CN118064127A - Quantum dot, preparation method thereof and light-emitting device - Google Patents

Abstract

The application discloses a quantum dot, a preparation method thereof and a light-emitting device, wherein the preparation method comprises the following steps: providing a first solution containing quantum dot nanoparticles and an acid; adding an alkaline substance to the first solution to adsorb the acid and free hydrogen in the quantum dot nanoparticles. According to the application, the alkaline substance is added, and the concentration of free hydrogen in the quantum dot nano-particles is reduced by utilizing the reaction of the alkaline substance with redundant acid in the solution and the hydrogen element free between the quantum dot lattices, so that the stability of the quantum dot nano-particles in an electric field environment is improved, and the quantum yield of the quantum dots is improved.

Description

Quantum dot, preparation method thereof and light-emitting device

Technical Field

The application relates to the field of semiconductors, in particular to a quantum dot, a preparation method thereof and a light-emitting device.

Background

Quantum dots are nanocrystalline particles with a radius less than or close to the radius of a bohr exciton, have quantum confinement effect, and can emit fluorescence after excitation. And the quantum dot has unique luminescence characteristics, such as wide excitation peak, narrow emission peak, adjustable luminescence spectrum and the like, so that the quantum dot has wide application prospect in the field of photoelectric luminescence.

In quantum dot synthesis, an acidic solvent such as oleic acid is generally used. The solvent has proper boiling point and melting point, is convenient for synthesis at high temperature and cleaning at low temperature, can be used as a ligand to exist on the surface of the quantum dot, and has great influence on the synthesis, dispersion and final electrical property of the quantum dot. However, a large amount of hydrogen atoms or hydrogen ions are dissolved in the crystal lattice of such quantum dots, and such hydrogen atoms or hydrogen ions dissociated in the crystal lattice are collectively called free hydrogen. Free hydrogen is extremely easy to gather under an electric field, so that larger lattice stress is generated, the quantum dot structure is destroyed, and the Quantum Yield (QY) of the quantum dot is reduced.

Disclosure of Invention

In view of the above, the application provides a quantum dot, a preparation method thereof and a light-emitting device, and aims to solve the problem that QY of the quantum dot prepared by the existing quantum dot preparation method is easy to be reduced in an electric field environment.

The embodiment of the application is realized as follows:

in a first aspect, the present application provides a method for preparing a quantum dot, comprising the steps of:

Providing a first solution containing quantum dot nanoparticles and an acid;

adding an alkaline substance to the first solution to adsorb the acid and free hydrogen in the quantum dot nanoparticles.

Optionally, in some embodiments of the present application, the quantum dot nanoparticle includes a single structure quantum dot, a quantum dot core of a core-shell structure quantum dot, or a core-shell structure quantum dot having M shells, wherein M is a positive integer greater than 0;

And/or the alkaline substance has an alkaline structure, the alkaline structure comprising at least one of an amino group and a hydroxyl group; and adding an alkaline substance into the first solution, wherein in the step of adsorbing the acid and the free hydrogen in the quantum dot nano particles, the amount of the substance with the alkaline structure is more than or equal to the amount of the substance with the acid.

Alternatively, in some embodiments of the present application, in the step of adding an alkaline substance to the first solution, the temperature of the first solution is 100 to 200 ℃.

Optionally, in some embodiments of the present application, the step of adding an alkaline substance to the first solution to adsorb the acid and the free hydrogen in the quantum dot nanoparticles has an adsorption time of 10 to 60 minutes.

Optionally, in some embodiments of the application, the alkaline substance comprises one or more of an organic base and an inorganic base;

the inorganic base is selected from one or more of alkali metal oxide, alkali metal hydroxide, alkali metal bicarbonate, alkali metal carbonate, alkaline earth metal oxide, alkaline earth metal hydroxide and alkaline earth metal bicarbonate;

the organic base is selected from one or more of amine compounds and alkyl ammonium hydroxide, wherein the alkyl in the alkyl ammonium hydroxide contains 1-20 carbon atoms.

Alternatively, in some embodiments of the present application, the amine compound is selected from the group consisting of alkylamine compounds having 1 to 40 carbon atoms in the alkyl group, further, the alkylamine compounds including one or more of octylamine, dioctylamine, trioctylamine, and oleylamine; and/or the number of the groups of groups,

The alkyl ammonium hydroxide comprises one or more of tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide and tetrapropyl ammonium hydroxide; and/or the number of the groups of groups,

The inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium oxide, potassium oxide, calcium oxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, calcium bicarbonate and barium hydroxide.

Optionally, in some embodiments of the application, the basic substance is selected from one or more of an inorganic base and an alkyl ammonium hydroxide;

After the step of adding an alkaline substance to the first solution, further comprising: the first solution is placed in a pressure environment or a gas flow environment so as to remove water generated in the reaction process, wherein the pressure of the pressure environment is 10-10000 Pa, and the gas of the gas flow environment comprises inert gas.

Optionally, in some embodiments of the application, the basic substance is selected from one or more of the organic amines;

after the step of adding an alkaline substance to the first solution to adsorb the acid and the free hydrogen in the quantum dot nanoparticles, the method further comprises: and regulating the temperature of the first solution to 180-350 ℃, and preserving heat for 30-60 min.

Optionally, in some embodiments of the present application, when the quantum dot nanoparticle is a single structure quantum dot, the step of providing a first solution containing the quantum dot nanoparticle and an acid includes: providing a cationic precursor solution, an anionic precursor solution, and an organic solvent; mixing the cation precursor solution with an organic solvent, then adding the anion precursor solution, and reacting to obtain the first solution containing the quantum dots with the single structure; wherein at least one of the cationic precursor solution and the anionic precursor solution contains an acid; or alternatively

When the quantum dot nano-particles are quantum dot cores of quantum dots with core-shell structures, providing a first solution, wherein the first solution contains the quantum dot nano-particles and acid, and the method comprises the following steps of: providing a nuclear cation precursor solution, a nuclear anion precursor solution and an organic solvent; mixing the nuclear cation precursor solution with an organic solvent, and then adding the nuclear anion precursor solution to react to obtain a nuclear solution containing quantum dot nuclei; wherein at least one of the nuclear cation precursor solution and the nuclear anion precursor solution contains an acid; the first solution is the core solution; or alternatively

When the quantum dot nano-particles are core-shell structure quantum dots with M shell layers, providing a first solution, wherein the first solution contains the quantum dot nano-particles and acid, and the method comprises the following steps of: providing a nuclear cation precursor solution, a nuclear anion precursor solution and an organic solvent; mixing the nuclear cation precursor solution with an organic solvent, and then adding the nuclear anion precursor solution to react to obtain a nuclear solution containing quantum dot nuclei; forming a first shell layer on the surface of the quantum dot core to obtain a first mixed solution containing quantum dot nanoparticles with one shell layer, repeating the step n times, wherein n is an integer greater than or equal to 0, sequentially obtaining second to n+1th shell layers, and correspondingly obtaining second mixed solution containing quantum dot nanoparticles with two shell layers to n+1th mixed solution containing quantum dot nanoparticles with n+1th shell layers; wherein at least one of the nuclear cation precursor solution and the nuclear anion precursor solution contains an acid; the first solution is the Mth mixed solution, and M is more than or equal to 1 and less than or equal to n+1.

Alternatively, in some embodiments of the application, the acid comprises at least one of oleic acid, octadecanesulfonic acid, and octadecanesulfonic acid.

In a second aspect, the application also proposes a quantum dot, obtainable by a preparation method as described above.

