particles, ceramic semiconductor materials, IIB-VIA semiconductor materials, IIIA-VA semiconductor materials and IB-IIIA-VIA semiconductor materials, the metal oxide in the undoped metal oxide particles comprises one or more of ZnO, TiO2, SnO2, ZrO2 and Ta2O5, the metal oxide in the doped metal oxide comprises ZnO, TiO2, SnO 2. One or more of ZrO2, Ta2O5, and Al2O3, the doping elements in the doped metal oxide include one or more of Al, Mg, Li, Mn, Y, La, Cu, Ni, Zr, Ce, In, Ga, and Sn, the IIB-VIA semiconductor materials include one or more of ZnS, ZnSe, and CdS, the IIIA-VA semiconductor materials include one or more of InP and GaP, the IB-IIIA-VIA semiconductor materials include one or more of CuInS and CuGaS, and the organic electron transport material includes one or more of quinoxaline compounds, imidazole compounds, triazine compounds, fluorene compounds, and hydroxyquinoline compounds.

[0050] The quantum dot purification method described in the present application purifies the quantum dot stock solution by adding the fatty alcohol with 12 to 18 main chain carbon atoms as a purifying agent into the quantum dot stock solution. The fatty alcohol with 12 to 18 main chain carbon atoms can react with the cationic precursor dissolved in the solvent of the quantum dot stock solution, and can also react with the cationic precursor ligand attached to the surface of the quantum dots to generate a substance that is easily washed and removed, thereby removing the cationic precursor and obtaining quantum dots with higher purity that do not contain cationic precursors. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0052] Figure 1 is a flow chart of a quantum dot purification method provided in an embodiment of the present application;

[0053] Figure 2is a schematic structural diagram of a light-emitting device provided in an embodiment of the present application;

[0054] Figure 3 is a schematic structural diagram of another light-emitting device provided in an embodiment of the present application;

[0055] Figure 4 is a structural schematic diagram of another light-emitting device provided in an embodiment of the present application;

[0056] Figure 5 is a structural schematic diagram of another light-emitting device provided in an embodiment of the present application;

[0057] Figure 6 is a structural schematic diagram of another light-emitting device provided in an embodiment of the present application;

[0058] Figure 7 is a voltage-current density curve diagram of the light-emitting devices of device embodiments 1 to 10 and device comparative examples 1 to 3;

[0059] Figure 8 It is a current density-external quantum efficiency curve diagram of the light-emitting devices of device embodiments 1 to 10 and device comparison examples 1 to 3.

[0060] Reference numerals

[0061] Light-emitting device 100 ; anode 10 ; light-emitting layer 20 ; cathode 30 ; hole transport layer 40 ; electron transport layer 50 ; hole injection layer 60 . DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0063] In this application, unless otherwise stated, directional words such as "upper" and "lower" generally refer to the upper and lower parts of the device in actual use or working state, 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 this application, the term "including" means "including but not limited to". The terms first, second, third, etc. are used only as labels and do not impose numerical requirements or establish an order.

[0064] In this application, "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0065] In the present application, "at least one" means one or more, and "plurality" means two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0066] In the present application, when a layer is formed "on" another layer, the so-called "on" is a broad concept, which may indicate that the formed another layer is adjacent to the certain layer, or may indicate that there are other spacing structural layers between the another layer and the certain layer. For example, when a second electrode is formed "on" the first carrier functional layer, the so-called "on" may indicate that the formed second electrode is adjacent to the first carrier functional layer, or may indicate that there are other spacing structural layers between the second electrode and the first carrier functional layer, such as a light-emitting layer.

[0067] Various embodiments of the present application may be presented 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 understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0068] Existing quantum dots are usually prepared by solution method, and a higher ratio of cationic precursor to anionic precursor is generally used in the preparation process to make the shell grow evenly and reduce the defects of lattice mismatch, thereby improving the quantum yield of quantum dots. However, there will be a large amount of cationic precursor residues in the quantum dot stock solution prepared by a higher ratio of cationic precursor to anionic precursor. These residual cationic precursors will connect and attach to the surface of the quantum dots to form cationic precursor ligands. On the one hand, the cationic precursors attached to the surface of the quantum dots, such as zinc oleate, have low solubility in the commonly used solvents for dispersing quantum dots, thereby reducing the dispersion effect of the quantum dots in the solvent; on the other hand, the cationic precursors attached to the surface of the quantum dots will also form co-precipitations with the quantum dots during the precipitation process when the quantum dots are washed, thereby seriously affecting the purity of the quantum dots; on the other hand, cationic precursors such as zinc oleate will be converted into solid state when the temperature of the liquid system is lower than a certain temperature and become more difficult to remove; on the other hand, cationic precursors such as zinc oleate are insulators, and mixing in quantum dots will affect the conductivity of the quantum dots.

[0069] The technical solution of this application is as follows:

[0070] See also Figure 1 The present invention provides a method for purifying quantum dots, comprising the following steps:

[0071] Step S11: providing a quantum dot stock solution, wherein the quantum dot stock solution includes a cationic precursor;

[0072] Step S12: adding a purifying agent to the quantum dot stock solution, allowing the purifying agent to react with the cationic precursor to obtain a reaction solution, wherein the purifying agent is a fatty alcohol having a main chain carbon number of 12 to 18;

[0073] Step S13: washing the reaction solution to obtain purified quantum dots.

[0074] The quantum dot purification method described in the present application purifies the quantum dot stock solution by adding the fatty alcohol with 12 to 18 main chain carbon atoms as a purifying agent into the quantum dot stock solution. The fatty alcohol with 12 to 18 main chain carbon atoms has a similar chain length and polarity to the cationic precursor, and can react with the cationic precursor dissolved in the solvent of the quantum dot stock solution, and can also react with the cationic precursor ligand attached to the surface of the quantum dots to generate a substance that is easily washed and removed, thereby effectively removing the cationic precursor, obtaining quantum dots with higher purity that do not contain cationic precursors, and further obtaining purified quantum dots with good luminescence performance, stability and conductivity.

