Nanoparticle ink, method of making and electroluminescent device

Abstract

The present application relates to the technical field of printed display, in particular to a nanoparticle ink, a preparation method thereof and an electroluminescent device. The preparation method comprises the following steps: mixing nanoparticles with an auxiliary solvent, adding a target solvent, and then removing the auxiliary solvent to obtain the nanoparticle ink; or directly dispersing the nanoparticles in a mixed solvent composed of the auxiliary solvent and the target solvent, and removing the auxiliary solvent to obtain the nanoparticle ink. The present application can reduce the problem of uneven dispersion and easy agglomeration of nanoparticles during the preparation and preservation of the ink.

Description

Technical Field

[0001] This invention relates to the field of printed display technology, and in particular to nanoparticle inks, their preparation methods, and electroluminescent devices. Background Technology

[0002] QLED devices are semiconductor light-emitting devices based on the stacking of different functional layers. Their structure is similar to that of OLED devices. However, the important functional layers of QLED devices, EML (emissive layer) and ETL (electron transport layer), are made of inorganic nanoparticles. Inorganic nanoparticles cannot be vapor-deposited, so QLED devices cannot be prepared by referring to the small molecule vapor deposition process of OLEDs.

[0003] Printed display technology is a technology for fabricating displays using solution-processable organic, inorganic, and nano-functional materials. Employing printing or coating techniques, it can replace the traditional vacuum fabrication process for semiconductors, enabling the fabrication of novel display devices. Compared to the vacuum fabrication process for semiconductors, it represents a revolutionary industrial technology with significant advantages.

[0004] Printing QLED devices using printing display technology is a disruptive new trend in the emerging display industry, with the solution formation of different functional layers being a key aspect. However, nanoparticles are prone to agglomeration during dispersion and printing processes, leading to degraded device performance or even partial loss of function, thus hindering the development of functional layer solution formation. Summary of the Invention

[0005] Based on this, the present invention provides a nanoparticle ink, a method for preparing the same, and an electroluminescent device to reduce the problem of nanoparticle aggregation in ink.

[0006] The first aspect of this invention provides a method for preparing nanoparticle ink. The technical solution is as follows:

[0007] A method for preparing nanoparticle ink includes the following steps:

[0008] The nanoparticles are mixed with an auxiliary solvent, then the target solvent is added, and then the auxiliary solvent is removed to obtain the nanoparticle ink.

[0009] Alternatively, the nanoparticles can be directly dispersed in a mixed solvent consisting of an auxiliary solvent and a target solvent, and the auxiliary solvent can be removed to obtain the nanoparticle ink.

[0010] In some embodiments, the nanoparticles are transition metal oxide nanoparticles.

[0011] In some embodiments, the transition metal oxide nanoparticles include at least one of undoped metal oxide particles and doped metal oxide particles;

[0012] The undoped metal oxide particles are selected from at least one of ZnO, BaO, TiO2, SnO2, Ta2O3, and ZrO2; and / or,

[0013] The doped metal oxide particles include a dopant element and metal oxide particles; the dopant element is selected from at least one of aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, and gadolinium; the material of the metal oxide particles is selected from at least one of ZnO, BaO, TiO2, SnO2, Ta2O3, and ZrO2.

[0014] In some embodiments, the boiling point of the auxiliary solvent is denoted as T1 and its volume as V1, and the boiling point of the target solvent is denoted as T2 and its volume as V2. T1, T2, V1 and V2 simultaneously satisfy the following conditions: T1 < T2 and V1 ≤ V2.

[0015] In some embodiments, the method for removing the auxiliary solvent is vacuum distillation.

[0016] In some embodiments, the nanoparticles are fresh zinc oxide-based nanoparticles prepared by a solvothermal method or a sol-gel method.

[0017] In some of these embodiments, T2 ≥ 130°C.

[0018] In some embodiments, the fresh zinc oxide-based nanoparticles still contain solvent A, and the method for preparing the nanoparticle ink further includes a step of removing solvent A, and the step of removing solvent A is performed simultaneously with the step of removing the auxiliary solvent.

[0019] In some embodiments, solvent A includes one or more of the solvent and precipitant originally present in the stock solution, wherein the original solvent in the stock solution is derived from the reaction solvent used in the preparation of zinc oxide-based nanoparticles by the solvothermal method or the sol-gel method, and the reaction solvent is a polar solvent.

[0020] In some embodiments, the method for preparing the fresh zinc oxide-based nanoparticles with residual solvent A includes the following steps:

[0021] The stock solution for preparing zinc oxide-based nanoparticles is prepared by solvothermal method or sol-gel method. The precipitant is added to the stock solution for precipitation treatment, and the precipitate is collected. The precipitate contains the fresh zinc oxide-based nanoparticles and the residual solvent A.

[0022] In some embodiments, the precipitant is selected from one or more of the following: halogenated or unsubstituted alkanes with less than 18 carbon atoms; halogenated or unsubstituted cycloalkanes with less than 18 carbon atoms; halogenated or unsubstituted alkenes with less than 18 carbon atoms; halogenated or unsubstituted cycloalkenes with less than 18 carbon atoms; halogenated or unsubstituted alkynes with less than 18 carbon atoms; halogenated or unsubstituted aromatic hydrocarbons with less than 18 carbon atoms; halogenated or unsubstituted heteroaromatic compounds with less than 18 cyclic atoms; halogenated or unsubstituted ethers with less than 18 carbon atoms; halogenated or unsubstituted ketones with less than 18 carbon atoms; and halogenated or unsubstituted esters with less than 18 carbon atoms.

[0023] In some embodiments, the precipitant is selected from one or more of ethyl acetate, acetone, diethyl ether, n-pentane, n-hexane, cyclohexane, heptane, n-octane, and chlorobenzene.

[0024] In some embodiments, the reaction solvent is selected from one or more of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol, dimethyl sulfoxide, formamide, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolinone, acetonitrile, and tributylphosphine.

[0025] In some embodiments, the auxiliary solvent is selected from one or more monohydric alcohols having 1 to 5 carbon atoms.

