Composite material, preparation method and luminescent device

Abstract

The invention provides a composite material, a preparation method and a light-emitting device, and belongs to the technical field of display. According to the composite material, the first quantum dots with the N-type ligands and the second quantum dots with the P-type ligands are compounded, so that the carrier injection balance of the photoelectric device with the composite material can be improved, and the service life of the photoelectric device is prolonged.

Description

Technical Field

[0001] The present application relates to the technical field of light-emitting devices, and in particular to composite materials and preparation methods, and light-emitting devices. Background Art

[0002] Quantum dot materials are widely used in optoelectronic devices. The unbalanced carrier injection in optoelectronic devices leads to a rapid roll-off of device performance and a generally short lifetime. Summary of the invention

[0003] The invention provides a composite material and a preparation method thereof, a light-emitting device and a display device.

[0004] In a first aspect, the present application provides a composite material, comprising a first quantum dot and a second quantum dot; wherein the surface of the first quantum dot has an N-type ligand, and the surface of the second quantum dot has a P-type ligand.

[0005] In some embodiments of the present application, the first quantum dot includes a metal element M, and the N-type ligand is selected from halides of the metal element M;

[0006] And / or, the P-type ligand is selected from any one or more of the compounds shown in Formula I,

[0007]

[0008] Among them, R 1 and R 2 are independently selected from -H, -SH, -COOH, -NH 2 、-OH、-NHR 3 、-NR 4 R 5 ,-PO 3 H 2 ,-PO 3 HR 6 ,-PO 3 R 7 R 8 、-SO 3 H, -SO 3 R 9 One of them, but not all of them are H;

[0009] R is selected from a C1-C30 aliphatic group, a C6-C30 arylene group, or a C3-C30 heteroarylene group, wherein the heteroatom of the heteroarylene group is selected from O, S, N, and P;

[0010] R 3 , R 4 , R 5 , R 6 , R 7 , R8 , R 9 A hydrocarbon group selected from C1-C6.

[0011] In some embodiments of the present application, the N-type ligand includes one or more of zinc halide, cadmium halide, mercury halide, lead halide, tin halide, copper halide, silver halide, gallium halide, and indium halide;

[0012] And / or, R in the P-type ligand is selected from a C3 to C15 aliphatic group, a C6-C18 arylene group, or a C6-C18 heteroarylene group.

[0013] In some embodiments of the present application, the N-type ligand includes one or more of zinc fluoride, zinc chloride, zinc bromide, zinc iodide, cadmium fluoride, cadmium chloride, cadmium bromide, and cadmium iodide;

[0014] And / or, the P-type ligand includes one or more of propylene glycol, butanediol, pentanediol, hexanediol, 2-mercaptoethanol, 2-mercaptophenol, 3-mercaptophenol, 4-hydroxythiophenol, 4-hydroxythiophene cysteamine, 2-aminothiophenol, 3-aminothiophenol, 4-aminothiophenol, oxalic acid, malonic acid, succinic acid, adipic acid, and maleic acid.

[0015] In some embodiments of the present application, the ratio of the first quantum dot to the second quantum dot is 0.25 to 25 in terms of molar ratio;

[0016] And / or, the average particle size of the first quantum dots is in the range of 7nm-12nm;

[0017] And / or, the average particle size of the second quantum dots is in the range of 7nm-12nm.

[0018] In some embodiments of the present application, the first quantum dot and the second quantum dot are independently selected from one or more of a single structure quantum dot, a core-shell structure quantum dot and a perovskite semiconductor material, and the material of the single structure quantum dot, the core material of the core-shell structure quantum dot and the shell material of the core-shell structure quantum dot are selected from at least one of a II-VI group compound, a IV-VI group compound, a III-V group compound and a I-III-VI group compound, and the II-VI group compound is selected from CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe , ZnO, CdSeS, ZnSeS, ZnSeTe, ZnSTe, CdZnSeS, the III-V group compound is selected from at least one of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, GaNP, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, GaAlNP, GaAlNAs, GaInNP, InAlNP, the I-III-VI group compound is selected from at least one of CuInS 2 、CuInSe 2 and AgInS 2 At least one of;

[0019] And / or, the material of the first quantum dots is the same as the material of the second quantum dots.

[0020] A second aspect of the present application provides a method for preparing a composite material, the method comprising:

[0021] Providing a first quantum dot having an N-type ligand on the surface and a second quantum dot having a P-type ligand on the surface;

[0022] The first quantum dot solution having the N-type ligand and the second quantum dot solution having the P-type ligand are mixed in a preset ratio to obtain a quantum dot mixed solution, and the solvent in the quantum dot mixed solution is removed to obtain the composite material.

[0023] In some embodiments of the present application, the step of providing a first quantum dot having an N-type ligand on the surface and a second quantum dot having a P-type ligand on the surface comprises: providing an initial quantum dot solution, wherein the initial quantum dot solution comprises quantum dots and initial ligands bonded to the surface of the quantum dots;

[0024] A solution having an N-type ligand is added dropwise to the initial quantum dot solution to obtain a first ligand-replacement precursor solution, and the N-type ligand in the first ligand-replacement precursor solution is subjected to a ligand exchange with the initial ligand through a solution ligand exchange method to obtain a first quantum dot having the N-type ligand on its surface; and / or a solution having a P-type ligand is added dropwise to the first quantum dot solution to obtain a second ligand-replacement precursor solution, and the P-type ligand in the second ligand-replacement precursor solution is subjected to a ligand exchange with the N-type ligand through a solution ligand exchange method to obtain a second quantum dot having the P-type ligand on its surface.

[0025] In some embodiments of the present application, the P-type ligand is selected from any one or more of the compounds shown in Formula I,

[0026]

[0027] Among them, R 1 and R 2 are independently selected from -H, -SH, -COOH, -NH 2 、-OH、-NHR 3 、-NR 4 R 5 ,-PO 3 H 2 ,-PO 3 HR 6 ,-PO 3 R 7 R 8 、-SO 3 H, -SO 3 R 9 one of, but not all of them are H; R is selected from a C1-C30 aliphatic group, a C6-C30 arylene group, or a C3-C30 heteroarylene group, wherein the heteroatom of the heteroarylene group is selected from O, S, N, P; R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 A hydrocarbon group selected from C1-C6;

[0028] And / or, the first quantum dot includes a metal element M, and the N-type ligand is selected from a halide of the metal element M.

