Thin film and preparation method thereof, light-emitting device and display device

Abstract

The invention provides a thin film, a preparation method thereof, a light-emitting device and a display device. The preparation method of the thin film comprises the following steps: providing a base film which comprises quantum dots; a modified solution is applied to the base film, the thin film is obtained, and the modified solution comprises alkalescent organic salt and a solvent. According to the preparation method of the thin film, impurities on the surface of the base film can be reduced or removed, when the thin film is applied to the light-emitting device, the light-emitting efficiency and the operation stability of the light-emitting device can be improved, the service life of the light-emitting device is prolonged, and the reliability of the light-emitting device is improved.

Description

Technical Field

[0001] This application relates to the field of light-emitting devices, and particularly to a thin film, a preparation method thereof, a light-emitting device, and a display device. Background Art

[0002] QLED (Quantum Dot Light Emitting Diodes) has the advantages of high color saturation, wet processability, and high stability, which has attracted more and more attention in the research of QLED, and has a wide range of applications in the fields of display, lighting, smart wear, etc.

[0003] The light-emitting layer in a QLED device includes quantum dots. Quantum dots refer to semiconductor crystal particles with a nanoscale particle size. They have high luminous brightness and high luminous efficiency. Since their bandgap changes with the particle size, quantum dots have the characteristic of being able to control the emission wavelength. When quantum dots are used in a display device, a wider color gamut and lower power consumption can be achieved compared to conventional phosphor materials.

[0004] Currently, the presence of impurities in quantum dots will affect the recombination of electrons and holes, resulting in a decrease in the luminous efficiency and stability of QLED devices. Summary of the Invention

[0005] Based on this, embodiments of the present application provide a thin film, a preparation method thereof, a light-emitting device, and a display device.

[0006] In a first aspect, an embodiment of the present application provides a preparation method of a thin film, including:

[0007] Providing a base film, the base film including quantum dots;

[0008] Applying a modification solution on the base film to obtain the thin film, the modification solution including a weakly basic organic salt and a solvent.

[0009] In some embodiments, the weakly basic organic salt includes at least one of an organic ammonium salt with C1-C6 and an organic zinc salt with C1-C6;

[0010] Optionally, the organic ammonium salt is ammonium acetate, and the organic zinc salt is zinc acetate.

[0011] In some embodiments, the modification solution includes zinc acetate, ammonium acetate, and a solvent. The concentration of zinc acetate is 5wt% - 10wt%, the concentration of ammonium acetate is 0.1wt% - 5wt%, and the solvent includes an alcohol compound; and / or

[0012] The volume of the modification solution applied on each square centimeter of the base film is 0.1 ml - 2 ml.

[0013] In some embodiments, applying the modification solution on the base film to obtain the thin film includes:

[0014] Applying the modification solution on the base film, allowing the modification solution to remain on the base film for 5 minutes to 30 minutes, removing the modification solution, and obtaining the thin film.

[0015] In some embodiments, under a temperature condition of 50°C to 70°C, allowing the modification solution to remain on the base film for 5 minutes to 30 minutes; and / or

[0016] Removing the modification solution on the surface of the base film includes: rinsing the modification solution with a cleaning solution, where the cleaning solution includes an alcohol compound.

[0017] In some embodiments, preparing the base film includes:

[0018] Depositing a quantum dot solution to form a base film, where the quantum dot solution includes quantum dots and a solvent, and in the quantum dot solution, the concentration of the quantum dots is 10 mg / mL to 100 mg / mL.

[0019] In some embodiments, depositing the quantum dot solution to form a base film includes: depositing the quantum dot solution to obtain a wet film layer, and annealing the wet film layer to obtain the base film, where the annealing temperature is 80°C to 120°C and the annealing time is 5 minutes to 10 minutes.

[0020] In some embodiments, the quantum dots include at least one of single-structure quantum dots and core-shell structure quantum dots. The material of the single-structure quantum dots, the core material of the core-shell structure quantum dots, and the shell material of the core-shell structure quantum dots each include 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 compounds are selected from at least one of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, and HgZnSTe. The IV-VI group compounds are selected from at least one of SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, and SnPbSTe. The III-V group compounds are selected from at least one of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, and InAlPSb. The I-III-VI group compounds are selected from at least one of CuInS2, CuInSe2, CuInSeS, and AgInS2; and / or

[0021] The surface of the quantum dots is connected with ligands, and the ligands include at least one of acid ligands, thiol ligands, amine ligands, phosphine oxide ligands, phospholipids, lecithins, and polyvinylpyridines. The acid ligands include at least one of decanoic acid, undecylenic acid, myristic acid, oleic acid, and stearic acid. The thiol ligands include at least one of octyl mercaptan, dodecyl mercaptan, and octadecyl mercaptan. The amine ligands include at least one of oleylamine, octadecylamine, and octylamine. The phosphine oxide ligands include at least one of trioctylphosphine and trioctyloxidephosphine; and / or

[0022] The thickness of the thin film is 40 nm - 100 nm.

[0023] In a second aspect, an embodiment of the present application provides a thin film prepared by using the preparation method of the thin film as described above. The thin film includes a base film, and the base film includes quantum dots modified by a weak basic organic salt.

[0024] In a third aspect, an embodiment of the present application provides a light-emitting device, including a first electrode and a second electrode disposed opposite to each other, and a thin film disposed between the first electrode and the second electrode. The thin film is a thin film prepared by using the preparation method of the thin film as described above or is the thin film as described above.

[0025] In some embodiments, when the first electrode is an anode and the second electrode is a cathode, a hole injection layer and a hole transport layer are disposed in a stacked manner between the first electrode and the thin film. Among them, the hole injection layer is disposed close to the first electrode, the hole transport layer is disposed close to the thin film, and an electron transport layer is disposed between the second electrode and the base film; or

[0026] When the first electrode is a cathode and the second electrode is an anode, an electron transport layer is disposed between the first electrode and the thin film, and a hole injection layer and a hole transport layer are disposed in a stacked manner between the second electrode and the thin film. Among them, the hole injection layer is disposed close to the second electrode, and the hole transport layer is disposed close to the base film.