[0026] In some embodiments, the auxiliary solvent is selected from one or more of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, and 3-pentanol.

[0027] In some embodiments, the target solvent is selected from one or more of the following: monohydric alcohols with not less than 6 carbon atoms, polyhydric alcohols with 2 to 6 carbon atoms, and alcohol ether solvents formed by polyhydric alcohols with 2 to 6 carbon atoms and monohydric alcohols with 1 to 5 carbon atoms.

[0028] In some embodiments, the monohydric alcohol having at least 6 carbon atoms is selected from one or more of the following: n-hexanol, n-heptanol, 2-heptanol, 3-heptanol, 2-ethylhexanol, 2-methylcyclohexanol, n-octanol, 2-octanol, 3,5,5-trimethylhexanol, nonanol, 2,6-dimethyl-4-heptanol, n-decanol, 5-ethyl-2-nonanol, undecanol, 5-ethyl-2-nonanol, dodecanol, trimethylnonanol, cis-2-methylcyclohexanol, cis-3-methylcyclohexanol, cis-4-methylcycloethanol, 2-butoxyethanol, benzyl alcohol, α-phenylethanol, and β-phenylethanol.

[0029] In some embodiments, the polyol having 2 to 6 carbon atoms is selected from one or more of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-buten-1,4-diol, 2-methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanediol, 2-ethyl-1,3-hexanediol, 1,2,4-butanetriol, 1,2,6-hexanetriol, and pentaerythritol.

[0030] In some embodiments, the alcohol ether solvent is selected from one or more of ethylene glycol propyl ether, ethylene glycol butyl ether, propylene glycol n-butyl ether, propylene glycol tert-butyl ether, 3-methoxybutanol, diethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl ether, diethylene glycol diethyl ether, diethylene glycol butyl ether, diethylene glycol dibutyl ether, diethylene glycol hexyl ether, triethylene glycol monobutyl ether, dipropylene glycol methyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol diethyl ether, dipropylene glycol butyl ether, triethylene glycol monomethyl ether, triethylene glycol ethyl ether, tetraethylene glycol monomethyl ether, tripropylene glycol methyl ether, and tripropylene glycol butyl ether.

[0031] In some embodiments, the weight-to-volume ratio of the nanoparticles, auxiliary solvent, and target solvent is 1.5 g : (0.1–50) mL : (3.75–150) mL.

[0032] A second aspect of this invention provides a nanoparticle ink, which is prepared by the method described above.

[0033] A third aspect of the present invention provides an electroluminescent device. It includes a light-emitting layer and a functional layer, the functional layer including an electron transport layer, the electron transport layer being prepared from a raw material comprising the aforementioned nanoparticle ink.

[0034] Compared with traditional solutions, the present invention has the following advantages:

[0035] This invention incorporates an auxiliary solvent and a target solvent into nanoparticles. The auxiliary solvent not only rapidly disperses the nanoparticles but also quickly determines their polarity, thus dissolving them in the target solvent. The auxiliary solvent's assistance prevents agglomeration caused by slow dissolution. After the nanoparticles have dissolved in the target solvent, the auxiliary solvent is completely removed, leaving only the nanoparticles in the target solvent, significantly reducing the likelihood of collisions and agglomeration. In summary, this invention maintains uniform dispersion of nanoparticles during preparation and storage, minimizing agglomeration. This method solves the problem of nanoparticle dispersion uniformity, reducing the risk of printer tubing and nozzle clogging. When used in QLED devices, this ink improves device efficiency and lifespan, enhances device performance stability, and provides crucial material and technological support for the industrialization of QLED printed displays. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application and to more completely understand this application and its beneficial effects, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 The hydration size distribution (DLS) of the ZnO-based nanoparticle ink in Comparative Example 1 is shown.

[0038] Figure 2 The image shows the hydration size distribution (DLS) of the ZnO-based nanoparticle ink from Example 1.

[0039] Figure 3 The hydrated particle size (DLS) distribution of the ZnO-based nanoparticle inks prepared in Example 2 and Comparative Example 2 after being stored at room temperature for 6 months is shown in the figure.

[0040] Figure 4 AFM morphology images of the spin-coated films of Comparative Example 1 and Example 1;

[0041] Figure 5 AFM morphology images of the spin-coated films of Comparative Example 2 and Example 2;

[0042] Figure 6 The diagram shows the electroluminescence (EL) of the QLED devices in Comparative Example 1 and Example 1.

[0043] Figure 7 The diagram shows the electroluminescence (EL) of the QLED devices in Comparative Example 2 and Example 2. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to specific embodiments. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0046] the term

[0047] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0048] In this invention, the selection range of "and / or", "or / and", and "and / or" includes any one of two or more related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that the technical solution undoubtedly includes technical solutions connected by "logical AND", and also undoubtedly includes technical solutions connected by "logical OR". For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0049] In this invention, terms such as "multiple", "various", "multiple times", and "multi-dimensional" are used, unless otherwise specified, to refer to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0050] In this invention, the terms "combinations thereof", "any combination thereof", and "any combination thereof" include all suitable combinations of any two or more of the listed items.

[0051] In this invention, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this invention, solve the technical problem of this invention, and achieve the expected technical effect of this invention.

[0052] In this invention, terms such as "preferred," "better," "more suitable," and "ideal" are used only to describe implementation methods or embodiments with better effects, and should be understood not to limit the scope of protection of this invention.

[0053] In this invention, terms such as "further," "even more," and "particularly" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0054] In this invention, the terms "optionally," "optionally," and "optional" refer to options that are optional, meaning they are selected from either "with" or "without." If multiple "optional" options appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" option is independent.

[0055] In this invention, the terms "first aspect," "second aspect," "third aspect," and "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," and "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0056] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0057] In this invention, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0058] Unless otherwise specified, the temperature parameters in this invention can be either constant temperature treatment or variations within a certain temperature range. It should be understood that the constant temperature treatment allows temperature fluctuations within the precision range controlled by the instrument. Fluctuations are permitted within ranges such as ±5℃, ±4℃, ±3℃, ±2℃, and ±1℃.