[0029] A third aspect of the present application provides a light-emitting device, which includes a light-emitting layer, and the light-emitting layer includes the composite material or the composite material obtained by the preparation method.

[0030] A fourth aspect of the present application provides a display device, which includes the composite material; or the composite material obtained by the preparation method; or includes the light-emitting device.

[0031] The composite material in the present application can improve the carrier injection balance of the optoelectronic device having the composite material and increase the service life of the optoelectronic device by compounding the first quantum dots having N-type ligands and the second quantum dots having P-type ligands. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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 invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A schematic diagram of the energy level structure of a light-emitting device of the present application;

[0034] Figure 2 It is a schematic diagram of an energy level structure of an embodiment of a light emitting device;

[0035] Figure 3 A schematic structural diagram of an embodiment of a light emitting device of the present application;

[0036] Figure 4 A schematic diagram of a process flow of a method for preparing a composite material in the present application.

[0037] Reference numerals: 100, light-emitting device; 110, first electrode; 120, second electrode; 130, hole injection layer; 140, hole transport layer; 150, light-emitting layer; 160, electron transport layer. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0039] In this application, the word "exemplary" is used to mean "serving as an example, illustration, or illustration." Any embodiment described in this application as "exemplary" is not necessarily to be construed as being preferred or advantageous over other embodiments. The following description is given to enable any person skilled in the art to implement and use the invention. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the invention can be implemented without using these specific details. In other instances, well-known structures and processes are not elaborated in detail to avoid obscuring the description of the invention with unnecessary details. Therefore, the present invention is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in this application.

[0040] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0041] The embodiment of the present application provides a quantum dot light-emitting device (hereinafter referred to as the light-emitting device). The light-emitting device in the present application has a long service life.

[0042] See also Figure 3 , Figure 3 1 is a schematic diagram of a light emitting device according to an embodiment of the present application. The light emitting device 100 comprises a first electrode 110 and a second electrode 120 arranged opposite to each other. The first electrode 110 and the second electrode 120 are used to be connected to a power source so that the power source supplies power to the light emitting device 100.

[0043] Specifically, in the embodiment of the present application, the first electrode 110 is an anode and the second electrode 120 is a cathode. Of course, in other embodiments of the present application, the first electrode 110 may be a cathode and the second electrode 120 may be an anode, which is not limited here.

[0044] The first electrode 110, for example, can be selected from but not limited to 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. The 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. The composite electrode of metal and metal oxide is selected from AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO 2 / Ag / TiO 2 、TiO 2 / Al / TiO 2 , ZnS / Ag / ZnS, ZnS / Al / ZnS, the material of the metal electrode is selected from one or more of Ag, Al, Cu, Mo, Au, Pt, Si, Ca, Mg and Ba. Further, the thickness of the first electrode 110 is 20-200 nm.

[0045] The second electrode 120, for example, can be selected from but not limited to 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. The 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. The composite electrode of metal and metal oxide is selected from AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO 2 / Ag / TiO 2 、TiO 2 / Al / TiO 2 , ZnS / Ag / ZnS, ZnS / Al / ZnS, the material of the metal electrode is selected from one or more of Ag, Al, Cu, Mo, Au, Pt, Si, Ca, Mg and Ba. Further, the thickness of the first electrode 110 is 20-200 nm.

[0046] It should be noted that the method for preparing the first electrode 110 and the second electrode 120 may be a method known in the art, which will not be further elaborated herein.

[0047] Understandably, see Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the energy level structure of a light-emitting device of the present application. Figure 2This is a schematic diagram of the energy level structure of an embodiment of the light-emitting device of the present application. When the light-emitting device is electrically connected to a power source, under the action of the electric field, the holes generated by the anode and the electrons generated by the cathode move, and when the two meet in the light-emitting layer, energy excitons are generated, thereby exciting the light-emitting molecules and finally generating visible light.

[0048] It should be noted that in the prior art, due to the strong electron transport capability and the poor hole transport capability, the unbalanced carrier injection causes the light emitting device to have a rapid performance roll-off and a generally short lifespan.

[0049] In view of the problem in the prior art that unbalanced carrier injection leads to a rapid performance roll-off and a generally short life of light-emitting devices, the present application provides a composite material, the composite material comprising a first quantum dot and a second quantum dot; wherein the surface of the first quantum dot has an N-type ligand, and the surface of the second quantum dot has a P-type ligand. Exemplarily, the composite material is used to prepare a light-emitting layer 150 of a light-emitting device, that is, the light-emitting layer 150 comprises a compounded first quantum dot and a second quantum dot. The composite material of the present application can improve the carrier injection balance of an optoelectronic device having the composite material and increase the service life of the optoelectronic device by compounding the first quantum dot having an N-type ligand and the second quantum dot having a P-type ligand. Figure 2As shown in , the hole transport layer is TFB, and the electron transport layer is zinc oxide nanoparticles. For example, a composite material with a Fermi level between TFB and zinc oxide nanoparticles is prepared by compounding a first quantum dot with an N-type ligand and a second quantum dot with a P-type ligand. The light-emitting layer prepared from the composite material can minimize the barrier caused by the band bending in the light-emitting device, thereby improving the carrier injection balance of the optoelectronic device having the composite material and improving the service life of the optoelectronic device. It should be noted that the compounded first quantum dots and second quantum dots in the present application refer to a mixture obtained by mixing the first quantum dots and the second quantum dots in a certain proportion, that is, the light-emitting layer includes substantially uniformly distributed first quantum dots and second quantum dots. Due to the large differences in the energy levels of electron transport layers or hole transport layers prepared from different materials, the molar ratio of the first quantum dots to the second quantum dots in the light-emitting layer of the present application needs to be determined based on the specifically selected electron transport layer material, hole transport layer material, first quantum dots and second quantum dots. Preferably, the molar ratio of the first quantum dot to the second quantum dot is 0.25 to 25. For example, the molar ratio of the first quantum dot to the second quantum dot is 0.25, or 0.35, or 0.4, or 0.5, or 0.7, or 0.9, or 1.0, or 1.1, or 1.5, or 2.0, or 3.0, or 3.5, or 4.0, or 5.0, or 6.0, or 8.0, or 11.0, or 13.0, or 15.0, or 18.0, or 20.0, or 25.0, etc. The inventors have found through experiments that the molar ratio of the first quantum dot to the second quantum dot in the quantum dot light-emitting layer is 0.25 to 25, and the light-emitting layer can match the hole transport layer and the electron transport layer of different energy levels, and the obtained light-emitting device has more stable performance and longer service life.

