Quantum dot ink, quantum dot film, light-emitting device and display panel

Abstract

Provided in the embodiments of the present disclosure are a quantum dot ink, a quantum dot film, a light-emitting device and a display panel, which relate to the technical field of display. The quantum dot ink comprises a quantum dot solution and a functional auxiliary agent which is mutually soluble with the quantum dot solution, wherein the volume percentage of the functional auxiliary agent in the quantum dot ink is 0.1% -50%, and the functional auxiliary agent is configured to enable the viscosity of the quantum dot ink to be greater than or equal to 2.0 mPa·s. The quantum dot ink is used for preparing quantum dot films.

Description

Quantum dot ink, quantum dot film, light-emitting device and display panel Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to a quantum dot ink, a quantum dot film, a light-emitting device and a display panel. Background Art

[0002] Quantum dots (QDs) are semiconductor nanocrystals with unique optoelectronic properties. When stimulated by light or electricity, they emit pure, high-quality monochromatic light, depending on their molecular size. Due to their nanoparticle nature, QD materials are solution processable, and QD films can be formed by coating or spraying QD ink.

[0003] Summary of the Invention

[0004] In one aspect, a quantum dot ink is provided. The quantum dot ink comprises a quantum dot solution and a functional additive that is miscible with the quantum dot solution; the volume percentage of the functional additive in the quantum dot ink is 0.1% to 50%; and the functional additive is configured to ensure a viscosity of the quantum dot ink greater than or equal to 2.0 mPa·s.

[0005] In some embodiments, a quantum dot solution includes a quantum dot material and a solvent; the quantum dot material includes a quantum dot matrix; and a functional agent includes a first molecular backbone and at least one first ligand group grafted onto the first molecular backbone. Furthermore, when the functional agent includes at least two first ligand groups, the at least two first ligand groups may be the same or different. The one or more first ligand groups of the functional agent are coordinated with the quantum dot matrix.

[0006] In some embodiments, the quantum dot material further includes a ligand material coordinated to the quantum dot body; at least a portion of the quantum dot body is coordinated to both the ligand material and the functional auxiliary agent.

[0007] In some embodiments, when the functional agent includes a first ligand, the first ligand is a first selected ligand. When the functional agent includes at least two first ligands, the first ligand with the strongest coordination ability with the quantum dot is the first selected ligand. The ligand material includes a second ligand, and the ligand is coordinated to the quantum dot via the second ligand. The first selected ligand is the same as the second ligand; or the first selected ligand is different from the second ligand, and the coordination ability of the first selected ligand with the quantum dot is stronger than the coordination ability of the second ligand with the quantum dot.

[0008] In some embodiments, the second coordinating group is a thiol group, and the first selected coordinating group is a thiol group; or, the second coordinating group is a carboxyl group, and the first selected coordinating group is any one of a carboxyl group and a thiol group; or, the second coordinating group is a sulfonic acid group, and the first selected coordinating group is any one of a thiol group, a carboxyl group, and a sulfonic acid group; or, the second coordinating group is a phosphate group, and the first selected coordinating group is any one of a thiol group, a carboxyl group, a sulfonic acid group, and a phosphate group; or, the second coordinating group is an amine group, and the first selected coordinating group is any one of a thiol group, a carboxyl group, a sulfonic acid group, a phosphate group, and an amine group; or, the second coordinating group is a phospholipid group, and the first selected coordinating group is any one of a thiol group, a carboxyl group, a sulfonic acid group, a phosphate group, an amine group, and a phospholipid group.

[0009] In some embodiments, when the functional agent includes a first ligand, the first ligand is a first selected ligand. When the functional agent includes at least two first ligands, the first ligand with the strongest coordination ability with the quantum dot body is the first selected ligand. The ligand material includes a second ligand, and the ligand material is coordinated with the quantum dot body via the second ligand. The coordination ability of the second ligand with the quantum dot body is stronger than the coordination ability of the first selected ligand. The volume percentage of the functional agent in the quantum dot ink is greater than or equal to 5%.

[0010] In some embodiments, when the functional auxiliary agent includes one first ligand, the first ligand is a first selected ligand. When the functional auxiliary agent includes at least two first ligands, the first ligand with the strongest coordination ability with the quantum dot is the first selected ligand. The ligand material includes a second molecular backbone and a second ligand grafted to the second molecular backbone, and the ligand material is coordinated with the quantum dot via the second ligand. The coordination ability of the second ligand with the quantum dot is stronger than that of the first selected ligand; the steric hindrance of the second molecular backbone is greater than that of the first molecular backbone.

[0011] In some embodiments, the first selected coordinating group is a carboxyl group and the second coordinating group is a sulfhydryl group; or; the first selected coordinating group is a sulfonic acid group and the second coordinating group is any one of a sulfhydryl group and a carboxyl group; or, the first selected coordinating group is a phosphate group and the second coordinating group is any one of a sulfhydryl group, a carboxyl group and a sulfonic acid group; or, the first selected coordinating group is an amine group and the second coordinating group is any one of a sulfhydryl group, a carboxyl group, a sulfonic acid group and a phosphate group; or, the first selected coordinating group is a phospholipid group and the second coordinating group is any one of a sulfhydryl group, a carboxyl group, a sulfonic acid group, a phosphate group and an amine group.

[0012] In some embodiments, the number of carbon atoms in the first molecular backbone is greater than or equal to 4 and less than or equal to 8.

[0013] In some embodiments, the quantum dot solution includes a quantum dot material and a solvent; the boiling point of the functional aid is greater than the boiling point of the solvent.

[0014] In some embodiments, the viscosity of the functional aid is greater than or equal to 5.0 mPa·s.

[0015] In some embodiments, the first coordination group includes a thiol group and / or a carboxyl group; and the volume percentage of the functional additive in the quantum dot ink is 0.1% to 50%.

[0016] In some embodiments, the functional auxiliary agent is selected from any one or more combinations of 3-mercaptobutyric acid, 5-mercaptopentanoic acid, heptyl mercaptan, octyl mercaptan, isooctyl mercaptan, 2-mercapto-2,4-pentanediol, 2-methyl-2,4-pentanedithiol, 1,5-pentanedithiol, oligomercaptans and 5-aminopentanoic acid.

[0017] In some embodiments, the first coordination group includes an amino group and / or an amine group; and the volume percentage of the functional additive in the quantum dot ink is 0.1% to 30%.

[0018] In some embodiments, the functional auxiliary agent is selected from any one or more combinations of ethanolamine, dimethylethanolamine, N,N-dimethylethylenediamine, 1.2-propylenediamine, 2-methylbutylenediamine, 2-methylpentanediamine and 5-aminovaleric acid.

[0019] In some embodiments, the first coordination group includes a phosphate group and / or a phospholipid group; and the volume percentage of the functional additive in the quantum dot ink is 0.1% to 30%.

[0020] In some embodiments, the functional auxiliary agent is selected from any one or more combinations of fatty alcohol ether phosphate and fatty alcohol polyoxyethylene ether phosphate.

[0021] In some embodiments, the first coordination group includes a sulfonic acid group; and the volume percentage of the functional additive in the quantum dot ink is 0.1% to 30%.

[0022] In some embodiments, the functional auxiliary agent is selected from any one or more combinations of octane sulfonic acid, decane sulfonic acid, dodecyl sulfonic acid, tetradecyl sulfonic acid, hexadecyl sulfonic acid, octadecyl sulfonic acid, 4-decylbenzenesulfonic acid, dodecylbenzenesulfonic acid, tetradecylbenzenesulfonic acid, hexadecylbenzenesulfonic acid and octadecylbenzenesulfonic acid.

[0023] In some embodiments, the concentration of the quantum dot material in the quantum dot solution is greater than or equal to 5.0 mg / mL and less than or equal to 50 mg / mL.

[0024] In another aspect, a quantum dot film is provided, wherein the quantum dot film is made of the quantum dot ink described in any of the above embodiments.

[0025] In some embodiments, the material of the quantum dot film includes a functional aid.

[0026] In another aspect, a display panel is provided. The display panel includes a plurality of quantum dot films according to any of the above embodiments and a barrier layer. The barrier layer includes a plurality of openings, and the plurality of quantum dot films are located in the plurality of openings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the technical solutions of the present disclosure, the following briefly introduces the drawings required for use in some embodiments of the present disclosure. Obviously, the drawings described below are only drawings of some embodiments of the present disclosure, and those skilled in the art can also derive other drawings based on these drawings. Furthermore, the drawings described below are schematic diagrams and are not intended to limit the actual dimensions of the products, actual processes of the methods, actual timing of signals, and the like involved in the embodiments of the present disclosure.

[0028] FIG1 is a structural diagram of a light-emitting substrate according to some embodiments;

[0029] FIG2 is a structural diagram of a display panel according to some embodiments;

[0030] FIG3 is a topographical diagram of a quantum dot film according to some embodiments;

[0031] FIG4 is a morphology diagram of a quantum dot film according to some further embodiments;

[0032] FIG5 is a morphology diagram of a quantum dot film according to some other embodiments;

[0033] FIG6 is a morphology diagram of a quantum dot film according to some further embodiments;

[0034] FIG7 is a morphology diagram of a quantum dot film according to some other embodiments;

[0035] FIG8 is a morphology diagram of a quantum dot film according to yet other embodiments;

[0036] FIG9 is a morphology diagram of a quantum dot film according to yet other embodiments;

[0037] FIG10 is a morphology diagram of a quantum dot film according to some other embodiments;

[0038] FIG11 is a graph showing current versus voltage according to some embodiments;

[0039] FIG12 is a graph showing changes in brightness as a function of current density according to some embodiments;

[0040] FIG. 13 is a graph showing current efficiency versus current density according to some embodiments. DETAILED DESCRIPTION

[0041] The following, in conjunction with the accompanying drawings, clearly and completely describes the technical solutions in some embodiments of the present disclosure. Obviously, the embodiments described are only some of the embodiments of the present disclosure, and not all of them. Based on the embodiments provided by this disclosure, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this disclosure.

[0042] Unless the context requires otherwise, throughout the specification and claims, the term "comprise" and its other forms, such as the third person singular form "comprises" and the present participle form "comprising", are to be interpreted as open and inclusive, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific example" or "some examples" are intended to indicate that the particular features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the particular features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0043] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "plurality" means two or more.

[0044] “At least one of A, B and C” has the same meaning as “at least one of A, B or C” and both include the following combinations of A, B and C: A only, B only, C only, the combination of A and B, the combination of A and C, the combination of B and C, and the combination of A, B and C.

[0045] “A and / or B” includes the following three combinations: A only, B only, and a combination of A and B.

[0046] As used herein, "about," "substantially," or "approximately" includes the stated value and an average value that is within an acceptable range of deviation from the particular value as determined by one of ordinary skill in the art taking into account the measurements in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system).

[0047] As used herein, "parallel", "perpendicular", and "equal" include the situations described and situations similar to the situations described, and the range of the similar situations is within an acceptable deviation range, wherein the acceptable deviation range is as determined by a person of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system). For example, "parallel" includes absolute parallelism and approximate parallelism, wherein the acceptable deviation range of approximate parallelism can be, for example, a deviation within 5°; "perpendicular" includes absolute perpendicularity and approximate perpendicularity, wherein the acceptable deviation range of approximate perpendicularity can also be, for example, a deviation within 5°. "Equal" includes absolute equality and approximate equality, wherein the acceptable deviation range of approximate equality can be, for example, that the difference between the two equals is less than or equal to 5% of either one.

[0048] It will be understood that when a layer or element is referred to as being on another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may be present therebetween.