[0027] In some embodiments, the material of the hole transport layer includes at least one of 4,4'-N,N'-dicarbazolyl-biphenyl, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4”-diamine, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine, poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine), N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine, 4,4',4'-tris(N-carbazolyl)-triphenylamine, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))], poly(N-vinylcarbazole) and its derivatives, N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4-4'-diamine, poly(phenylenevinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene], 2,2',7,7'-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene, 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline], 1,3-bis(carbazol-9-yl)benzene, polyaniline, polypyrrole, poly(p-phenylenevinylene), aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid and its derivatives, polymethacrylate and its derivatives, poly(9,9-octylfluorene) and its derivatives, polysfluorene and its derivatives, polythiophene and its derivatives; and / or

[0028] the material of the hole injection layer includes at least one of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid and its derivatives, copper phthalocyanine, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, poly(dioxoethylthiophene), 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, tetracyanoquinodimethane, transition metal oxides and transition metal chalcogenides; and / or

[0029] The material of the electron transport layer includes at least one of metal oxides, doped metal oxides, II-VI group semiconductor materials, III-V group semiconductor materials, and I-III-VI group semiconductor materials. The metal oxide is selected from at least one of ZnO, BaO, TiO2, and SnO2; the metal oxide in the doped metal oxide is selected from at least one of ZnO, TiO2, and SnO2, and the doping element is selected from at least one of Al, Mg, Li, In, and Ga. The II-VI group semiconductor material is selected from at least one of ZnS, ZnSe, and CdS; the III-V group semiconductor material is selected from at least one of InP and GaP; the I-III-VI group semiconductor material is selected from at least one of CuInS and CuGaS; and / or

[0030] The cathode and the anode are independently selected from doped metal oxide particle electrodes, composite electrodes, graphene electrodes, carbon nanotube electrodes, metal single electrodes, or alloy electrodes. The material of the doped metal oxide particle electrode includes one or more of indium-doped tin oxide, fluorine-doped tin oxide, antimony-doped tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, indium-doped zinc oxide, magnesium-doped zinc oxide, and aluminum-doped magnesium oxide. The composite electrode includes 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 material of the metal single electrode includes one or more of Ag, Al, Cu, Mo, Au, Pt, Ca, Mg, and Ba.

[0031] In some embodiments, the thickness of the hole transport layer is 10 nm - 100 nm, the thickness of the hole injection layer is 20 nm - 120 nm, the thickness of the thin film is 40 nm - 100 nm, the thickness of the electron transport layer is 15 nm - 60 nm, and the thicknesses of the first electrode and the second electrode are each 10 nm - 125 nm.

[0032] Fourthly, an embodiment of the present application provides a display device including the light-emitting device as described above.

[0033] The preparation method of the thin film provided by the embodiment of the present application can reduce or remove impurities on the surface of the base film by applying a modified solution to the base film. The obtained thin film has good carrier transport performance. When the thin film is applied to a light-emitting device, the light-emitting efficiency and operating stability of the light-emitting device can be improved. Description of the Drawings

[0034] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments.

[0035] Figure 1 It is a flowchart of the preparation method of the thin film provided by the embodiment of the present application.

[0036] Figure 2 It is a flowchart of the preparation method of the light-emitting device provided by the embodiment of the present application.

[0037] Figure 3 It is a first schematic structural diagram of the light-emitting device provided by the embodiment of the present application.

[0038] Figure 4 It is a second schematic structural diagram of the light-emitting device provided by the embodiment of the present application.

[0039] Reference numerals:

[0040] 100 - light-emitting device; 10 - first electrode; 20 - hole injection layer; 30 - hole transport layer; 40 - thin film; 50 - electron transport layer; 60 - second electrode. Specific embodiments

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present application.

[0042] In the present application, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural.

[0043] In the present application, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one item (piece) below" or similar expressions refer to any combination of these items, including any combination of single item (piece) or plural items (pieces). For example, "at least one item (piece) of a, b or c", or, "at least one item (piece) of a, b and c" can both represent: a, b, c, a + b, a + c, b + c, or a + b + c, where a, b, and c can be single or multiple respectively.

[0044] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within that range, such as 1, 2, 3, 4, 5, and 6. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0045] Please refer to Figure 1 , an embodiment of the present application provides a method for preparing a thin film, including:

[0046] S110, providing a base film, the base film including quantum dots.

[0047] Exemplarily, the providing of the base film includes: depositing a quantum dot solution to form a base film, wherein the quantum dot solution includes quantum dots and a solvent, and in the quantum dot solution, the concentration of the quantum dots is 10 mg / mL to 100 mg / mL, such as 10 mg / mL, 20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL, 60 mg / mL, 70 mg / mL, 80 mg / mL, 90 mg / mL, 100 mg / mL, etc. In some embodiments, in the quantum dot solution, the concentration of the quantum dots is 20 mg / mL to 50 mg / mL.

[0048] Optionally, the depositing of the quantum dot solution to form a base film includes: depositing the quantum dot solution to obtain a wet film layer, and annealing the wet film layer to obtain a base film, wherein the annealing temperature is 80°C to 120°C (such as 80°C, 90°C, 100°C, 110°C, 120°C, etc.), and the annealing time is 5 minutes to 10 minutes (such as 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, etc.).

[0049] Exemplarily, the solvent in the quantum dot solution includes at least one of n-hexane, n-octane, n-heptane, toluene, and chlorobenzene.

[0050] Exemplarily, the quantum dots include at least one of single-structure quantum dots and core-shell structure quantum dots. The materials of the single-structure quantum dots, the core materials of the core-shell structure quantum dots, and the shell materials of the core-shell structure quantum dots each include 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 compounds are selected from at least one of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, and HgZnSTe. The IV-VI group compounds are selected from at least one of SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, and SnPbSTe. The III-V group compounds are selected from at least one of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, and InAlPSb. The I-III-VI group compounds are selected from at least one of CuInS2, CuInSe2, CuInSeS, and AgInS2.

[0051] Exemplarily, ligands are connected to the surface of the quantum dots. The ligands include at least one of acid ligands, thiol ligands, amine ligands, phosphine oxide ligands, phospholipids, lecithins, and polyvinylpyridines. The acid ligands are at least one of decanoic acid, undecylenic acid, myristic acid, oleic acid, and stearic acid. The thiol ligands are at least one of octyl mercaptan, dodecyl mercaptan, and octadecyl mercaptan. The amine ligands are at least one of oleylamine, octadecylamine, and octylamine. The phosphine oxide ligands are at least one of trioctylphosphine and trioctylphosphine oxide.