[0059] In this invention, percentage content refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures, unless otherwise specified.

[0060] In this invention, percentage concentrations, unless otherwise specified, refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0061] In this invention, % (w / w) and wt% both represent weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass-volume percentage.

[0062] One embodiment of the present invention provides a method for preparing nanoparticle ink, comprising the following steps:

[0063] The nanoparticles are mixed with an auxiliary solvent, then the target solvent is added, and then the auxiliary solvent is removed to obtain the nanoparticle ink.

[0064] Alternatively, the nanoparticles can be directly dispersed in a mixed solvent consisting of an auxiliary solvent and a target solvent, and the auxiliary solvent can be removed to obtain the nanoparticle ink.

[0065] This embodiment incorporates an auxiliary solvent and a target solvent into the nanoparticles. The auxiliary solvent not only rapidly disperses the nanoparticles but also quickly determines their polarity, thus dissolving them in the target solvent. The auxiliary solvent helps prevent agglomeration caused by slow dissolution of the nanoparticles. After the nanoparticles have dissolved in the target solvent, the auxiliary solvent is completely removed, leaving only the nanoparticles in the target solvent. This significantly reduces the likelihood of nanoparticle collisions and agglomeration. In summary, this invention maintains uniform dispersion of nanoparticles during preparation and storage, minimizing agglomeration. This method solves the problem of uniform nanoparticle dispersion, reducing the risk of printer tubing and nozzle clogging. When used in QLED devices, this ink improves device efficiency and lifespan, enhances device performance stability, and provides key material and technological support for the industrialization of QLED printed displays.

[0066] Optionally, the boiling point of the auxiliary solvent is denoted as T1 and its volume as V1, and the boiling point of the target solvent is denoted as T2 and its volume as V2. T1, T2, V1 and V2 simultaneously satisfy the following conditions: T1 < T2 and V1 ≤ V2.

[0067] Optionally, T2 ≥ 130℃.

[0068] Optionally, the nanoparticles are transition metal oxide nanoparticles.

[0069] Further optionally, the transition metal oxide nanoparticles include at least one of undoped metal oxide particles and doped metal oxide particles;

[0070] The undoped metal oxide particles are selected from at least one of ZnO, BaO, TiO2, SnO2, Ta2O3, and ZrO2; and / or,

[0071] The doped metal oxide particles include a dopant element and metal oxide particles; the dopant element is selected from at least one of aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, and gadolinium; the material of the metal oxide particles is selected from at least one of ZnO, BaO, TiO2, SnO2, Ta2O3, and ZrO2.

[0072] The average particle size of the nanoparticles is 1nm to 20nm, specifically 1nm to 15nm, 1nm to 10nm, 3nm to 15nm, 3nm to 13nm, 5nm to 10nm, 5nm to 12nm, 5nm to 15nm, etc.

[0073] In this embodiment, the nanoparticles are fresh zinc oxide-based nanoparticles prepared by solvothermal or sol-gel methods.

[0074] The ETL (electron transport layer) material in QLED devices is currently mainly zinc oxide-based nanoparticles, including zinc oxide nanoparticles or zinc oxide nanoparticles doped with metals / transition metals. However, zinc oxide nanoparticles have numerous defect states, unstable surface ligands, and are highly sensitive to water and oxygen. Furthermore, to ensure the dispersibility of zinc oxide-based nanoparticles, many methods involve semi-drying a solution containing zinc oxide-based nanoparticles prepared by solution methods, and then dispersing the moistened nanoparticles in an ink solvent. Ink prepared using this method is prone to agglomeration of zinc oxide-based nanoparticles during preparation or storage, leading to unstable device performance or clogging of printer tubing and printheads. The method described in this embodiment maintains uniform dispersion of zinc oxide-based nanoparticles during preparation and storage, preventing agglomeration. This method solves the problem of uniform dispersion of zinc oxide-based nanoparticles and reduces the risk of printer tubing and printhead clogging. The ink used in QLED devices improves device efficiency and lifespan, enhances device performance stability, and provides key material and technological support for the industrialization of QLED printed displays.

[0075] Optionally, the method for removing the auxiliary solvent is vacuum distillation.

[0076] In this embodiment, the fresh zinc oxide-based nanoparticles still contain solvent A, and the preparation method of the nanoparticle ink further includes a step of removing solvent A, and the step of removing solvent A is performed simultaneously with the step of removing the auxiliary solvent.

[0077] Optionally, solvent A includes one or more of the solvent and precipitant originally present in the stock solution, wherein the solvent originally present in the stock solution is the reaction solvent used in the preparation of zinc oxide-based nanoparticles by the solvothermal method or the sol-gel method, and the reaction solvent is a polar solvent.

[0078] In this embodiment, the method for preparing the fresh zinc oxide-based nanoparticles with residual solvent A includes the following steps:

[0079] The stock solution for preparing zinc oxide-based nanoparticles is prepared by solvothermal method or sol-gel method. The precipitant is added to the stock solution for precipitation treatment, and the precipitate is collected. The precipitate contains the fresh zinc oxide-based nanoparticles and the residual solvent A.

[0080] In this embodiment, after obtaining the stock solution containing zinc oxide-based nanoparticles, a precipitant is added for precipitation treatment, and the precipitate is collected. At this time, solvent A remains in the precipitate. Solvent A includes one or more of the solvent originally in the stock solution and the precipitant. The original solvent in the stock solution is present in very small amounts and its role is negligible. The precipitant, etc., adheres to the surface of the nano-sized zinc oxide-based particles. The residue of the precipitant, etc., can create larger gaps between the zinc oxide-based nanoparticles, thus preventing them from agglomerating in a short period of time. However, the long-term presence of the precipitant can easily lead to a decrease in the stability of the zinc oxide-based nanoparticles, causing them to agglomerate. Combining the addition of the above-mentioned auxiliary solvent and target solvent is more conducive to maintaining the uniform dispersion of zinc oxide-based nanoparticles during preparation and storage, making them less prone to agglomeration.