[0049] Exemplary embodiments are described herein with reference to cross-sectional and / or plan views that are idealized exemplary drawings. In the drawings, the thickness of layers and the area of ​​regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are contemplated. Therefore, the exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include deviations in shape due to, for example, manufacturing. For example, an etched region shown as a rectangle will typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shape of regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0050] It should be noted that, for example, 11-1 in the drawings of this disclosure indicates that component 11 belongs to component 1, and for example, 241-240 in FIG2 indicates that light absorption pattern 241 belongs to light blocking layer 240. Other similar reference numerals in the drawings also follow the above description. For example, 1 / 2 in the drawings of this disclosure indicates that both structure 1 and structure 2 can refer to this structure, and for example, 10G / 10 in FIG1 indicates that both green light-emitting device 10G and light-emitting device 10 can refer to this structure. Other similar reference numerals in the drawings also follow the above description.

[0051] Nanomaterials often possess unique mechanical, optical, magnetic, electrical, and catalytic properties, making them highly valuable. Quantum dots (QDs), also known as nanocrystals, have been extensively studied in recent years due to their unique photophysical properties. They have found numerous applications in optoelectronic devices, sensors, and energy storage.

[0052] In recent years, the application of quantum dot materials in optoelectronic devices has become increasingly widespread, and many researchers have done a lot of research on device efficiency and lifespan. At present, the efficiency of quantum dot devices can reach very high levels. In some examples, the efficiency of red light-emitting devices, green light-emitting devices, and blue light-emitting devices can reach external quantum efficiencies (EQE) of 25%, 20%, and 20%, respectively. Among them, the lifespan of some light-emitting devices (such as red light-emitting devices and green light-emitting devices) has reached a relatively high level, reaching a level that can be mass-produced and promoted.

[0053] The preparation process of quantum dot film includes slit coating process, inkjet printing process, photolithography process, transfer process, etc. Among them, in the slit coating process, inkjet printing process, etc., the quantum dot film is formed by coating or spraying quantum dot ink.

[0054] Among them, the slit coating process is different from the spin coating process used in the laboratory and is more suitable for large-area film formation on the production line. The working principle of the slit coating process is, for example: the coating solution is squeezed and sprayed along the slit lip of the coating die under a certain pressure and at a certain flow rate to be coated on the surface of the substrate. Compared with other coating methods and processes, the slit coating process has many advantages, such as fast coating speed, high precision, uniform wet thickness, closed system, high slurry utilization rate, and the ability to perform multiple layers of coating simultaneously.

[0055] Based on the above principles, the slit coating process has certain performance requirements for the solution used. For example, the solution viscosity must be above a set viscosity value, which can range from 2.0mPa·s to 4.0mPa·s; and / or the solid content of the quantum dot material in the solution must be at a set solid content value, which can range from 20% to 30%.

[0056] In some implementations, when a quantum dot film is prepared using a slit coating process, the thickness of a single-layer quantum dot film is required to be in the range of 20nm to 50nm. Within this thickness range, the viscosity of the quantum dot ink is usually less than the above-mentioned set viscosity value, for example, less than 2.0mPa·s. In this case, due to the inherent viscosity of the quantum dot ink, the process controllability during large-area coating and drying is poor, making large-area uniform coating and drying a greater challenge. Therefore, how to improve the uniformity of large-area film formation and drying is the key to the early industrial application of quantum dot luminescence technology.

[0057] In other implementation methods, such as the slit coating process and the inkjet printing process, due to the low viscosity and high fluidity of the quantum dot ink, large-area quantum dot ink is prone to liquid migration during the drying process, resulting in the dried quantum dot film having a coffee ring-like mark, which is commonly known as the coffee ring effect, affecting the film quality.

[0058] Based on this, some embodiments of the present disclosure provide a quantum dot ink. The quantum dot ink includes a quantum dot solution and a functional additive that is miscible with the quantum dot solution; the functional additive comprises 0.1% to 50% by volume of the quantum dot ink; and the functional additive is configured to impart a viscosity of the quantum dot ink greater than or equal to 2.0 mPa·s.

[0059] The quantum dot solution and the functional additive are mutually soluble, which means that the quantum dot solution and the functional additive can form a homogeneous system with relatively uniform physical and chemical properties after mixing. Here, the state of the functional additive (for example, liquid or solid) is not limited.

[0060] In some examples, a quantum dot solution includes a quantum dot material and a solvent. In this case, as a possible implementation, the solvent can be miscible with the functional agent to achieve miscibility between the quantum dot solution and the functional agent. Furthermore, the solvent can be a single solvent or a mixed solvent, and there is no limitation here. The type of single solvent, as well as the type and amount of mixed solvents, are not limited here, as long as they can form a quantum dot solution with the quantum dot material and the quantum dot solution is miscible with the functional agent.

[0061] For example, the volume percentage of the functional additive in the quantum dot ink can be 0.1%, 0.5%, 1.0%, 5.0%, 10.0%, 15.0%, 20.0%, 24.0%, 30.0%, 35.0%, 40.0%, 46.0% or 50%, etc.

[0062] For example, under the action of functional additives, the viscosity of the quantum dot ink can be 2.0 mPa·s, 2.3 mPa·s, 2.6 mPa·s, 3.0 mPa·s, 3.5 mPa·s, 4.0 mPa·s, 5.0 mPa·s, or 6.0 mPa·s. It should be noted that the viscosity values ​​listed above are examples of the viscosity of quantum dot inks and do not limit the viscosity of quantum dot inks.

[0063] It can be understood that when the viscosity of the quantum dot ink is greater than or equal to 2.0 mPa·s, the viscosity of the quantum dot ink is relatively high. First, it can improve the process controllability during the film formation and drying process, so that the uniformity of large-area coating and drying during the preparation of the quantum dot film can be improved; second, it can reduce the fluidity of the quantum dot solution and the volatility of the quantum dot ink, reduce the migration of the quantum dot solution, and alleviate the coffee ring effect that occurs during the drying process; in this way, the film formation quality of the formed quantum dot film can be improved.

[0064] Here, there is no limitation on the manner and principle of adjusting the viscosity of the quantum dot ink by the functional additive, as long as the viscosity of the quantum dot ink can be greater than or equal to 2.0 mPa·s.

[0065] In some examples, the functional additive itself has a relatively high viscosity. In this case, after the functional additive and the quantum dot solution are mutually dissolved, a quantum dot ink having a viscosity greater than or equal to 2.0 mPa·s can be formed. In other examples, the functional additive can increase the viscosity of the quantum dot ink by reacting biochemically with the quantum dot solution to form a material with a higher viscosity.

[0066] In some embodiments, the viscosity of the functional aid is greater than or equal to 5.0 mPa·s.

[0067] For example, the viscosity of the functional additive can be 5.0 mPa·s, 10.0 mPa·s, 20.5 mPa·s, 50.0 mPa·s, 100.0 mPa·s, 250.0 mPa·s, 400.0 mPa·s, 500.0 mPa·s, 800.0 mPa·s, 1000.0 mPa·s or 5000.0 mPa·s, etc. It should be noted that the viscosity values ​​listed above are examples of the viscosity of the functional additive and are not intended to limit the viscosity of the functional additive.

[0068] It can be understood that when the viscosity of the functional additive is greater than or equal to 5.0 mPa·s, the viscosity of the functional additive is relatively high. In this way, when the functional additive is miscible with the quantum dot solution, a quantum dot ink with a viscosity greater than or equal to 2.0 mPa·s can be formed. In this way, the uniformity of large-area coating and drying during the preparation of the quantum dot film can be improved; at the same time, the coffee ring effect that occurs during the drying process can be alleviated.

[0069] In some embodiments, a quantum dot solution includes a quantum dot material and a solvent; the quantum dot material includes a quantum dot matrix; and a functional agent includes a first molecular backbone and at least one first ligand group grafted onto the first molecular backbone. Furthermore, when the functional agent includes at least two first ligand groups, the at least two first ligand groups may be the same or different. The one or more first ligand groups of the functional agent are coordinated with the quantum dot matrix.

[0070] It should be understood that the quantum dot body is the portion of the quantum dot material that can emit monochromatic light when stimulated by light or electricity, and has nanoparticle properties. Here, there is no limitation on the type of quantum dot body.

[0071] In some examples, the quantum dot body may include any one of: II-VI group quantum dots, III-V group quantum dots, IV-VI group quantum dots, core-shell structured quantum dots, and ABX3 type perovskite quantum dots.

[0072] II-VI quantum dots can be selected from: binary compounds such as one or more of CdS, CdSe, CdTe, ZnS, ZnO, ZnSe, ZnTe, HgSe, HgTe and HgS; ternary compounds such as Hg x Cd 1-x Te, Hg x Cd 1-x S, Hg x Cd 1- x Se, Hg x Zn 1-x Te, Cd x Zn 1-x Se and Cd x Zn 1-x One or more of S, wherein 0<x<1, but not limited thereto.

[0073] The III-V quantum dots may be selected from: InP, InAs, InSb, GaAs, GaP, GaN, GaSb, GaNk, InN, AlP, AlN, AlAs, InGaAs, InGaN, or a mixture thereof; but are not limited thereto.

[0074] The Group IV-VI quantum dots may be selected from: PbS, PbSe, PbTe, or a mixture thereof, but are not limited thereto.

[0075] Core-shell quantum dots refer to quantum dots in which one material is the core and the other is the shell. For example, a quantum dot is CdS@ZnS, which means that the core material of the quantum dot is CdS and the shell material is ZnS. The quantum dots with core-shell structures can be selected from: CdS@ZnS, CdSe@CdS, InP@ZnS, CdTe@CdSe, CdSe@ZnTe, CdSe@ZnS, PdS@ZnS, ZnTe@CdSe, ZnSe@CdS and Cd 1-x Zn x One or more of S@ZnS, wherein 0<x<1, but not limited thereto.

[0076] In ABX3 type perovskite quantum dots, A can be CH3NH3 + (methylamine), NH2CH=NH2(formamidine) and Cs + One or more of, B can be Pb 2+ and Sn 2+ One or two of the following, X can be Cl - Br - and I - One or more of the ABX3 type perovskite quantum dots may include CH3NH3PbBr3, CH3NH3PbCl3, CH3NH3PbI3, CsPbBr3, CsPbCl3 and CsPbI3, but are not limited thereto.

[0077] In other examples, the quantum dot body may be other nanoscale materials, such as nanorods, nanosheets, etc. Components of other nanoscale materials may include at least one of CuInS2, CuInSe2, AgInS2, etc., but are not limited thereto.

[0078] As previously mentioned, the solvent may be a single solvent or a mixed solvent, and is not limited thereto. Furthermore, the type of single solvent, as well as the type and amount of mixed solvent, are not limited here, as long as they can form a quantum dot solution with the quantum dot material.

[0079] In some examples, the solvent is a mixed solvent, for example, a mixed solvent consisting of propylene glycol methyl ether acetate, propylene glycol methyl ether and 3-ethoxyethyl propionate, and the volume fraction of propylene glycol methyl ether acetate is 55% to 65%, the volume fraction of propylene glycol methyl ether is 5% to 30%, and the volume fraction of 3-ethoxyethyl propionate is 5% to 15%.

[0080] The first ligand group is grafted onto the first molecular skeleton, which means that at least one first ligand group is connected to a portion of the first molecular skeleton via a chemical bond.

[0081] In some examples, the first molecular skeleton may be a linear molecular skeleton; for example, a carbon chain molecular skeleton, which may be an alkane molecular skeleton, an alkene molecular skeleton, or an alkyne molecular skeleton.