[0052] It can be understood that by connecting ligands to the surface of the quantum dots, it is beneficial to improve the affinity between the quantum dots and the organic solvent, enhance the solubility and dispersion uniformity of the quantum dots, and avoid the agglomeration of the quantum dots in the organic solvent.

[0053] Exemplarily, 0.1 mmol to 0.5 mmol (such as 0.1 mmol, 0.2 mmol, 0.3 mmol, 0.4 mmol, 0.5 mmol, etc.) of ligands are connected to the surface of every 1 mg of quantum dots.

[0054] S120, applying a modification solution on the base film to obtain a thin film. The modification solution includes a weak basic organic salt and a solvent.

[0055] Exemplarily, the weak basic organic salt includes at least one of C1-C6 organic ammonium salts and C1-C6 organic zinc salts.

[0056] Optionally, the organic ammonium salt is ammonium acetate, and the organic zinc salt is zinc acetate.

[0057] It should be noted that since the modification solution contains a weak basic organic salt, the modification solution is weakly basic, so that impurities such as oleic acid, zinc oleate, and cadmium oleate and ligands on the surface of the base film will dissolve and fall off, reducing the impurities on the surface of the base film. When zinc acetate is contained in the modification solution, the vacancies and ligand defects formed on the surface of the base film after the impurities and ligands on the surface of the base film fall off will be filled by the zinc acetate in the modification solution. Since the impurities on the surface of the base film are reduced, when the thin film is applied to a QLED device, the recombination efficiency of electrons and holes in the base film can be improved, thereby improving the luminous efficiency and operation stability of the QLED device.

[0058] It should be noted that when the modification solution contains both zinc acetate and ammonium acetate, since the alkalinity of ammonium acetate is slightly greater than that of zinc acetate, the alkalinity of the modification solution can be adjusted by controlling the ratio of zinc acetate to ammonium acetate, and then the impurity removal effect of the modification solution can be adjusted. That is to say, zinc acetate and ammonium acetate can play a synergistic role.

[0059] It should be noted that since zinc acetate can fill the vacancies and ligand defects formed on the surface of the base film after removing impurities, when the electron transport layer (zinc oxide or doped zinc oxide) is subsequently formed on the surface of the base film by the solution method, since the surface of the zinc oxide nanoparticles itself carries zinc acetate, the spreading effect of the electron transport layer can be improved, and thus the film thickness uniformity of the electron transport layer can be improved.

[0060] It should be noted that the purpose of removing the modification solution on the surface of the base film is to remove the impurities dissolved in the modification solution and the weakly basic organic salts (zinc acetate and / or ammonium acetate) that are not connected to the base film.

[0061] Exemplarily, the modification solution includes zinc acetate, ammonium acetate and a solvent. The concentration of zinc acetate ((CH3COO)2Zn) is 5 wt% to 10 wt%, such as 5 wt%, 6 wt%, 7 wt%, 5 wt%, 5 wt%, 5 wt%, etc.; the concentration of ammonium acetate (CH3COONH4) is 0.1 wt% to 5 wt%, such as 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, etc.

[0062] Exemplarily, in the modification solution, the solvent includes alcohol compounds, for example, alcohol compounds with 1 to 4 carbon atoms. In some embodiments, the solvent includes at least one of methanol, ethanol, propanol, n-butanol, and isobutanol.

[0063] Exemplarily, the volume of the modification solution applied to each square centimeter (cm 2 ) of the base film is 0.1 ml to 2 ml, such as 0.1 ml, 0.3 ml, 0.5 ml, 0.8 ml, 1 ml, 1.2 ml, 1.5 ml, 1.8 ml, 2 ml, etc.

[0064] Exemplarily, applying the modification solution on the base film to obtain the thin film includes:

[0065] Applying the modification solution on the base film, allowing the modification solution to remain on the base film for 5 minutes to 30 minutes, and removing the modification solution to obtain the thin film.

[0066] Exemplarily, under the temperature condition of 50°C to 70°C (such as 50°C, 55°C, 60°C, 65°C, 70°C, etc.), allow the modification solution to remain on the base film for 5 minutes to 30 minutes (such as 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 12 minutes, 15 minutes, 18 minutes, 20 minutes, 22 minutes, 25 minutes, 28 minutes, 30 minutes, etc.).

[0067] It should be noted that when the modified solution infiltrates the base film at a temperature of 50°C to 70°C, the infiltration effect of the modified solution is better, which can effectively remove impurities and ligands such as oleic acid, zinc oleate, and cadmium oleate on the surface of the base film. After the impurities and ligands are removed, the vacancies and ligand defects formed on the surface of the base film are filled by zinc acetate in the modified solution. The inventor found in the experiment that when the infiltration temperature is less than 50°C, the infiltration effect is poor, and the impurity removal effect on the surface of the base film is poor; while when the infiltration temperature is greater than 70°C, it is easy to cause the solvent in the modified solution to violently vaporize, resulting in the inability to achieve the infiltration effect, and thus the inability to achieve the shedding of impurities on the surface of the quantum film.

[0068] Exemplarily, the modified solution for removing the surface of the base film includes: rinsing the modified solution with a cleaning solution, and the cleaning solution includes alcohol compounds, such as alcohol compounds with 1 to 4 carbon atoms, such as methanol, ethanol, propanol, etc.

[0069] In some embodiments, the cleaning solution is the same as the solvent in the modified solution.

[0070] The method for preparing a thin film provided by the embodiments of the present application applies a modified solution to the base film. Since the modified solution contains zinc acetate and ammonium acetate, both zinc acetate and ammonium acetate have weak alkalinity, so that the modified solution is weakly alkaline, and impurities and ligands such as oleic acid, zinc oleate, and cadmium oleate on the surface of the base film will dissolve and fall off. After the impurities and ligands fall off, some vacancies and ligand defects are formed on the surface of the base film, and these vacancies and ligand defects are filled by zinc acetate in the modified solution; when the prepared thin film is applied to a light-emitting device, since the impurities on the surface of the base film are reduced, the impurities between the base film and its adjacent functional film layer (such as the electron transport layer) are reduced, so that the carrier transport performance at the interface between the base film and the adjacent functional film layer can be improved, thereby improving the light-emitting efficiency and operating stability of the light-emitting device, and further enhancing the service life and reliability of the light-emitting device.