[0075] In the step S11:

[0076] The fatty alcohol with 12 to 18 carbon atoms in the main chain includes, but is not limited to, one or more of monohydric fatty alcohol with 12 to 18 carbon atoms in the main chain and dihydric fatty alcohol with 12 to 18 carbon atoms in the main chain. The monohydric fatty alcohol with 12 to 18 carbon atoms in the main chain includes, but is not limited to, one or more of dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, and octadecanol. The dihydric fatty alcohol with 12 to 18 carbon atoms in the main chain includes, but is not limited to, one or more of dodecandiol, tridecandiol, tetradecandiol, pentadecandiol, hexadecandiol, heptadecandiol, and octadecandiol. In at least one preferred embodiment, the fatty alcohol with 12 to 18 carbon atoms in the main chain is selected from tetradecanol.

[0077] The quantum dot stock solution is a quantum dot solution prepared by a known solution method, that is, a quantum dot solution prepared by mixing a cationic precursor solution and an anionic precursor solution. The quantum dot stock solution contains quantum dots, a first solvent and a cationic precursor.

[0078] It can be understood that the cationic precursor is a cationic precursor that does not participate in the reaction during the preparation of quantum dots and remains in the quantum dot stock solution. The cationic precursor includes a cationic precursor dissolved in the first solvent and / or a cationic precursor connected to the quantum dots. The cationic precursor connected to the quantum dots includes a cationic precursor connected to the surface of the quantum dots as a ligand and / or a cationic precursor adsorbed on a ligand on the surface of the quantum dots.

[0079] The cationic precursor is a cationic precursor known in the art for preparing quantum dots, and may include, but is not limited to, one or more of a zinc ion precursor, a cadmium ion precursor, a lead ion precursor, a silver ion precursor, an indium ion precursor, a mercury ion precursor, a gallium ion precursor, and a copper ion precursor.

[0080] The zinc ion precursor may be, but is not limited to, one or more of zinc oleate, zinc stearate, zinc palmitate, and zinc myristate.

[0081] The cadmium ion precursor includes, but is not limited to, one or more of cadmium oleate, cadmium stearate, cadmium palmitate, and cadmium myristate.

[0082] The lead ion precursor may be, but is not limited to, one or more of lead oleate, lead stearate, lead palmitate, and lead tetradecanoate.

[0083] The silver ion precursor may be, but is not limited to, one or more of silver oleate, silver stearate, silver palmitate, and silver myristate.

[0084] The indium ion precursor may be, but is not limited to, one or more of indium oleate, indium stearate, indium palmitate, and indium tetradecanoate.

[0085] The mercury ion precursor may be, but is not limited to, one or more of mercury oleate, mercury stearate, mercury palmitate, and mercury tetradecanoate.

[0086] The gallium ion precursor may be, but is not limited to, one or more of gallium oleate, gallium stearate, gallium palmitate, and gallium tetradecanoate.

[0087] The cadmium ion precursor may be, but is not limited to, one or more of cadmium oleate, cadmium stearate, cadmium palmitate, and cadmium myristate.

[0088] The quantum dots may include, but are not limited to, one or more of single structure quantum dots and core-shell structure quantum dots.

[0089] The material of the single structure quantum dots, the core material of the core-shell structure quantum dots and the shell material of the core-shell structure quantum dots may respectively include but are 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 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 compound may include, but is 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 compound may include, but is not limited to, one or more of CuInS2, CuInSe2, and AgInS2.

[0090] It is understandable that the core material and the shell material of the core-shell structured quantum dot may be the same or different. In at least one embodiment, the core material and the shell material of the core-shell structured quantum dot are different.

[0091] As an example, the core-shell structured quantum dots 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.

[0092] The first solvent is a solvent known in the art for preparing or dispersing quantum dots, and may include one or more of a coordinating solvent and a non-coordinating solvent. The coordinating solvent may include, but is not limited to, one or more of saturated or unsaturated fatty acids having a carbon number greater than or equal to 5, and saturated or unsaturated amines having a carbon number greater than or equal to 6, and the non-coordinating solvent may include, but is not limited to, one or more of alkane compounds having a carbon number greater than or equal to 10, olefin compounds having a carbon number greater than or equal to 10, ether compounds having a carbon number greater than or equal to 10, and aromatic compounds having a carbon number greater than or equal to 10. As an example, the first solvent may include, but is not limited to, one or more of n-hexane, n-octane, toluene, tetradecene, hexadecene, octadecene, eicosene, and paraffin oil.

[0093] It is understood that there is no limit to the concentration of the quantum dot stock solution, and any concentration of quantum dot solution can be purified by the purification method of the present application. In at least some embodiments, the mass concentration of quantum dots in the quantum dot stock solution is 30-50 mg / mL, for example, 32-40 mg / mL, 34-42 mg / mL, 36-44 mg / mL, 38-46 mg / mL, 39-48 mg / mL, etc., and for example, 30 mg / mL, 32 mg / mL, 35 mg / mL, 36 mg / mL, 38 mg / mL, 40 mg / mL, 42 mg / mL, 43 mg / mL, 45 mg / mL, 46 mg / mL, 48 mg / mL, 50 mg / mL, etc.

[0094] In step S12:

[0095] The ratio of the volume of the purifying agent to the volume of the quantum dot stock solution is (0.02-2):1, for example, (0.02-1):1, (0.5-1.2):1, (0.8-1.5):1, (1-1.6):1, (1.2-1.8):1, (1.4-2):1, etc., and for example, 0.02:1, 0.1:1, 0.3:1, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.4:1, 1.5:1, 1.6:1, 1.8:1, 2:1, etc. Within the ratio range, the residual cationic precursor in the quantum dot stock solution can be fully reacted with the purifying agent, which is conducive to fully removing the cationic precursor.