[0050] In some embodiments of the present application, the average particle size of the first quantum dot and the second quantum dot ranges from 7nm to 12nm. For example, the average particle size of the first quantum dot is 7nm, or 8nm, or 9nm, or 10nm, or 11nm, or 12nm. The average particle size of the second quantum dot is 7nm, or 8nm, or 9nm, or 10nm, or 11nm, or 12nm.

[0051] In some embodiments of the present application, the hole transport layer is TFB, the electron transport layer is zinc oxide nanoparticles, and the molar ratio of the first quantum dot to the second quantum dot is 0.25 to 3. Preferably, the molar ratio of the first quantum dot to the second quantum dot is 0.4 to 2.0, and the service life of the obtained light-emitting device is increased by more than 50%. The molar ratio of the first quantum dot to the second quantum dot is about 1.0, and the service life of the obtained light-emitting device is doubled.

[0052] In some embodiments of the present application, the hole transport layer is poly (9-vinyl carbazole), the electron transport layer is Mg-doped zinc oxide nanoparticles, and the molar ratio of the first quantum dots to the second quantum dots is 2.0 to 25.0. Preferably, the molar ratio of the first quantum dots to the second quantum dots is 3.5 to 20.0, and the service life of the obtained light-emitting device is increased by more than 50%.

[0053] In some embodiments of the present application, the first quantum dot includes a metal element M, and the N-type ligand is selected from the halide of the metal element M, for example, the N-type ligand includes one or more of zinc fluoride, zinc chloride, zinc bromide, zinc iodide, cadmium fluoride, cadmium chloride, cadmium bromide, and cadmium iodide. For example, the first quantum dot is a CdSe quantum dot, and the N-type ligand can be one or more of cadmium chloride, cadmium iodide, or cadmium fluoride. For another example, the first quantum dot is ZnSe, and the N-type ligand can be one or more of zinc chloride, zinc iodide, or zinc fluoride. This structural setting can avoid the introduction of metal impurities in the light-emitting layer, which is beneficial to improving the control accuracy of the light-emitting layer. Of course, in other embodiments of the present application, the metal element in the N-type ligand can also be different from the metal element in the first quantum dot. For example, the first quantum dot is a CdSe quantum dot, and the N-type ligand can be one or more of zinc chloride, zinc iodide, or zinc fluoride.

[0054] In some embodiments of the present application, the material of the first quantum dot is the same as the material of the second quantum dot. It should be noted that in the present application, the material of the quantum dot refers to the material of the quantum dot that is not bonded to the ligand, that is, the material of the quantum dot does not include the ligand material bonded to the surface of the quantum dot. Taking CdSe quantum dots as an example, the material of the first quantum dot is the same as the material of the second quantum dot, that is, the material of the first quantum dot is CdSe, and the material of the second quantum dot is CdSe. Specifically in this embodiment, the first quantum dot includes CdSe quantum dots (also the first quantum dot) and N-type ligands bonded to the surface of CdSe quantum dots. The second quantum dot includes CdSe quantum dots (also the second quantum dot) and P-type ligands bonded to the surface of CdSe quantum dots. Taking ZnSe quantum dots as an example, the material of the first quantum dot and the material of the second quantum dot are both ZnSe. Specifically in this embodiment, the first quantum dot includes ZnSe quantum dots (also the first quantum dot) and N-type ligands bonded to the surface of ZnSe quantum dots. The second quantum dot includes a ZnSe quantum dot (also known as the second quantum dot) and a P-type ligand bonded to the surface of the ZnSe quantum dot. For another example, the first quantum dot is CdSeS, and the second quantum dot is CdSeS. This embodiment can further avoid introducing luminescent impurities into the light-emitting layer by setting the first quantum dot and the second quantum dot to be the same, which is beneficial to improving the control accuracy of the light-emitting device. Of course, in other embodiments of the present application, the first quantum dot and the second quantum dot may also be different, and no further limitation is made here.

[0055] In some embodiments of the present application, the P-type ligand has a general structural formula of an organic compound as shown in Formula I;

[0056]

[0057] Among them, R 1 and R 2 are independently selected from -H, -SH, -COOH, -NH 2 、-OH、-NHR 3 、-NR 4 R 5 ,-PO 3 H 2 ,-PO 3 HR 6 ,-PO 3 R 7 R 8 、-SO 3 H, -SO 3 R 9One of, but not all of them are H; R is selected from C1-C30 aliphatic groups, or C6-C30 arylene groups, or C3-C30 heteroarylene groups, further, R is selected from C1 to C15 aliphatic groups, or C6-C18 arylene groups, or C6-C18 heteroarylene groups, further, R is selected from C2 to C10 aliphatic groups, or C6-C18 arylene groups, or C6-C18 heteroarylene groups, further, R is selected from C2 to C6 aliphatic groups, or C6-C10 arylene groups, or C6-C10 heteroarylene groups. The heteroatoms of the heteroaryl groups are selected from O, S, N, P; R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 The hydrocarbon group is selected from C1-C6, and the hydrocarbon group can be C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, or C1-C6 phenyl.

[0058] It should be noted that aliphatic refers to the remaining part after removing two hydrogen atoms from the same carbon atom or two different carbon atoms in an aliphatic hydrocarbon compound. For example, aliphatic includes alkylene, alkenylene and alkynylene. Alkylene includes but is not limited to -CH2-, -CH(CH3)-, -C(CH3)2-, -CH2CH2-, -CH2CH(CH3)-, -CH2C(CH3)2-, -CH2CH2CH2- and -CH2CH2CH2CH2-. Alkenylene includes but is not limited to -CH=CH-, -CH=CHCH2- and -CH2CH=CH-. Alkynylenes include but are not limited to -C≡C-, -CH2C≡C- and -CH2CH2CH2C≡C-. Similarly, arylene refers to the remaining part after removing two hydrogen atoms from two different carbon atoms in an aromatic compound. For example, arylene includes but is not limited to phenylene and naphthylene.