[0071] The embodiments of the present application also provide a thin film, which is prepared by using the method for preparing a thin film in any of the above embodiments. The thin film includes a base film, and the base film includes quantum dots modified by a weakly basic organic salt.

[0072] Exemplarily, zinc acetate is connected to the surface of the thin film.

[0073] Exemplarily, the thickness of the thin film is 40nm - 100nm, such as 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc.

[0074] Please refer to Figure 2 and at the same time combine Figure 3 and Figure 4 The embodiments of the present application also provide a method for preparing a light-emitting device, including:

[0075] S210, Provide a light-emitting device preform, the light-emitting device preform including a first electrode 10.

[0076] Exemplarily, the light-emitting device preform may further include a substrate disposed on one side of the first electrode 10. The step of providing the light-emitting device preform may include: cleaning the light-emitting device preform with a cleaning agent to remove stains on the surface of the light-emitting device preform, and then ultrasonically cleaning the light-emitting device preform in deionized water, acetone, absolute ethanol, and deionized water for 20 minutes respectively to remove impurities on the surface of the light-emitting device preform, and finally drying the light-emitting device preform with high-purity nitrogen.

[0077] Exemplarily, the substrate may be a rigid substrate or a flexible substrate. In some embodiments, the material of the substrate may be selected from but not limited to at least one of glass, silicon wafer, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, and polyethersulfone.

[0078] S220, Prepare a thin film 40 on the light-emitting device preform by using the thin film preparation method in any of the above embodiments.

[0079] S230, Form a second electrode 60 on the thin film 40 to obtain a light-emitting device 100.

[0080] Please refer to Figure 3 , when the first electrode 10 is an anode and the second electrode 60 is a cathode, the light-emitting device preform includes a first electrode 10, a hole injection layer 20, and a hole transport layer 30 which are sequentially stacked;

[0081] The step of forming the second electrode 60 on the thin film 40 includes: forming an electron transport layer 50 on the thin film 40, and forming a second electrode 60 on the electron transport layer 50.

[0082] It should be noted that since the material of the electron transport layer 50 is usually zinc oxide nanoparticles, and a large number of zinc acetate ligands are usually carried on the surface of the zinc oxide nanoparticles, when zinc acetate is connected to the surface of the thin film 40, there is stronger adaptability between the thin film 40 and the electron transport layer 50. Therefore, when the solution method (such as spin coating method) is used to prepare the electron transport layer 50 (zinc oxide or doped zinc oxide), the spreading performance of the electron transport material solution on the thin film 40 can be improved, and thus the film thickness uniformity of the electron transport layer 50 can be improved.

[0083] Please refer to Figure 4 , when the first electrode 10 is a cathode and the second electrode 60 is an anode, the light-emitting device preform includes a first electrode 10 and an electron transport layer 50 which are sequentially stacked;

[0084] Forming the second electrode 60 on the thin film 40 includes: forming a hole transport layer 30 on the thin film 40, forming a hole injection layer 20 on the hole transport layer 30, and forming the second electrode 60 on the hole injection layer 20.

[0085] Exemplarily, the hole injection layer 20, the hole transport layer 30, and the electron transport layer 50 can each be prepared by methods such as drop coating, spin coating, dipping, coating, printing, or evaporation. When the hole injection layer 20, the hole transport layer 30, or the electron transport layer 50 is prepared by spin coating, the spin coating speed is 2000 rpm to 6000 rpm. After spin coating, the spin-coated film layer is annealed at a temperature of 100°C to 150°C (such as 130°C).

[0086] Exemplarily, after obtaining the light-emitting device 100, the light-emitting device 100 can also be subjected to a packaging process, and the packaging process can be machine packaging or manual packaging. Preferably, in the environment of the packaging process, both the oxygen content and the water content are lower than 0.1 ppm to ensure the stability of the light-emitting device 100.

[0087] Please refer to Figure 3 and Figure 4 , this embodiment of the present application also provides a light-emitting device 100, including a first electrode 10 and a second electrode 60 disposed opposite to each other and a thin film 40 disposed between the first electrode 10 and the second electrode 60. The thin film 40 is a thin film 40 prepared by the preparation method of the thin film in any of the above embodiments or is the thin film 40 in any of the above embodiments.

[0088] Please refer to Figure 3 , when the first electrode 10 is an anode and the second electrode 60 is a cathode, a hole injection layer 20 and a hole transport layer 30 are disposed in a stacked manner between the first electrode 10 and the thin film 40. Among them, the hole injection layer 20 is disposed close to the first electrode 10, the hole transport layer 30 is disposed close to the thin film 40, and an electron transport layer 50 is disposed between the second electrode 60 and the thin film 40.

[0089] Please refer to Figure 4 , when the first electrode 10 is a cathode and the second electrode 60 is an anode, an electron transport layer 50 is disposed between the first electrode 10 and the thin film 40, and a hole injection layer 20 and a hole transport layer 30 are disposed in a stacked manner between the second electrode 60 and the thin film 40. Among them, the hole injection layer 20 is disposed close to the second electrode 60, and the hole transport layer 30 is disposed close to the thin film 40.

[0090] Exemplarily, the material of the hole transport layer 30 may include at least one of 4,4'-N,N'-dicarbazolyl-biphenyl (CBP), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4”-diamine (α-NPD), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD), poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (Poly-TPD), N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine (DNTPD), 4,4',4'-tris(N-carbazolyl)-triphenylamine (TCTA), 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine (m-MTDATA), poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))] (TFB), poly(N-vinylcarbazole) (PVK) and its derivatives, N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4-4'-diamine (NPB), poly(phenylene vinylene) (PPV), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV), poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MOMO-PPV), 2,2',7,7'-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-omeTAD), 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline] (TAPC), 1,3-bis(carbazol-9-yl)benzene (MCP), polyaniline, polypyrrole, poly(p-phenylene vinylene), aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) and its derivatives, polymethacrylate and its derivatives, poly(9,9-octylfluorene) and its derivatives, polysfluorene and its derivatives, polythiophene (TPH) and its derivatives.