[0081] In a solvent, an organic zinc salt and an alkaline source are reacted in a reaction solvent to obtain a stock solution of zinc oxide-based nanoparticles.

[0082] Further optionally, the organic zinc salt includes one or more of organic zinc alcohols and organic zinc acids.

[0083] Further optionally, the organic zinc alcohol includes one or more of zinc methoxide, zinc ethanol, zinc isopropoxide, zinc methoxide dihydrate, and zinc ethanol dihydrate.

[0084] Further optionally, the organic zinc acid includes one or more of zinc acetate, zinc formate, zinc propionate, zinc butyrate, zinc oleate, zinc formate dihydrate, zinc propionate dihydrate, and zinc butyrate dihydrate.

[0085] Further optionally, the alkali source includes one or more of anhydrous tetramethylammonium hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, barium hydroxide, ethanolamine, propanolamine, lithium propionate, lithium acetate, lithium formate, sodium acetate, and potassium acetate.

[0086] Optionally, the reaction solvent is one or more of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol, dimethyl sulfoxide (DMSO), formamide, N,N-dimethylformamide (DMF), 1,3-dimethyl-2-imidazolinone (DMI), acetonitrile, and tributylphosphine.

[0087] Optionally, the reaction conditions are stirring for 5 min to 72 h, ultrasonic reaction for 5 min to 72 h, or heating reaction for 5 min to 72 h.

[0088] In this embodiment, adding a precipitant for precipitation treatment can achieve the effect of cleaning zinc oxide-based nanoparticles. After precipitation treatment, the original solvent in the original solution in the precipitate can be reduced.

[0089] Optionally, the precipitation process can be performed once or multiple times. When performing multiple precipitation processes, the precipitate from the previous step can be dispersed before the current precipitation process.

[0090] Understandably, after precipitation treatment, the precipitate can be collected by centrifugation or filtration, at which point the precipitate is in a moist state.

[0091] Optionally, the precipitant is selected from one or more of the following: halogenated or unsubstituted alkanes with less than 18 carbon atoms; halogenated or unsubstituted cycloalkanes with less than 18 carbon atoms; halogenated or unsubstituted alkenes with less than 18 carbon atoms; halogenated or unsubstituted cycloalkenes with less than 18 carbon atoms; halogenated or unsubstituted alkynes with less than 18 carbon atoms; halogenated or unsubstituted aromatic hydrocarbons with less than 18 carbon atoms; halogenated or unsubstituted heteroaromatic compounds with less than 18 cyclic atoms; halogenated or unsubstituted ethers with less than 18 carbon atoms; halogenated or unsubstituted ketones with less than 18 carbon atoms; and halogenated or unsubstituted esters with less than 18 carbon atoms. Zinc oxide-based nanoparticles have numerous defect states on their surface, which can attract precipitants. Taking 1.5g of zinc oxide-based nanoparticles as an example, depending on the synthesis scheme and cleaning process, 0.2mL-20mL of precipitant can be attracted. However, precipitants are poor solvents, and their presence is detrimental to the long-term stability of zinc oxide-based nanoparticles.

[0092] In this embodiment, the precipitation process is performed twice. The precipitation process includes the following steps: adding a first precipitant, dispersing the resulting first precipitate in a dispersant, adding a second precipitant, and collecting the second precipitate, which is the precipitate.

[0093] Optionally, the first precipitant is selected from one or more of halogen-substituted or unsubstituted ether compounds with less than 18 carbon atoms, halogen-substituted or unsubstituted ketone compounds with less than 18 carbon atoms, and halogen-substituted or unsubstituted ester compounds with less than 18 carbon atoms. For example, the first precipitant is selected from one or more of diethyl ether, ethyl acetate, acetone, butyl acetate, and methyl formate.

[0094] Optionally, the second precipitant is selected from one or more of the following: halogenated or unsubstituted alkanes with less than 18 carbon atoms; halogenated or unsubstituted cycloalkanes with less than 18 carbon atoms; halogenated or unsubstituted alkenes with less than 18 carbon atoms; halogenated or unsubstituted cycloalkenes with less than 18 carbon atoms; halogenated or unsubstituted alkynes with less than 18 carbon atoms; halogenated or unsubstituted aromatic hydrocarbons with less than 18 carbon atoms; and heteroaromatic compounds with less than 18 cyclic atoms. For example, the second precipitant is selected from one or more of heptane, n-pentane, n-hexane, cyclohexane, n-octane, 1-hexene, 1-hexyne, chloroform, toluene, chlorobenzene, and kerosene.

[0095] In this embodiment, the methods for collecting the first precipitate and the second precipitate are each independent of centrifugation or filtration.

[0096] Understandably, when precipitation treatment is performed multiple times, the first precipitant is used for the first time, and the second precipitant can be used for the second and subsequent times.

[0097] In this embodiment, the fresh zinc oxide-based nanoparticles contain 20wt% to 90wt% of solvent A, and an auxiliary solvent and a target solvent are added to the precipitate.

[0098] Optionally, the weight-to-volume ratio of the nanoparticles, auxiliary solvent, and target solvent is 1.5 g: (0.1–50) mL: (3.75–150) mL.

[0099] Optionally, the weight-volume ratio of the nanoparticles, auxiliary solvent, and target solvent is (0.15–1.2) g: (0.1–50) mL: (3.75–150) mL.

[0100] Optionally, the auxiliary solvent is selected from one or more monohydric alcohols having 1 to 5 carbon atoms.

[0101] In some embodiments, the auxiliary solvent is selected from one or more of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, and 3-pentanol. These auxiliary solvents are low-boiling-point good solvents with relatively small molecular weights, relatively simple molecular structures, wide adjustable polarity ranges, relatively high amounts of polar groups per unit volume, and relatively low viscosity, resulting in fast molecular motion and strong polarity regularity, which is beneficial for the rapid solventization of zinc oxide in the target solvent.