[0059] In some embodiments of the present application, the P-type ligand is a multifunctional ligand, that is, the P-type ligand includes at least -SH, -COOH, -NH 2 、-OH、-NHR 3 、-NR 4 R 5 ,-PO 3 H 2 ,-PO 3 HR 6 ,-PO 3 R 7 R 8 、-SO 3 H, -SO 3 R 9At least two of. For example, HO-R-OH, NH2-R-OH, NH2-R-SH, HOOC-R-COOH, HO-R-SH, NH2-R-SH, etc. Exemplarily, the P-type ligand includes but is not limited to propylene glycol, butanediol, pentanediol, hexanediol, 2-mercaptoethanol, 2-mercaptophenol, 3-mercaptophenol, 4-hydroxythiophenol, 4-hydroxythiophene cysteamine, 2-aminothiophenol, 3-aminothiophenol, 4-aminothiophenol, oxalic acid, malonic acid, succinic acid, adipic acid, and maleic acid.

[0060] In some embodiments of the present application, the first quantum dot and the second quantum dot are independently selected from one or more of a single structure quantum dot, a core-shell structure quantum dot and a perovskite semiconductor material, and the material of the single structure quantum dot, the core material of the core-shell structure quantum dot and the shell material of the core-shell structure quantum dot are selected from at least one of a II-VI group compound, a IV-VI group compound, a III-V group compound and a I-III-VI group compound, and the II-VI group compound is selected from CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe , ZnO, CdSeS, ZnSeS, ZnSeTe, ZnSTe, CdZnSeS, the III-V group compound is selected from at least one of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, GaNP, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, GaAlNP, GaAlNAs, GaInNP, InAlNP, the I-III-VI group compound is selected from at least one of CuInS 2 、CuInSe 2 and AgInS 2 At least one of .

[0061] In some embodiments of the present application, the functional layer further includes a hole injection layer 130. The material of the hole injection layer 130 is selected from at least one 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.

[0062] In some embodiments of the present application, the thickness of the hole injection layer 130 is 10-50 nm.

[0063] In some embodiments of the present application, the functional layer further includes a hole transport layer 140. The material of the hole transport layer 140 is selected from 4,4'-N,N'-dicarbazolyl-biphenyl (CBP), 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, N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-spiro(spiro-TPD), N, N'-bis(4-(N,N'-diphenyl-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(4-butylphenyl-diphenylamine)(poly-T PD), polyaniline, polypyrrole, poly(p-phenylene vinylene), poly(phenylene vinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene] and poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene], copper phthalocyanine, aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N', N'-Tetraarylbenzidine, PEDOT:PSS and its derivatives, poly(N-vinylcarbazole) (PVK) and its derivatives, polymethacrylate and its derivatives, poly(9,9-octylfluorene) and its derivatives, poly(spirofluorene) and its derivatives, N,N'-di(naphthalene-1-yl)-N,N'-diphenylbenzidine, spiro NPB, doped graphene, undoped graphene, C60, doped or undoped NiO, doped or undoped MoO 3 , doped or undoped WO 3 , doped or undoped V 2 O 5 , doped or undoped P-type GaN, doped or undoped CrO 3 , doped or undoped CuO.

[0064] In some embodiments of the present application, the thickness of the hole transport layer is 15-40 nm.

[0065] In some embodiments of the present application, the functional layer further includes an electron transport layer 160. The material of the electron transport layer is selected from at least one of metal oxides, doped metal oxides, 2-6 group semiconductor materials, 3-5 group semiconductor materials and 1-3-6 group semiconductor materials, the metal oxide is selected from at least one of ZnO, BaO, TiO2, SnO2; the metal oxide in the doped metal oxide is selected from at least one of ZnO, TiO2, SnO2, the doping element is selected from at least one of Al, Mg, Li, In, Ga, the 2-6 group semiconductor material is selected from at least one of ZnS, ZnSe, CdS; the 3-5 group semiconductor material is selected from at least one of InP and GaP; the 1-3-6 group semiconductor material is selected from at least one of CuInS and CuGaS.

[0066] The present application also provides a method for preparing a composite material, the preparation method comprising:

[0067] S100 provides a first quantum dot having an N-type ligand on the surface and a second quantum dot having a P-type ligand on the surface.

[0068] Specifically, in some embodiments of the present application, an initial quantum dot solution can be synthesized first, wherein the initial quantum dot solution includes quantum dots and initial ligands bonded to the surface of the quantum dots, and then a first quantum dot solution and a second quantum dot solution are obtained through a ligand replacement process. Wherein, the step of preparing the first quantum dot solution includes dripping a solution having an N-type ligand into the initial quantum dot solution to obtain a first ligand replacement precursor solution, and using a solution ligand exchange method to cause the N-type ligand in the first ligand replacement precursor solution to exchange ligands with the initial ligand to obtain a first quantum dot having the N-type ligand on the surface. Wherein, the step of preparing the second quantum dot solution includes dripping a solution having a P-type ligand into the first quantum dot solution to obtain a second ligand replacement precursor solution, and using a solution ligand exchange method to cause the P-type ligand in the second ligand replacement precursor solution to exchange ligands with the N-type ligand to obtain a second quantum dot having the P-type ligand on the surface. It should be noted that the specific conditions of the ligand replacement process do not belong to the main improvement points of the present application and are not limited here.

[0069] S200: Mix the first quantum dot solution having the N-type ligand and the second quantum dot solution having the P-type ligand in a preset ratio to obtain a quantum dot mixed solution, and remove the solvent in the quantum dot mixed solution to obtain the composite material. Exemplarily, the molar ratio of the first quantum dot to the second quantum dot is 0.25 to 25. The composite material is obtained by heating and removing the solvent in the quantum dot mixed solution under vacuum conditions. It is understandable that the mixed solution in the present application can be a mixed solution directly configured by the first quantum dots, the second quantum dots and the solvent. It is also possible to first configure the first quantum dot solution and the second quantum dot solution, and then mix the first quantum dot solution and the second quantum dot solution according to a preset configuration to obtain a mixed solution.