[0096] In step S13:

[0097] The cleaning of the reaction liquid comprises: adding a precipitant to the reaction liquid to precipitate the quantum dots in the reaction liquid, and then centrifuging and separating.

[0098] The precipitant includes but is not limited to polar solvents, the polar solvents include but are not limited to alcohol solvents, and the alcohol solvents include but are not limited to one or more of methanol, ethanol, acetone, and isopropanol.

[0099] The volume ratio of the precipitant to the reaction solution is (1-1.5):1, for example, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, etc. Within the range of the volume ratio, the quantum dots can be fully precipitated, and the precipitated quantum dots have sufficient ligands, are not easy to agglomerate, and have better performance.

[0100] In some embodiments, the adding of the purifying agent to the quantum dot stock solution includes: adding a first extractant and a first precipitant to the quantum dot stock solution, centrifuging and separating the quantum dots, dissolving them in a first non-polar solvent, and then adding the purifying agent to the solution system. That is, the quantum dot stock solution is first extracted and redispersed, and then the purifying agent purification process is performed. In this way, the first solvent, cationic precursors and other impurities in the quantum dot stock solution can be effectively removed, which is conducive to obtaining quantum dots with higher purity.

[0101] In some other embodiments, the cleaning of the reaction solution includes: adding a second extractant and a second precipitant to the reaction solution, centrifuging and separating the quantum dots, dissolving them in a second non-polar solvent, and then adding a third precipitant, precipitating, centrifuging, and separating. That is, the extraction process can be performed after the purification reaction. In this way, the first solvent in the reaction solution, the reactants of the cationic precursor and the purifying agent, and other impurities in the quantum dot stock solution can be effectively removed, which is conducive to obtaining quantum dots with higher purity.

[0102] The first extractant and the second extractant are independently selected from one or more of hydrocarbon solvents and ester solvents. The hydrocarbon solvents include but are not limited to C6-C 10 One or more of alkanes, benzene, toluene and xylene, wherein the C6-C 10 The alkane may include but is not limited to one or more of n-hexane and n-octane. The ester solvent includes R1COOR2, wherein R1 and R2 are independently selected from C1-C5 alkyl groups. As an example, the ester solvent includes but is not limited to one or more of ethyl acetate, butyl acetate, ethyl butyrate, and methyl acetate.

[0103] The first precipitant, the second precipitant and the third precipitant are independently selected from the precipitants described above, and will not be described in detail here.

[0104] The first non-polar solvent and the second non-polar solvent independently include but are not limited to chloroform, toluene, chlorobenzene, C6-C 14 One or more of alkanes, decahydronaphthalene, and octadecene. 14 The alkane may include, but is not limited to, one or more of n-hexane, n-octane, and tridecane.

[0105] The volume ratio of the first extractant to the quantum dot stock solution is in the range of (1.2-2):1, for example, (1.2-1.6):1, (1.4-1.8):1, (1.5-2):1, etc. Within the range, the first solvent, part of the cationic precursor and other impurities in the quantum dot stock solution can be effectively removed.

[0106] The volume ratio of the first precipitant to the quantum dot stock solution is in the range of (0.5-1.5):1, for example, (0.5-1.2):1, (0.6-1.3):1, (0.8-1.4):1, (1-1.5):1, etc. Within the said ratio range, it is beneficial for the quantum dots to be fully precipitated and for the precipitated quantum dots to have sufficient ligands, not to agglomerate easily and to have better performance.

[0107] There is no limitation on the amount of the first non-polar solvent added, as long as the quantum dots can be fully dissolved.

[0108] The volume ratio of the second extractant to the reaction solution is (1.2-2):1, for example, (1.2-1.6):1, (1.4-1.8):1, (1.5-2):1, etc. Within the above range, the first solvent in the reaction solution, the reactants of the cationic precursor and the purifying agent, and other impurities in the quantum dot stock solution can be effectively removed, which is conducive to obtaining quantum dots with higher purity.

[0109] The mass ratio of the second precipitant to the reaction solution is in the range of (0.5-1.5):1, for example, (0.5-1.2):1, (0.6-1.3):1, (0.8-1.4):1, (1-1.5):1, etc. Within the range, the first solvent in the reaction solution, the reactants of the cationic precursor and the purifying agent, and other impurities in the quantum dot stock solution can be effectively removed, which is conducive to obtaining quantum dots with higher purity.

[0110] There is no limitation on the amount of the second non-polar solvent added, as long as the quantum dots can be fully dissolved.

[0111] The volume ratio of the third precipitant to the second non-polar solvent is (0.3-0.6):1, for example, 0.3:1, 0.4:1, 0.5:1, 0.6:1, etc. Within the above range, it is beneficial to remove impurities and obtain quantum dots with higher purity.

[0112] In some embodiments, the surface of the quantum dots in the quantum dot stock solution is further connected with a long-chain organic ligand, and the long-chain organic ligand includes one or more of oleic acid ligand, trioctylphosphine ligand, stearic acid ligand, palmitic acid ligand, and tetradecanoic acid ligand. The long-chain organic ligand has a weak coordination binding ability with the quantum dots, resulting in weak stability of the quantum dots.

[0113] To enhance the stability of quantum dots, the purification method further includes adding thiol. Thiol can undergo ligand exchange with the organic ligand on the surface of the quantum dots, so that the organic ligand is detached from the surface of the quantum dots, and a thiol ligand is formed to be connected to the surface of the quantum dots. The thiol ligand has a strong binding ability with the quantum dots and is not easy to detach from the surface of the quantum dots, which is conducive to making the prepared purified quantum dots have strong stability. The thiol ligand can also undergo ligand exchange with a fatty alcohol with a main chain carbon number of 12 to 18 connected to the surface of the quantum dots, so that the fatty alcohol with a main chain carbon number of 12 to 18 is detached from the surface of the quantum dots, and a thiol ligand is formed to be connected to the surface of the quantum dots. The thiol ligand has a strong binding ability with the quantum dots and is not easy to detach from the surface of the quantum dots, which is conducive to making the prepared purified quantum dots have strong stability.