[0082] In other examples, the first molecular skeleton can be a dendritic molecular skeleton. Here, the dendritic molecular skeleton refers to an organic molecular skeleton with a dendritic structure. Dendritic molecules are synthesized by repeated growth reactions, and each repeated cycle reaction adds a branching layer, called a "generation". It includes a main structure (core, branching unit, peripheral group) and a microenvironment (cavity). The core can be a single atom (such as a nitrogen atom), a dendritic structure (such as triphenylamine, etc.), a straight-chain structure (such as alkanes, alkenes, etc.) or a ring structure (such as aromatic hydrocarbons, fluorene, carbazole, etc.), and the branching unit can be a straight-chain bonding group or a branched bonding group. Here, the branched bonding group is relative to the straight-chain bonding group and has multiple bifurcations (i.e., a structure with branches connected to the main chain). The straight-chain bonding group or the branched bonding group can be an alkane bonding group, or an olefin bonding group, an aromatic bonding group, etc. It can be understood that when the first molecular skeleton is a dendritic molecular skeleton, compared with a linear molecular skeleton, due to the multiple terminal positions, the number of first coordination groups grafted to the first molecular skeleton can be relatively large.

[0083] Here, one or more first coordination groups of the functional auxiliary agent can coordinate with one quantum dot entity, or can coordinate with multiple quantum dot entities; that is, there is no limit on the number of quantum dot entities that undergo coordination reaction with the first coordination group of the functional auxiliary agent.

[0084] Understandably, since the surface of quantum dots often contain some defects that cannot be passivated, and the defect locations often have dangling bonds that are not coordinated by ligands, the quantum dot material is relatively unstable. When one or more first ligand groups of the functional additive coordinate with the quantum dot, the coordination between the first ligand groups and the dangling bonds can passivate the defects on the surface of the quantum dot, thereby improving the stability of the quantum dot material.

[0085] In some embodiments, the concentration of the quantum dot material in the quantum dot solution is greater than or equal to 5.0 mg / mL and less than or equal to 50 mg / mL.

[0086] For example, in the quantum dot solution, the concentration of the quantum dot material can be 5.0 mg / mL, 10.0 mg / mL, 10.8 mg / mL, 12.0 mg / mL, 15.0 mg / mL, 20.0 mg / mL, 25.0 mg / mL, 30.0 mg / mL, 40.0 mg / mL or 50.0 mg / mL, etc.

[0087] It can be understood that, on the one hand, when the concentration of the quantum dot material in the quantum dot solution is greater than or equal to 5.0 mg / mL, the concentration of the quantum dot material in the quantum dot solution is relatively high, which can make the solid content of the quantum dot material in the quantum dot solution relatively high, and can improve the process controllability during the film forming and drying process, so that the uniformity of large-area coating and drying during the preparation of the quantum dot film is improved. On the other hand, because when the concentration of the quantum dot material in the quantum dot solution is higher than a certain value, the solid content of the quantum dot material is high, making it more difficult to prepare a thinner quantum dot film. Therefore, by setting the concentration of the quantum dot material in the quantum dot solution to less than or equal to 50.0 mg / mL, a quantum dot film with an appropriate film thickness, such as a quantum dot film with a film thickness of 20 nm to 50 nm, can be prepared using quantum dot ink.

[0088] In some embodiments, the quantum dot material further includes a ligand material coordinated to the quantum dot body.

[0089] It should be understood that the ligand material is the original ligand material in the quantum dot material that coordinates with the quantum dot body. The type of ligand material is not limited herein. In some examples, the ligand material can be selected from any one or more combinations of organic acids, organic amines, organic phosphorus compounds, and organic thiols. For example, the ligand material can be oleic acid, oleylamine, or dodecanethiol.

[0090] It is understandable that when the quantum dot material further includes a ligand material, when one or more first coordination groups of the functional auxiliary agent coordinate with the quantum dot body, there are at least two possible implementation methods:

[0091] In the first implementation, the first coordination group directly coordinates with the dangling bonds of the quantum dot body that are not coordinated by the ligand material; at this time, at least part of the quantum dot body is coordinated with both the ligand material and the functional auxiliary agent.

[0092] For example, when the first coordination group directly coordinates with the dangling bonds of the quantum dot body that are not coordinated by the ligand material, the coordination reaction can be shown as follows.

[0093] The second implementation method involves a ligand exchange reaction between the functional agent and the ligand material. This means that the existing coordination bond between the ligand material and the quantum dot body is broken, and a new coordination bond is formed between the functional agent and the quantum dot material using the first coordination group. In this case, the functional agent can undergo a ligand exchange reaction with a portion of the ligand material coordinated to the quantum dot body, or it can undergo a ligand exchange reaction with all of the ligand material coordinated to the quantum dot body.

[0094] For example, when the functional auxiliary agent undergoes a ligand exchange reaction with the ligand material, the ligand exchange reaction may be as shown in the following formula.

[0095] It should be noted that the above two implementation methods do not exist independently, but can exist simultaneously. For example, as shown in the following formula, among multiple functional auxiliary agent molecules, some functional auxiliary agent molecules coordinate with the dangling bonds of the quantum dot body that are not coordinated by the ligand material, and another part of the functional auxiliary agent molecules undergoes a ligand exchange reaction with the ligand material. Alternatively, the same functional auxiliary agent molecule contains multiple first coordination groups, some of which coordinate with the dangling bonds of the quantum dot body that are not coordinated by the ligand material, and another part of the first coordination groups undergoes a ligand exchange reaction with the ligand material.

[0096] Based on the above two possible implementations, in some embodiments, at least a portion of the quantum dot body is coordinated with both the ligand material and the functional auxiliary agent.

[0097] It can be understood that when at least a portion of the quantum dot body is coordinated with both the ligand material and the functional additive, the stability of the quantum dot material can be improved. Furthermore, in this case, due to the coordination bond, the functional additive can be present in the quantum dot ink throughout the process of preparing the quantum dot film from the quantum dot ink. This can maintain the viscosity of the quantum dot ink within a relatively high range, improve the uniformity of large-area coating and drying during the quantum dot film preparation process, and mitigate the coffee ring effect that occurs during the drying process. Furthermore, in this case, the quantum dot film prepared from the quantum dot ink can contain the functional additive, and the presence of the functional additive does not affect the electrical performance of the quantum dot device.

[0098] Some examples of ligand exchange reactions between functional additives and ligand materials are exemplarily introduced below.

[0099] In some embodiments, when the functional agent includes a first ligand, the first ligand is a first selected ligand. When the functional agent includes at least two first ligands, the first ligand with the strongest coordination ability with the quantum dot is the first selected ligand. The ligand material includes a second ligand, and the ligand is coordinated to the quantum dot via the second ligand. The first selected ligand is the same as the second ligand; or the first selected ligand is different from the second ligand, and the coordination ability of the first selected ligand with the quantum dot is stronger than the coordination ability of the second ligand with the quantum dot.

[0100] It can be understood that when the functional auxiliary agent includes a first selected coordination group, the functional auxiliary agent can react with the quantum dot body at least through the first selected coordination group. Specifically, when the first selected coordination group and the second coordination group are simultaneously present in the quantum dot ink, and the first selected coordination group and the second coordination group are different, based on the principle of higher coordination binding energy, the quantum dot body is more likely to react with the coordination group with stronger coordination ability to form a coordination bond. Therefore, when the coordination ability of the first selected coordination group with the quantum dot body is stronger than the coordination ability of the second coordination group with the quantum dot body, the quantum dot body is more likely to react with the first selected coordination group (i.e., the functional auxiliary agent) to form a coordination bond, so that the functional auxiliary agent can undergo a ligand exchange reaction with the ligand material.

[0101] When the first selected coordination group and the second coordination group exist simultaneously in the quantum dot ink, and the first selected coordination group and the second coordination group are the same (for example, both are carboxyl groups), the coordination reaction between the quantum dot body and the functional auxiliary agent, and the coordination reaction between the quantum dot body and the ligand material can form a competitive reaction. Moreover, under normal circumstances, the process of the competitive reaction is a dynamic equilibrium process, so that the functional auxiliary agent and at least a part of the ligand material can undergo a ligand exchange reaction.

[0102] Here, when the functional auxiliary agent includes at least two first coordination groups, the coordination ability of the first coordination group other than the first selected coordination group with the quantum dot body may be stronger than the coordination ability of the second coordination group with the quantum dot body, or may be weaker than the coordination ability of the second coordination group with the quantum dot body, and there is no limitation here.

[0103] In some embodiments, the second coordinating group is a thiol group and the first selected coordinating group is a thiol group.

[0104] It can be understood that, since the first selected ligand group is the same as the second ligand group, as described above, the functional auxiliary agent and the ligand material can undergo a ligand exchange reaction.

[0105] In some examples, the functional agent is 2-methyl-2,4-pentanedithiol, and the first selected ligand group is a thiol group; the ligand material is dodecanethiol, and the second ligand group is a thiol group. Although the coordination ability of the first and second selected ligand groups with the quantum dot body is comparable, the functional agent 2-methyl-2,4-pentanedithiol has a dithiol structure, and compared to the second molecular skeleton of the ligand material dodecanethiol, the chain segment of the first molecular skeleton of the functional agent 2-methyl-2,4-pentanedithiol is shorter, which can increase the probability of coordination reaction between the quantum dot body and the functional agent 2-methyl-2,4-pentanedithiol. Therefore, the functional agent 2-methyl-2,4-pentanedithiol can coordinate with the quantum dot body through ligand exchange reaction and / or direct coordination reaction to generate a quantum dot material with a dual ligand structure. In the obtained quantum dot film, the proportion of the number of dodecanethiol ligands to the total number of ligands is between 5% and 95%, and the proportion of the number of 2-methyl-2,4-pentanedithiol ligands to the total number of ligands is between 5% and 95%. Here, the total number of ligands refers to the sum of the number of dodecanethiol ligands and the number of 2-methyl-2,4-pentanedithiol ligands.

[0106] In some embodiments, the second coordinating group is a carboxyl group, and the first selected coordinating group is any one of a carboxyl group and a thiol group.

[0107] Understandably, because the coordination ability of the thiol group with the quantum dot body is stronger than that of the carboxyl group with the quantum dot body, when the second ligand group is a carboxyl group and the first selected ligand group is either a carboxyl group or a thiol group, the first selected ligand group is the same as the second ligand group; or, the coordination ability of the first selected ligand group with the quantum dot body is stronger than that of the second ligand group with the quantum dot body, then, as described above, the functional auxiliary agent and the ligand material can undergo a ligand exchange reaction.

[0108] In some embodiments, the second coordinating group is a sulfonic acid group, and the first selected coordinating group is any one of a thiol group, a carboxyl group, and a sulfonic acid group.

[0109] Understandably, since the coordination ability of the thiol and carboxyl groups with the quantum dot body is stronger than that of the sulfonic acid group with the quantum dot body, when the second ligand is a sulfonic acid group and the first selected ligand is any one of the thiol, carboxyl, and sulfonic acid groups, the first selected ligand is the same as the second ligand; or, the coordination ability of the first selected ligand with the quantum dot body is stronger than that of the second ligand. In this way, as described above, the functional auxiliary agent and the ligand material can undergo a ligand exchange reaction.

[0110] In some embodiments, the second coordinating group is a phosphate group, and the first selected coordinating group is any one of a thiol group, a carboxyl group, a sulfonic acid group, and a phosphate group.

[0111] Understandably, since the coordination ability of thiol, carboxyl, and sulfonic acid groups with the quantum dot body is stronger than that of phosphate groups with the quantum dot body, when the second ligand group is a phosphate group and the first selected ligand group is any one of thiol, carboxyl, sulfonic acid, and phosphate groups, the first selected ligand group is the same as the second ligand group; or, the coordination ability of the first selected ligand group with the quantum dot body is stronger than that of the second ligand group with the quantum dot body, then, as described above, the functional auxiliary agent and the ligand material can undergo a ligand exchange reaction.