[0070] The following is an explanation by taking the preparation of CdSe quantum dots having cadmium iodide and cadmium bromide ligands (ie, first quantum dots) and CdSe quantum dots having 2-aminoethanethiol ligands (ie, second quantum dots) as examples.

[0071] S110 Preparation of CdSe quantum dots with tetradecanoic acid ligands.

[0072] 34mg cadmium oxide, 161mg tetradecanoic acid and 16ml octadecene were added to a 100ml three-necked flask, and heated to 200°C under an argon atmosphere to completely dissolve the cadmium oxide, and then naturally cooled to room temperature. Then 15mg selenium powder was added to the above-mentioned cadmium tetradecanoate solution, and argon was introduced in a bubbling form for 20 minutes and then the bubbling was stopped, but the reaction system was kept in an argon atmosphere. The reaction system was then heated to 200°C for 1.5 hours and then naturally cooled to room temperature. Finally, CdSe quantum dots with tetradecanoic acid ligands were precipitated by a precipitation centrifugation method.

[0073] S120 prepares a first quantum dot (cadmium iodide and cadmium bromide as ligands) solution.

[0074] Take an appropriate amount of the CdSe quantum dots (tetradecanoic acid ligand) obtained in step S11 and dissolve it in n-octane to prepare a 7 mg / mL CdSe quantum dot n-octane solution. The molar concentration of the CdSe quantum dot n-octane solution can be measured by UV-visible absorption spectroscopy.

[0075] 192.3 mg of cadmium iodide, 30.2 mg of cadmium bromide and 25.6 mg of ammonium acetate were dissolved in 5 mL of methylformamide to prepare the first ligand replacement precursor solution. Then 5 mL of the above-mentioned CdSe quantum dot n-octane solution was mixed evenly with the first ligand replacement precursor solution until all quantum dots were transferred to the first ligand replacement precursor solution, and then the n-octane solution was poured out, and then the n-octane solvent was mixed with the first ligand replacement precursor solution for three times. Then toluene was added to the first ligand replacement precursor solution to precipitate CdSe quantum dots, and then the CdSe quantum dots were vacuum dried to obtain the first quantum dots (cadmium iodide and cadmium bromide as ligands).

[0076] An appropriate amount of first quantum dots (cadmium iodide and cadmium bromide as ligands) is dispersed in an n-butylamine solvent to obtain a first quantum dot solution. The molar concentration of the first quantum dot solution can be measured by ultraviolet-visible light absorption spectroscopy.

[0077] S130 prepares a second quantum dot (2-aminoethanethiol as a ligand) solution.

[0078] Slowly add 0.1M 2-aminoethanethiol / DMF solution to the first quantum dot solution, stir for 10 minutes to allow it to be fully mixed, then pour the mixed solution into toluene to precipitate to obtain a precipitate, wash and purify the precipitate with DMF-toluene, and then dry it in a vacuum drying oven to obtain a second quantum dot powder.

[0079] The second quantum dot powder is dispersed in n-butylamine to obtain a second quantum dot (2-aminoethanethiol as a ligand) solution. The molar concentration of the second quantum dot solution can be measured by ultraviolet-visible light absorption spectroscopy.

[0080] It should be noted that the specific method for preparing the initial quantum dots, the first quantum dot solution and the second quantum dot solution does not belong to the main improvement of the present application. Those skilled in the art can select a suitable quantum dot preparation method according to their needs, and no limitation is made here.

[0081] S140: Mix the first quantum dot solution and the second quantum dot solution in a preset ratio to obtain a mixed quantum dot solution. It should be noted that after obtaining the mixed quantum dot solution, the solvent in the quantum dot mixed solution is removed to obtain the composite material.

[0082] Exemplarily, the molar concentration of the first quantum dot solution is 5 mg / ml. The molar concentration of the second quantum dot solution is 5 mg / ml. 5 ml of the first quantum dot solution and 5 ml of the second quantum dot solution are mixed evenly to obtain a mixed quantum dot solution with a molar ratio of the first quantum dot to the second quantum dot of 1:1.

[0083] S150: applying the mixed quantum dot solution on a substrate to obtain a quantum dot light-emitting layer.

[0084] Exemplarily, the substrate is a glass substrate, and a mixed quantum dot solution is applied to the substrate by a spin coating process to obtain a wet film, and the wet film is dried to obtain a quantum dot light-emitting layer. It should be noted that the preparation of a quantum dot light-emitting layer from a mixed quantum dot solution does not belong to the main improvement of the present application, and those skilled in the art can select a suitable preparation method according to their needs, which is not limited here.

[0085] Another aspect of the present application provides a display device, which includes a substrate (ie, a base substrate) and a light-emitting device, wherein the light-emitting device is disposed on the substrate. The display device having the light-emitting device also has the excellent performance of the light-emitting device in the present application, which will not be repeated here.

[0086] Quantum dot preparation example 1

[0087] Step 1: Prepare CdSe quantum dots with tetradecanoic acid ligands.

[0088] 34mg cadmium oxide, 161mg tetradecanoic acid and 16ml octadecene were added to a 100ml three-necked flask, and heated to 200°C under an argon atmosphere to completely dissolve the cadmium oxide, and then naturally cooled to room temperature. Then 15mg selenium powder was added to the above-mentioned cadmium tetradecanoate solution, and argon was introduced in a bubbling form for 20 minutes and then the bubbling was stopped, but the reaction system was kept in an argon atmosphere. The reaction system was then heated to 200°C for 1.5 hours and then naturally cooled to room temperature. Finally, CdSe quantum dots with tetradecanoic acid ligands were precipitated by a precipitation centrifugation method.

[0089] Step 2: Prepare CdSe quantum dots with cadmium iodide and cadmium bromide as ligands.

[0090] An appropriate amount of the CdSe quantum dots with tetradecanoic acid ligands obtained in step 1 was dissolved in n-octane to prepare a 7 mg / mL CdSe quantum dot n-octane solution.

[0091] 192.3 mg of cadmium iodide, 30.2 mg of cadmium bromide and 25.6 mg of ammonium acetate were dissolved in 5 mL of methylformamide to prepare the first ligand replacement precursor solution. Then 5 mL of the above-mentioned CdSe quantum dot n-octane solution was mixed evenly with the first ligand replacement precursor solution until all quantum dots were transferred to the first ligand replacement precursor solution, and then the n-octane solution was poured out, and then the first ligand replacement precursor solution was mixed and washed three times with n-octane solvent. Toluene was then added to the first ligand replacement precursor solution for precipitation, and the obtained precipitate was then vacuum dried to obtain CdSe quantum dots with cadmium iodide and cadmium bromide as ligands.