[0114] The thiol can be added before the purifying agent is added to the quantum dot stock solution, can be added at the same time as the purifying agent, or can be added after the purifying agent is added. In at least one embodiment, the thiol and the purifying agent are added at the same time, which is conducive to preparing purified quantum dots with good luminescence performance and stability.

[0115] The thiol includes alkylthiol, and the alkylthiol includes but is not limited to one or more of hexylthiol, n-octylthiol, isooctylthiol, dodecanethiol, tetradecanethiol.

[0116] The mass ratio of the thiol to the quantum dots is (1.2-2.5):1, for example, (1.2-1.8):1, (1.4-2):1, (1.5-2.2):1, (1.6-2.5):1, etc., and another example is 1.2:1, 1.4:1, 1.5:1, 1.6:1, 1.8:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, etc. Within the range, the organic ligands on the surface of the quantum dots can be fully removed, and the added thiol can participate in the ligand exchange reaction as much as possible, saving resources.

[0117] In some implementations, before adding the thiol to the system, the process further includes: cooling the temperature of the system to 230-260° C., for example, 230-245° C., 235-250° C., 240-255° C., 242-260° C., etc., and for example, 230° C., 235° C., 240° C., 245° C., 250° C., 255° C., 260° C., etc. In this way, the thiol is conducive to a rapid and sufficient ligand exchange reaction between the thiol and the organic ligand connected to the surface of the quantum dot, while above the temperature range, the thiol is easily decomposed, which affects the ligand exchange.

[0118] In some embodiments, after obtaining the purified quantum dots, the method further includes: dispersing the purified quantum dots in a third non-polar solvent to obtain a dispersion of purified quantum dots.

[0119] The third non-polar solvent is a known solvent for dispersing quantum dots, for example, it may include but is not limited to chloroform, toluene, chlorobenzene, C6-C 14 One or more of alkanes, decahydronaphthalene, and octadecene.

[0120] It is understood that there is no limit to the amount of the third non-polar solvent added, as long as the purified quantum dots can be fully dispersed. In at least one embodiment, the concentration of the purified quantum dots in the dispersion of the purified quantum dots is 80-120 mg / mL.

[0121] In some embodiments, before cleaning the reaction liquid, the temperature of the reaction liquid is also lowered to 110-130°C within the temperature range, which is conducive to dissolving impurities in the quantum dots in solvents such as extractants or precipitants, thereby separating the impurities from the quantum dots, and further facilitating obtaining quantum dots with higher purity.

[0122] It can be understood that the temperature of the reaction solution is lowered to 110-130°C after adding thiol for ligand exchange, so that the process of ligand exchange between thiol and the surface ligand of quantum dots can be ensured to be carried out at 230-260°C.

[0123] In a second aspect, an embodiment of the present application further provides a purifying agent for purifying quantum dots, wherein the purifying agent comprises a fatty alcohol having a main chain carbon atom number of 12 to 18.

[0124] In some embodiments, the fatty alcohol having 12 to 18 carbon atoms in the main chain includes dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, dodecandiol, tridecandiol, tetradecandiol, pentadecandiol, hexadecandiol, heptadecandiol, octadecandiol. Preferably, the fatty alcohol having 12 to 18 carbon atoms in the main chain is selected from tetradecanol.

[0125] In a third aspect, an embodiment of the present application also provides an application of the purifying agent described above in the purification of quantum dots.

[0126] In a fourth aspect, an embodiment of the present application further provides a quantum dot, wherein the quantum dot is the purified quantum dot described above.

[0127] The surface of the quantum dot is connected with a thiol ligand, and the thiol ligand includes the thiol described above.

[0128] Fifth, please refer to Figure 2 The embodiment of the present application further provides a light emitting device 100, comprising an anode 10, a light emitting layer 20 and a cathode 30 stacked in sequence. The light emitting layer 20 comprises the purified quantum dots described above.

[0129] See also Figure 3 In some embodiments, the light emitting device 100 further includes a hole transport layer 40 between the anode 10 and the light emitting layer 20. In other words, the light emitting device 100 includes the anode 10, the hole transport layer 40, the light emitting layer 20 and the cathode 30 stacked in sequence.

[0130] See also Figure 4 In some embodiments, the light emitting device 100 further includes an electron transport layer 50 between the light emitting layer 20 and the cathode 30. In other words, the light emitting device 100 includes an anode 10, a light emitting layer 20, an electron transport layer 50 and a cathode 30 stacked in sequence.

[0131] See also Figure 5 In some embodiments, the light-emitting device 100 includes an anode 10, a hole transport layer 40, a light-emitting layer 20, an electron transport layer 50 and a cathode 30 stacked in sequence.

[0132] See also Figure 6 In some embodiments, the light emitting device 100 further includes a hole injection layer 60 located between the anode 10 and the hole transport layer 40 .

[0133] The anode 10 and the cathode 30 are anodes and cathodes for light-emitting devices known in the art, and can be independently, but not limited to, doped metal oxide particle electrodes, composite electrodes, graphene electrodes, carbon nanotube electrodes, metal single-substance electrodes or alloy electrodes. The material of the doped metal oxide particle electrode can be, but not limited to, one or more 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). The composite electrode is a composite electrode in which metal is sandwiched between doped or undoped transparent metal oxide particles, such as 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., wherein " / " represents a stacked structure, for example, AZO / Ag / AZO represents a composite electrode including an AZO layer, an Ag layer and an AZO layer stacked in sequence. The material of the metal single substance electrode may include but is not limited to one or more of Ag, Al, Cu, Mo, Au, Pt, Ca, Mg and Ba.