[0091] Exemplarily, the material of the hole injection layer 20 may include at least one of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS), copper phthalocyanine (CuPc), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN), poly(2,3-dihydrothieno[3,4-b][1,4]dioxin) (PEDOT), a derivative of PEDOT:PSS doped with MoO3 (PEDOT:PSS-MoO3), 4,4',4'-tris(N-(3-methylphenyl)-N-phenylamino)triphenylamine (m-MTDATA), tetracyanoquinodimethane (F4-TCNQ), transition metal oxides, and transition metal chalcogenides. Exemplarily, the transition metal oxides may include at least one of MoO x 、VO x 、WO x 、CrO x 、CuO. Exemplarily, the metal chalcogenides may include at least one of MoS2, MoSe2, WS2, WSe2, CuS.

[0092] Exemplarily, the material of the electron transport layer 50 may include at least one of metal oxides, doped metal oxides, Group II-VI semiconductor materials, Group III-V semiconductor materials, and Group I-III-VI semiconductor materials. The metal oxides are selected from at least one of ZnO, BaO, TiO2, and SnO2; the metal oxides in the doped metal oxides are selected from at least one of ZnO, TiO2, and SnO2, and the doping elements are selected from at least one of Al, Mg, Li, In, and Ga. The Group II-VI semiconductor materials are selected from at least one of ZnS, ZnSe, and CdS; the Group III-V semiconductor materials are selected from at least one of InP and GaP; the Group I-III-VI semiconductor materials are selected from at least one of CuInS and CuGaS.

[0093] In some embodiments, the material of the electron transport layer 50 is ZMO (magnesium-doped zinc oxide), which refers to magnesium-doped zinc oxide obtained by adding a Mg precursor (such as magnesium acetate, magnesium chloride, magnesium nitrate, etc.) during the synthesis of zinc oxide.

[0094] Exemplarily, the material of the electron transport layer 50 may be nanoparticles with various morphologies such as nanospheres, nanosheets, and nanorods. The average particle size of the material of the electron transport layer 50 is 2 nm to 15 nm, such as 2 nm, 5 nm, 10 nm, 12 nm, 15 nm, etc.

[0095] Exemplarily, the first electrode 10 and the second electrode 60 can each independently be selected from doped metal oxide electrodes, composite electrodes, graphene electrodes, carbon nanotube electrodes, elemental metal electrodes, or alloy electrodes. The materials of the doped metal oxide electrodes can include, but are not limited to, one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), magnesium-doped zinc oxide (MZO), aluminum-doped magnesium oxide (AMO), and cadmium-doped zinc oxide. The composite electrode is an electrode formed by laminating two or more layers of conductive materials, such as AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, Ca / Al, LiF / Ca, LiF / Al, BaF2 / Al, CsF / Al, CaCO3 / Al, BaF2 / Ca / Al, etc., where " / " represents a laminated structure. For example, AZO / Ag / AZO represents a composite electrode including an AZO layer, an Ag layer, and an AZO layer laminated in sequence. The materials of the elemental metal electrodes can include, but are not limited to, one or more of silver (Ag), magnesium (Mg), aluminum (Al), gold (Au), gallium (Ga), nickel (Ni), platinum (Pt), iridium (Ir), copper (Cu), molybdenum (Mo), calcium (Ca), and barium (Ba). The alloy electrodes include, but are not limited to, Au:Mg alloy electrodes or Ag:Mg alloy electrodes.

[0096] In some embodiments, the anode can be an electrode with a relatively high work function, such as including, but not limited to, one or more of doped metal oxide electrodes with a relatively high work function, elemental metal electrodes with a relatively high work function, and carbon nanotube electrodes; the materials of the elemental metal electrodes with a relatively high work function can be Ni, Pt, Au, Ag, or Ir, etc.

[0097] In some embodiments, the cathode can be an electrode with a relatively low work function, such as including, but not limited to, elemental metal electrodes with a relatively low work function, composite electrodes with a relatively low work function, and alloy electrodes with a relatively low work function; the materials of the elemental metal electrodes with a relatively low work function can be Ca, Ba, Al, Mg, etc.; the structures of the composite electrodes with a relatively low work function can be Ca / Al, LiF / Ca, LiF / Al, BaF2 / Al, CsF / Al, CaCO3 / Al, BaF2 / Ca / Al, etc.; the alloy electrodes with a relatively low work function can be Au:Mg or Ag:Mg, etc.

[0098] Exemplarily, the thickness of the hole transport layer 30 is 10 nm - 100 nm, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc. In some embodiments, the thickness of the hole transport layer 30 is 70 nm - 90 nm.

[0099] Exemplarily, the thickness of the hole injection layer 20 is 20 nm - 120 nm, such as 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, etc. In some embodiments, the thickness of the hole injection layer 20 is 70 nm - 90 nm.

[0100] Exemplarily, the thickness of the thin film 40 is 10 nm - 80 nm, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, etc. In some embodiments, the thickness of the thin film 40 is 60 nm - 80 nm.

[0101] Exemplarily, the thickness of the electron transport layer 50 is 15 nm - 60 nm, such as 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, etc. In some embodiments, the thickness of the electron transport layer 50 is 40 nm - 60 nm.

[0102] Exemplarily, the thicknesses of the first electrode 10 and the second electrode 60 are each 10 nm - 125 nm, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 125 nm, etc. In some embodiments, the thickness of the anode is 115 nm - 125 nm, and the thickness of the cathode is 55 nm - 65 nm.

[0103] The embodiments of the present application further provide a display device, including the light-emitting device 100 prepared by the preparation method of the light-emitting device in any of the above embodiments or the light-emitting device 100 in any of the above embodiments.

[0104] Exemplarily, the display device can be a terminal such as a television, a mobile phone, a tablet computer, a display, an advertising display screen, etc., and can also be a device with a display screen such as a game device, an augmented reality (AR) device, a virtual reality (VR) device, a data storage device, an audio playback device, a video playback device, a wearable device, etc., where the wearable device can be a smart bracelet, smart glasses, a smart watch, smart decoration, etc.