[0092] Quantum dot preparation example 2

[0093] The difference between it and Example 1 is step 2. 192.3 mg of cadmium iodide and 25.6 mg of ammonium acetate are dissolved in 5 mL of methylformamide to prepare a second ligand replacement precursor solution. Then 5 mL of the above-mentioned CdSe quantum dot n-octane solution is mixed evenly with the second ligand replacement precursor solution until all quantum dots are transferred to the second ligand replacement precursor solution, and then the n-octane solution is poured out, and then the n-octane solvent is mixed with the second ligand replacement precursor solution and washed three times. Toluene is then added to the second ligand replacement precursor solution for precipitation, and the obtained precipitate is then vacuum dried to obtain CdSe quantum dots with cadmium iodide as a ligand.

[0094] Quantum dot preparation example 3

[0095] The difference between it and Example 1 is step 2. 30.2 mg of cadmium iodide and 25.6 mg of ammonium acetate are dissolved in 5 mL of methylformamide to prepare a third ligand replacement precursor solution. Then 5 mL of the above-mentioned CdSe quantum dot n-octane solution is mixed evenly with the third ligand replacement precursor solution until all quantum dots are transferred to the third ligand replacement precursor solution, and then the n-octane solution is poured out, and then the n-octane solvent is mixed with the third ligand replacement precursor solution and washed three times. Toluene is then added to the third ligand replacement precursor solution for precipitation, and the obtained precipitate is then vacuum dried to obtain CdSe quantum dots with cadmium bromide as ligands.

[0096] Quantum dot preparation example 4

[0097] The difference between this embodiment and Example 3 is that the quantum dots are CdZnS.

[0098] Quantum dot preparation example 5

[0099] The difference between it and Example 3 is that the quantum dots are of a core-shell structure, wherein the core material of the core-shell structure is CdTe, and the shell material of the core-shell structure is ZnTe.

[0100] Quantum dot preparation example 6

[0101] An appropriate amount of CdSe quantum dots having cadmium iodide as ligands is dispersed in an n-butylamine solvent to obtain a first quantum dot solution with a concentration of 10 mg / mL.

[0102] Slowly add 0.1 ml of 0.1 M 2-aminoethanethiol / DMF solution to 20 ml of the first quantum dot solution, stir for 10 minutes to allow it to be fully mixed, then pour the mixed solution into toluene to precipitate to obtain a precipitate, and the precipitate is washed and purified with DMF-toluene and then dried in a vacuum drying oven to obtain a CdSe quantum dot powder with 2-aminoethanethiol as a ligand.

[0103] Quantum dot preparation example 7

[0104] The difference between it and Example 6 is that the 2-aminoethanethiol / DMF solution is replaced by a 2-mercaptoethanol / DMF solution.

[0105] Quantum dot preparation example 8

[0106] The difference between this embodiment and Example 6 is that the 2-aminoethanethiol / DMF solution is replaced by a 4-hydroxythiophenol / DMF solution.

[0107] Quantum dot preparation example 9

[0108] The difference between this embodiment and Example 6 is that the 2-aminoethanethiol / DMF solution is replaced by a 4-hydroxythiophene / DMF solution.

[0109] Quantum dot preparation example 10

[0110] The difference between it and Example 6 is that the 2-aminoethanethiol / DMF solution is replaced by oxalic acid / DMF solution.

[0111] Quantum dot preparation example 11

[0112] The difference between this embodiment and Example 6 is that the CdSe quantum is replaced by CdZnS.

[0113] Quantum dot preparation example 12

[0114] The difference between the embodiment 1 and the embodiment 6 is that the CdSe quantum dots are replaced by quantum dots of a core-shell structure, wherein the core material of the core-shell structure is InP, and the shell material of the core-shell structure is ZnS.

[0115] Composite material preparation example 1

[0116] An appropriate amount of CdSe quantum dots with cadmium iodide as ligands was dispersed in n-butylamine solvent to obtain a first quantum dot solution with a concentration of 10 mg / mL. An appropriate amount of CdSe quantum dots with 2-aminoethanethiol as ligands was dispersed in n-butylamine solvent to obtain a second quantum dot solution with a concentration of 10 mg / mL.

[0117] 1 ml of the first quantum dot solution and 1 ml of the second quantum dot solution were mixed evenly to obtain a quantum dot mixed solution, and the solvent in the quantum dot mixed solution was removed to obtain a composite material sample 1.

[0118] Composite material preparation example 2

[0119] The difference between this and composite material preparation example 1 is that 1 ml of the first quantum dot solution and 5 ml of the second quantum dot solution are mixed evenly to obtain a quantum dot mixed solution, and the solvent in the quantum dot mixed solution is removed to obtain composite material sample 2.

[0120] Composite material preparation example 3

[0121] The difference between this and composite material preparation example 1 is that 1 ml of the first quantum dot solution and 10 ml of the second quantum dot solution are mixed evenly to obtain a quantum dot mixed solution, and the solvent in the quantum dot mixed solution is removed to obtain composite material sample 3.

[0122] Composite material preparation example 4

[0123] The difference between this and composite material preparation example 1 is that 5 ml of the first quantum dot solution and 1 ml of the second quantum dot solution are mixed evenly to obtain a quantum dot mixed solution, and the solvent in the quantum dot mixed solution is removed to obtain composite material sample 4.

[0124] Composite material preparation example 5

[0125] The difference between this and composite material preparation example 1 is that 10 ml of the first quantum dot solution and 1 ml of the second quantum dot solution are mixed evenly to obtain a quantum dot mixed solution, and the solvent in the quantum dot mixed solution is removed to obtain composite material sample 5.

[0126] Composite material preparation example 6

[0127] The difference between the composite material example 1 is that the CdSe quantum dots in the first quantum dot solution and the second quantum dot solution are replaced by CdZnS quantum dots.

[0128] Composite material preparation example 7

[0129] The difference between the composite material example 1 is that the ligand of the CdSe quantum dots in the first quantum dot solution is replaced by cadmium bromide.