[0112] In some embodiments, the second coordinating group is an amine group, and the first selected coordinating group is any one of a thiol group, a carboxyl group, a sulfonic acid group, a phosphate group, and an amine group.

[0113] Understandably, since the coordination ability of thiol, carboxyl, sulfonic acid, and phosphate groups with the quantum dot body is stronger than that of amine groups with the quantum dot body, when the second ligand group is an amine group and the first selected ligand group is any one of thiol, carboxyl, sulfonic acid, phosphate, and amine groups, the first selected ligand group is the same as the second ligand group; or, the coordination ability of the first selected ligand group with the quantum dot body is stronger than that of the second ligand group with the quantum dot body, then, as described above, the functional auxiliary agent and the ligand material can undergo a ligand exchange reaction.

[0114] In some embodiments, the second coordinating group is a phospholipid group, and the first selected coordinating group is any one of a sulfhydryl group, a carboxyl group, a sulfonic acid group, a phosphate group, an amine group, and a phospholipid group.

[0115] Understandably, because the coordination ability of thiol, carboxyl, sulfonic acid, phosphate, and amine groups with the quantum dot body is stronger than the coordination ability of phospholipid groups with the quantum dot body, when the second ligand group is a phospholipid group and the first selected ligand group is any one of thiol, carboxyl, sulfonic acid, phosphate, amine, and phospholipid groups, the first selected ligand group is the same as the second ligand group; or, the coordination ability of the first selected ligand group with the quantum dot body is stronger than the coordination ability of the second ligand group with the quantum dot body, then, as described above, the functional auxiliary agent and the ligand material can undergo a ligand exchange reaction.

[0116] In some embodiments, when the functional agent includes a first ligand, the first ligand is a first selected ligand. When the functional agent includes at least two first ligands, the first ligand with the strongest coordination ability with the quantum dot body is the first selected ligand. The ligand material includes a second ligand, and the ligand material is coordinated with the quantum dot body via the second ligand. The coordination ability of the second ligand with the quantum dot body is stronger than the coordination ability of the first selected ligand. The volume percentage of the functional agent in the quantum dot ink is greater than or equal to 5%.

[0117] For example, the volume percentage of the functional additive in the quantum dot ink can be 5.0%, 10.0%, 16.0%, 21.0%, 25.0%, 31.0%, 36.0%, 40.0%, 46.0% or 50%, etc.

[0118] It can be understood that when the functional auxiliary agent includes a first selected coordination group, the functional auxiliary agent can react with the quantum dot body at least through the first selected coordination group. Specifically, since the coordination ability of the second coordination group with the quantum dot body is stronger than the coordination ability of the first selected coordination group with the quantum dot body, the possibility of the quantum dot body and the second coordination group reacting with each other is relatively large. In this case, since the combination of the ligand (for example, a ligand material or a functional auxiliary agent) and the quantum dot body is a dynamic equilibrium process, when the concentration of the functional auxiliary agent around the quantum dot body is high, the functional auxiliary agent can coordinate with the quantum dot body. Therefore, by setting the volume percentage of the functional auxiliary agent in the quantum dot ink to be greater than or equal to 5%, the concentration of the first selected coordination group in the quantum dot ink can be increased, so that the probability of the quantum dot body and the functional auxiliary agent reacting with each other can be increased, so that the functional auxiliary agent and the ligand material can undergo a ligand exchange reaction.

[0119] In some embodiments, when the functional auxiliary agent includes one first ligand, the first ligand is a first selected ligand. When the functional auxiliary agent includes at least two first ligands, the first ligand with the strongest coordination ability with the quantum dot is the first selected ligand. The ligand material includes a second molecular backbone and a second ligand grafted to the second molecular backbone, and the ligand material is coordinated with the quantum dot via the second ligand. The coordination ability of the second ligand with the quantum dot is stronger than that of the first selected ligand; the steric hindrance of the second molecular backbone is greater than that of the first molecular backbone.

[0120] Here, steric hindrance, also known as spatial hindrance, refers to the mutual repulsion caused by the spatial arrangement of groups within a molecule. This steric effect can alter the molecular configuration, symmetry, and reactivity. Correspondingly, the steric effect is the effect of atoms or groups near the reaction center occupying a certain spatial position in the molecule, which affects the reactivity of the molecule.

[0121] It is understandable that when the functional auxiliary agent includes a first selected ligand group, the functional auxiliary agent can undergo a coordination reaction with the quantum dot body at least through the first selected ligand group. Specifically, because the second ligand group has a stronger coordination ability with the quantum dot body than the first selected ligand group, the possibility of a coordination reaction between the quantum dot body and the second ligand group is relatively high. In this case, by reducing the steric hindrance of the first molecular skeleton, the functional auxiliary agent can be made more accessible to the quantum dot body in the quantum dot ink relative to the ligand material. In this way, the probability of a coordination reaction between the quantum dot body and the functional auxiliary agent can be increased, and a ligand exchange reaction can be generated between the functional auxiliary agent and the ligand material.

[0122] In some embodiments, the first selected coordinating group is a carboxyl group and the second coordinating group is a thiol group.

[0123] Understandably, because the coordination ability of the thiol group with the quantum dot body is stronger than that of the carboxyl group with the quantum dot body, when the first coordinating group is a carboxyl group and the second coordinating group is a thiol group, the functional agent can be increased in concentration in the quantum dot ink by increasing the volume percentage of the functional agent to be greater than or equal to 5%, and / or the steric hindrance of the second molecular skeleton is greater than the steric hindrance of the first molecular skeleton, and / or the steric hindrance of the first molecular skeleton is reduced, thereby enabling the functional agent to undergo a ligand exchange reaction with the ligand material.

[0124] In some embodiments, the first selected coordinating group is a sulfonic acid group, and the second coordinating group is any one of a thiol group and a carboxyl group.

[0125] Understandably, because the coordination ability of thiol and carboxyl groups with the quantum dot body is stronger than that of sulfonic acid groups with the quantum dot body, when the first selected coordination group is a sulfonic acid group and the second coordination group is either a thiol or carboxyl group, the functional agent can undergo a ligand exchange reaction with the ligand material by setting the volume percentage of the functional agent in the quantum dot ink to be greater than or equal to 5% and / or the steric hindrance of the second molecular backbone to be greater than the steric hindrance of the first molecular backbone.

[0126] In some embodiments, the first selected coordinating group is a phosphate group, and the second coordinating group is any one of a thiol group, a carboxyl group, and a sulfonic acid group.

[0127] Understandably, because the coordination ability of thiol, carboxyl, and sulfonic acid groups with the quantum dot body is stronger than that of phosphate groups with the quantum dot body, when the first selected coordination group is a phosphate group and the second coordination group is any one of thiol, carboxyl, and sulfonic acid groups, the functional agent can undergo a ligand exchange reaction with the ligand material by setting the volume percentage of the functional agent in the quantum dot ink to be greater than or equal to 5% and / or the steric hindrance of the second molecular backbone to be greater than the steric hindrance of the first molecular backbone.

[0128] In some embodiments, the first selected coordinating group is an amine group, and the second coordinating group is any one of a thiol group, a carboxyl group, a sulfonic acid group, and a phosphate group.

[0129] Understandably, because the coordination ability of thiol, carboxyl, sulfonic acid, and phosphate groups with the quantum dot body is stronger than that of amine groups with the quantum dot body, when the first selected coordination group is an amine group and the second coordination group is any one of thiol, carboxyl, sulfonic acid, and phosphate groups, the functional agent can undergo a ligand exchange reaction with the ligand material by setting the volume percentage of the functional agent in the quantum dot ink to be greater than or equal to 5% and / or the steric hindrance of the second molecular backbone to be greater than the steric hindrance of the first molecular backbone.

[0130] In some examples, the functional agent is N,N-dimethylethylenediamine, the first selected coordination group is an amine group; the ligand material is oleic acid, the second coordination group is a carboxyl group; and the volume percentage of the functional agent in the quantum dot ink is 10%. As a result, due to the high volume percentage of the functional agent in the quantum dot ink and the shorter chain segments of the first molecular backbone of the functional agent N,N-dimethylethylenediamine compared to the second molecular backbone of the ligand material oleic acid, the probability of coordination reaction between the quantum dot body and the functional agent N,N-dimethylethylenediamine can be increased. Therefore, the functional agent can be coordinated with the quantum dot body through ligand exchange reaction and / or direct coordination reaction to generate a quantum dot material with a dual-ligand structure. In the obtained quantum dot film, the proportion of oleic acid ligands to the total ligands is 50% to 90%, and the proportion of N,N-dimethylethylenediamine ligands to the total ligands is 10% to 50%; here, the total ligand number refers to the sum of the oleic acid ligands and the N,N-dimethylethylenediamine ligands.

[0131] In some embodiments, the first selected coordinating group is a phospholipid group, and the second coordinating group is any one of a sulfhydryl group, a carboxyl group, a sulfonic acid group, a phosphate group, and an amine group.

[0132] Understandably, because the coordination ability of thiol, carboxyl, sulfonic acid, phosphate, and amine groups with the quantum dot body is stronger than that of phospholipid groups with the quantum dot body, when the first selected coordination group is a phospholipid group and the second coordination group is any one of thiol, carboxyl, sulfonic acid, phosphate, and amine groups, the functional agent can undergo a ligand exchange reaction with the ligand material by setting the volume percentage of the functional agent in the quantum dot ink to be greater than or equal to 5% and / or the steric hindrance of the second molecular backbone to be greater than the steric hindrance of the first molecular backbone.

[0133] In some embodiments, the number of carbon atoms in the first molecular backbone is greater than or equal to 4 and less than or equal to 8.

[0134] For example, the number of carbon atoms in the first molecular backbone can be 4, 5, 6, 7 or 8.

[0135] It can be understood that, on the one hand, when the number of carbon atoms in the first molecular skeleton is greater than or equal to 4 and less than or equal to 8, the steric hindrance of the first molecular skeleton can be reduced, making it easier for the functional auxiliary agent to approach the quantum dot body, thus making it easier for the functional auxiliary agent to undergo a ligand exchange reaction with the ligand material; on the other hand, it should be understood that when the ligand chain segment coordinated with the quantum dot body is long, the charge transfer between the quantum dot bodies is hindered to a certain extent due to the steric hindrance effect. Therefore, when the number of carbon atoms in the first molecular skeleton is greater than or equal to 4 and less than or equal to 8, the chain segment of the first molecular skeleton is shorter. In this way, after the functional auxiliary agent undergoes a ligand exchange reaction with the ligand material, the chain segment of the ligand coordinated with the quantum dot body can be shorter. In this way, the charge transfer between the quantum dot bodies can be easier, which is beneficial to charge transfer and can improve the conductive properties of the quantum dot film prepared from the quantum dot ink.

[0136] In some embodiments, the quantum dot solution includes a quantum dot material and a solvent; the boiling point of the functional aid is greater than the boiling point of the solvent.

[0137] In some examples, the boiling point of the quantum dot solution is greater than the boiling point of the solvent, and the boiling point of the functional agent is greater than the boiling point of the quantum dot solution.

[0138] It can be understood that when the boiling point of the functional additive is greater than the boiling point of the solvent, the volatility of the quantum dot ink including the functional additive is relatively low compared to the quantum dot ink not including the functional additive; in this way, the volatilization of the quantum dot ink can be reduced to reduce the migration of the quantum dot solution and alleviate the coffee ring effect that occurs during the drying process.