Optionally, in some embodiments of the present application, the quantum dot is selected from at least one of a single structure quantum dot selected from at least one of a group II-VI compound 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, a group IV-VI compound selected from at least one of SnS、SnSe、SnTe、PbS、PbSe、PbTe、SnSeS、SnSeTe、SnSTe、PbSeS、PbSeTe、PbSTe、SnPbS、SnPbSe、SnPbTe、SnPbSSe、SnPbSeTe、SnPbSTe, and a core-shell structure quantum dot selected from at least one of a group IV-VI compound 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, a group III-V compound selected from at least one of CuInS ₂、CuInSe₂ and AgInS ₂; the core of the quantum dot with the core-shell structure is selected from any one of the quantum dots with the single structure, and the shell material of the quantum dot with the core-shell structure is selected from at least one of CdS, cdTe, cdSeTe, cdZnSe, cdZnS, cdSeS, znSe, znSeS and ZnS.

In a third aspect, the application also proposes a light emitting device comprising a first electrode, a functional layer and a second electrode, the functional layer comprising a light emitting layer comprising quantum dots as described above.

Optionally, in some embodiments of the present application, the first electrode and the second electrode are each independently selected from a doped metal oxide particle electrode, a composite electrode of metal and metal oxide, a graphene electrode, a carbon nanotube electrode, a metal electrode or an alloy electrode, wherein a material of the doped metal oxide particle electrode is selected from one or more of indium doped tin oxide, fluorine doped tin oxide, antimony doped tin oxide, aluminum doped zinc oxide, gallium doped zinc oxide, indium doped zinc oxide, magnesium doped zinc oxide and aluminum doped magnesium oxide, a material of the composite electrode of metal and metal oxide is selected from 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、ZnS/Al/ZnS, and a material of the metal electrode is selected from Ag, al, cu, mo, au, pt, si, ca, mg and Ba; and/or the number of the groups of groups,

The functional layer further comprises an electron transport layer, wherein the material of the electron transport layer is at least one selected from metal oxide, doped metal oxide, II-VI semiconductor material, III-V semiconductor material and I-III-VI semiconductor material, and the metal oxide is at least one selected from ZnO, baO, tiO ₂、SnO₂; the metal oxide in the doped metal oxide is at least one of ZnO and TiO ₂、SnO₂, the doping element is at least one of Al, mg, li, in, ga, and the II-VI semiconductor material is at least one of ZnS, znSe, cdS; the III-V semiconductor group material is at least one of InP and GaP; the I-III-VI semiconductor material is at least one selected from CuInS and CuGaS; and/or the number of the groups of groups,

The functional layer further comprises an electron injection layer, and the material of the electron injection layer is at least one selected from cesium carbonate, cesium fluoride, cesium azide and lithium fluoride; and/or the number of the groups of groups,

The functional layer further comprises a hole transport layer, the material of which is selected from the group consisting of 4,4'-N, N' -dicarbazolyl-biphenyl (CBP), N '-diphenyl-N, N' -bis (1-naphthyl) -1,1 '-biphenyl-4, 4 "-diamine, N' -diphenyl-N, N '-bis (3-methylphenyl) - (1, 1' -biphenyl) -4,4 '-diamine, N' -bis (3-methylphenyl) -N, N '-bis (phenyl) -spiro (spiro-TPD), N' -bis (4- (N, N '-diphenyl-amino) phenyl) -N, N' -diphenyl benzidine, 4 '-tris (N-carbazolyl) -triphenylamine, 4' -tris (N-3-methylphenyl-N-phenylamino) triphenylamine, poly [ (9, 9 '-dioctylfluorene-2, 7-diyl) -co- (4, 4' - (N- (4-sec-butylphenyl) diphenylamine)) ], poly (4-butylphenyl-diphenylamine) (poly-TPD), polyaniline, polypyrrole, poly (p-phenylene vinylene, poly (phenylene vinylene), poly [ 2-methoxy-5- (2-ethylhexyl oxy) -1, 4-phenylenevinylene ] and poly [ 2-methoxy-5- (3 ',7' -dimethyloctyl oxy) -1, 4-phenylenevinylene ], copper phthalocyanines, aromatic tertiary amines, polynuclear aromatic tertiary amines, 4' -bis (P-carbazolyl) -1,1' -biphenyl compounds, N ' -tetraarylbenzidine, PEDOT: at least one of PSS and derivatives thereof, poly (N-vinylcarbazole) (PVK) and derivatives thereof, polymethacrylate and derivatives thereof, poly (9, 9-octylfluorene) and derivatives thereof, poly (spirofluorene) and derivatives thereof, N ' -di (naphthalen-1-yl) -N, N ' -diphenyl benzidine, spironpb, doped graphene, undoped graphene, C60, doped or undoped NiO, doped or undoped MoO ₃, doped or undoped WO ₃, doped or undoped V ₂O₅, doped or undoped P-type gallium nitride, doped or undoped CrO ₃, doped or undoped CuO; and/or the number of the groups of groups,

The functional layer further comprises a hole injection layer, and the material of the hole injection layer is selected from at least one of 2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-hexaazabenzophenanthrene, PEDOT, PSS doped with s-MoO ₃ derivatives, 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.

According to the technical scheme provided by the application, the alkaline substance is added, and is utilized to react with redundant acid in the solution and hydrogen elements dissociated among quantum dot lattices, so that the concentration of the free hydrogen elements in the quantum dot nano-particles is reduced, the stability of the quantum dot nano-particles in an electric field environment is improved, and the quantum yield of the quantum dots is improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural view of a light emitting device according to an embodiment of the present application;

fig. 2 is a schematic structural view of a light emitting device according to another embodiment of the present application;

fig. 3 is a schematic flow chart of a method for preparing quantum dots according to an embodiment of the present application;

Reference numerals:

100-a light emitting device; 10-anode; a 20-light emitting layer; 30-cathode; 40-a hole injection layer; a 50-hole transport layer; 60-electron transport layer.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to be within the scope of the present application based on the embodiments of the present application. Furthermore, it should be understood that the detailed description is presented herein for purposes of illustration and description only, and is not intended to limit the application. In the present application, unless otherwise specified, terms such as "upper" and "lower" are used specifically to refer to the orientation of the drawing in the figures. In addition, in the description of the present specification, the term "including" means "including but not limited to". Various embodiments of the application may exist in a range of forms; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the application; it is therefore to be understood that the range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that a description of a 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., as well as single numbers within the range, such as 1, 2,3, 4, 5, and 6, wherever applicable. In addition, whenever a numerical range is referred to herein, it is meant to include any reference number (fractional or integer) within the indicated range.

In the present application, "and/or" describing the association relationship of the association object means that there may be three relationships, for example, a and/or B may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural.

In the present application, "at least one" means one or more, and "a plurality" means two or more. "at least one", "at least one" or the like refer to any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple, respectively.

The application provides a quantum dot, wherein the crystal lattice of the quantum dot contains no or a small amount of free hydrogen, the structure of the quantum dot is not easy to break under the electric field environment, and the quantum dot has good crystal lattice stability and Quantum Yield (QY).