[0130] Composite material preparation example 8

[0131] The difference between the composite material example 1 and the first quantum dot solution is that the ligands of the CdSe quantum dots in the first quantum dot solution are cadmium bromide and cadmium iodide, wherein the molar ratio of cadmium bromide to cadmium iodide is 3:2.

[0132] Composite material preparation example 9

[0133] The difference between the composite material example 1 is that the ligand of the CdSe quantum dots in the second quantum dot solution is 2-mercaptoethanol.

[0134] Composite material preparation example 10

[0135] The difference between the composite material example 1 is that the ligand of the CdSe quantum dots in the second quantum dot solution is 4-hydroxythiophenol.

[0136] Composite material preparation example 11

[0137] The difference between the composite material example 1 is that the ligand of the CdSe quantum dots in the second quantum dot solution is 4-hydroxythiophene.

[0138] Composite material preparation example 12

[0139] The difference between the composite material example 1 is that the ligand of the CdSe quantum dots in the second quantum dot solution is oxalic acid.

[0140] Composite material preparation example 13

[0141] The difference between it and composite material embodiment 1 is that the CdSe quantum dots in the first quantum dot solution and the second quantum dot solution are replaced by quantum dots of core-shell structure, wherein the core material of the core-shell structure is CdTe and the shell material of the core-shell structure is ZnTe.

[0142]

[0143]

[0144] Device Example 1

[0145] Step 1: Prepare the first electrode ITO on the glass substrate with a thickness of 110 nm.

[0146] Step 2: Prepare a hole injection layer on the first electrode ITO. The material is PEDOT:PSS and the thickness is 100nm.

[0147] Step 3: Prepare a hole transport layer on the hole injection layer. The material is TFB and the thickness is 70 nm.

[0148] Step 4: Prepare a quantum dot light-emitting layer on the hole transport layer with a thickness of 20 nm; wherein the quantum dot light-emitting layer includes a composite first quantum dot and a second quantum dot, and the molar ratio of the first quantum dot to the second quantum dot is 1:1. The first quantum dot is a CdSe quantum dot (cadmium iodide and cadmium bromide as ligands). The second quantum dot is a CdSe quantum dot (2-aminoethanethiol as a ligand).

[0149] Step 5: Prepare an electron transport layer ZnO on the quantum dot light-emitting layer with a thickness of 70 nm.

[0150] Step 6: Prepare a second electrode on the electron transport layer. The second electrode is silver with a thickness of 60 nm.

[0151] Device Example 2

[0152] The difference between this embodiment and implementation 1 is that in step 4, the molar ratio of the first quantum dot to the second quantum dot is 1:2.5.

[0153] Device Example 3

[0154] The difference between this embodiment and implementation 1 is that in step 4, the molar ratio of the first quantum dot to the second quantum dot is 2:1.

[0155] Device Example 4

[0156] The difference between this embodiment and implementation 1 is that in step 4, the molar ratio of the first quantum dot to the second quantum dot is 1:4.

[0157] Device Example 5

[0158] The difference between this embodiment and implementation 1 is that in step 4, the molar ratio of the first quantum dot to the second quantum dot is 3:1.

[0159] Device Example 6

[0160] The difference between this and implementation 1 is that:

[0161] Step 3: Prepare a hole transport layer on the hole injection layer. The material is PVK (poly(9-vinylcarbazole)) and the thickness is 80 nm.

[0162] Step 4: Prepare a quantum dot light-emitting layer on the hole transport layer with a thickness of 20 nm; wherein the quantum dot light-emitting layer includes a composite first quantum dot and a second quantum dot, and the molar ratio of the first quantum dot to the second quantum dot is 5:1. The first quantum dot is a CdSe quantum dot (cadmium iodide and cadmium bromide as ligands). The second quantum dot is a CdSe quantum dot (2-aminoethanethiol as a ligand).

[0163] Step 5: Prepare an electron transport layer (Mg-doped ZnO, Mg-doping ratio 10%) on the quantum dot light-emitting layer with a thickness of 80 nm.

[0164] Device Example 7

[0165] The difference between this embodiment and implementation 6 is that in step 4, the molar ratio of the first quantum dots to the second quantum dots is 20:1.

[0166] Device Example 8

[0167] The difference between this embodiment and implementation 6 is that in step 4, the molar ratio of the first quantum dots to the second quantum dots is 3.5:1.

[0168] Device Example 9

[0169] The difference between this embodiment and implementation 6 is that in step 4, the molar ratio of the first quantum dots to the second quantum dots is 25:1.

[0170] Device Example 10

[0171] The difference between this embodiment and implementation 6 is that in step 4, the molar ratio of the first quantum dots to the second quantum dots is 2:1.

[0172] Device Comparison Example 1

[0173] The difference between it and Example 1 is that:

[0174] Step 4: Prepare a quantum dot light-emitting layer on the hole transport layer with a thickness of 20 nm; wherein the material of the quantum dot light-emitting layer is CdSe quantum dots (tetradecanoic acid is a ligand).

[0175] Device Comparison Example 2

[0176] The difference between it and Example 1 is that:

[0177] Step 4: Prepare a quantum dot light-emitting layer on the hole transport layer with a thickness of 20 nm; wherein the material of the quantum dot light-emitting layer is CdSe quantum dots (2-aminoethanethiol is a ligand).

[0178] Device Comparison Example 3

[0179] The difference between it and Example 1 is that:

[0180] Step 4: Prepare a quantum dot light-emitting layer on the hole transport layer with a thickness of 20 nm; wherein the material of the quantum dot light-emitting layer is CdSe quantum dots (cadmium iodide and cadmium bromide as ligands).

[0181] Device Comparison Example 4

[0182] The difference between it and Example 6 is that:

[0183] A quantum dot light-emitting layer is prepared on the hole transport layer, with a thickness of 20 nm; wherein the material of the quantum dot light-emitting layer is CdSe quantum dots (tetradecanoic acid is a ligand).

[0184] Device Comparison Example 5

[0185] The difference between it and Example 1 is that:

[0186] Step 4: Prepare a quantum dot light-emitting layer on the hole transport layer with a thickness of 20 nm; wherein the material of the quantum dot light-emitting layer is CdSe quantum dots (2-aminoethanethiol is a ligand).