[0139] It should be noted that when the boiling point of the functional additive in the quantum dot ink is greater than the boiling point of the solvent, the functional additive may include a first coordination group coordinated with the quantum dot body, or may not include a first coordination group coordinated with the quantum dot body, and there is no limitation here.

[0140] In some examples, the boiling point of the functional agent in the quantum dot ink is greater than that of the solvent. Furthermore, the functional agent includes a first molecular backbone and at least one first ligand group grafted onto the first molecular backbone, with the one or more first ligand groups of the functional agent coordinated with the quantum dot body. In this case, the functional agent can not only improve the uniformity of large-area coating and drying, and reduce the fluidity of the quantum dot solution, but also passivate surface defects of the quantum dot body, thereby improving the stability of the quantum dot material. Furthermore, it can reduce the migration of the quantum dot solution and alleviate the coffee ring effect that occurs during the drying process.

[0141] In some embodiments, the first coordination group includes a thiol group and / or a carboxyl group; and the volume percentage of the functional additive in the quantum dot ink is 0.1% to 50%.

[0142] In some examples, the first coordination group includes a thiol group; the volume percentage of the functional additive in the quantum dot ink can be 0.1%, 0.5%, 1.0%, 10.0%, 20.0%, 30.1%, 40.0% or 50.0%, etc.

[0143] In this case, illustratively, the functional auxiliary agent can be selected from any one or more combinations of heptyl mercaptan, octyl mercaptan, isooctyl mercaptan, 2-mercapto-2,4-pentanediol, 2-methyl-2,4-pentanedithiol, 1,5-pentanedithiol and oligomercaptans.

[0144] In other examples, the first coordination group includes a carboxyl group; the volume percentage of the functional additive in the quantum dot ink can be 0.1%, 0.7%, 2.0%, 10.5%, 20.0%, 30.0%, 42.0% or 50.0%, etc.

[0145] In this case, illustratively, the functional auxiliary agent may be 5-aminovaleric acid.

[0146] In some other examples, the functional additive includes at least two first coordination groups, which are thiol and carboxyl groups; the volume percentage of the functional additive in the quantum dot ink can be 0.1%, 0.4%, 3.0%, 10.5%, 20.6%, 30.0%, 40.0% or 50.0%, etc.

[0147] In this case, illustratively, the functional aid may be selected from any one or more combinations of 3-mercaptobutyric acid and 5-mercaptovaleric acid.

[0148] It is understandable that when the functional additive contains a thiol and / or carboxyl group (for example, a combination of any one or more of the above materials), the functional additive can increase the viscosity of the quantum dot ink to greater than or equal to 2.0 mPa·s, which can improve the uniformity of large-area coating and drying and reduce the fluidity of the quantum dot solution. Moreover, in the case where the functional additive includes a first coordination group coordinated with the quantum dot body, the functional additive can passivate the defects on the surface of the quantum dot body, thereby improving the stability of the quantum dot material. In the case where the boiling point of the functional additive is greater than the boiling point of the solvent, the functional additive can reduce the migration of the quantum dot solution and alleviate the coffee ring effect that occurs during the drying process.

[0149] In some embodiments, the first coordination group includes an amino group and / or an amine group; and the volume percentage of the functional additive in the quantum dot ink is 0.1% to 30%.

[0150] In some examples, the first coordination group includes an amino group; the volume percentage of the functional additive in the quantum dot ink can be 0.1%, 0.4%, 1.0%, 10.0%, 15.0%, 20.5%, 25.0% or 30.0%, etc.

[0151] In other examples, the first coordination group includes an amine group; the volume percentage of the functional additive in the quantum dot ink can be 0.1%, 0.5%, 3.0%, 10.0%, 16.0%, 20.5%, 24.0% or 30.0%, etc.

[0152] In this case, illustratively, the functional auxiliary agent can be selected from any one or more combinations of ethanolamine, dimethylethanolamine, N,N-dimethylethylenediamine, 1.2-propylenediamine, 2-methylbutylenediamine, 2-methylpentanediamine and 5-aminovaleric acid.

[0153] It is understandable that when the functional additive contains an amino group and / or an amine group (for example, a combination of any one or more of the above materials), the functional additive can increase the viscosity of the quantum dot ink to greater than or equal to 2.0 mPa·s, which can improve the uniformity of large-area coating and drying and reduce the fluidity of the quantum dot solution. Moreover, when the functional additive includes a first coordination group coordinated with the quantum dot body, the functional additive can passivate the defects on the surface of the quantum dot body, thereby improving the stability of the quantum dot material. When the boiling point of the functional additive is greater than the boiling point of the solvent, the functional additive can reduce the migration of the quantum dot solution and alleviate the coffee ring effect that occurs during the drying process.

[0154] In some embodiments, the first coordination group includes a phosphate group and / or a phospholipid group; and the volume percentage of the functional additive in the quantum dot ink is 0.1% to 30%.

[0155] In some examples, the first coordination group includes a phosphate group; the volume percentage of the functional additive in the quantum dot ink can be 0.1%, 0.5%, 1.5%, 12.0%, 16.0%, 20.5%, 27.0% or 30.0%, etc.

[0156] In some examples, the first coordination group includes a phospholipid group; the volume percentage of the functional additive in the quantum dot ink can be 0.1%, 0.6%, 1.5%, 11.0%, 16.0%, 20.5%, 25.0% or 30.0%, etc.

[0157] In this case, illustratively, the functional auxiliary agent may be any one or more combinations of fatty alcohol ether phosphate and fatty alcohol polyoxyethylene ether phosphate.

[0158] In some examples, the first coordination group includes a phosphate group and a phospholipid group; the volume percentage of the functional additive in the quantum dot ink can be 0.1%, 0.4%, 1.5%, 10.0%, 15.0%, 20.5%, 25.0% or 30.0%, etc.

[0159] It is understandable that when the functional additive contains a phosphate group and / or a phospholipid group (for example, a combination of any one or more of the above materials), the functional additive can increase the viscosity of the quantum dot ink to greater than or equal to 2.0 mPa·s, which can improve the uniformity of large-area coating and drying and reduce the fluidity of the quantum dot solution. Moreover, when the functional additive includes a first coordination group coordinated with the quantum dot body, the functional additive can passivate the defects on the surface of the quantum dot body, thereby improving the stability of the quantum dot material. When the boiling point of the functional additive is greater than the boiling point of the solvent, the functional additive can reduce the migration of the quantum dot solution and alleviate the coffee ring effect that occurs during the drying process.

[0160] In some embodiments, the first coordination group includes a sulfonic acid group; and the volume percentage of the functional additive in the quantum dot ink is 0.1% to 30%.

[0161] For example, when the first coordination group includes a sulfonic acid group, the volume percentage of the functional additive in the quantum dot ink can be 0.1%, 0.8%, 3.0%, 10.0%, 15.5%, 20.0%, 26.0% or 30.0%, etc.

[0162] In this case, illustratively, the functional auxiliary agent can be selected from any one or more combinations of octane sulfonic acid, decane sulfonic acid, dodecyl sulfonic acid, tetradecyl sulfonic acid, hexadecyl sulfonic acid, octadecyl sulfonic acid, 4-decylbenzenesulfonic acid, dodecylbenzenesulfonic acid, tetradecylbenzenesulfonic acid, hexadecylbenzenesulfonic acid and octadecylbenzenesulfonic acid.

[0163] It can be understood that when the functional additive contains a sulfonic acid group (for example, a combination of any one or more of the above materials), the functional additive can increase the viscosity of the quantum dot ink to greater than or equal to 2.0 mPa·s, which can improve the uniformity of large-area coating and drying and reduce the fluidity of the quantum dot solution. Moreover, when the functional additive includes a first coordination group coordinated with the quantum dot body, the functional additive can passivate the defects on the surface of the quantum dot body, thereby improving the stability of the quantum dot material. When the boiling point of the functional additive is greater than the boiling point of the solvent, the functional additive can reduce the migration of the quantum dot solution and alleviate the coffee ring effect that occurs during the drying process.

[0164] Some embodiments of the present disclosure further provide a quantum dot film, wherein the quantum dot film is made of the quantum dot ink described in any of the above embodiments.

[0165] In some examples, a method for preparing a quantum dot film from quantum dot ink includes steps S1 to S2:

[0166] S1: Applying quantum dot ink to a predetermined position on a surface of a substrate; wherein the quantum dot ink comprises a quantum dot solution and a functional additive miscible with the quantum dot solution; the volume percentage of the functional additive in the quantum dot ink is 0.1% to 50%; and the functional additive is configured to make the viscosity of the quantum dot ink greater than or equal to 2.0 mPa·s.

[0167] Illustratively, the process of coating the quantum dot ink is, for example, a slit coating process, a spin coating process, a doctor blade coating process, or an inkjet printing process.

[0168] Illustratively, the predetermined position on the surface of the substrate may be within the opening Q of the barrier layer N described in detail below.

[0169] S2: Drying the quantum dot ink by heating; or curing the quantum dot ink by light irradiation; to form a quantum dot film.

[0170] The beneficial effects that can be achieved by a quantum dot film provided by some embodiments of the present disclosure are the same as the beneficial effects that can be achieved by a quantum dot ink provided by the above technical solution, and will not be repeated here.

[0171] In some embodiments, the material of the quantum dot film includes a functional aid.

[0172] Here, the material of the quantum dot film includes a functional auxiliary agent. In this case, the functional auxiliary agent may be coordinated with the quantum dot body or may not be coordinated with the quantum dot body, and there is no limitation here.

[0173] In some examples, the functional auxiliary agent is coordinated with the quantum dot body through the first coordination group. At this time, the functional auxiliary agent present in the quantum dot film can passivate defects on the surface of the quantum dot body, thereby improving the stability of the quantum dot material.

[0174] It can be understood that the presence of functional additives will not affect the electrical properties of quantum dot devices; moreover, when the material of the quantum dot film includes functional additives, the functional additives can be present in the quantum dot ink throughout the process, so that the viscosity of the quantum dot ink can be maintained within a higher range, and the uniformity of large-area coating and drying during the preparation of the quantum dot film can be improved; at the same time, the coffee ring effect that occurs during the drying process can be alleviated.

[0175] In addition, when quantum dot ink is formed into a quantum dot film by heating and drying, the boiling point of the functional additive included in the quantum dot film is usually high and higher than that of the solvent. In this way, during the heating process, the functional additive can reduce the volatilization of the quantum dot ink and alleviate the coffee ring effect that occurs during the drying process.

[0176] Some embodiments of the present disclosure further provide a display panel. As shown in FIG1 and FIG2 , the display panel 1000 includes a plurality of quantum dot films M as described in any of the above embodiments and a barrier layer N. The barrier layer N includes a plurality of openings Q, and the plurality of quantum dot films M are located in the plurality of openings Q.

[0177] Here, as shown in FIG. 1 , the plurality of quantum dot films M may be located in the plurality of openings Q in a one-to-one correspondence, or, as shown in FIG. 2 , the plurality of quantum dot films M may be located in a portion of the plurality of openings Q.

[0178] In some examples, as shown in FIG1 , the display panel 1000 further includes a light-emitting substrate 100 including a quantum dot film M and a barrier layer N. In other examples, as shown in FIG2 , the display panel 1000 further includes a color conversion substrate 200 including a quantum dot film M and a barrier layer N. The following describes an example in which the light-emitting substrate 100 includes the quantum dot film M and the barrier layer N.

[0179] In some examples, as shown in FIG1 , the quantum dot film M may be a light-emitting layer 11, which is applied to a light-emitting substrate 100. The light-emitting substrate 100 includes a plurality of regularly arranged (e.g., arrayed) light-emitting devices 10. In this case, the light-emitting devices 10 are quantum dot light-emitting diodes (QLEDs).