The quantum dot can be at least one of a quantum dot with a single structure and a quantum dot with a core-shell structure. The single-structure quantum dot refers to a quantum dot composed of a single quantum dot core, wherein the single-structure quantum dot is selected from at least one of II-VI compound, IV-VI compound, III-V compound and I-III-VI compound, the II-VI compound is 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 compound is selected from at least one of SnS、SnSe、SnTe、PbS、PbSe、PbTe、SnSeS、SnSeTe、SnSTe、PbSeS、PbSeTe、PbSTe、SnPbS、SnPbSe、SnPbTe、SnPbSSe、SnPbSeTe、SnPbSTe, the III-V compound is 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, and the I-III-VI compound is selected from at least one of CuInS ₂、CuInSe₂ and AgInS ₂. The quantum dot with the core-shell structure is formed by a quantum dot core and a shell layer coated outside the quantum dot core, wherein the core of the quantum dot with the core-shell structure is selected from any one of the quantum dots with the single structure, and the shell layer material of the quantum dot with the core-shell structure is selected from at least one of CdS, cdTe, cdSeTe, cdZnSe, cdZnS, cdSeS, znSe, znSeS and ZnS; in addition, the number of the shell layers of the quantum dot with the core-shell structure is not limited, and the number of the shell layers can be one layer, or can be two layers, three layers or more layers. As an example, the quantum dot of the core-shell structure may be selected from, but not limited to, at least one of CdZnSe/CdZnSe/ZnSe/CdZnS/ZnS、CdZnSe/CdZnSe/CdZnS/ZnS CdSe/CdSeS/CdS、InP/ZnSeS/ZnS、CdZnSe/ZnSe/ZnS、CdSeS/ZnSeS/ZnS、CdSe/ZnS、CdSe/ZnSe/ZnS、ZnSe/ZnS、ZnSeTe/ZnS、CdSe/CdZnSeS/ZnS and InP/ZnSe/ZnS.

The application also provides a preparation method of the quantum dot, which is used for preparing the quantum dot. Referring to fig. 3, the preparation method includes the following steps:

Step S10, providing a first solution, wherein the first solution contains quantum dot nano particles and acid;

and step S20, adding an alkaline substance into the first solution to adsorb the acid and free hydrogen in the quantum dot nano particles.

According to the technical scheme provided by the application, the alkaline substance is added, and is utilized to react with redundant acid in the solution and hydrogen elements dissociated among quantum dot lattices, so that the concentration of the free hydrogen elements in the quantum dot nano-particles is reduced, the stability of the quantum dot nano-particles in an electric field environment is improved, and the quantum yield of the quantum dots is improved.

In some embodiments, the quantum dot nanoparticle comprises a single structure quantum dot, a quantum dot core of a core-shell structure quantum dot, or a core-shell structure quantum dot having M shells, wherein M is a positive integer greater than 0; correspondingly, the first solution can be a solution at any stage after the formation of the quantum dot core in the quantum dot synthesis process, and the solution at least contains the quantum dot core and acid. For example:

In some embodiments, when the quantum dot nanoparticle is a quantum dot with a single structure, the first solution may be a solution after the quantum dot with a single structure is formed, and in particular, step S10 may include: providing a cationic precursor solution, an anionic precursor solution, and an organic solvent; mixing the cation precursor solution with an organic solvent, then adding the anion precursor solution, and reacting to obtain the first solution containing the quantum dots with the single structure; wherein at least one of the cationic precursor solution and the anionic precursor solution contains an acid.

In other embodiments, when the quantum dot is a quantum dot with a core-shell structure and the quantum dot nanoparticle is a quantum dot core of a quantum dot with a core-shell structure, the first solution may be a post-nucleation solution, and specifically, step S10 includes: providing a nuclear cation precursor solution, a nuclear anion precursor solution and an organic solvent; mixing the nuclear cation precursor solution with an organic solvent, and then adding the nuclear anion precursor solution to react to obtain a nuclear solution containing quantum dot nuclei; wherein at least one of the nuclear cation precursor solution and the nuclear anion precursor solution contains an acid; the first solution is the core solution.

In still other embodiments, the quantum dot is a core-shell quantum dot, having n+1 layers of shells, where n is an integer greater than or equal to 0, and accordingly, the quantum dot nanoparticle is a core-shell quantum dot having M shells, where 1.ltoreq.m.ltoreq.n+1, and if the quantum dot to be prepared is a core-shell quantum dot having three shells, the quantum dot nanoparticle may be a core-shell quantum dot having one shell, a core-shell quantum dot having two shells, or a core-shell quantum dot having three shells. In view of this, step S10 may include: providing a nuclear cation precursor solution, a nuclear anion precursor solution and an organic solvent; mixing the nuclear cation precursor solution with an organic solvent, and then adding the nuclear anion precursor solution to react to obtain a nuclear solution containing quantum dot nuclei; forming a first shell layer on the surface of the quantum dot core to obtain a first mixed solution containing quantum dot nanoparticles with one shell layer, repeating the step n times, wherein n is an integer greater than or equal to 0, sequentially obtaining second to n+1th shell layers, and correspondingly obtaining second mixed solution containing quantum dot nanoparticles with two shell layers to n+1th mixed solution containing quantum dot nanoparticles with n+1th shell layers; wherein at least one of the nuclear cation precursor solution and the nuclear anion precursor solution contains an acid; the first solution is the Mth mixed solution, and M is more than or equal to 1 and less than or equal to n+1.

It can be understood that when the equivalent quantum dot is a quantum dot with a core-shell structure, the subsequent shell forming step can be further included after the alkaline substance is added to adsorb free hydrogen.

The nuclear cation precursor comprises at least one of a cadmium source, a zinc source, an indium source, a copper source and a silver source.

The nuclear anion precursor comprises at least one of a selenium source, a sulfur source, a tellurium source and a phosphorus source.

The organic solvent comprises at least one of alkane, alkene, halohydrocarbon, aromatic hydrocarbon, ether, amine, ketone and ester. As an example, the organic solvent is at least one of tetradecene, pentadecene, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, and paraffin oil.

It will be appreciated that the nuclear cation precursor solution and the nuclear anion precursor solution may be selected according to the type of quantum dot to be produced, for example, when the type of quantum dot to be produced is CdSe, the required nuclear cation precursor is a cadmium source, and the nuclear anion precursor is a selenium source.

The acid may be an inorganic acid, an organic acid, or a group that is easily dissociated into hydrogen ions, including, but not limited to, carboxylic acid compounds, sulfonic acid compounds, sulfinic acid compounds, thiocarboxylic acid compounds, and the like. As an example, the acid includes at least one of oleic acid, octadecanesulfonic acid, and octadecanesulfonic acid. The acid is added during preparation of the nuclear cation precursor solution or the nuclear anion precursor solution, and a cadmium source is taken as an example, wherein the cadmium source can be cadmium oleate, and specifically, the cadmium oleate can be obtained by dissolving cadmium oxide in oleic acid.

In some embodiments, the alkaline substance comprises one or more of an organic base and an inorganic base. The organic base is selected from one or more of amine compounds and alkyl ammonium hydroxide. Wherein, the organic amine can react with acid in the first solution and free hydrogen in the quantum dot nano particles to generate ammonium salt substances; the inorganic base and the alkyl ammonium hydroxide are capable of neutralizing the acid and the free hydrogen to produce water; thereby enabling a reduction in the free hydrogen content of the quantum dot nanoparticles.

The alkyl group in the alkylammonium hydroxide contains 1-20 carbon atoms, for example, the number of carbon atoms of the alkyl group can be 1, 2, 3, 4, 5, 6, 7, 10, 12, 14, 16, 18, 20 and integer values between any two of the values recited above; in particular, the alkylammonium hydroxide may be selected from, but is not limited to, one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide.