[0187] Device Comparative Example 6

[0188] The difference between it and Example 6 is that:

[0189] Step 4: Prepare a quantum dot light-emitting layer on the hole transport layer with a thickness of 20 nm; wherein the material of the quantum dot light-emitting layer is CdSe quantum dots (cadmium iodide and cadmium bromide as ligands).

[0190] The performance of the light-emitting diodes obtained from device embodiments 1-10 and device comparative examples 1-6 was tested, and the test results are shown in Tables 1 and 2 below.

[0191] Table 1

[0192]

[0193] Table 2

[0194]

Claims

1. A composite material, It is characterized in that The composite material includes a first quantum dot and a second quantum dot; wherein the surface of the first quantum dot has an N-type ligand, and the surface of the second quantum dot has a P-type ligand.

2. The composite material according to claim 1, It is characterized in that The first quantum dot includes a metal element M, and the N-type ligand is selected from halides of the metal element M; And / or, the P-type ligand is selected from any one or more of the compounds shown in Formula I, Among them, R 1 and R 2 are independently selected from -H, -SH, -COOH, -NH 2 、-OH、-NHR 3 、-NR 4 R 5 ,-PO 3 H 2 ,-PO 3 HR 6 ,-PO 3 R 7 R 8 、-SO 3 H, -SO 3 R 9 One of them, but not all of them are H; R is selected from a C1-C30 aliphatic group, a C6-C30 arylene group, or a C3-C30 heteroarylene group, wherein the heteroatom of the heteroarylene group is selected from O, S, N, and P; R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 A hydrocarbon group selected from C1-C6.

3. The composite material according to claim 2, It is characterized in that The N-type ligand includes one or more of zinc halide, cadmium halide, mercury halide, lead halide, tin halide, copper halide, silver halide, gallium halide, and indium halide; And / or, R in the P-type ligand is selected from a C3 to C15 aliphatic group, a C6-C18 arylene group, or a C6-C18 heteroarylene group.

4. The composite material according to claim 2, It is characterized in that The N-type ligand includes one or more of zinc fluoride, zinc chloride, zinc bromide, zinc iodide, cadmium fluoride, cadmium chloride, cadmium bromide, and cadmium iodide; And / or, the P-type ligand includes one or more of propylene glycol, butanediol, pentanediol, hexanediol, 2-mercaptoethanol, 2-mercaptophenol, 3-mercaptophenol, 4-hydroxythiophenol, 4-hydroxythiophene cysteamine, 2-aminothiophenol, 3-aminothiophenol, 4-aminothiophenol, oxalic acid, malonic acid, succinic acid, adipic acid, and maleic acid.

5. The composite material according to claim 1, It is characterized in that Calculated by molar ratio, the ratio of the first quantum dot to the second quantum dot is 0.25 to 25; And / or, the average particle size of the first quantum dots is in the range of 7 nm to 12 nm; And / or, the average particle size of the second quantum dots is in the range of 7nm-12nm quantum dots.

6. The composite material according to claim 1, It is characterized in that The first quantum dot and the second quantum dot are independently selected from one or more of a single structure quantum dot, a core-shell structure quantum dot and a perovskite semiconductor material. The material of the single structure quantum dot, the core material of the core-shell structure quantum dot and the shell material of the core-shell structure quantum dot are selected from at least one of II-VI group compounds, IV-VI group compounds, III-V group compounds and I-III-VI group compounds. The II-VI group compound is selected from at least one of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, CdSeS, ZnSeS, ZnSeTe, ZnSTe and CdZnSeS. The III-V group compound is selected from at least one of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, GaNP, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, GaAlNP, GaAlNAs, GaInNP and InAlNP. The I-III-VI group compound is selected from at least one of CuInS 2 、CuInSe 2 and AgInS 2 At least one of; And / or, the material of the first quantum dots is the same as the material of the second quantum dots.

7. A method for preparing a composite material, It is characterized in that The preparation method comprises: Providing a first quantum dot having an N-type ligand on the surface and a second quantum dot having a P-type ligand on the surface; The first quantum dot solution having the N-type ligand and the second quantum dot solution having the P-type ligand are mixed in a preset ratio to obtain a quantum dot mixed solution, and the solvent in the quantum dot mixed solution is removed to obtain the composite material.

8. The method for preparing the composite material according to claim 7, It is characterized in that The step of providing a first quantum dot having an N-type ligand on the surface and a second quantum dot having a P-type ligand on the surface comprises: Providing an initial quantum dot solution, wherein the initial quantum dot solution comprises quantum dots and initial ligands bonded to the surface of the quantum dots; Adding a solution having an N-type ligand to the initial quantum dot solution to obtain a first ligand replacement precursor solution, and exchanging the N-type ligand in the first ligand replacement precursor solution with the initial ligand by a solution ligand exchange method to obtain a first quantum dot having the N-type ligand on the surface; And / or, a solution having a P-type ligand is added dropwise to the first quantum dot solution to obtain a second ligand replacement precursor solution, and the P-type ligand in the second ligand replacement precursor solution is subjected to ligand exchange with the N-type ligand through a solution ligand exchange method to obtain a second quantum dot having the P-type ligand on its surface.

9. A method for preparing a composite material according to claim 7 or 8, It is characterized in that The P-type ligand is selected from any one or more of the compounds shown in Formula I, Among them, R 1 and R 2 are independently selected from -H, -SH, -COOH, -NH 2 、-OH、-NHR 3 、-NR 4 R 5 ,-PO 3 H 2 ,-PO 3 HR 6 ,-PO 3 R 7 R 8 、-SO 3 H, -SO 3 R 9 one of, but not all of them are H; R is selected from a C1-C30 aliphatic group, a C6-C30 arylene group, or a C3-C30 heteroarylene group, wherein the heteroatom of the heteroarylene group is selected from O, S, N, P; R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 A hydrocarbon group selected from C1-C6; And / or, the first quantum dot includes a metal element M, and the N-type ligand is selected from a halide of the metal element M.

10. A light emitting device, It is characterized in that The light-emitting device comprises a light-emitting layer, and the light-emitting layer comprises the composite material according to any one of claims 1 to 6; or the composite material obtained by the preparation method according to claims 7 to 9.

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