[0180] Exemplarily, as shown in Figure 1, the light-emitting substrate 100 also includes a substrate 20 and a pixel defining layer 30 arranged on the substrate 20. It should be understood that the pixel defining layer 30 is the above-mentioned blocking layer N. The pixel defining layer 30 has multiple openings Q, and multiple light-emitting devices 10 can be arranged in a one-to-one correspondence with the multiple openings Q; in this way, multiple quantum dot films M can be arranged in a one-to-one correspondence in the multiple openings Q.

[0181] In some examples, multiple light-emitting devices 10 emit the same kind of light, such as blue light. In this case, the quantum dot bodies of the quantum dot film 11 are blue quantum dots. In this case, a color conversion substrate 200 can be used to convert part of the light emitted by the light-emitting substrate 100 into light of other colors (for example, red light or green light) to achieve full-color display of the display panel 1000.

[0182] In other examples, as shown in FIG1 , a plurality of light-emitting devices 10 emit light of multiple colors. In this case, the plurality of light-emitting devices 10 may include a red light-emitting device 10R, a green light-emitting device 10G, and a blue light-emitting device 10B arranged along a first direction X. The quantum dot bodies of the quantum dot film of the red light-emitting device 10R are red quantum dots; the quantum dot bodies of the quantum dot film of the green light-emitting device 10G are green quantum dots; and the quantum dot bodies of the quantum dot film of the blue light-emitting device 10B are blue quantum dots.

[0183] For example, as shown in FIG1 , each of the plurality of light-emitting devices 10 further includes an anode 12 and a cathode 13; a quantum dot film 11 is disposed between the anode 12 and the cathode 13. The light-emitting principle of the QLED light-emitting device 10 can be as follows: through a circuit connected to the anode 12 and the cathode 13, the anode 12 injects holes into the quantum dot film 11, and the cathode 13 injects electrons into the quantum dot film 11. The electrons and holes form excitons in the quantum dot film 11, and the excitons return to the ground state through radiation transition, emitting photons.

[0184] For example, as shown in FIG1 , the light-emitting device 10 may further include an electron transport functional layer 15 located between the quantum dot film 11 and the cathode 13, and a hole transport functional layer 14 located between the quantum dot film 11 and the anode 12. The electron transport functional layer includes at least one of an electron injection layer, an electron transport layer 151, and a hole blocking layer; the hole transport functional layer includes at least one of a hole injection layer 141, a hole transport layer 142, and an electron blocking layer.

[0185] For example, as shown in FIG1 , the anodes 12 of a plurality of light-emitting devices 10 can be separately provided, and the cathodes 13 of a plurality of light-emitting devices 10 can be shared; or, the cathodes 13 of a plurality of light-emitting devices 10 can be separately provided, and the anodes 12 of a plurality of light-emitting devices 10 can be shared; in this way, under the action of different driving currents, a plurality of light-emitting devices 10 can emit light separately as needed, thereby realizing full-color display of the display panel 1000.

[0186] The above exemplifies the case where the light-emitting substrate 100 includes the quantum dot film M and the barrier layer N. The following exemplifies the case where the color conversion substrate 200 includes the quantum dot film M and the barrier layer N.

[0187] In some examples, the quantum dot film M may be a color conversion portion 210 , which is applied to the color conversion substrate 200 . The color conversion substrate 200 includes a plurality of color conversion portions 210 .

[0188] Exemplarily, as shown in FIG2 , the color conversion substrate 200 further includes a substrate 220 and a blocking pattern 230 disposed on the substrate 220. It should be understood that the blocking pattern 230 is the above-mentioned blocking layer N. The blocking pattern 230 has a plurality of openings Q, and a plurality of color conversion portions 210 can be disposed in a portion of the openings Q, such as an opening for emitting red light and an opening for emitting green light.

[0189] In some examples, as shown in FIG2 , multiple color conversion units 210 convert and generate multiple colors of light. In this case, the display panel 1000 may also include a light-emitting substrate 100 that emits blue light, such as an organic light emitting diode (OLED) light-emitting substrate. In this case, the multiple color conversion units 210 may include red color conversion units 210R and green color conversion units 210G arranged along the second direction Y. The red color conversion unit 210R includes red quantum dots and is configured to convert blue light into red light; the green color conversion unit 210G includes green quantum dots and is configured to convert blue light into green light. In this case, the display panel 1000 is a QD-OLED display panel, which combines the advantages of quantum dots (high brightness, high color volume, and high efficiency) with the true black state, high contrast, wide viewing angle, and wide color gamut of OLED devices to achieve high-quality display effects with the advantages of a wide color gamut, high color conversion efficiency (CCE), and wide viewing angle.

[0190] In some embodiments, as shown in FIG2 , the display panel 1000 further includes a filling layer 300 located between the light-emitting substrate 100 and the color conversion substrate 200. Thus, the filling layer 300 can be used to fill the gap between the color conversion substrate 200 and the light-emitting substrate 100, thereby bonding the light-emitting substrate 100 and the color conversion substrate 200 together.

[0191] In some examples, as shown in FIG. 2 , the color conversion substrate 200 further includes a light-transmitting portion 211 , and the light-transmitting portion 211 is arranged along the second direction Y with the red color conversion portion 210R and the green color conversion portion 210G.

[0192] In some embodiments, as shown in FIG2 , the color conversion substrate 200 may further include a light-blocking layer 240 positioned between the blocking pattern 230 and the substrate 220. The light-blocking layer 240 may include a light-absorbing pattern 241 and a plurality of color filter portions 242. The light-absorbing pattern 241 includes a plurality of second openings D that face the plurality of openings Q. The plurality of color filter portions 242 are disposed within the plurality of second openings D in a one-to-one correspondence. The plurality of color filter portions 242 include a red color filter portion 243 facing the red color conversion portion 210R, a green color filter portion 244 facing the green color conversion portion 210G, and a blue color filter portion 245 facing the light-transmitting portion 211. The color filter portions 242 may be configured to transmit light of the same color as the color thereof and to filter out light of a different color. This may enhance the color gamut of the display panel 1000.

[0193] Based on the above embodiment, the display panel 1000 can be any product or component with a display function, such as an OLED panel, an OLED TV, a QLED panel, a QLED TV, a Micro LED panel, a Micro LED TV, a Mini LED panel, a Mini LED TV, a monitor, a mobile phone, a navigation system, etc. The display panel 1000 can be any display panel 1000 that displays either moving (e.g., video) or fixed (e.g., still images), and whether text or images. More specifically, it is expected that the display panel 1000 of the described embodiments may be implemented in or associated with a variety of electronic devices, such as (but not limited to) mobile phones, wireless devices, personal data assistants (PDAs), handheld or portable computers, GPS receivers / navigators, cameras, MP4 video players, camcorders, game consoles, watches, clocks, calculators, television monitors, flat-panel displays, computer monitors, automotive displays (e.g., odometer displays, etc.), navigators, cockpit controls and / or displays, displays of camera views (e.g., displays of rearview cameras in vehicles), electronic photographs, electronic billboards or signs, projectors, architectural structures, packaging, and aesthetic structures (e.g., displays of images of a piece of jewelry), etc.

[0194] The beneficial effects that can be achieved by a display panel provided by some embodiments of the present disclosure are the same as the beneficial effects that can be achieved by a quantum dot film provided by the above technical solution, and will not be repeated here.

[0195] To objectively evaluate the technical effects of the embodiments of the present disclosure, the following experimental examples and comparative examples are used to provide a detailed, exemplary description of the technical solutions provided by the present disclosure. Based on the differences in functional additives, quantum dot solutions, and measurement data, the following experimental examples and comparative examples are divided into a first group of experimental examples, a second group of experimental examples, a third group of experimental examples, a fourth group of experimental examples, and a fifth group of experimental examples.

[0196] (First group of test examples)

[0197] In this group of experimental examples, different quantum dot inks were used to prepare quantum dot films using a doctor blade coating and drying process, and the morphology and ligand ratio of the prepared quantum dot films were measured.

[0198] The scraping and drying processes of Example 1 and Comparative Example 1 were the same. The scraping process specifically involved using scraping equipment for thin film coating, setting the scraping speed to 10 mm / s and the distance between the scraper and the substrate to 20 μm. The drying process specifically involved using vacuum decompression equipment for drying.

[0199] The quantum dot ink of Comparative Example 1 is composed of a quantum dot solution, wherein the quantum dot body is CdSe quantum dots, the ligand material is oleic acid, the solvent is propylene glycol methyl ether acetate, and the concentration of the quantum dot material is 12 mg / mL.

[0200] The quantum dot ink of Example 1 is composed of a quantum dot solution and a functional additive. The quantum dot ink of Example 1 is prepared by mixing the quantum dot ink (i.e., the quantum dot solution) of Comparative Example 1 with the functional additive N,N-dimethylethylenediamine at a volume ratio of 90:10 and stirring thoroughly to obtain a uniform mixture.

[0201] Based on the quantum dot inks of Comparative Example 1 and Example 1, quantum dot films were prepared using the above-mentioned doctor blade coating and drying processes. The morphology of the quantum dot film prepared in Comparative Example 1 is shown in FIG3 , and the morphology of the quantum dot film prepared in Example 1 is shown in FIG4 .

[0202] As can be seen from Figures 3 and 4, the quantum dot film prepared in Comparative Example 1 partially produces circular and other irregularly shaped patterns, with a significant coffee ring effect, showing an uneven appearance. In contrast, the quantum dot film prepared in Example 1 has a significant improvement in morphology compared to Comparative Example 1, with the coffee ring effect suppressed and the quantum dot film having better uniformity. This is because the quantum dot solution in Comparative Example 1 itself evaporates at a relatively fast rate, resulting in a significant coffee ring effect and poor uniformity of the resulting quantum dot film. In Example 1, the functional additive N,N-dimethylethylenediamine is added to the quantum dot ink to increase the viscosity of the quantum dot ink, thereby improving the uniformity of large-area coating and drying during the preparation of the quantum dot film. It also reduces the fluidity of the quantum dot solution and the volatility of the quantum dot ink, thereby alleviating the coffee ring effect that occurs during the drying process.

[0203] In addition, in Example 1, the ligand material oleic acid has a relatively long chain segment. Due to the steric hindrance effect of the long chain coordination, some defects that cannot be passivated will exist on the surface of the quantum dot body CdSe. In this case, the addition of the functional auxiliary agent N,N-dimethylethylenediamine can passivate the dangling bonds on the surface of the quantum dot body CdSe that are not coordinated by the coordination material, thereby reducing surface defects. Specifically, the functional auxiliary agent N,N-dimethylethylenediamine includes a first coordination group amino group. Although, compared to the first coordination group amino group of the functional auxiliary agent N,N-dimethylethylenediamine, the second coordination group carboxyl group of the ligand material oleic acid has a higher coordination binding energy and relatively strong coordination ability with the quantum dot body CdSe. However, on the one hand, the volume percentage of the functional auxiliary agent in the quantum dot ink in Example 1 is 10%, so that the quantum dot body CdSe is surrounded by a large number of functional auxiliary agent molecules, which can increase the probability of the quantum dot body CdSe and the functional auxiliary agent N,N-dimethylethylenediamine undergoing a coordination reaction. On the other hand, compared to the second molecular skeleton of the ligand material oleic acid, the chain segment of the first molecular skeleton of the functional auxiliary agent N,N-dimethylethylenediamine is shorter and easier to approach the quantum dot body CdSe, which can also increase the probability of the quantum dot body CdSe and the functional auxiliary agent N,N-dimethylethylenediamine to undergo a coordination reaction. Therefore, in the process of stirring and mixing the quantum dot solution and the functional auxiliary agent, the functional auxiliary agent N,N-dimethylethylenediamine can coordinate with the quantum dot body CdSe through a ligand exchange reaction, replacing some long-chain oleic acid ligands with short-chain N,N-dimethylethylenediamine ligands. The reaction process is shown in the following formula (I); and / or, the functional auxiliary agent N,N-dimethylethylenediamine can passivate the dangling bonds on the surface of the quantum dot body CdSe that are not coordinated by oleic acid through a direct coordination reaction. The reaction process is shown in the following formula (II). In this way, after drying and removing excess solvent, a quantum dot material with a dual ligand structure can be generated. After multiple tests and measurements, the proportion of oleic acid ligands in the quantum dot film to the total number of ligands is between 50% and 90%, and the proportion of N,N-dimethylethylenediamine ligands to the total number of ligands is between 10% and 50%; here, the total number of ligands refers to the sum of the number of oleic acid ligands and the number of N,N-dimethylethylenediamine ligands.