The amine compound may be selected from alkylamine compounds wherein the alkyl group contains 1 to 40 carbon atoms, for example, the number of carbon atoms of the alkyl group may be 1,2, 3, 4, 5, 6, 7, 10, 12, 14, 16, 18, 20, 25, 30, 35, 40 and integer values between any two of the values recited above; specifically, the alkylamine compounds include, but are not limited to, one or more of octylamine, dioctylamine, trioctylamine, oleylamine.

The inorganic base is selected from one or more of alkali metal oxide, alkali metal hydroxide, alkali metal bicarbonate, alkali metal carbonate, alkaline earth metal oxide, alkaline earth metal hydroxide and alkaline earth metal bicarbonate. Further, in some embodiments, the alkali metal may include, but is not limited to, one of Li ⁺、K⁺、Na⁺; the alkaline earth metal may include, but is not limited to, one of Mg ²⁺、Ca²⁺、Ba²⁺; accordingly, the inorganic base may include, but is not limited to, one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium oxide, potassium oxide, calcium oxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, calcium bicarbonate, barium hydroxide.

In some embodiments, in the step of adding an alkaline substance to the first solution, the temperature of the first solution is 100 to 200 ℃, for example, the temperature may be 100 ℃, 105 ℃, 110 ℃,120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, and any value between any two of the values listed above. That is, step S20 may include: and regulating the temperature of the first solution to 100-200 ℃, and then adding alkaline substances to adsorb the acid and the free hydrogen. By adjusting the temperature of the first solution, the separation of free hydrogen from the crystal lattice is facilitated, and the adsorption of free hydrogen by alkaline substances is facilitated, so that the content of free hydrogen in the quantum dot core and/or shell is greatly reduced.

It can be appreciated that in some embodiments, when the alkaline substance is a substance with a relatively low boiling point, such as octylamine, the temperature of the first solution may be selected to be lower than the boiling point of the substance, which is helpful to improve the utilization rate of the alkaline substance, save materials, and improve the adsorption effect on free hydrogen. For example, octylamine has a boiling point of 179.4deg.C at 760mmHg, and accordingly, the temperature of the first solution may be selected in a range of 100 deg.C or more and less than 179.4deg.C.

In some embodiments, in step S20, the adsorption time is 10 to 60 minutes, for example, the adsorption time may be 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, and any value between any two of the values listed above. Controlling the adsorption time within the above range helps to fully adsorb the acid and the free hydrogen in the quantum dot core.

In some embodiments, when the alkaline substance is selected from one or more of inorganic base and alkyl ammonium hydroxide, water is generated after the alkaline substance is added, and accordingly, after the step of adding the alkaline substance to the first solution, the method may further include: the first solution is placed in a pressurized environment or a gaseous environment to remove water produced during the reaction. The pressure of the pressure environment is 10 to 10000Pa, for example, the pressure can be 10Pa, 20Pa, 30Pa, 50Pa, 100Pa, 200Pa, 500Pa, 1000Pa, 5000Pa, 10000Pa, and a value between any two values listed above; the gas of the gas flow environment comprises inert gas, and the inert gas can be any one or more gases which do not react with the first solution and the alkaline substances, including but not limited to one or more of nitrogen, helium and argon. The pressure environment is created, so that water and other volatile components in the solution are volatilized, water generated by the reaction is removed sufficiently, on one hand, water dissociation can be avoided, free hydrogen is introduced again, the content of free hydrogen in a crystal lattice is reduced further, and on the other hand, for the quantum dot with a core-shell structure, if alkaline substances are added before the outermost shell is formed, the water removal is beneficial to reducing the free hydrogen in the shell formed subsequently. It is understood that the pressure environment or the gas flow environment may be provided immediately after the alkaline substance is added, or may be provided after a period of time after the reaction starts, and the time for maintaining the pressure environment or the gas flow environment may be controlled to be 10 to 60 minutes, for example, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, and any value between any two of the values listed above.

In other embodiments, when the basic substance is one or more of organic amines, the reaction product includes ammonium salts, and correspondingly, after step S20 provided in this embodiment, the method further includes: and step S30, regulating the temperature of the first solution to 180-350 ℃, and preserving heat for 30-60 min.

Wherein the temperature of the first solution may be 180 ℃, 185 ℃, 190 ℃, 200 ℃, 220 ℃, 240 ℃, 250 ℃, 280 ℃, 300 ℃, 320 ℃, 340 ℃, 350 ℃ or any value between any two of the values recited above; the incubation time may be 30min, 40min, 50min, 60min, and any value between any two of the values listed above. By heating the solution to the above range, the conversion of the ammonium salt species into the amide compound is facilitated, thereby reducing the influence of the ammonium salt species on the subsequent long shell, facilitating the improvement of the long shell quality and the improvement of the quantum yield.

It will be appreciated that when the basic substance is alkylammonium hydroxide, ammonium salts are generated in addition to water, and thus, the step of adding basic substance to the first solution may further include: placing the first solution in a pressure environment or an air flow environment to remove water generated in the reaction process, reacting for 10-60 min at 100-200 ℃ in a reaction system, adjusting the temperature of the first solution to 180-350 ℃, and preserving the heat for 30-60 min.

In some embodiments, when the alkaline substance is solid, the alkaline substance may be added to the first solution in the form of a solution of the alkaline substance, where the solvent includes one or more of ethanol, propanol, and butanol, so that the alkaline substance can be rapidly and better dispersed in the first solution, and not only can effectively and rapidly adsorb free hydrogen, but also can not adsorb on the quantum dot core, thereby contributing to the improvement of quantum yield.

The alkaline substance has an alkaline structure, and the alkaline structure comprises at least one of amino and hydroxyl; in the step of adding an alkaline substance to the first solution and adsorbing the acid and the free hydrogen in the quantum dot nanoparticles, the amount of the substance having an alkaline structure is equal to or greater than the amount of the substance having an acid, thereby sufficiently adsorbing the acid and the free hydrogen. In some embodiments, the ratio of the amount of the basic structural material to the amount of the acid material may be (1-2): 1, e.g., 1:1, 1.1:1, 1.5:1, 1.7:1, 1.8:1, 2:1, and any values between any two of the values recited above.

In addition, referring to fig. 1, the light emitting device 100 further includes a first electrode, a functional layer, and a second electrode, where the functional layer includes a light emitting layer 20, and the light emitting layer 20 includes quantum dots as described above.

The first electrode is selected from one of the anode 10 and the cathode 30, and the second electrode is selected from the other of the anode 10 and the cathode 30. In some embodiments, the anode 10 comprises a metal electrode, a carbon-silicon material electrode, a metal oxide electrode, or a composite electrode, the material of the metal electrode comprising at least one of Ag, al, mg, au, cu, mo, pt, ca and Ba, the material of the carbon-silicon material electrode comprising at least one of silicon, graphite, carbon nanotubes, graphene, and carbon fibers, the material of the metal oxide electrode comprising at least one 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, and the composite electrode comprising 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.

The cathode 30 includes a metal electrode, a carbon-silicon material electrode, a metal oxide electrode or a composite electrode, wherein the material of the metal electrode includes at least one of Ag, al, mg, au, cu, mo, pt, ca and Ba, the material of the carbon-silicon material electrode includes at least one of silicon, graphite, carbon nanotubes, graphene and carbon fibers, the material of the metal oxide electrode includes at least one 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, and the composite electrode includes 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.