[0134] The material of the hole transport layer 40 may also be a material known in the art for a hole transport layer, for example, it may include but is 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 ...1-naphthyl)-1,1'-biphenyl-4,4"-diamine (α-NPD), (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'-tri(N-carbazolyl)-triphenylamine (TCTA), 4,4',4'-tri(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'-di(1-naphthyl)-N,N'-diphenyl -1,1'-biphenyl-4-4'-diamine (NPB), spiro NPB, poly(phenylene vinylene) (PPV), poly[2-methoxy-5-(2-ethylhexyloxy)-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-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-omeTAD), 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline] (TAPC), 1,3-bis(carbazol-9-yl)benzene (MCP ), polyaniline, polypyrrole, poly(p-)phenylene vinylene, aromatic tertiary amine, polynuclear aromatic tertiary amine, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compound, 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.

[0135] The material of the electron transport layer 50 is a material known in the art for electron transport layers, for example, it 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 material includes but is not limited to doped metal oxide particles, undoped metal oxide particles, ceramic semiconductor materials, IIB-VIA semiconductor materials, IIIA-VA semiconductor materials and IB-IIIA-VIA semiconductor materials. The metal oxide in the undoped metal oxide particles includes but is not limited to one or more of ZnO, TiO2, SnO2, ZrO2, Ta2O5. The metal oxide in the doped metal oxide includes but is not limited to one or more of ZnO, TiO2, SnO2, ZrO2, Ta2O5, and Al2O3. The doping element in the doped metal oxide includes but is not limited to one or more of Al, Mg, Li, Mn, Y, La, Cu, Ni, Zr, Ce, In, Ga, and Sn. As an example, the doped metal oxide can be aluminum zinc oxide (AZO), lithium-doped zinc oxide (LZO), magnesium-doped zinc oxide (MZO), tin-doped zinc oxide (Sn-ZnO), etc. The ceramic semiconductor material includes but is not limited to barium titanate. The IIB-VIA semiconductor material includes but is not limited to one or more of ZnS, ZnSe, and CdS. The IIIA-VA semiconductor material includes but is not limited to one or more of InP and GaP. The IB-IIIA-VIA semiconductor material includes but is not limited to one or more of CuInS and CuGaS. The organic electron transport material includes one or more of quinoxaline compounds, imidazole compounds, triazine compounds, fluorene-containing compounds, and hydroxyquinoline compounds.

[0136] The material of the hole injection layer 60 can be a material known in the art for a hole injection layer, for example, it 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, a derivative 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.

[0137] In some embodiments, the thickness of the anode 10 is 20 to 200 nm; the thickness of the light-emitting layer 20 is 30 to 180 nm; the thickness of the cathode 30 is 40 to 190 nm; the thickness of the hole transport layer 40 is 30 to 180 nm; the thickness of the electron transport layer 50 is 10 to 180 nm; and the thickness of the hole injection layer 60 is 20 to 200 nm.

[0138] It is understandable that the light emitting device 100 may also be further provided with some functional layers conventionally used in light emitting devices to help improve the performance of the light emitting device, such as an electron blocking layer, a hole blocking layer, an electron injection layer, an interface modification layer, etc.

[0139] It can be understood that the materials of each layer of the light emitting device 100 can be adjusted according to the light emitting requirements of the light emitting device 100 .

[0140] In some embodiments, the light emitting device 100 further includes a substrate, and the substrate is disposed on a side of the anode 10 away from the light emitting layer 20 , or the substrate is disposed on a side of the cathode 30 away from the light emitting layer 20 .

[0141] The substrate may be a rigid substrate or a flexible substrate. In some embodiments, the material of the substrate may include but is not limited to one or more of glass, silicon wafer, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyamide and polyether sulfone.

[0142] It can be understood that the light emitting device 100 can be an upright light emitting device or an inverted light emitting device. The light emitting device 100 can be a quantum dot light emitting device or an organic light emitting device.

[0143] The light-emitting layer 20 of the light-emitting device 100 includes quantum dots purified by the purification method described in the present application, and thus has higher light-emitting efficiency and longer lifespan.

[0144] In a sixth aspect, an embodiment of the present application further provides a display device, which includes the light-emitting device 100 .

[0145] The display device can be any electronic product with a display function, including but not limited to smart phones, tablet computers, laptops, digital cameras, digital video cameras, smart wearable devices, smart weighing electronic scales, car displays, televisions or e-book readers, among which smart wearable devices can be, for example, smart bracelets, smart watches, virtual reality (VR) helmets, etc.

[0146] The present application is described in detail below through specific embodiments. The following embodiments are only partial embodiments of the present application and are not limitations of the present application.

[0147] Example 1

[0148] Preparation of quantum dot stock solution:

[0149] 15 mmol zinc acetate, 30 mmol oleic acid, and 10 ml octadecene were weighed and placed in a 100 ml three-necked flask, and treated at 80°C under vacuum for 60 min, then switched to an argon atmosphere and heated at 150°C for 30 min, and then heated to 330°C to obtain a cationic precursor zinc oleate;

[0150] Inject 1.3 mmol of Se precursor solution into the zinc oleate, wherein the Se precursor solution includes Se powder, solvent TOP (trioctylphosphine) and solvent DPP (diphenylphosphine), inject 0.13 mmol of cadmium oleate after 60 seconds, and react at 330° C. for 120 minutes to obtain CdZnSe core;

[0151] Adding 3 mmol of Se precursor solution to the reaction system, wherein the Se precursor solution contains Se powder and solvent TOP, and reacting for 120 minutes to form a ZnSe shell layer on the CdZnSe core;