[0102] In some embodiments, the target solvent is selected from one or more of the following: monohydric alcohols with at least 6 carbon atoms, polyhydric alcohols with 2 to 6 carbon atoms, and alcohol ether solvents formed by polyhydric alcohols with 2 to 6 carbon atoms and monohydric alcohols with 1 to 5 carbon atoms. The polarity of the target solvent is similar to that of zinc oxide, with a relatively large molecular weight, relatively complex molecular structure, relatively high viscosity, and a relatively small amount of polar groups per unit volume. While it itself dissolves zinc oxide slowly, it can rapidly dissolve zinc oxide with the assistance of an auxiliary solvent, preventing the aggregation of zinc oxide-based nanoparticles. Simultaneously, due to the relatively large molecular weight, relatively complex molecular structure, and relatively high viscosity of the target solvent, the zinc oxide-based nanoparticles are less prone to collision and aggregation during storage.

[0103] Optionally, the monohydric alcohol having not less than 6 carbon atoms is selected from one or more of the following: n-hexanol, n-heptanol, 2-heptanol, 3-heptanol, 2-ethylhexanol, 2-methylcyclohexanol, n-octanol, 2-octanol, 3,5,5-trimethylhexanol, nonanol, 2,6-dimethyl-4-heptanol, n-decanol, 5-ethyl-2-nonanol, undecanol, 5-ethyl-2-nonanol, dodecanol, trimethylnonanol, cis-2-methylcyclohexanol, cis-3-methylcyclohexanol, cis-4-methylcycloethanol, 2-butoxyethanol, benzyl alcohol, α-phenylethanol, and β-phenylethanol.

[0104] Optionally, the polyol having 2 to 6 carbon atoms is selected from one or more of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-buten-1,4-diol, 2-methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanediol, 2-ethyl-1,3-hexanediol, 1,2,4-butanetriol, 1,2,6-hexanetriol, and pentaerythritol.

[0105] Optionally, the alcohol ether solvent is selected from one or more of ethylene glycol propyl ether, ethylene glycol butyl ether, propylene glycol n-butyl ether, propylene glycol tert-butyl ether, 3-methoxybutanol, diethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl ether, diethylene glycol diethyl ether, diethylene glycol butyl ether, diethylene glycol dibutyl ether, diethylene glycol hexyl ether, triethylene glycol monobutyl ether, dipropylene glycol methyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol diethyl ether, dipropylene glycol butyl ether, triethylene glycol monomethyl ether, triethylene glycol ethyl ether, tetraethylene glycol monomethyl ether, tripropylene glycol methyl ether, and tripropylene glycol butyl ether.

[0106] The zinc oxide-based nanoparticle ink described above can accelerate the dispersion of zinc oxide-based nanoparticles and reduce agglomeration by using auxiliary solvents and target solvents during the preparation process. After removing the auxiliary solvent and storing it in the target solvent, collisions between zinc oxide-based nanoparticles can be reduced, thus maintaining the ink's uniformity and stability.

[0107] One embodiment of the present invention also provides a nanoparticle ink prepared by the above-described preparation method. Further, one embodiment of the present invention also provides a zinc oxide-based nanoparticle ink prepared by the above-described preparation method.

[0108] When using the above-mentioned zinc oxide-based nano-ink, its concentration can be adjusted to 10 mg / mL to 200 mg / mL, and the coating can be spin-coated at a speed of 1000 rpm to 4000 rpm, which can form a thin film with an adjustable thickness of 3 nm to 200 nm.

[0109] One embodiment of the present invention also provides an electroluminescent device comprising a light-emitting layer and a functional layer, wherein the functional layer includes an electron transport layer, the electron transport layer being prepared from a raw material comprising the aforementioned nanoparticle ink. Further, the electron transport layer is prepared from a raw material comprising the aforementioned zinc oxide-based nanoparticle ink.

[0110] The following description, in conjunction with specific embodiments and comparative examples, will provide further details. Unless otherwise specified, all raw materials and instruments used in the following specific embodiments are commercially available. Unless otherwise specified, all processes involved are conventionally selected by those skilled in the art.

[0111] Example 1

[0112] This embodiment provides a zinc oxide-based nanoparticle ink and its preparation method, the steps of which are as follows:

[0113] Step 1: 50 mmol of zinc acetate and zinc formate (molar ratio 7:3) mixed powder was ultrasonically dispersed in 300 mL of DMSO to prepare a DMSO solution of organic zinc acid; 55 mmol of lithium hydroxide powder was ultrasonically dispersed in 300 mL of ethanol to prepare an ethanol solution of lithium hydroxide; the ethanol solution of lithium hydroxide was added dropwise to the DMSO solution of organic zinc acid and reacted at 25 °C for 20 h to obtain a stock solution of ZnO-based nanoparticles; acetone was added to the stock solution as the first precipitant, and the first precipitate (containing ZnO-based nanoparticles) was collected by centrifugation; ethanol was added to the first precipitate as the dispersant to obtain a clear and transparent solution; n-hexane was added as the second precipitant, and 1.5 g of the second precipitate was obtained by centrifugation, which is the fresh ZnO-based nanoparticles containing residual solvent A, including acetone, n-hexane, and ethanol.

[0114] Step 2: Disperse the fresh ZnO-based nanoparticles with residual solvent A obtained in Step 1 using 10 mL of auxiliary solvent methanol, add 30 mL of the target solvent n-octanol, shake and mix until clear to obtain a mixture.

[0115] Step 3: The mixture obtained in Step 2 is then connected to a vacuum pump and vacuumed slowly for 1 hour. The auxiliary solvents methanol and solvent A are removed by vacuum distillation to obtain ZnO-based nanoparticle ink.

[0116] Step 4: Dilute the zinc oxide-based nanoparticle ink obtained in Step 3 to obtain a ZnO-based nanoparticle ink with a concentration of 40 mg / mL.