Referring to fig. 2, the functional layer further includes an electron transport layer 60, and the electron transport layer 60 is disposed between the cathode 30 and the light emitting layer 20. The material of the electron transport layer 60 may be selected from, but not limited to, one or more of metal oxides, doped metal oxides, group II-VI semiconductor materials, group III-V semiconductor materials, and group I-III-VI semiconductor materials. In particular, the metal oxide may be selected from, but is not limited to, one or more of ZnO, tiO ₂、SnO₂、Al₂O₃; the metal oxide in the doped metal oxide can be selected from one or more of ZnO and TiO ₂、SnO₂, the doping element can be selected from one or more of Al, mg, li, in, ga, and the doped metal oxide can be Aluminum Zinc Oxide (AZO), lithium Zinc Oxide (LZO), magnesium Zinc Oxide (MZO) and the like; the II-VI semiconductor group material may be selected from, but is not limited to, one or more of ZnS, znSe, cdS; the III-V semiconductor group material may be selected from, but is not limited to, one or more of InP, gaP; the group I-III-VI semiconductor material may be selected from, but is not limited to, one or more of CuInS, cuGaS.

The functional layer further includes a hole transport layer 50, and the hole transport layer 50 is disposed between the anode 10 and the light emitting layer 20. The material of the hole transport layer 50 may be selected from organic materials having hole transport ability, including but not limited to 4,4'-N, N' -dicarbazolyl-biphenyl (CBP), N '-diphenyl-N, N' -bis (1-naphthyl) -1,1 '-biphenyl-4, 4 "-diamine, N' -diphenyl-N, N '-bis (3-methylphenyl) - (1, 1' -biphenyl) -4,4 '-diamine, N' -bis (3-methylphenyl) -N, N '-bis (phenyl) -spiro (spiro-TPD), N' -bis (4- (N, N '-diphenyl-amino) phenyl) -N, N' -diphenyl benzidine, 4 '-tris (N-carbazolyl) -triphenylamine, 4' -tris (N-3-methylphenyl-N-phenylamino) triphenylamine, poly [ (9, 9 '-dioctylfluorene-2, 7-diyl) -co- (4, 4' - (N- (4-sec-butylphenyl) diphenylamine)) ], poly (4-butylphenyl-diphenylamine) (poly-TPD), polyaniline, polypyrrole, poly (p-phenylene vinylene, poly (phenylene vinylene), poly [ 2-methoxy-5- (2-ethylhexyl oxy) -1, 4-phenylenevinylene ] and poly [ 2-methoxy-5- (3 ',7' -dimethyloctyl oxy) -1, 4-phenylenevinylene ], copper phthalocyanines, aromatic tertiary amines, polynuclear aromatic tertiary amines, 4' -bis (P-carbazolyl) -1,1' -biphenyl compounds, N ' -tetraarylbenzidine, PEDOT: PSS and derivatives thereof, poly (N-vinylcarbazole) (PVK) and derivatives thereof, polymethacrylate and derivatives thereof, poly (9, 9-octylfluorene) and derivatives thereof, poly (spirofluorene) and derivatives thereof, N ' -di (naphthalen-1-yl) -N, N ' -diphenyl benzidine, spironpb, doped graphene, undoped graphene, C60, doped or undoped NiO, doped or undoped MoO ₃, doped or undoped WO ₃, doped or undoped V ₂O₅, doped or undoped P-type gallium nitride, doped or undoped CrO ₃, doped or undoped CuO.

The functional layer further includes a hole injection layer 40, the hole injection layer 40 being disposed between the anode 10 and the light emitting layer 20; when the functional layer also includes the hole transport layer 50, the hole injection layer 40 is located between the anode 10 and the hole transport layer 50. The material of the hole injection layer 40 may be a material known in the art for the hole injection layer 40, including but not limited to at least one of poly (3, 4-ethylenedioxythiophene) (PEDOT), poly (3, 4-ethylenedioxythiophene) -polystyrene sulfonic acid (PEDOT: PSS), PSS doped with a derivative of s-MoO ₃, 4' -tris (N-3-methylphenyl-N-phenylamino) triphenylamine, 2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-Hexaazabenzophenanthrene (HATCN), tetracyanoquinone dimethane, copper phthalocyanine, nickel oxide, molybdenum oxide, tungsten oxide, vanadium oxide, molybdenum sulfide, tungsten sulfide, and copper oxide.

Furthermore, in some embodiments, the functional layer further includes an electron injection layer disposed between the cathode 30 and the light emitting layer 20; when the functional layer also includes an electron transport layer 60, an electron injection layer is located between the cathode 30 and the electron transport layer 60. The material of the electron injection layer is at least one selected from cesium carbonate, cesium fluoride, cesium azide and lithium fluoride.

The application also provides a preparation method of the light-emitting device, which comprises the following steps: providing a first electrode; forming a functional layer on the first electrode; forming a second electrode on the functional layer; when the functional layer is the light-emitting layer 20, the preparation of the light-emitting layer 20 includes disposing quantum dots on the first electrode to form the light-emitting layer 20; when the functional layer further includes one or more of the electron injection layer, the hole injection layer 40, the hole transport layer 50, and the electron transport layer 60, the preparation of the functional layer includes, arranging different film materials in the order of the film layers to form a plurality of stacked film layers, to obtain the functional layer, taking the light emitting device 100 shown in fig. 2 as an example, the preparation of the functional layer includes: providing a hole injection material on the first electrode to form a hole injection layer 40; providing a hole transport material on the hole injection layer 40 to form a hole transport layer 50; disposing quantum dots on the hole transport layer 50 to form the light emitting layer 20; an electron transport material is disposed on the light emitting layer 20 to form an electron transport layer 60.

The method of forming the light emitting layer 20 and other functional layers such as the hole injection layer 40, the hole transport layer 50, and the electron transport layer 60 may be a chemical method or a physical method. The chemical method can be chemical vapor deposition, continuous ion layer adsorption and reaction, anodic oxidation, electrolytic deposition, coprecipitation, etc. The physical method can be a physical plating method or a solution processing method, and the physical plating method can be a thermal evaporation plating method CVD, an electron beam evaporation plating method, a magnetron sputtering method, a multi-arc ion plating method, a physical vapor deposition method PVD, an atomic layer deposition method, a pulse laser deposition method and the like; the solution processing method may be spin coating, printing, inkjet printing, knife coating, printing, dip-coating, dipping, spraying, roll coating, casting, slit coating, bar coating, or the like. The individual film layers of the optoelectronic device according to the embodiments of the present application can be prepared by those skilled in the art according to the preparation method of the light emitting device 100 known in the art, and will not be described herein.

The technical scheme and effect of the present application will be described in detail by the following specific examples and comparative examples, which are only some examples of the present application, and are not intended to limit the present application in any way.

Example 1

(1) 5Mmol of zinc acetate is dissolved in a mixed solvent of 5mL of oleic acid and 10mL of octadecene, kept for 10min under the condition of 100 ℃ and 10Pa, and then heated to 200 ℃ under argon flow for 30min to obtain a zinc precursor. 2mmol of cadmium oxide is dissolved in a mixed solvent of 2mL of oleic acid and 8mL of octadecene, kept for 10min under the condition of 100 ℃ and 10Pa, and then heated to 200 ℃ under argon flow for 30min to obtain a cadmium precursor.

(2) Under the argon flow, continuously heating the zinc precursor to 300 ℃, rapidly injecting 1mmol of trioctyl phosphorus selenium, curing for 1min, injecting 0.1mmol of cadmium precursor, and continuously curing for 30min to obtain the nuclear solution containing ZnCdSe cores.