[0152] 0.6 mmol of cadmium oleate and 2 mmol of S precursor solution were added to the reaction system, wherein the S precursor solution included S powder and solvent TOP, and the reaction was continued for 20 minutes, and finally 15 ml of oleic acid was added to obtain a CdZnSe / ZnSe / CdZnS core-shell structured quantum dot stock solution;

[0153] The quantum dot stock solution was cooled to 120°C, and then evenly added to three tubes of cleaning solution, wherein each tube of cleaning solution included 10 ml of n-hexane (first extractant), 10 ml of ethyl acetate (first extractant) and 15 ml of ethanol (first precipitant), and placed in a centrifugal device, and centrifuged at a speed of 7300 rpm for 3 minutes. After separation, the supernatant was poured out, and 8 ml of n-hexane was added to the remaining solid quantum dot product for dispersion, and then re-dispersed by shaking on an oscillator;

[0154] After mixing the three tubes of redispersed solutions, 5 ml of tetradecanol (purifying agent) was added and reacted for 10 min. Then 12 ml of ethanol was added for precipitation. Then, the solution was placed in a centrifugal device and centrifuged at 7300 rpm for 3 min to obtain purified quantum dots.

[0155] Example 2

[0156] This embodiment is basically the same as Embodiment 1, except that, after obtaining the quantum dot stock solution, this embodiment further includes reducing the temperature of the quantum dot stock solution to 250° C., adding 2 mL of n-octyl mercaptan, and reacting for 5 minutes.

[0157] Example 3

[0158] This embodiment is basically the same as Embodiment 1, except that, after obtaining the quantum dot stock solution, this embodiment includes:

[0159] The temperature of the quantum dot stock solution was lowered to 250° C., and then 5 mL of tetradecanol (purifying agent) and 2 mL of n-octyl mercaptan were added to the quantum dot stock solution, and the reaction was carried out for 10 minutes to obtain a quantum dot solution to be purified;

[0160] The temperature of the quantum dot solution to be purified was lowered to 130°C, and then evenly added to three tubes of cleaning solution, wherein each tube of cleaning solution includes 10 ml of n-hexane (second extractant), 10 ml of ethyl acetate (second extractant) and 15 ml of ethanol (second precipitant), placed in a centrifugal device, and centrifuged at 7300 rpm for 3 minutes. After separation, the supernatant was poured out, and 8 ml of n-hexane was added to the remaining solid quantum dot product in each tube for dispersion, and re-dispersed by shaking on an oscillator;

[0161] The three tubes of redispersed solutions were mixed, 12 ml of ethanol (third precipitant) was added for precipitation, and then placed in a centrifugal device and centrifuged at 7300 rpm for 3 minutes to obtain purified quantum dots.

[0162] Example 4

[0163] This embodiment is substantially the same as embodiment 3, except that dodecanethiol is used in this embodiment to replace n-octanethiol in embodiment 1.

[0164] Example 5

[0165] This embodiment is substantially the same as embodiment 3, except that in this embodiment, palmitic acid is used to replace oleic acid in embodiment 3 when preparing the cationic precursor.

[0166] Example 6

[0167] This embodiment is substantially the same as embodiment 3, except that hexadecanediol is used to replace tetradecanol in embodiment 3 in this embodiment.

[0168] Example 7

[0169] This example is substantially the same as Example 3, except that the amount of tetradecanol added in this example is 0.96 mL.

[0170] Example 8

[0171] This embodiment is substantially the same as embodiment 3, except that the amount of tetradecanol added in this embodiment is 16 mL.

[0172] Example 9

[0173] This embodiment is substantially the same as embodiment 3, except that the amount of n-octyl mercaptan added in this embodiment is 1.1 mL.

[0174] Example 10

[0175] This embodiment is substantially the same as embodiment 3, except that the amount of n-octyl mercaptan added in this embodiment is 2.4 mL.

[0176] Comparative Example 1

[0177] 15 mmol zinc acetate, 30 mmol oleic acid, and 10 ml octadecene were weighed and placed in a 100 ml three-necked flask, and treated at 80°C under vacuum for 60 min, then switched to an argon atmosphere and heated at 150°C for 30 min, and then heated to 330°C to obtain a cationic precursor zinc oleate;

[0178] Inject 1.3 mmol of Se precursor solution into the zinc oleate, wherein the Se precursor solution includes Se powder, solvent TOP (trioctylphosphine) and solvent DPP (diphenylphosphine), inject 0.13 mmol of cadmium oleate after 60 seconds, and react at 330° C. for 120 minutes to obtain CdZnSe core;

[0179] Adding 3 mmol of Se precursor solution to the reaction system, wherein the Se precursor solution contains Se powder and solvent TOP, and reacting for 120 minutes to form a ZnSe shell layer on the CdZnSe core;

[0180] 0.6 mmol of cadmium oleate and 2 mmol of S precursor solution were added to the reaction system, wherein the S precursor solution included S powder and solvent TOP, and the reaction was continued for 20 minutes, and finally 15 ml of oleic acid was added to obtain a CdZnSe / ZnSe / CdZnS core-shell structured quantum dot stock solution;

[0181] 12 ml of ethanol was added to the quantum dot stock solution for precipitation, and then the solution was placed in a centrifugal device and centrifuged at 7300 rpm for 3 minutes to obtain quantum dots.

[0182] Comparative Example 2

[0183] This example is substantially the same as Example 1, except that tetramethylethylenediamine is used in this comparative example to replace tetradecanol in Example 1.

[0184] Comparative Example 3

[0185] This example is substantially the same as Example 3, except that tetramethylethylenediamine is used in this comparative example to replace tetradecanol in Example 3.

[0186] The purified quantum dots of Examples 1 to 10, the quantum dots of Comparative Example 1, and the purified quantum dots of Comparative Examples 2 to 3 were tested for fluorescence quantum yield (PLQY). The fluorescence quantum yield (PLQY) was tested using a steady-state fluorescence spectrometer of Edinburgh Instruments, the model of the instrument was FS5, and the accessory for measuring fluorescence quantum yield was SC-30. The test results are shown in Table 1.