[0117] Example 2

[0118] This embodiment provides a zinc oxide-based nanoparticle ink and its preparation method, the steps of which are as follows:

[0119] Step 1: Take the stock solution of ZnO-based nanoparticles from Example 1, add the first precipitant ethyl acetate to the stock solution, centrifuge to collect the first precipitate (containing ZnO-based nanoparticles), add the dispersant ethanol to the first precipitate to obtain a clear and transparent solution, add the second precipitant kerosene, centrifuge to obtain 1.5g of the second precipitate, which is the fresh ZnO-based nanoparticles with residual solvent A. Solvent A includes kerosene, ethyl acetate and ethanol, etc.

[0120] Step 2: Disperse the precipitate containing residual solvent A obtained in Step 1 using 10 mL of auxiliary solvent ethanol, add 20 mL of the target solvent diethylene glycol butyl ether, shake and mix until clear to obtain a mixture.

[0121] Step 3: After letting the mixture obtained in Step 2 stand for 1 hour, connect it to a vacuum pump and slowly evacuate for 1 hour. Remove the auxiliary solvent ethanol and solvent A by vacuum distillation to obtain ZnO-based nanoparticle ink.

[0122] Step 4: Dilute the zinc oxide-based nanoparticle ink obtained in Step 3 to obtain a ZnO-based nanoparticle ink with a concentration of 60 mg / mL.

[0123] Example 3

[0124] This embodiment provides a zinc oxide-based nanoparticle ink and its preparation method, the steps of which are as follows:

[0125] Step 1: Take the stock solution of ZnO-based nanoparticles from Example 1, add the first precipitant methyl formate to the stock solution, centrifuge to collect the first precipitate (containing ZnO-based nanoparticles), add the dispersant ethanol to the first precipitate to obtain a clear and transparent solution, add the second precipitant chloroform, centrifuge to obtain 1.5g of the second precipitate, which is the fresh ZnO-based nanoparticles with residual solvent A. Solvent A includes heptane, ethyl acetate and ethanol, etc.

[0126] Step 2: Mix the auxiliary solvent ethanol and the target solvent diethylene glycol butyl ether at a volume ratio of 1:2 to obtain a mixed solvent. Take 30 mL of the obtained mixed solvent to disperse the precipitate containing solvent A obtained in Step 1, shake and mix until clear to obtain a mixed solution.

[0127] Step 3: After letting the mixture obtained in Step 2 stand for 1 hour, connect it to a vacuum pump and slowly evacuate for 1 hour. Remove the auxiliary solvent ethanol and solvent A by vacuum distillation to obtain ZnO-based nanoparticle ink.

[0128] Step 4: Dilute the zinc oxide-based nanoparticle ink obtained in Step 3 to obtain a ZnO-based nanoparticle ink with a concentration of 60 mg / mL.

[0129] Example 4

[0130] This embodiment provides a zinc oxide-based nanoparticle ink and its preparation method, the steps of which are as follows:

[0131] Step 1: Take the stock solution of ZnO-based nanoparticles from Example 1, add the first precipitant diethyl ether to the stock solution, centrifuge to collect the first precipitate (containing ZnO-based nanoparticles), add the dispersant ethanol to the first precipitate to obtain a clear and transparent solution, add the second precipitant 1-hexene, centrifuge to obtain 1.5g of the second precipitate, which is the fresh ZnO-based nanoparticles with residual solvent A. Solvent A includes diethyl ether, 1-hexene and ethanol, etc.

[0132] Step 2: Disperse the precipitate containing residual solvent A obtained in Step 1 using 10 mL of auxiliary solvent butanol, add 10 mL of target solvent ethylene glycol monomethyl ether, shake and mix until clear to obtain a mixture.

[0133] Step 3: After letting the mixture obtained in Step 2 stand overnight (16h), connect it to a vacuum pump and slowly evacuate for 1h. Remove the auxiliary solvent ethanol and solvent A by vacuum distillation to obtain ZnO-based nanoparticle ink.

[0134] Step 4: Dilute the zinc oxide-based nanoparticle ink obtained in Step 3 to obtain a ZnO-based nanoparticle ink with a concentration of 100 mg / mL.

[0135] Step 5: Add an equal volume of dipropylene glycol butyl ether to a ZnO-based nanoparticle ink with a concentration of 100 mg / mL to obtain a ZnO-based nanoparticle ink with a two-component solvent concentration of 50 mg / mL.

[0136] Comparative Example 1

[0137] This comparative example provides a zinc oxide-based nanoparticle ink and its preparation method, the steps of which are as follows:

[0138] Step 1: Take the stock solution of ZnO-based nanoparticles from Example 1, add acetone as the first precipitant to the stock solution, centrifuge to collect the first precipitate (containing ZnO-based nanoparticles), add ethanol as the dispersant to the first precipitate to obtain a clear and transparent solution, add n-hexane as the second precipitant, centrifuge to obtain 1.5g of the second precipitate, which is the fresh ZnO-based nanoparticles with residual solvent A. Solvent A includes acetone, n-hexane, and ethanol, etc.

[0139] Step 2: Disperse the precipitate containing residual solvent A obtained in Step 1 using 30 mL of the target solvent n-octanol, shake well, and obtain ZnO-based nanoparticle ink.

[0140] Step 3: Dilute the zinc oxide-based nanoparticle ink obtained in Step 2 to obtain a ZnO-based nanoparticle ink with a concentration of 40 mg / mL.

[0141] Comparative Example 2

[0142] This comparative example provides a zinc oxide-based nanoparticle ink and its preparation method, the steps of which are as follows:

[0143] Step 1: Take the stock solution of ZnO-based nanoparticles from Example 1, add the first precipitant ethyl acetate to the stock solution, centrifuge to collect the first precipitate (containing ZnO-based nanoparticles), add the dispersant ethanol to the first precipitate to obtain a clear and transparent solution, add the second precipitant kerosene, centrifuge to obtain 1.5g of the second precipitate, which is the fresh ZnO-based nanoparticles with residual solvent A. Solvent A includes kerosene, ethyl acetate and ethanol, etc.

[0144] Step 2: Disperse the precipitate containing residual solvent A obtained in Step 1 using 20 mL of the target solvent diethylene glycol butyl ether, shake well, and obtain ZnO-based nanoparticle ink.