(3) The temperature of the nuclear solution is reduced to 100 ℃, 6mmol of oleylamine is added for reaction for 20min, and an alkali treatment solution is obtained;

(4) Heating the alkali treatment solution to 200 ℃, and preserving heat for 60min;

(5) Injecting 1mmol of trioctyl phosphose, curing for 30min to form ZnSe shell, and obtaining the solution containing ZnSSe/ZnSe.

(6) Maintaining the temperature of the solution containing ZnCdSe/ZnSe at 300 ℃, injecting 1mmol of trioctylphosphine sulfide into the solution, curing for 30min to form a ZnS shell, and obtaining the solution containing quantum dots ZnCdSe/ZnSe/ZnS.

(7) Ethanol is added into the solution containing quantum dots ZnCdSe/ZnSe/ZnS, the quantum dots are separated after being precipitated, then the quantum dots are dissolved in n-octane, and the precipitation-dissolution steps are repeated twice to obtain the n-octane solution of blue quantum dots with the concentration of 30 mg/mL.

Example 2

This embodiment is substantially the same as that of example 1 except that in this embodiment, in the step (3), the alkaline substance is changed from oleylamine to trioctylamine.

Example 3

The embodiment is basically the same as that of embodiment 1, except that in the embodiment, in the step (3), the alkaline substance is changed from oleylamine to octylamine.

Example 4

This example is substantially identical to example 1, except that in this example, in step (3), the alkaline substance is changed from oleylamine to a mixture of dioctylamine and trioctylamine (molar ratio 1:1).

Example 5

The embodiment is substantially the same as that of embodiment 1 except that in this embodiment, the temperature of the alkali treatment solution in step (4) is changed to 350 ℃.

Example 6

This embodiment is substantially identical to embodiment 1, except that in this embodiment, the oleylamine is added after the ZnSe shell is formed, i.e., steps (3) to (5) are changed to:

Injecting 1mmol of trioctyl phosphose, curing for 30min to form a ZnSe shell, and obtaining a solution containing ZnSSe/ZnSe; and (3) reducing the temperature of the solution containing ZnCdSe/ZnSe to 100 ℃, adding 6mmol of oleylamine, reacting for 20min to obtain an alkali treatment solution, then heating the alkali treatment solution to 200 ℃ under argon flow, and preserving the temperature for 60min to obtain the ZnCdSe/ZnSe solution, wherein the solution is used in the step (6).

Example 7

This example scheme is essentially the same as example 1 except that in this example, the oleylamine is added after the shell of ZnS is formed, i.e., steps (3) to (6) are changed to:

Injecting 1mmol of trioctyl phosphose, curing for 30min to form a ZnSe shell, and obtaining a solution containing ZnSSe/ZnSe; injecting 1mmol of trioctylphosphine sulfide into the solution, curing for 30min to form a ZnS shell, and obtaining a solution containing quantum dots ZnCdSe/ZnSe/ZnS; and (3) reducing the temperature of the solution containing the quantum dots ZnCdSe/ZnSe/ZnS to 100 ℃, adding 6mmol of oleylamine, reacting for 20min to obtain an alkali treatment solution, and then heating the temperature of the alkali treatment solution to 200 ℃ under argon flow, and preserving the temperature for 60min to obtain the quantum dot solution, wherein the quantum dot solution is used in the step (7).

Example 8

This example is essentially identical to example 1, except that in this example, the core solution temperature in step (3) is changed from 100℃to 200 ℃.

Example 9

The embodiment is substantially the same as that of embodiment 1 except that in this embodiment, the temperature of the alkali treatment solution in step (4) is changed to 180 ℃.

Example 10

The embodiment is basically the same as embodiment 1, except that in this embodiment:

in the step (3), the alkaline substance is changed from oleylamine to tetramethylammonium hydroxide;

step (4) is performed in an argon stream.

Example 11

The embodiment is substantially the same as that of embodiment 1 except that in this embodiment, the temperature of the alkali treatment solution in step (4) is changed from 200℃to 170 ℃.

Example 12

The embodiment is substantially the same as that of embodiment 1 except that in this embodiment, the temperature of the alkali treatment solution in step (4) is changed from 200℃to 360 ℃.

Example 13

The embodiment is substantially the same as embodiment 1, except that in this embodiment, steps (3) and (4) are changed to:

The temperature of the nuclear solution was lowered to 110 ℃, a butanol solution of sodium hydroxide (equivalent to 6mmol of sodium hydroxide) was added, after 20 minutes of reaction, the ambient pressure was adjusted to 100Pa, and then the reaction was continued for 20 minutes, to obtain an alkali-treated solution, which was used in step (5).

Example 14

The scheme of this embodiment is basically the same as that of embodiment 13, except that in this embodiment, in step (3):

The alkaline substance is changed from butanol solution of sodium hydroxide to butanol solution of sodium hydroxide and sodium bicarbonate (the mol ratio of sodium hydroxide to sodium bicarbonate is 1:1).

Example 15

This embodiment is substantially the same as embodiment 13 except that in this embodiment, steps (3) and (4) are changed to:

The temperature of the nuclear solution was lowered to 110 ℃, a butanol solution of sodium hydroxide (equivalent to 6mmol of sodium hydroxide) was added, after 20 minutes of reaction, a stream of argon was introduced, and then the reaction was continued for 20 minutes, to obtain an alkali-treated solution, which was used in step (5).

Example 16

This embodiment is substantially the same as embodiment 13 except that in this embodiment, the ambient pressure is adjusted from 100Pa to 11KPa when performing steps (3) and (4).

Example 17

This example is essentially identical to example 13, except that in this example, the temperature of the core solution is reduced to 90℃while steps (3) and (4) are performed.

Example 18

This example is essentially identical to example 13, except that in this example, the temperature of the core solution is reduced to 220 ℃ while steps (3) and (4) are performed.

Example 19

The embodiment is substantially the same as embodiment 1, except that in this embodiment,

Step (4) is removed.

Example 20

This comparative example was substantially identical to example 16, except that in this example,

The step "the ambient pressure was adjusted to 100Pa and then the reaction was continued for 20min".

Comparative example 1

This comparative example was substantially identical to example 1, except that in this comparative example,

Steps (3) and (4) are removed.

Device example 1

The preparation method of the QLED device of the embodiment of the device is as follows:

(1) A layer of base glass substrate was provided, the thickness of the substrate being 0.4mm. An anode was formed on a substrate base plate using ITO to a thickness of 50nm. Ultrasonic treating the anode with alkaline washing solution with pH >12 for 15min, ultrasonic treating with deionized water for 15min twice, ultrasonic cleaning with isopropanol for 15min, oven drying at 80deg.C for 2 hr, and ultraviolet treating with ozone for 15min.

(2) An aqueous solution of PEDOT: PSS (molar ratio 1:1) was spin-coated on the anode at 5000rpm for 40s, followed by annealing at 150℃for 15min to obtain a hole injection layer having a thickness of 20 nm. The flakes were then transferred to a glove box with a water oxygen content of less than 0.1ppm for subsequent steps (3) (4) (5).

(3) And spin-coating a chlorobenzene solution of TFB with a concentration of 8mg/mL on the hole injection layer at 3000rpm, and then annealing at 150 ℃ for 30min to obtain a hole transport layer with a thickness of 20 nm.

(4) The n-octane solution of the blue quantum dot prepared in example 1 was spin-coated on the hole transport layer to obtain a light emitting layer having a thickness of 20 nm.

(5) And spin-coating an ethanol solution of nano zinc oxide with the concentration of 30mg/mL on the luminescent layer at 3000rpm, and then annealing at 80 ℃ for 30min to obtain the electron transport layer with the thickness of 50 nm.