[0105] The thin films of the present application, their preparation methods, light-emitting devices and their preparation methods will be described in detail below in the form of specific embodiments.

[0106] Thin Film Example 1

[0107] A thin film, the preparation method thereof comprising:

[0108] Step 11: Deposit a quantum dot solution to obtain a wet film layer, and perform annealing treatment on the wet film layer. The annealing temperature is 80 °C and the annealing time is 10 minutes to obtain a base film. Among them, the quantum dot solution includes quantum dots (CdSeS / ZnS green quantum dots) and a solvent (n-hexane), and the concentration of the quantum dot solution is 50 mg / mL;

[0109] Step 12: Apply a layer of modified solution on the surface of the base film. The modified solution is composed of zinc acetate, ammonium acetate and a solvent (ethanol). The volume of the modified solution applied per square centimeter of the base film is 1 ml. Among them, the concentration of zinc acetate is 5 wt%, and the concentration of ammonium acetate is 5 wt%. After allowing the modified solution to remain on the surface of the base film for 10 minutes at a temperature of 60 °C, wash the surface of the base film with ethanol to remove the modified solution to obtain a thin film, and the thickness of the thin film is 70 nm.

[0110] Thin Film Example 2

[0111] A thin film, the difference in its preparation method compared with Thin Film Example 1 is that:

[0112] In Step 12, in the modified solution, the concentration of zinc acetate is 10 wt%.

[0113] Thin Film Example 3

[0114] A thin film, the difference in its preparation method compared with Thin Film Example 1 is that:

[0115] In Step 12, in the modified solution, the concentration of zinc acetate is 7.5 wt%.

[0116] Thin Film Example 4

[0117] A thin film, the difference in its preparation method compared with Thin Film Example 1 is that:

[0118] In Step 12, in the modified solution, the concentration of ammonium acetate is 0.1 wt%.

[0119] Thin Film Example 5

[0120] A thin film, the difference in its preparation method compared with Thin Film Example 1 is that:

[0121] In Step 12, in the modified solution, the concentration of ammonium acetate is 2.5 wt%.

[0122] Thin Film Example 6

[0123] A film, compared with Film Example 1 in its preparation method, is characterized in that:

[0124] In Step 12, the solvent in the modification solution is methanol.

[0125] Film Example 7

[0126] A film, compared with Film Example 1 in its preparation method, is characterized in that:

[0127] In Step 12, the solvent in the modification solution is n-butanol.

[0128] Film Example 8

[0129] A film, compared with Film Example 1 in its preparation method, is characterized in that:

[0130] In Step 12, the volume of the modification solution applied to each square centimeter of the base film is 0.1 ml.

[0131] Film Example 9

[0132] A film, compared with Film Example 1 in its preparation method, is characterized in that:

[0133] In Step 12, the volume of the modification solution applied to each square centimeter of the base film is 2 ml.

[0134] Film Example 10

[0135] A film, compared with Film Example 1 in its preparation method, is characterized in that:

[0136] In Step 12, the modification solution is composed of ammonium acetate and a solvent (ethanol), wherein the concentration of ammonium acetate is 5 wt%.

[0137] Film Example 11

[0138] A film, compared with Film Example 1 in its preparation method, is characterized in that:

[0139] In Step 12, the modification solution is composed of zinc acetate and a solvent (ethanol), wherein the concentration of zinc acetate is 5 wt%.

[0140] Film Comparative Example 1

[0141] A film, its preparation method includes:

[0142] Deposit the quantum dot solution to obtain a wet film layer, and anneal the wet film layer at an annealing temperature of 80 °C for 10 minutes to obtain a thin film. Among them, the quantum dot solution includes quantum dots (CdSeS / ZnS green quantum dots) and a solvent (n-hexane), and the concentration of the quantum dot solution is 50 mg / mL;

[0143] It can be seen that compared with Thin Film Example 1, the difference is that the thin film prepared in Thin Film Comparative Example 1 is not treated with the modification solution.

[0144] Device Example 1

[0145] A light-emitting device, the preparation method of which includes:

[0146] Step 21: Provide an ITO substrate. The ITO substrate includes a substrate and an anode (IZO) provided on the substrate. The thickness of the anode is 70 nm. In an argon atmosphere, the hole injection layer (80 nm) and the hole transport layer (80 nm) are sequentially deposited on the ITO substrate by spin coating. Among them, the material of the hole transport layer is TFB, and the material of the hole injection layer is PEDOT:PSS;

[0147] Step 22: Prepare a thin film on the hole transport layer by the method of Thin Film Example 1;

[0148] Step 23: Spin coat the zinc oxide dispersion solution on the thin film. The zinc oxide dispersion solution includes zinc oxide nanoparticles and ethanol. Among them, the average particle size of the zinc oxide nanoparticles is 3.5 nm, and the concentration of the zinc oxide nanoparticles is 30 mg / mL. Anneal the zinc oxide dispersion solution at 80 °C for 10 minutes to completely volatilize the solvent ethanol in the zinc oxide dispersion solution to obtain an electron transport layer;

[0149] Step 24: Form a cathode (60 nm) on the surface of the electron transport layer by evaporation, and the material of the cathode is silver (Ag) to obtain a light-emitting device.

[0150] Device Example 2

[0151] A light-emitting device, the difference in its preparation method compared with Device Example 1 is that:

[0152] In Step 22, a thin film is prepared on the hole transport layer by the method of Thin Film Example 2.

[0153] Device Example 3

[0154] A light-emitting device, the difference in its preparation method compared with Device Example 1 is that:

[0155] In Step 22, a thin film is prepared on the hole transport layer by the method of Thin Film Example 3.

[0156] Device Embodiment 4

[0157] A light-emitting device, the difference in its preparation method compared with Device Embodiment 1 is that:

[0158] In Step 22, a thin film is prepared on the hole transport layer by using the method of Thin Film Embodiment 4.

[0159] Device Embodiment 5

[0160] A light-emitting device, the difference in its preparation method compared with Device Embodiment 1 is that: In Step 22, a thin film is prepared on the hole transport layer by using the method of Thin Film Embodiment 5.