[0145] Step 3: Dilute the zinc oxide-based nanoparticle ink obtained in Step 2 to obtain a ZnO-based nanoparticle ink with a concentration of 60 mg / mL.

[0146] Test 1

[0147] The hydrated particle size (DLS) distribution of the ZnO-based nanoparticle inks prepared in Example 1 and Comparative Example 1, as well as the hydrated particle size (DLS) distribution of the ZnO-based nanoparticle inks after being stored at room temperature for 6 months, are shown in the figures. Figure 1 and Figure 2 As shown, where, Figure 1 (a) is a hydration particle size distribution diagram of freshly prepared ZnO-based nanoparticle ink in Comparative Example 1; Figure 1 (b) is the hydration particle size distribution of the ZnO-based nanoparticle ink of Comparative Example 1 after being stored at room temperature for 6 months. Figure 2 (a) is a hydration particle size distribution diagram of the freshly prepared ZnO-based nanoparticle ink in Example 1; Figure 2 (b) is a hydration particle size distribution diagram of the ZnO-based nanoparticle ink from Example 1 after being stored at room temperature for 6 months. Figure 1 and Figure 2 It can be seen that, in the freshly prepared ZnO-based nanoparticle ink of Comparative Example 1, in addition to the main peak of about 6 nm, there are also agglomerated ZnO-based nanoparticles with particle sizes of about 13 nm and 200 nm. After being stored for half a year, a large number of zinc oxide nanoparticles agglomerate, with the largest particle size exceeding 1 μm, which easily leads to problems such as uneven film formation, poor printing stability, and printhead clogging. In the ink of Example 1, the ZnO-based nanoparticles have a single hydration particle size peak and are relatively uniformly dispersed. After being stored at room temperature for 6 months, the hydration particle size increases slightly, but the particle size is uniform, and the various properties are relatively stable, with good printing consistency, making it easy for industrial production.

[0148] The hydrated particle size (DLS) distribution of the ZnO-based nanoparticle inks prepared in Example 2 and Comparative Example 2 after being stored at room temperature for 6 months is shown in the figure. Figure 3 As shown, where, Figure 3 (a) is the hydration particle size distribution of the ZnO-based nanoparticle ink of Comparative Example 2 after being stored at room temperature for 6 months. Figure 3 (b) is a hydration particle size distribution diagram of the ZnO-based nanoparticle ink from Example 2 after being stored at room temperature for 6 months. Figure 3 As can be seen from the data, after the ZnO-based nanoparticle ink of Comparative Example 2 was left at room temperature for 6 months, the hydrated particle size distribution showed a main peak of about 6 nm, as well as aggregated ZnO-based nanoparticles with a particle size of about 100 nm. After the ZnO-based nanoparticles of Example 2 were left at room temperature for 6 months, the hydrated particle size showed a single hydrated particle size peak, and the various properties were relatively stable, with good printing consistency, making it easy for industrial production.

[0149] Test 2

[0150] Freshly prepared 40 mg / mL ZnO-based nanoparticle inks from Examples 1 and 2, and Comparative Examples 1 and 2, were spin-coated onto ITO substrates at 3000 rpm to obtain films with a thickness of approximately 30 nm. The AFM morphology images of the spin-coated films are shown below. Figure 4 and Figure 5 As shown, where, Figure 4 (a) is the spin-coated film of Comparative Example 1; Figure 4 (b) is the spin-coated film of Example 1. Figure 5 (a) is the spin-coated film of Comparative Example 2; Figure 5 (b) is the spin-coated film of Example 2. From... Figure 4 It can be seen that the spin-coated film of Comparative Example 1 has a very rough film, with a large number of large particles of about 80 nm on the film surface, and a roughness Ra of about 9 nm; while the spin-coated film of Example 1 has a relatively uniform film, with a roughness Ra of about 0.69 nm. Figure 5 It can be seen that the spin-coated film of Comparative Example 2 is very rough; while the spin-coated film of Example 2 is relatively uniform.

[0151] Test 3

[0152] Using a 100 nm thick transparent conductive thin film ITO as the anode, MCC was spin-coated onto the anode using a solution method to form a 100 nm thick hole injection layer. TFB was then spin-coated onto the hole injection layer using a solution method to form a 30 nm thick hole transport layer. CdSe / ZnS quantum dots were then spin-coated onto the hole transport layer using a solution method to form a 35 nm thick blue quantum dot emitting layer. Following the method described in Test 2, freshly prepared ZnO-based nanoparticle inks from Examples 1, 2, Comparative Examples 1, and 2 were dispersed and spin-coated to prepare an electron transport layer with a thickness of 35 nm. Ag was then evaporated to form a 60 nm thick cathode, resulting in the QLED devices of Examples 1, 2, 1, and 2.

[0153] The electroluminescence (EL) of the QLED devices in Examples 1, 2, 1, and 2 are shown in the figure below. Figure 6 and Figure 7 As shown, where, Figure 6 (a) is the QLED device of Comparative Example 1; Figure 6 (b) is the QLED device of Example 1; Figure 7 (a) is the QLED device of Comparative Example 2; Figure 7 (b) shows the QLED device of Example 2. Figure 6 and Figure 7 It can be seen that Comparative Example 1 and Comparative Example 2 have a large number of uneven black spots, while the electroluminescence (EL) of Example 1 and Example 2 is very uniform.

[0154] Test 4

[0155] Following the method described in Test 3, QLED devices of Examples 3 and 4 were prepared respectively, and the luminous efficiency and lifetime of QLED devices of Examples 1-4 and Comparative Examples 1-2 were tested respectively. The structures are shown in Table 1.

[0156] Table 1

[0157]

[0158]

[0159] It can be seen that the ZnO-based nanoparticle inks prepared by the methods in Examples 1 to 4 can be uniformly dispersed during the preparation process and are not prone to agglomeration. When used in QLED devices, they are beneficial to improving the efficiency and lifespan of the devices.