(6) And evaporating Ag on the electron transport layer to obtain a cathode with the thickness of 100nm, and then packaging by adopting epoxy resin glue and a cover glass to obtain the QLED device.

Device examples 2 to 20

Device examples 2 to 20 the same as device example 1 except that in device example N, the light emitting layer material was N-octane solution of blue quantum dots prepared in example N, N being 2 to 20.

Device comparative example 1

Device comparative example 1 the scheme was essentially the same as device example 1 except that in device comparative example 1, the light emitting layer material was an n-octane solution of blue quantum dots prepared in comparative example 1.

The quantum dots prepared in examples 1 to 20 and comparative examples 1 to 3 were stored under natural light at normal temperature, and then their Quantum Yields (QY) were examined at different days (1 day, 3 days, 7 days, 14 days, 30 days) of storage, and the results are reported in table 1.

The detection method comprises the following steps:

The method for testing the Quantum Yield (QY) is as follows: and putting the quantum dot solution into an integrating sphere arranged in the Edinburgh spectrometer to compare the incident photons with photons emitted by the quantum dot solution.

TABLE 1

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As can be seen from table one:

Compared with comparative example 1, after the quantum dots prepared in examples 1 to 20 are stored for 30 days under the condition of normal temperature natural light, the decrease of QY is small, which indicates that the preparation method provided by the application is helpful for improving the stability of the luminous efficiency of the quantum dots, and probably because the quantum dots in comparative example 1 contain more free hydrogen, the quantum dots are gathered and increased in lattice stress after being excited under the condition of normal temperature natural light, so that the lattice defects of cores and shells are increased, the luminous efficiency (QY) is reduced, and the stability of the luminous efficiency of the quantum dots is obviously improved under the same condition because free hydrogen is eliminated in each example;

Comparing examples 1 and 19, examples 13 and 20, respectively, it can be seen that the quantum dots of examples 1 and 13 have higher QY and better QY stability, demonstrating that ammonium salt conversion and H ₂ O removal after free hydrogen adsorption by the addition of alkaline substances contribute to the improvement of the light-emitting efficiency and stability of the quantum dots.

Comparing examples 13, 17 and 18, it can be seen that example 13 exhibits a more stable, higher luminous efficiency, demonstrating that the addition of alkaline material at temperatures of 100-200 c facilitates adsorption of free hydrogen.

The light-emitting devices produced in device examples 1, 13, 19, and 20 and device comparative example 1 were subjected to lifetime detection, and the results are shown in table 2.

The test method of the service life T95@1000nit comprises the following steps: the time required for the device to decrease in brightness to a certain proportion of the maximum brightness under constant current or voltage drive is defined as T95, and the lifetime is the measured lifetime. To shorten the test period, the device lifetime test is usually performed by accelerating the aging of the device at high brightness, and fitting the device lifetime at high brightness by an extended exponential decay brightness decay fitting formula, for example: the lifetime meter at 1000nit is T95@1000nit. The specific calculation formula is as follows:

Wherein, T95 _L is the life under low luminance, T95 _H is the actual measurement life under high luminance, L _H is the device acceleration to the highest luminance, L _L is 1000nit, A is the acceleration factor, and this experiment obtains that A value is 1.7 through measuring the life of a plurality of groups of green QLED devices under rated luminance.

TABLE 2

As can be seen from table 2:

Compared with the device of the comparative example 1, the light-emitting device prepared by the device example has longer service life, which indicates that the preparation method provided by the application is beneficial to prolonging the service life of the device, probably because the quantum dots in the comparative example 1 contain more free hydrogen, after being excited under normal-temperature natural illumination, the aggregation increases the lattice stress, so that the lattice defects of a core and a shell are increased, the light-emitting efficiency (QY) is reduced, and the free hydrogen is eliminated by each example, so that the stability of the light-emitting efficiency of the quantum dots is obviously improved under the same condition, and the service life of the device is prolonged;

Comparing device example 1, device example 13, device example 19 and device example 20, it can be seen that device examples 1 and 13 have longer lifetimes, which means that ammonium salt conversion and H ₂ O removal after adsorption of free hydrogen by adding alkaline substances contribute to the improvement of the light-emitting efficiency and stability of the quantum dots and to the extension of the lifetime of the devices.

The quantum dot, the preparation method thereof and the light emitting device provided by the embodiment of the application are described in detail, and specific examples are applied to illustrate the principle and the implementation of the application, and the description of the above examples is only used for helping to understand the method and the core idea of the application; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in light of the ideas of the present application, the present description should not be construed as limiting the present application.

Claims (14)

1. The preparation method of the quantum dot is characterized by comprising the following steps of:

Providing a first solution containing quantum dot nanoparticles and an acid;

adding an alkaline substance to the first solution to adsorb the acid and free hydrogen in the quantum dot nanoparticles.

2. The method of preparing a quantum dot according to claim 1, wherein the quantum dot nanoparticle comprises a single-structure quantum dot, a quantum dot core of a core-shell structure quantum dot, or a core-shell structure quantum dot having M shells, wherein M is a positive integer greater than 0;

And/or the alkaline substance has an alkaline structure, the alkaline structure comprising at least one of an amino group and a hydroxyl group; and adding an alkaline substance into the first solution, wherein in the step of adsorbing the acid and the free hydrogen in the quantum dot nano particles, the amount of the substance with the alkaline structure is more than or equal to the amount of the substance with the acid.

3. The method of preparing a quantum dot according to claim 1 or 2, wherein in the step of adding an alkaline substance to the first solution, the temperature of the first solution is 100 to 200 ℃.

4. A method of producing a quantum dot according to any one of claims 1 to 3, wherein in the step of adding an alkaline substance to the first solution to adsorb the acid and the free hydrogen in the quantum dot nanoparticles, the adsorption time is 10 to 60 minutes.

5. The method of producing a quantum dot according to any one of claims 1 to 4, wherein the basic substance comprises one or more of an organic base and an inorganic base;

the inorganic base is selected from one or more of alkali metal oxide, alkali metal hydroxide, alkali metal bicarbonate, alkali metal carbonate, alkaline earth metal oxide, alkaline earth metal hydroxide and alkaline earth metal bicarbonate;

the organic base is selected from one or more of amine compounds and alkyl ammonium hydroxide, wherein the alkyl in the alkyl ammonium hydroxide contains 1-20 carbon atoms.

6. The method of preparing quantum dots according to claim 5, wherein the amine compound is selected from alkylamine compounds, wherein the alkyl group in the alkylamine compound contains 1-40 carbon atoms, and further wherein the alkylamine compound comprises one or more of octylamine, dioctylamine, trioctylamine, and oleylamine; and/or the number of the groups of groups,

The alkyl ammonium hydroxide comprises one or more of tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide and tetrapropyl ammonium hydroxide; and/or the number of the groups of groups,

The inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium oxide, potassium oxide, calcium oxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, calcium bicarbonate and barium hydroxide.

7. The method for preparing quantum dots according to claim 5 or 6, wherein the alkaline substance is one or more selected from inorganic base and alkyl ammonium hydroxide;

After the step of adding an alkaline substance to the first solution, further comprising: the first solution is placed in a pressure environment or a gas flow environment so as to remove water generated in the reaction process, wherein the pressure of the pressure environment is 10-10000 Pa, and the gas of the gas flow environment comprises inert gas.

8. The method of preparing a quantum dot according to claim 5 or 6, wherein the basic substance is one or more selected from organic amines;

after the step of adding an alkaline substance to the first solution to adsorb the acid and the free hydrogen in the quantum dot nanoparticles, the method further comprises: and regulating the temperature of the first solution to 180-350 ℃, and preserving heat for 30-60 min.