[0161] Device Embodiment 7

[0162] A light-emitting device, the difference in its preparation method compared with Device Embodiment 1 is that: In Step 22, a thin film is prepared on the hole transport layer by using the method of Thin Film Embodiment 7.

[0163] Device Embodiment 8

[0164] A light-emitting device, the difference in its preparation method compared with Device Embodiment 1 is that: In Step 22, a thin film is prepared on the hole transport layer by using the method of Thin Film Embodiment 8.

[0165] Device Embodiment 9

[0166] A light-emitting device, the difference in its preparation method compared with Device Embodiment 1 is that: In Step 22, a thin film is prepared on the hole transport layer by using the method of Thin Film Embodiment 9.

[0167] Device Embodiment 10

[0168] A light-emitting device, the difference in its preparation method compared with Device Embodiment 1 is that: In Step 22, a thin film is prepared on the hole transport layer by using the method of Thin Film Embodiment 10.

[0169] Device Embodiment 11

[0170] A light-emitting device, the difference in its preparation method compared with Device Embodiment 1 is that: In Step 22, a thin film is prepared on the hole transport layer by using the method of Thin Film Embodiment 11.

[0171] Device Comparative Example 1

[0172] A light-emitting device, the difference in its preparation method compared with Device Embodiment 1 is that: In Step 22, a thin film is prepared on the hole transport layer by using the method of Thin Film Comparative Example 1.

[0173] Performance Test:

[0174] Performance tests were conducted on the light-emitting devices prepared in Device Examples 1-11 and Device Comparative Example 1. The test indicators and test methods are as follows:

[0175] Luminous efficiency C.E. (cd / A): Measured using an optical test instrument (FushiDA FPD Optical Characteristic Measurement Equipment, F-STAR Optical Measurement Systems);

[0176] Device T95_1knit life (hours): Refers to the life of the device when the brightness decays to 95% at an initial brightness of 1000 nits;

[0177] Efficiency fluctuation of device turn-on / turn-off: The device operates at 1000 nits for 30 minutes, and then the efficiency change after restarting 1 minute after turning off. Efficiency change = (C.E Max -C.E 1min ) / C.E, where C.E Max refers to the luminous efficiency of the light-emitting device before turning off, and C.E 1min refers to the luminous efficiency of the light-emitting device after restarting 1 minute after turning off.

[0178] The test results are shown in Table 1.

[0179] Table 1

[0180] T95 - 1 knit / h C.E. (cd / A) Efficiency fluctuation (%) of device turn - on / turn - off Device Example 1 42941 102.9 1.7％ Device Example 2 43178 103.4 2％ Device Example 3 44648 105.8 0.9％ Device Example 4 38145 95.8 2.5％ Device Example 5 43267 104.5 1.3％ Device Example 6 42316 102.1 1.8％ Device Example 7 42395 101.7 1.7％ Device Example 8 39024 96.2 2.3％ Device Example 9 43125 103.6 1.6％ Device Example 10 37824 94.5 2.4％ Device Example 11 36937 93.1 2.6％ Device Comparative Example 1 24841 67.8 14％

[0181] It can be seen from the data in Table 1 that the luminous efficiency C.E. and T95_1knit life of the light-emitting devices in Device Examples 1-11 are both greater than those of the light-emitting devices in Device Comparative Example 1. That is to say, compared with Device Comparative Example 1, the light-emitting devices in Device Examples 1-11 have higher device efficiency and longer service life. Moreover, the efficiency fluctuation of device turn-on / turn-off of the light-emitting devices in Device Examples 1-11 is smaller than that of the light-emitting devices in Device Comparative Example 1. That is to say, compared with Device Comparative Example 1, the light-emitting devices in Device Examples 1-11 have more stable efficiency performance when restarting after power-off.

[0182] By comparing Device Example 1, Device Example 2, and Device Example 3, it can be seen that among Device Examples 1 - 3, the light-emitting device of Device Example 3 has the maximum luminous efficiency C.E. and T95_1knit life, and at the same time has the smallest efficiency fluctuation of device turn-on / turn-off. That is to say, compared with Device Examples 1 - 2, the light-emitting device of Device Example 3 has the highest device efficiency, the longest service life, and the most stable efficiency performance. It is known that the only difference among Device Examples 1 - 3 is the concentration of zinc acetate in the modification solution, which indicates that when the concentration of zinc acetate is 7.5 wt%, the surface treatment effect of the modification solution on the base film is the best.

[0183] By comparing Device Example 1, Device Example 4, and Device Example 5, it can be seen that among Device Examples 1, 4, and 5, the light-emitting device of Device Example 5 has the maximum luminous efficiency C.E. and T95_1knit life, and at the same time has the smallest efficiency fluctuation of device turn-on / turn-off. That is to say, compared with Device Examples 1 and 4, the light-emitting device of Device Example 5 has the highest device efficiency, the longest service life, and the most stable efficiency performance. It is known that the only difference among Device Examples 1, 4, and 5 is the concentration of ammonium acetate in the modification solution, which indicates that when the concentration of ammonium acetate is 2.5 wt%, the surface treatment effect of the modification solution on the base film is the best.

[0184] The above has introduced in detail the thin film, its preparation method, light-emitting device, and display device provided by the embodiments of the present application. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the present application. At the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A method for preparing a thin film, characterized in that, Comprising: Providing a base film, the base film comprising quantum dots; Applying a modification solution on the base film to obtain the thin film, the modification solution comprising a weakly basic organic salt and a solvent.

2. The method for preparing a thin film according to claim 1, characterized in that, The weakly basic organic salt comprises at least one of an organic ammonium salt having 1 to 6 carbon atoms and an organic zinc salt having 1 to 6 carbon atoms; Optionally, the organic ammonium salt is ammonium acetate and the organic zinc salt is zinc acetate.

3. The method for preparing the thin film according to claim 2, characterized in that, The modification solution comprises zinc acetate, ammonium acetate and a solvent, the concentration of zinc acetate is 5 wt% to 10 wt%, the concentration of ammonium acetate is 0.1 wt% to 5 wt%, and the solvent comprises an alcohol compound; and / or The volume of the modification solution applied on each square centimeter of the base film is 0.1 ml to 2 ml.