[0160] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0161] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing nanoparticle ink, characterized in that, Includes the following steps: The nanoparticles are mixed with an auxiliary solvent, then the target solvent is added, and then the auxiliary solvent is removed to obtain the nanoparticle ink. Alternatively, the nanoparticles can be directly dispersed in a mixed solvent consisting of an auxiliary solvent and a target solvent, and the auxiliary solvent can be removed to obtain the nanoparticle ink. The nanoparticles are fresh zinc oxide-based nanoparticles prepared by solvothermal or sol-gel methods. The fresh zinc oxide-based nanoparticles still contain solvent A, and the preparation method of the nanoparticle ink further includes a step of removing solvent A, which is performed simultaneously with the step of removing the auxiliary solvent. Solvent A includes one or more of the original solvent and precipitant in the stock solution, wherein the original solvent in the stock solution is the reaction solvent used in the preparation of zinc oxide-based nanoparticles by the solvothermal or sol-gel methods, and the reaction solvent is a polar solvent. Let T1 be the boiling point of the auxiliary solvent and V1 be the volume of the auxiliary solvent, and T2 be the boiling point of the target solvent and V2 be the volume of the target solvent. T1, T2, V1 and V2 simultaneously satisfy the following conditions: T1 < T2 and V1 ≤ V2. The auxiliary solvent is selected from one or more monohydric alcohols having 1 to 5 carbon atoms; The target solvent is selected from one or more of the following: monohydric alcohols with not less than 6 carbon atoms, polyhydric alcohols with 2 to 6 carbon atoms, and alcohol ether solvents formed by polyhydric alcohols with 2 to 6 carbon atoms and monohydric alcohols with 1 to 5 carbon atoms. The weight-to-volume ratio of the nanoparticles, auxiliary solvent, and target solvent is 1.5 g : (0.1~50) mL : (3.75~150) mL.

2. The method for preparing nanoparticle ink according to claim 1, characterized in that, The nanoparticles include at least one of undoped metal oxide particles and doped metal oxide particles; The undoped metal oxide particles are selected from at least one of ZnO, BaO, TiO2, SnO2, Ta2O3, and ZrO2; and / or, The doped metal oxide particles include a doping element and metal oxide particles; the doping element is selected from at least one of aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, and gadolinium; the material of the metal oxide particles is selected from at least one of ZnO, BaO, TiO2, SnO2, Ta2O3, and ZrO2. And / or, the method for removing the auxiliary solvent is vacuum distillation.

3. The method for preparing nanoparticle ink according to claim 2, characterized in that, T2≥130℃。 4. The method for preparing nanoparticle ink according to claim 1, characterized in that, The precipitant is selected from one or more of the following: halogenated or unsubstituted alkanes with less than 18 carbon atoms; halogenated or unsubstituted cycloalkanes with less than 18 carbon atoms; halogenated or unsubstituted alkenes with less than 18 carbon atoms; halogenated or unsubstituted cycloalkenes with less than 18 carbon atoms; halogenated or unsubstituted alkynes with less than 18 carbon atoms; halogenated or unsubstituted aromatic hydrocarbons with less than 18 carbon atoms; halogenated or unsubstituted heteroaromatic compounds with less than 18 cyclic atoms; halogenated or unsubstituted ethers with less than 18 carbon atoms; halogenated or unsubstituted ketones with less than 18 carbon atoms; and halogenated or unsubstituted esters with less than 18 carbon atoms.

5. The method for preparing nanoparticle ink according to claim 1, characterized in that, The reaction solvent is selected from one or more of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol, dimethyl sulfoxide, formamide, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolinone, acetonitrile, and tributylphosphine; And / or, the precipitant is selected from one or more of ethyl acetate, acetone, diethyl ether, n-pentane, n-hexane, cyclohexane, heptane, n-octane, and chlorobenzene.

6. The method for preparing nanoparticle ink according to claim 1, characterized in that, The auxiliary solvent is selected from one or more of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol and 3-pentanol.

7. The method for preparing nanoparticle ink according to claim 1, characterized in that, The monohydric alcohol having at least 6 carbon atoms is selected from one or more of the following: n-hexanol, n-heptanol, 2-heptanol, 3-heptanol, 2-ethylhexanol, 2-methylcyclohexanol, n-octanol, 2-octanol, 3,5,5-trimethylhexanol, nonanol, 2,6-dimethyl-4-heptanol, n-decanol, 5-ethyl-2-nonanol, undecanol, 5-ethyl-2-nonanol, dodecanol, trimethylnonanol, cis-2-methylcyclohexanol, cis-3-methylcyclohexanol, cis-4-methylcycloethanol, 2-butoxyethanol, benzyl alcohol, α-phenylethanol, and β-phenylethanol.

8. The method for preparing nanoparticle ink according to claim 1, characterized in that, The polyols with 2 to 6 carbon atoms are selected from one or more of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-buten-1,4-diol, 2-methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanediol, 2-ethyl-1,3-hexanediol, 1,2,4-butanetriol, 1,2,6-hexanetriol, and pentaerythritol.

9. The method for preparing nanoparticle ink according to claim 1, characterized in that, The alcohol ether solvent is selected from one or more of ethylene glycol propyl ether, ethylene glycol butyl ether, propylene glycol n-butyl ether, propylene glycol tert-butyl ether, 3-methoxybutanol, diethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl ether, diethylene glycol diethyl ether, diethylene glycol butyl ether, diethylene glycol dibutyl ether, diethylene glycol hexyl ether, triethylene glycol monobutyl ether, dipropylene glycol methyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol diethyl ether, dipropylene glycol butyl ether, triethylene glycol monomethyl ether, triethylene glycol ethyl ether, tetraethylene glycol monomethyl ether, tripropylene glycol methyl ether, and tripropylene glycol butyl ether.

10. A nanoparticle ink, characterized in that, Prepared by the preparation method according to any one of claims 1-9.

11. An electroluminescent device, characterized in that, It includes a light-emitting layer and a functional layer, wherein the functional layer includes an electron transport layer, and the electron transport layer is prepared from raw materials including the nanoparticle ink of claim 10.

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