[0187] Table 1:

[0188]

[0189]

[0190] From Table 1 we can see that:

[0191] Compared with the quantum dots in comparative example 1 and the purified quantum dots in comparative examples 2 to 3, the purified quantum dot solutions in Examples 1 to 13 have a higher fluorescence quantum yield, and the fluorescence quantum yield can be increased by at least 30%. It can be seen that the quantum dot purification method of the present application can effectively purify the quantum dot stock solution to obtain quantum dots with higher fluorescence intensity.

[0192] Device Example 1

[0193] Providing a glass substrate, depositing an indium tin oxide (ITO) material on the glass substrate to obtain an ITO anode 10 with a thickness of 80 nm;

[0194] Spin-coat a PEDOT:PSS material on the anode 10 and anneal at 150° C. for 20 min to obtain a hole injection layer 60 with a thickness of 20 nm;

[0195] Spin coating TFB material on the hole injection layer 60, annealing at 120°C for 20 minutes to obtain a hole transport layer 40 with a thickness of 20 nm;

[0196] Providing the purified quantum dots in Example 1, dispersing the purified quantum dots in n-octane to obtain a dispersion of purified quantum dots, and spin-coating the dispersion on the hole transport layer 40 to obtain a light-emitting layer 20 with a thickness of 40 nm;

[0197] Spin-coat a ZnO ethanol solution on the light-emitting layer 20, and anneal at 80°C for 20 minutes to obtain an electron transport layer 50 with a thickness of 35 nm;

[0198] Ag is evaporated on the electron transport layer 50 to obtain a cathode 30 with a thickness of 100 nm;

[0199] After packaging, the light emitting device 100 is obtained.

[0200] Device Examples 2 to 10

[0201] Device Examples 2 to 10 are substantially the same as Device Example 1, except that Device Examples 2 to 13 use the quantum dots purified in Examples 2 to 10 to replace the quantum dots purified in Example 1, respectively.

[0202] Device Comparison Example 1

[0203] Device Comparative Example 1 is substantially the same as Device Example 1, except that the device Comparative Example 1 uses the quantum dots in Comparative Example 1 to replace the purified quantum dots in Example 1.

[0204] Device Comparison Examples 2 to 3

[0205] Device Comparative Examples 2 to 3 are substantially the same as Device Example 1, except that the purified quantum dots in Example 1 are replaced by the purified quantum dots in Comparative Examples 2 to 3.

[0206] The electrical performance of the light emitting devices of device embodiments 1 to 10 and device comparative examples 1 to 3 was tested, and the results were respectively Figure 7 The voltage-current density curves and Figure 8 The current density-external quantum efficiency EQE curve is shown.

[0207] The test method is to control the efficiency test system built by QE PRO spectrometer, Keithley 2400, and Keithley 6485 through LabView, with a driving voltage of 0-8V and a step size of 0.1V. The voltage-current density curve and the current density-external quantum efficiency EQE curve are plotted.

[0208] Depend on Figure 7 It can be seen that under the same voltage, the light-emitting devices of Examples 1 to 10 have a higher current density. Figure 8 It can be seen that at the same current density, the light-emitting devices of Examples 1 to 10 have higher external quantum efficiency, and it can be seen that at the same voltage, the light-emitting device of Example 3 has higher external quantum efficiency. The reason may be that the purity of the quantum dots in the light-emitting layers of the light-emitting devices of Examples 1 to 10 is higher.

[0209] The maximum brightness L of the light-emitting devices of device embodiments 1 to 10 and device comparative examples 1 to 3 is max , lifespan T95 and lifespan T95@1000nit were tested. The test results are shown in Table 2.

[0210] Maximum brightness L maxThe test methods for lifespan T95 and lifespan T95@1000nit are as follows: In CDA gas, under constant current or voltage drive, the time taken for the device brightness to decay to a certain percentage of the maximum brightness is measured. The time taken for the brightness to decay to 95% of the maximum brightness is defined as T95, and the lifespan is the measured lifespan. In order to shorten the lifespan test cycle, device lifespan tests are usually performed at high brightness by accelerating device aging, and the lifespan at low brightness is obtained by fitting the decay fitting formula. For example, the lifespan at 1000nits is recorded as T95@1000nits, and the calculation formula is:

[0211]

[0212] Among them, T95 L The lifespan under low brightness, generally 1000nits, T95 H is the lifespan under high brightness, that is, the measured lifespan, L H is the maximum brightness that the device is accelerated to, L L Generally, it is 1000nits, A is the acceleration factor, which is 1.7. The constant current is 1mA.

[0213] Table 2:

[0214] <![CDATA[L max (cd / m 2 )]]> T95(h) T95@1000nits(h) Device Example 1 4823 3.98 49.34 Device Example 2 5653 4.99 79.75 Device Example 3 6015 5.83 102.91 Device Example 4 5724 5.38 87.72 Device Example 5 5913 5.64 96.87 Device Example 6 6010 5.81 102.42 Device Example 7 5071 4.57 61.39 Device Example 8 4897 3.90 45.33 Device Example 9 4986 4.23 55.30 Device Example 10 4816 3.99 45.64 Device Comparative Example 1 4568 3.53 40.12 Device Comparison Example 2 4723 3.87 41.39 Device Comparison Example 3 4748 3.85 41.74

[0215] From Table 2 we can see that:

[0216] Compared with the light-emitting devices of Comparative Examples 1 to 3, the light-emitting devices of Examples 1 to 10 have higher maximum brightness and longer lifespan. It can be seen that the quantum dots purified by the purification method of the present application can effectively improve the brightness and lifespan of the light-emitting devices.