9. The method of any one of claims 1-8, wherein when the quantum dot nanoparticle is a single structure quantum dot, providing a first solution, the first solution comprising the quantum dot nanoparticle and an acid, comprises: providing a cationic precursor solution, an anionic precursor solution, and an organic solvent; mixing the cation precursor solution with an organic solvent, then adding the anion precursor solution, and reacting to obtain the first solution containing the quantum dots with the single structure; wherein at least one of the cationic precursor solution and the anionic precursor solution contains an acid; or alternatively

When the quantum dot nano-particles are quantum dot cores of quantum dots with core-shell structures, providing a first solution, wherein the first solution contains the quantum dot nano-particles and acid, and the method comprises the following steps of: providing a nuclear cation precursor solution, a nuclear anion precursor solution and an organic solvent; mixing the nuclear cation precursor solution with an organic solvent, and then adding the nuclear anion precursor solution to react to obtain a nuclear solution containing quantum dot nuclei; wherein at least one of the nuclear cation precursor solution and the nuclear anion precursor solution contains an acid; the first solution is the core solution; or alternatively

When the quantum dot nano-particles are core-shell structure quantum dots with M shell layers, providing a first solution, wherein the first solution contains the quantum dot nano-particles and acid, and the method comprises the following steps of: providing a nuclear cation precursor solution, a nuclear anion precursor solution and an organic solvent; mixing the nuclear cation precursor solution with an organic solvent, and then adding the nuclear anion precursor solution to react to obtain a nuclear solution containing quantum dot nuclei; forming a first shell layer on the surface of the quantum dot core to obtain a first mixed solution containing quantum dot nanoparticles with one shell layer, repeating the step n times, wherein n is an integer greater than or equal to 0, sequentially obtaining second to n+1th shell layers, and correspondingly obtaining second mixed solution containing quantum dot nanoparticles with two shell layers to n+1th mixed solution containing quantum dot nanoparticles with n+1th shell layers; wherein at least one of the nuclear cation precursor solution and the nuclear anion precursor solution contains an acid; the first solution is the Mth mixed solution, and M is more than or equal to 1 and less than or equal to n+1.

10. The method of any one of claims 1-9, wherein the acid comprises at least one of oleic acid, octadecanesulfonic acid, and octadecanesulfonic acid.

11. A quantum dot produced by the production process according to any one of claims 1 to 10.

12. The quantum dot of claim 11, wherein the quantum dot is selected from at least one of a single structure quantum dot selected from at least one of a group II-VI compound 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, a group IV-VI compound selected from at least one of SnS、SnSe、SnTe、PbS、PbSe、PbTe、SnSeS、SnSeTe、SnSTe、PbSeS、PbSeTe、PbSTe、SnPbS、SnPbSe、SnPbTe、SnPbSSe、SnPbSeTe、SnPbSTe, and a core-shell structure quantum dot selected from at least one of a group IV-VI compound 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, a group III-V compound selected from at least one of CuInS ₂、CuInSe₂ and AgInS ₂; the core of the quantum dot with the core-shell structure is selected from any one of the quantum dots with the single structure, and the shell material of the quantum dot with the core-shell structure is selected from at least one of CdS, cdTe, cdSeTe, cdZnSe, cdZnS, cdSeS, znSe, znSeS and ZnS.

13. A light emitting device comprising a first electrode, a functional layer and a second electrode, the functional layer comprising a light emitting layer, characterized in that the light emitting layer comprises the quantum dot according to claim 11 or 12.

14. The light-emitting device according to claim 13, wherein the first electrode and the second electrode are each independently selected from a doped metal oxide particle electrode, a composite electrode of a metal and a metal oxide, a graphene electrode, a carbon nanotube electrode, a metal electrode or an alloy electrode, wherein a material of the doped metal oxide particle electrode is selected from one or more of indium-doped tin oxide, fluorine-doped tin oxide, antimony-doped tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, indium-doped zinc oxide, magnesium-doped zinc oxide and aluminum-doped magnesium oxide, and a material of the composite electrode of a metal and a metal oxide is selected from one or more of Ag, al, cu, mo, au, pt, si, ca, mg and Ba; and/or the number of the groups of groups,

The functional layer further comprises an electron transport layer, wherein the material of the electron transport layer is at least one selected from metal oxide, doped metal oxide, II-VI semiconductor material, III-V semiconductor material and I-III-VI semiconductor material, and the metal oxide is at least one selected from ZnO, baO, tiO ₂、SnO₂; the metal oxide in the doped metal oxide is at least one of ZnO and TiO ₂、SnO₂, the doping element is at least one of Al, mg, li, in, ga, and the II-VI semiconductor material is at least one of ZnS, znSe, cdS; the III-V semiconductor group material is at least one of InP and GaP; the I-III-VI semiconductor material is at least one selected from CuInS and CuGaS; and/or the number of the groups of groups,

The functional layer further comprises an electron injection layer, and the material of the electron injection layer is at least one selected from cesium carbonate, cesium fluoride, cesium azide and lithium fluoride; and/or the number of the groups of groups,

The functional layer also comprises a hole transport layer, the material of the hole transport layer is selected from 4,4' -N, N ' -dicarbazolyl-biphenyl, N ' -diphenyl-N, N ' -bis (1-naphthyl) -1,1' -biphenyl-4, 4' -diamine, N ' -diphenyl-N, N ' -bis (3-methylphenyl) - (1, 1' -biphenyl) -4,4' -diamine, N ' -bis (3-methylphenyl) -N, N ' -bis (phenyl) -spiro, N ' -bis (4- (N, N ' -diphenyl-amino) phenyl) -N, N ' -diphenyl benzidine, 4',4' -tris (N-carbazolyl) -triphenylamine, 4' -tris (N-3-methylphenyl-N-phenylamino) triphenylamine, poly [ (9, 9' -dioctylfluorene-2, 7-diyl) -co- (4, 4' - (N- (4-sec-butylphenyl) diphenylamine)) ] ], poly (4-butylphenyl-diphenylamine), polyaniline, polypyrrole, poly (p-phenylenevinylene, poly (phenylenevinylene), poly [ 2-methoxy-5- (2-ethylhexyl oxy) -1, 4-phenylenevinylene ] and poly [ 2-methoxy-5- (3 ', at least one of 7 '-dimethyloctyloxy) -1, 4-phenylenevinylene ], copper phthalocyanine, aromatic tertiary amine, polynuclear aromatic tertiary amine, 4' -bis (P-carbazolyl) -1,1 '-biphenyl compound, N' -tetraarylbenzidine, PEDOT: PSS and derivatives thereof, poly (N-vinylcarbazole) and derivatives thereof, polymethacrylate and derivatives thereof, poly (9, 9-octylfluorene) and derivatives thereof, poly (spirofluorene) and derivatives thereof, N '-bis (naphthalene-1-yl) -N, N' -diphenyl benzidine, spironpb, doped graphene, undoped graphene, C60, doped or undoped NiO, doped or undoped MoO ₃, doped or undoped WO ₃, doped or undoped V ₂O₅, doped or undoped P-type gallium nitride, doped or undoped CrO ₃, doped or undoped CuO; and/or the number of the groups of groups,

The functional layer further comprises a hole injection layer, and the material of the hole injection layer is selected from at least one of 2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-hexaazabenzophenanthrene, PEDOT, PSS doped with s-MoO ₃ derivatives, 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.