[0204] (Second group of test examples)

[0205] In this group of experimental examples, different quantum dot inks were used to prepare quantum dot films using a doctor blade coating and drying process, and the morphology and ligand ratio of the prepared quantum dot films were measured.

[0206] The scraping and drying processes of Example 2 and Comparative Example 2 were the same. The scraping process specifically involved using scraping equipment for thin film coating, setting the scraping speed to 10 mm / s and the distance between the scraper and the substrate to 15 μm. The drying process specifically involved using vacuum decompression equipment for drying.

[0207] The quantum dot ink of Comparative Example 2 is composed of a quantum dot solution. The quantum dot body is CdSe quantum dots, the ligand material is dodecanethiol, and the solvent is a mixed solvent of propylene glycol methyl ether and ethyl 3-ethoxypropionate, wherein the volume fraction of propylene glycol methyl ether is 65% to 75%, and the volume fraction of ethyl 3-ethoxypropionate is 25% to 35%. The concentration of the quantum dot material is 20 mg / mL.

[0208] The quantum dot ink of Example 2 is composed of a quantum dot solution and a functional additive. The quantum dot ink of Example 2 was prepared by mixing the quantum dot ink (i.e., the quantum dot solution) of Comparative Example 2 with the functional additive 2-methyl-2,4-pentanedithiol at a volume ratio of 50:50 and stirring thoroughly to obtain a uniform mixture. The concentration of the quantum dot material in the quantum dot ink was 10 mg / mL.

[0209] Based on the quantum dot inks of Comparative Example 2 and Example 2, quantum dot films were prepared using the above-described doctor blade coating and drying processes. The morphology of the quantum dot film prepared in Comparative Example 2 is shown in FIG5 , and the morphology of the quantum dot film prepared in Example 2 is shown in FIG6 .

[0210] As shown in Figures 5 and 6, the quantum dot film produced in Comparative Example 2 exhibits a large number of circular patterns at the edges, with the circular patterns being thicker at the edges and thinner in the middle. Circular patterns of varying sizes also form in the center of the quantum dot film. Overall, the film exhibits a pronounced coffee ring effect, resulting in a nonuniform appearance. In contrast, the quantum dot film produced in Example 2 exhibits a significant improvement in morphology compared to Comparative Example 2, suppressing the coffee ring effect and achieving better uniformity. This is due to the low viscosity of the quantum dot solution in Comparative Example 2, which results in a pronounced coffee ring effect and poor uniformity in the resulting quantum dot film. In Example 2, the addition of the functional additive 2-methyl-2,4-pentanedithiol to the quantum dot ink increases the viscosity of the quantum dot ink, improving the uniformity of large-area coating and drying during the quantum dot film preparation process. It also reduces the fluidity of the quantum dot solution and the volatility of the quantum dot ink, alleviating the coffee ring effect that occurs during the drying process.

[0211] In addition, in Example 2, the functional agent 2-methyl-2,4-pentanedithiol includes a first coordination group thiol, and the ligand material dodecanethiol includes a second coordination group thiol. Although the coordination ability of the first coordination group and the second coordination group with the quantum dot body CdSe is equivalent, the functional agent 2-methyl-2,4-pentanedithiol in the quantum dot ink in Example 2 has a dithiol structure, and compared with the second molecular skeleton of the ligand material dodecanethiol, the chain segment of the first molecular skeleton of the functional agent 2-methyl-2,4-pentanedithiol is shorter, which is easier to approach the quantum dot body CdSe, and can increase the probability of coordination reaction between the quantum dot body CdSe and the functional agent 2-methyl-2,4-pentanedithiol. Therefore, after adding a large amount of functional additive to the quantum dot solution, the functional additive 2-methyl-2,4-pentanedithiol can coordinate with the quantum dot matrix CdSe through a ligand exchange reaction, replacing some of the long-chain oleic acid ligands with short-chain N,N-dimethylethylenediamine ligands. The reaction process is shown in Formula (III). Alternatively, the functional additive 2-methyl-2,4-pentanedithiol can passivate existing surface defects on the quantum dot matrix CdSe through a direct coordination reaction. The reaction process is shown in Formula (IV). This results in a quantum dot material with a dual-ligand structure after drying. After multiple tests and measurements, the proportion of dodecanethiol ligands in the quantum dot film ranges from 5% to 95% of the total ligand count, and the proportion of 2-methyl-2,4-pentanedithiol ligands in the total ligand count ranges from 5% to 95%. Here, the total ligand count refers to the sum of the dodecanethiol and 2-methyl-2,4-pentanedithiol ligands.

[0212] (The third group of test examples)

[0213] In this group of experimental examples, different quantum dot inks were used to prepare quantum dot films using a doctor blade coating and drying process, and the morphology of the prepared quantum dot films was measured.

[0214] The scraping and drying processes of Example 3 and Comparative Example 3 were the same. The scraping process specifically involved using scraping equipment for thin film coating, setting the scraping speed to 15 mm / s and the distance between the scraper and the substrate to 20 μm. The drying process specifically involved using vacuum decompression equipment for drying.

[0215] The quantum dot ink of Comparative Example 3 is composed of a quantum dot solution, wherein the quantum dot bodies are ZnO quantum dots, the solvent is ethanol, and the concentration of the quantum dot bodies is 20 mg / mL.

[0216] The quantum dot ink of Example 3 is composed of a quantum dot solution and a functional additive. The quantum dot ink of Example 3 is prepared by mixing the quantum dot ink (i.e., the quantum dot solution) of Comparative Example 3 with the functional additive ethanolamine at a volume ratio of 90:10 and stirring thoroughly to obtain a uniform mixture. The viscosity of the quantum dot ink of Example 3 is 2.5 mPa·s.

[0217] Based on the quantum dot inks of Comparative Example 3 and Example 3, quantum dot films were prepared using the above-mentioned doctor blade coating and drying processes. The morphology of the quantum dot film prepared in Comparative Example 3 is shown in FIG7 , and the morphology of the quantum dot film prepared in Example 3 is shown in FIG8 .

[0218] As can be seen from Figures 7 and 8, the quantum dot film prepared in Comparative Example 3 has a locally circular pattern, and the film thickness of different parts of the quantum dot film is uneven, with large differences, and the overall phenomenon of inhomogeneity is presented; in contrast, the quantum dot film prepared in Example 3 has a greatly improved film uniformity. This is because the boiling point of the solvent ethanol in Comparative Example 3 is 78°C, which has a low boiling point and high volatility, resulting in poor uniformity of the resulting quantum dot film. In Example 3, a functional additive ethanolamine is added to the quantum dot ink, which has a boiling point of 170°C and a viscosity of 18.95mPa·s at 25°C. This can increase the viscosity of the quantum dot ink and reduce the volatility of the quantum dot ink, thereby reducing the migration of quantum dot ZnO caused by the evaporation of the solvent, and improving the film uniformity of the quantum dot film.

[0219] (The fourth group of test examples)

[0220] In this group of experimental examples, different quantum dot inks were used to prepare quantum dot films using a doctor blade coating and drying process, and the morphology of the prepared quantum dot films was measured.

[0221] The scraping and drying processes of Example 4 and Comparative Example 4 were the same. The scraping process specifically involved using scraping equipment for thin film coating, setting the scraping speed to 10 mm / s and the distance between the scraper and the substrate to 20 μm. The drying process specifically involved using vacuum decompression equipment for drying.

[0222] The quantum dot ink of Comparative Example 4 is composed of a quantum dot solution. The quantum dot bodies are InP quantum dots, the second coordination group of the ligand material is an amine group, and the solvent is a mixed solvent consisting of propylene glycol methyl ether acetate, propylene glycol methyl ether, and ethyl 3-ethoxypropionate, wherein the volume fraction of propylene glycol methyl ether acetate is 65% and the viscosity is 1.1 mPa·s; the volume fraction of propylene glycol methyl ether is 30% and the viscosity is 1.75 mPa·s; the volume fraction of ethyl 3-ethoxypropionate is 5% and the viscosity is 1.0 mPa·s; the concentration of the quantum dot material is 15 mg / mL and the viscosity is 1.4 mPa·s.

[0223] The quantum dot ink of Example 4 is composed of a quantum dot solution and a functional additive. The quantum dot ink of Example 4 was prepared by mixing the quantum dot ink (i.e., quantum dot solution) of Comparative Example 4 with the functional additive 5-mercaptovaleric acid at a volume ratio of 80:20 and stirring thoroughly to obtain a uniform mixture. The quantum dot ink had a viscosity of 3.2 mPa·s. The boiling point of 5-mercaptovaleric acid is 265°C.

[0224] Based on the quantum dot inks of Comparative Example 4 and Example 4, quantum dot films were prepared using the above-described doctor blade coating and drying processes. The morphology of the quantum dot film prepared in Comparative Example 4 is shown in FIG9 , and the morphology of the quantum dot film prepared in Example 4 is shown in FIG10 .

[0225] As shown in Figures 9 and 10, the quantum dot film prepared in Example 4 has improved film uniformity compared to Comparative Example 4. This is because in Example 4, the functional additive 5-mercaptovaleric acid is added to the quantum dot ink, which can adjust the viscosity and volatility of the quantum dot ink, thereby increasing the viscosity and boiling point of the quantum dot ink, reducing the fluidity of the quantum dot solution, and reducing the volatility of the quantum dot ink, thereby improving the uniformity of large-area coating and drying during the preparation of the quantum dot film.

[0226] In addition, in Example 4, the functional auxiliary agent 5-mercaptopentanoic acid includes a first coordination group thiol and a carboxyl group, both of which have strong coordination binding energy. Moreover, compared with the first coordination group thiol and carboxyl groups, the coordination binding energy of the second coordination group amine group is weaker. In this way, after the functional auxiliary agent is added to the quantum dot solution, the functional auxiliary agent 5-mercaptopentanoic acid can be coordinated with the quantum dot body InP through a ligand exchange reaction, so that the amino ligand on the surface of the quantum dot body InP is replaced by a 5-mercaptopentanoic acid ligand, thereby improving the stability of the quantum dot film.

[0227] (Fifth group of test examples)

[0228] In this group of experimental examples, different quantum dot inks were used to prepare quantum dot films using coating and drying processes; and green quantum dot light-emitting devices were prepared using the prepared quantum dot films, and the current density, brightness, and current efficiency of the prepared green quantum dot light-emitting devices were measured.