[0217] Compared with the light-emitting device of comparative example 2, the light-emitting device of embodiment 1 has a higher maximum brightness and a longer lifespan. It can be seen that the effect of purifying quantum dots by using the purifying agent of the present application is better than that of purifying quantum dots by using the existing purifying agent for purifying quantum dots.

[0218] Compared with the light-emitting device of comparative example 3, the light-emitting device of embodiment 3 has a higher maximum brightness and a longer lifespan. It can be seen that the effect of purifying quantum dots by using the purifying agent of the present application is better than that of purifying quantum dots by using the existing purifying agent for purifying quantum dots.

[0219] The quantum dot purification method, quantum dots and light-emitting devices provided in the embodiments of the present application are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for technicians in this field, according to the ideas of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for purifying quantum dots, characterized in that: The steps include: Providing a quantum dot stock solution, wherein the quantum dot stock solution includes a cationic precursor; Adding a purifying agent to the quantum dot stock solution, reacting, and obtaining a reaction solution, wherein the purifying agent comprises a fatty alcohol having a main chain carbon number of 12 to 18; The reaction solution is washed to obtain purified quantum dots.

2. The method for purifying quantum dots according to claim 1, wherein: The cationic precursor includes one or more of a zinc ion precursor, a cadmium ion precursor, a lead ion precursor, a silver ion precursor, an indium ion precursor, a mercury ion precursor, a gallium ion precursor, and a copper ion precursor; And / or, the quantum dot stock solution comes from a quantum dot solution prepared by a solution method; And / or, the fatty alcohol having 12 to 18 carbon atoms in the main chain includes dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, dodecanediol, tridecandiol, tetradecandiol, pentadecandiol, hexadecandiol, heptadecandiol, and octadecandiol. Preferably, the fatty alcohol having 12 to 18 carbon atoms in the main chain is selected from tetradecanol.

3. The method for purifying quantum dots according to claim 1, wherein: The step of adding a purifying agent to the quantum dot stock solution comprises: adding a first extractant and a first precipitant to the quantum dot stock solution, centrifuging and separating, dissolving the solid in a first non-polar solvent, and then adding a purifying agent to the solution system; And / or, the ratio of the volume of the purifying agent to the volume of the quantum dot stock solution is (0.02-2):

1. And / or, the cleaning of the reaction liquid includes: adding a precipitant to the reaction liquid, and then centrifuging and separating; or, the cleaning of the reaction liquid includes: adding a second extractant and a second precipitant to the reaction liquid, centrifuging and separating, dissolving the solid in a second non-polar solvent, and then adding a third precipitant, precipitating, centrifuging, and separating.

4. The method for purifying quantum dots according to any one of claims 1 to 3, characterized in that: The first extracting agent and the second extracting agent independently include one or more of a hydrocarbon solvent and an ester solvent; Optionally, the hydrocarbon solvent includes C6-C 10 One or more of alkanes, benzene, toluene and xylene, the ester solvent comprises R1COOR2, wherein R1 and R2 are independently selected from C1-C5 alkyl groups; And / or, the precipitant, the first precipitant, the second precipitant and the third precipitant each independently include a polar solvent; optionally, the polar solvent includes one or more of methanol, ethanol, acetone and isopropanol; And / or, the first non-polar solvent and the second non-polar solvent independently include chloroform, toluene, chlorobenzene, C6-C 14 One or more of alkanes, decahydronaphthalene, and octadecene.

5. The method for purifying quantum dots according to claim 1, characterized in that: Before adding the purifying agent to the quantum dot stock solution, the method further includes: adding thiol to the quantum dot stock solution; or When adding a purifying agent to the quantum dot stock solution, the method further includes: adding thiol to the quantum dot stock solution; or After obtaining the reaction liquid and before cleaning the reaction liquid, the method further includes: adding thiol to the reaction liquid.

6. The method for purifying quantum dots according to claim 5, characterized in that: The thiol includes alkyl mercaptan, and the alkyl mercaptan includes one or more of hexyl mercaptan, n-octyl mercaptan, isooctyl mercaptan, dodecanethiol, tetradecanethiol; And / or, the mass ratio of the thiol to the quantum dots in the quantum dot stock solution is (1.2-2.5):

1.

7. The method for purifying quantum dots according to claim 5, characterized in that: Before adding thiol to the quantum dot stock solution or adding thiol to the reaction solution, the method further includes: cooling the temperature of the quantum dot stock solution or the reaction solution to 230-260°C.

8. The method for purifying quantum dots according to claim 1, wherein: The quantum dots include one or more of single structure quantum dots and core-shell structure quantum dots, wherein the material of the single structure quantum dots, the core material of the core-shell structure quantum dots and the shell material of the core-shell structure quantum dots can respectively include one or more of II-VI group compounds, IV-VI group compounds, III-V group compounds and I-III-VI group compounds, and the II-VI group compounds include 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, and the IV-VI group compound includes SnS, SnSe, SnTe, PbS, PbSe , PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, SnPbSTe, the III-V group compound includes GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, One or more of AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs and InAlPSb, and the I-III-VI group compound includes one or more of CuInS2, CuInSe2 and AgInS2; And / or, the mass concentration of quantum dots in the quantum dot stock solution is 30 to 50 mg / mL.

9. A purifying agent for purifying quantum dots, characterized in that: The purifying agent includes a fatty alcohol having a main chain carbon number of 12 to 18; Optionally, the fatty alcohol having 12 to 18 main chain carbon atoms includes dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanediol, dodecanediol, tridecanediol, tetradecanediol, pentadecanediol, hexadecanediol, heptadecanediol and octadecanediol.

10. Use of the purifying agent as claimed in claim 9 in the purification of quantum dots.

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

12. A light emitting device, characterized in that: The invention comprises a stacked anode, a light-emitting layer and a cathode, wherein the light-emitting layer comprises quantum dots, and the quantum dots are purified by the quantum dot purification method according to any one of claims 1 to 8.

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