4. The method for preparing a thin film according to claim 1, characterized in that, The applying the modification solution on the base film to obtain the thin film comprises: Applying the modification solution on the base film, allowing the modification solution to remain on the base film for 5 minutes to 30 minutes, and removing the modification solution to obtain the thin film.

5. The method for preparing the thin film according to claim 4, wherein Under a temperature condition of 50 °C to 70 °C, allowing the modification solution to remain on the base film for 5 minutes to 30 minutes; and / or The removing the modification solution on the surface of the base film comprises: rinsing the modification solution with a cleaning solution, the cleaning solution comprising an alcohol compound.

6. The method for preparing a thin film according to claim 1, wherein The preparing the base film comprises: Depositing a quantum dot solution to form a base film, wherein the quantum dot solution comprises quantum dots and a solvent, and in the quantum dot solution, the concentration of the quantum dots is 10 mg / mL to 100 mg / mL.

7. The method for preparing the thin film according to claim 6, characterized in that, The depositing the quantum dot solution to form a base film comprises: depositing the quantum dot solution to obtain a wet film layer, and annealing the wet film layer to obtain the base film, wherein the annealing temperature is 80 °C to 120 °C and the annealing time is 5 minutes to 10 minutes.

8. The method for preparing the thin film according to any one of claims 1-7, characterized in that, The quantum dots include at least one of single-structure quantum dots and core-shell structure quantum dots. The material of the single-structure quantum dots, the core material of the core-shell structure quantum dots, and the shell material of the core-shell structure quantum dots each include 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 compounds are selected from at least one of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, and HgZnSTe. The IV-VI group compounds are selected from at least one of SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, and SnPbSTe. The III-V group compounds are selected from at least one of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, and InAlPSb. The I-III-VI group compounds are selected from at least one of CuInS2, CuInSe2, CuInSeS, and AgInS2; and / or The surface of the quantum dots is connected with ligands, and the ligands include at least one of acid ligands, thiol ligands, amine ligands, phosphine oxide ligands, phospholipids, lecithins, polyvinylpyridines. The acid ligands are at least one of decanoic acid, undecylenic acid, myristic acid, oleic acid, stearic acid. The thiol ligands are at least one of octyl mercaptan, dodecyl mercaptan, octadecyl mercaptan. The amine ligands are at least one of oleylamine, octadecylamine, octylamine. The phosphine oxide ligands are at least one of trioctylphosphine, trioctylphosphine oxide; and / or The thickness of the thin film is 40 nm - 100 nm.

9. A film, characterized in that, It is prepared by using the preparation method of the thin film according to any one of claims 1 - 8. The thin film includes a base film, and the base film includes quantum dots modified by a weak alkaline organic salt.

10. A light-emitting device, characterized in that, It includes a first electrode and a second electrode which are oppositely arranged, and a thin film disposed between the first electrode and the second electrode. The thin film is the thin film according to claim 9.

11. The light-emitting device according to claim 10, characterized in that, When the first electrode is an anode and the second electrode is a cathode, a hole injection layer and a hole transport layer are disposed in a stacked manner between the first electrode and the thin film. Among them, the hole injection layer is disposed close to the first electrode, the hole transport layer is disposed close to the thin film, and an electron transport layer is disposed between the second electrode and the thin film; or When the first electrode is a cathode and the second electrode is an anode, an electron transport layer is disposed between the first electrode and the thin film, and a hole injection layer and a hole transport layer are disposed in a stacked manner between the second electrode and the thin film. Among them, the hole injection layer is disposed close to the second electrode, and the hole transport layer is disposed close to the thin film.

12. The light-emitting device according to claim 11, characterized in that, The materials of the hole transport layer include at least one of 4,4'-N,N'-dicarbazolyl-biphenyl, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4”-diamine, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine, poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine), N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine, 4,4',4'-tris(N-carbazolyl)-triphenylamine, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))], poly(N-vinylcarbazole) and its derivatives, N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4-4'-diamine, poly(phenylene vinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene], poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene], 2,2',7,7'-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene, 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline], 1,3-bis(carbazol-9-yl)benzene, polyaniline, polypyrrole, poly(p-phenylene vinylene), aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid and its derivatives, polymethacrylate and its derivatives, poly(9,9-octylfluorene) and its derivatives, polysfluorene and its derivatives, polythiophene and its derivatives; and / or The materials of the hole injection layer include at least one of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid and its derivatives, copper phthalocyanine, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, poly(dioxyethylthiophene), 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, tetracyanoquinodimethane, transition metal oxides and transition metal chalcogenides; and / or The material of the electron transport layer includes at least one of metal oxides, doped metal oxides, II-VI group semiconductor materials, III-V group semiconductor materials, and I-III-VI group semiconductor materials. The metal oxide is selected from at least one of ZnO, BaO, TiO2, and SnO2; the metal oxide in the doped metal oxide is selected from at least one of ZnO, TiO2, and SnO2, and the doping element is selected from at least one of Al, Mg, Li, In, and Ga. The II-VI semiconductor group material is selected from at least one of ZnS, ZnSe, and CdS; the III-V semiconductor group material is selected from at least one of InP and GaP; the I-III-VI group semiconductor material is selected from at least one of CuInS and CuGaS; and / or The cathode and the anode are independently selected from doped metal oxide particle electrodes, composite electrodes, graphene electrodes, carbon nanotube electrodes, metal elemental electrodes, or alloy electrodes. The material of the doped metal oxide particle electrode includes one or more of indium-doped tin oxide, fluorine-doped tin oxide, antimony-doped tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, indium-doped zinc oxide, magnesium-doped zinc oxide, and aluminum-doped magnesium oxide. The composite electrode includes 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 material of the metal elemental electrode includes one or more of Ag, Al, Cu, Mo, Au, Pt, Ca, Mg, and Ba.

13. The light-emitting device according to claim 11, wherein, The thickness of the hole transport layer is 10 nm - 100 nm, the thickness of the hole injection layer is 20 nm - 120 nm, the thickness of the thin film is 40 nm - 100 nm, the thickness of the electron transport layer is 15 nm - 60 nm, and the thicknesses of the first electrode and the second electrode are each 10 nm - 125 nm.

14. A display device, characterized in that, Comprising a light-emitting device according to any one of claims 10 - 13.

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