[0229] Among them, the quantum dot ink for preparing the quantum dot film of Example 5 is composed of a quantum dot solution and a functional additive. Among them, the quantum dot body is CdSe quantum dots, the ligand material is oleic acid, the solvent is octane, and the concentration of the quantum dot material in the quantum dot solution is 15 mg / mL. During the preparation, the above-mentioned quantum dot solution and the functional additive 2-methyl-2,4-pentanedithiol are mixed in a volume ratio of 60:40, and the mixture is stirred thoroughly to make it uniform, thereby obtaining the quantum dot ink of Example 5. Then, the quantum dot film is prepared by a scraping and drying process. The scraping process is specifically as follows: a scraping device is used for thin film coating, the scraping speed is set to 10 mm / s during coating, and the distance between the scraper and the substrate is 15 μm. The drying process is specifically as follows: a vacuum decompression device is used for drying.

[0230] The structure of a green quantum dot light-emitting device is shown in structure 10G in Figure 1. Therefore, before preparing the quantum dot film, the hole injection layer and hole transport layer are prepared. After preparing the quantum dot film, the electron transport layer is also prepared. These three layers are prepared using a doctor blade coating and drying process. The materials used to form the hole injection layer, hole transport layer, and electron transport layer are PEDOT:PSS, TFB, and ZnO, respectively.

[0231] The preparation method for the green quantum dot light-emitting device in Comparative Example 5 was identical to that in Example 5, except for differences in the quantum dot ink and the process for forming the quantum dot film. The quantum dot ink in Comparative Example 5 did not include the functional additive 2-methyl-2,4-pentanedithiol and consisted of the aforementioned quantum dot solution. The quantum dot film in Comparative Example 5 was prepared using a spin coating process.

[0232] The voltage, brightness, and efficiency of the prepared green quantum dot light-emitting devices were measured based on the green quantum dot light-emitting devices of Comparative Example 5 and Example 5. The current density versus voltage curve is shown in Figure 11 , the brightness versus current density curve is shown in Figure 12 , and the current efficiency versus current density curve is shown in Figure 13 .

[0233] As shown in Figures 11 to 13, compared to Comparative Example 5, the green quantum dot light-emitting device in Example 5 has a relatively lower current density and higher brightness at the same current density. Furthermore, the maximum current efficiency of the green quantum dot light-emitting device in Comparative Example 5 is 20.58 cd / A, while the maximum current efficiency of the green quantum dot light-emitting device in Example 5 is 22.22 cd / A, with Example 5 having a slightly higher maximum current efficiency. This shows that the addition of a functional additive to the quantum dot ink not only does not affect the electrical performance of the green quantum dot light-emitting device, but also improves it.

[0234] Among them, in Example 5, compared with the ligand material oleic acid, the functional auxiliary agent 2-methyl-2,4-pentanedithiol has less steric hindrance; compared with the second ligand group carboxyl, the first ligand group thiol has a larger coordination binding energy, so that the coordination binding energy of the functional auxiliary agent 2-methyl-2,4-pentanedithiol is greater than the coordination binding energy of the ligand material oleic acid. Therefore, during the process of stirring and mixing the quantum dot solution and the functional auxiliary agent, the functional auxiliary agent 2-methyl-2,4-pentanedithiol can at least coordinate with the quantum dot body CdSe through a ligand exchange reaction, replacing some long-chain oleic acid ligands with short-chain 2-methyl-2,4-pentanedithiol ligands. The reaction process is shown in the following formula (V). In this way, the conductive properties of the quantum dot film can be improved.

[0235] It can be seen from the above embodiments and comparative examples that the present disclosure, through the provision of quantum dot ink including a quantum dot solution and a functional additive that is miscible with the quantum dot solution, can improve the uniformity of large-area coating and drying during the preparation of the quantum dot film; it can also reduce the fluidity of the quantum dot solution and alleviate the coffee ring effect that occurs during the drying process; in addition, it can also improve the conductive properties of the quantum dot film prepared from the quantum dot ink.

[0236] The above description is merely a specific embodiment of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that a person skilled in the art can conceive within the technical scope disclosed in the present disclosure should be included within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A quantum dot ink, comprising a quantum dot solution and a functional auxiliary that is miscible with the quantum dot solution; Wherein, The volume percentage of the functional auxiliary in the quantum dot ink is 0.1% - 50%; the functional auxiliary is configured to make the viscosity of the quantum dot ink greater than or equal to 2.0 mPa·s.

2. The quantum dot ink according to claim 1, Wherein, The quantum dot solution includes a quantum dot material and a solvent; the quantum dot material includes a quantum dot body; the functional auxiliary includes a first molecular skeleton and at least one first coordination group grafted on the first molecular skeleton; moreover, when the functional auxiliary includes at least two of the first coordination groups, the at least two first coordination groups may be the same or different; Wherein, one or more of the first coordination groups of the functional auxiliary coordinate with the quantum dot body.

3. The quantum dot ink according to claim 2, Wherein, The quantum dot material further includes a ligand material coordinated on the quantum dot body; at least part of the quantum dot body coordinates with both the ligand material and the functional auxiliary.

4. The quantum dot ink according to claim 3, Wherein, When the functional auxiliary includes one of the first coordination groups, the first coordination group is a first selected coordination group; when the functional auxiliary includes at least two of the first coordination groups, among the at least two coordination groups, the first coordination group with the strongest coordination ability with the quantum dot body is the first selected coordination group; The ligand material includes a second coordination group, and the ligand material coordinates with the quantum dot body through the second coordination group; The first selected coordination group is the same as the second coordination group; or, The first selected coordination group is different from the second coordination group, and the coordination ability of the first selected coordination group with the quantum dot body is stronger than the coordination ability of the second coordination group with the quantum dot body.

5. The quantum dot ink according to claim 4, Wherein, The second coordination group is a mercapto group, and the first selected coordination group is a mercapto group; or, The second coordination group is a carboxyl group, and the first selected coordination group is any one of a carboxyl group and a mercapto group; or, The second coordination group is a sulfonic acid group, and the first selected coordination group is any one of a mercapto group, a carboxyl group, and a sulfonic acid group; or, The second coordination group is a phosphoric acid group, and the first selected coordination group is any one of a mercapto group, a carboxyl group, a sulfonic acid group, and a phosphoric acid group; or, The second coordination group is an amino group, and the first selected coordination group is any one of a mercapto group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, and an amino group; or, The second coordination group is a phospholipid group, and the first selected coordination group is any one of a mercapto group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, an amino group, and a phospholipid group.

6. The quantum dot ink according to claim 3, Wherein, When the functional additive includes one of the first coordination groups, the first coordination group is the first selected coordination group; when the functional additive includes at least two of the first coordination groups, among the at least two coordination groups, the first coordination group with the strongest coordination ability with the quantum dot body is the first selected coordination group; The ligand material includes a second coordination group, and the ligand material coordinates with the quantum dot body through the second coordination group; the coordination ability of the second coordination group with the quantum dot body is stronger than that of the first selected coordination group with the quantum dot body; the volume percentage of the functional additive in the quantum dot ink is greater than or equal to 5%.

7. The quantum dot ink according to claim 3, wherein, When the functional additive includes one of the first coordination groups, the first coordination group is the first selected coordination group; when the functional additive includes at least two of the first coordination groups, among the at least two coordination groups, the first coordination group with the strongest coordination ability with the quantum dot body is the first selected coordination group; The ligand material includes a second molecular backbone and a second coordination group grafted to the second molecular backbone, and the ligand material coordinates with the quantum dot body through the second coordination group; The coordination ability of the second coordination group with the quantum dot body is stronger than that of the first selected coordination group with the quantum dot body; the steric hindrance of the second molecular backbone is greater than that of the first molecular backbone.

8. The quantum dot ink according to claim 6 or 7, wherein, The first selected coordination group is a carboxyl group, and the second coordination group is a mercapto group; or; The first selected coordination group is a sulfonic acid group, and the second coordination group is any one of a mercapto group and a carboxyl group; or, The first selected coordination group is a phosphoric acid group, and the second coordination group is any one of a mercapto group, a carboxyl group, and a sulfonic acid group; or, The first selected coordination group is an amino group, and the second coordination group is any one of a mercapto group, a carboxyl group, a sulfonic acid group, and a phosphoric acid group; or, The first selected coordination group is a phospholipid group, and the second coordination group is any one of a mercapto group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, and an amino group.

9. The quantum dot ink according to any one of claims 2 to 7, wherein, The number of carbon atoms in the first molecular backbone is greater than or equal to 4 and less than or equal to 8.

10. The quantum dot ink according to any one of claims 1 to 7, wherein, The quantum dot solution includes a quantum dot material and a solvent; the boiling point of the functional additive is greater than the boiling point of the solvent.

11. The quantum dot ink according to any one of claims 1 to 7, wherein, The viscosity of the functional additive is greater than or equal to 5.0 mPa·s.

12. The quantum dot ink according to any one of claims 1 to 7, wherein, The first coordination group includes a mercapto group and / or a carboxyl group; the volume percentage of the functional additive in the quantum dot ink is 0.1% to 50%.

13. The quantum dot ink according to claim 12, wherein, The functional auxiliary agent is selected from any one or a combination of more than one of 3-mercaptobutyric acid, 5-mercaptopentanoic acid, heptanethiol, octanethiol, isooctanethiol, 2-mercapto-2,4-pentanediol, 2-methyl-2,4-pentanedithiol, 1,5-pentanedithiol, oligomeric mercaptan, and 5-aminopentanoic acid.

14. The quantum dot ink according to any one of claims 1 to 7, wherein, the first coordination group includes amino group and / or amine group; the volume percentage of the functional auxiliary agent in the quantum dot ink is 0.1% to 30%.

15. The quantum dot ink according to claim 14, wherein, the functional auxiliary agent is selected from any one or a combination of more than one of ethanolamine, dimethylethanolamine, N,N-dimethylethylenediamine, 1,2-propanediamine, 2-methylbutanediamine, 2-methylpentanediamine, and 5-aminopentanoic acid.

16. The quantum dot ink according to any one of claims 1 to 7, wherein, the first coordination group includes phosphoric acid group and / or phospholipid group; the volume percentage of the functional auxiliary agent in the quantum dot ink is 0.1% to 30%.

17. The quantum dot ink according to claim 16, wherein, the functional auxiliary agent is selected from any one or a combination of more than one of fatty alcohol ether phosphate and fatty alcohol polyoxyethylene ether phosphate.

18. The quantum dot ink according to any one of claims 1 to 7, wherein, the first coordination group includes sulfonic acid group; the volume percentage of the functional auxiliary agent in the quantum dot ink is 0.1% to 30%.

19. The quantum dot ink according to claim 18, wherein, the functional auxiliary agent is selected from any one or a combination of more than one of octylsulfonic acid, decylsulfonic acid, dodecylsulfonic acid, tetradecylsulfonic acid, hexadecylsulfonic acid, octadecylsulfonic acid, 4-decylbenzenesulfonic acid, dodecylbenzenesulfonic acid, tetradecylbenzenesulfonic acid, hexadecylbenzenesulfonic acid, and octadecylbenzenesulfonic acid.

20. The quantum dot ink according to any one of claims 2 to 7, wherein, in the quantum dot solution, the concentration of the quantum dot material is greater than or equal to 5.0 mg / mL and less than or equal to 50 mg / mL.

21. A quantum dot film, which is made of the quantum dot ink according to any one of claims 1 to 20.

22. The quantum dot film according to claim 21, wherein, the material of the quantum dot film includes the functional auxiliary agent.

23. A display panel, comprising a plurality of quantum dot films according to any one of claims 21 and 22; further comprising: a barrier layer, the barrier layer includes a plurality of openings, and a plurality of the quantum dot films are located in the plurality of openings.

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