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

Abstract

This application belongs to the field of display technology and relates to a composite thin film, comprising a first thin film and a second thin film stacked together; the first thin film includes a MOF material and an electron transport material, wherein the conductivity of the MOF material is greater than or equal to 5 × 10⁻³ S / m; the electron affinity of the second thin film is greater than or equal to 4.7 eV. This application also relates to a method for preparing the composite thin film, a light-emitting device, and a display device. The technical solution provided by this application can reduce the electron injection barrier of the thin film and improve the electron injection efficiency.

Description

Technical Field

[0001] This application relates to the field of display technology, and more specifically, to a composite thin film and its preparation method, a light-emitting device, and a display apparatus. Background Technology

[0002] In multilayer organic light-emitting devices, the electrodes connecting two adjacent light-emitting units are usually replaced by a charge generation layer. However, conventional charge generation layers have a high electron injection barrier, resulting in low carrier injection efficiency. Summary of the Invention

[0003] This application provides a composite thin film and its preparation method, a light-emitting device, and a display device.

[0004] This application provides a composite film, which adopts the following technical solution:

[0005] A composite film includes a first film and a second film stacked together;

[0006] The first thin film comprises a MOF material and an electron transport material, wherein the conductivity of the MOF material is greater than or equal to 5 × 10⁻⁶. -3 S / m;

[0007] The electron affinity of the second thin film is greater than or equal to 4.7 eV.

[0008] This application also provides a method for preparing a composite thin film, which adopts the following technical solution:

[0009] A method for preparing a composite thin film includes the following steps:

[0010] A first solution comprising MOF material and electron transport material is provided, and the first solution is deposited to form a first thin film;

[0011] A second solution is provided, and the second solution is deposited on the first film to form a second film, thereby obtaining the composite film.

[0012] This application also provides a light-emitting device, which adopts the technical solution described below:

[0013] A light-emitting device includes an anode and a cathode disposed opposite to each other, and at least two layers of light-emitting units stacked between the anode and the cathode;

[0014] The light-emitting device further includes an intermediate layer disposed between two adjacent light-emitting units, wherein the intermediate layer is a composite film as described above or is prepared by the composite film preparation method described above.

[0015] This application also provides a display device that adopts the following technical solution:

[0016] A display device comprising the light-emitting device as described above.

[0017] Compared with the prior art, the embodiments of this application have the following main advantages:

[0018] The composite thin film provided in this application improves the conductivity of the first thin film by utilizing the high conductivity of MOF materials, thereby reducing the resistance within the first thin film and lowering the electron injection barrier between the first and second thin films. Simultaneously, the addition of electron transport materials facilitates electron injection. Furthermore, the high electron affinity of the second thin film promotes charge separation within the composite thin film, which is beneficial for the separation of electrons and holes, thereby improving both electron and hole injection efficiency. Attached Figure Description

[0019] To more clearly illustrate the solution of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the composite film according to an embodiment of this application;

[0021] Figure 2 This is a flowchart of a method for preparing a composite thin film according to an embodiment of this application;

[0022] Figure 3 This is a schematic diagram of the structure of the light-emitting device according to an embodiment of this application.

[0023] Figure label:

[0024] 1. First thin film; 2. Second thin film; 100. Anode; 200. First light-emitting unit; 201. First hole injection layer; 202. First hole transport layer; 203. First light-emitting layer; 204. First electron transport layer; 300. Intermediate layer; 400. Second light-emitting unit; 401. Second hole injection layer; 402. Second hole transport layer; 403. Second light-emitting layer; 404. Second electron transport layer; 500. Cathode. Detailed Implementation

[0025] 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 application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] Organic light-emitting diodes (OLEDs) based on solution-based technology have significant advantages in large-area and diverse form factor terminal displays due to their suitability for low-cost manufacturing processes. In their design, OLEDs typically combine two or more OLEDs in series to form a stacked OLED, which reduces the operating current at the same brightness, thereby extending the device's lifespan. This is a crucial direction for improving the lifespan of current OLEDs.

[0028] Typically, the electrodes connecting two adjacent light-emitting units in a stacked light-emitting device are replaced by a charge generation layer. When the stacked light-emitting device is working, the charge generation layer converts the absorbed photons into free charge carriers (electrons and holes) and effectively separates these charges, allowing them to move towards the electrodes under the influence of an electric field, thereby generating current and reducing the operating current of the device.

[0029] The interface between the deep electron acceptor layer and the hole transport layer can be regarded as the charge generation layer. Due to the large energy level difference between the electron transport layer and the deep electron acceptor layer (usually greater than or equal to 2 eV), a very high electron injection barrier is formed. The electron transport layer cannot generate enough free carriers to transfer to the deep electron acceptor layer, so it is difficult to form a sufficiently large interfacial potential difference to offset the energy level difference. Therefore, the carrier injection efficiency of the charge generation layer is low.

[0030] MOF (Metal-Organic Framework) materials are a class of porous materials formed by the coordination of metal ions or metal clusters with organic ligands. They possess highly porous structures, tunable pore sizes, and excellent chemical and thermal stability, thus finding wide applications in gas storage, separation, catalysis, sensing, and drug delivery.

[0031] The basic structure of MOF materials typically consists of two parts: a metal center and organic ligands.

[0032] Metal centers: Metal ions (such as zinc, copper, aluminum, iron, etc.) or metal clusters that are coordinated with organic ligands.

[0033] Organic ligands are typically organic molecules containing multiple coordination sites, such as phthalic acid, furan, and pyridine compounds. These molecules form coordination bonds with metal ions through their functional groups (such as carboxylic acid groups, pyridine groups, etc.).

[0034] Furthermore, MOF materials mainly have the following characteristics:

[0035] High specific surface area: MOF materials typically have a very high specific surface area (usually reaching thousands of m²). 2 ( / g), which makes them very effective in gas adsorption, storage and separation.

[0036] Porosity: Due to the arrangement of metal ions and organic ligands, MOF materials have adjustable pore sizes, which can be optimized for different molecular sizes and shapes, and are usually manifested as three-dimensional (3D) networks.

[0037] Adjustability: The structure and function of MOF materials can be precisely controlled by selecting different metal and organic ligands.

[0038] High stability: Many MOF materials exhibit excellent chemical and thermal stability, enabling them to operate in harsh environments.

[0039] Diversity: By selecting different metal ions and organic ligands, MOF materials can form countless different structures and chemical combinations.

[0040] Multifunctionality: MOF materials can be used not only as adsorbents, but also as catalysts, drug delivery systems, energy storage and conversion devices, etc.

[0041] Sustainability: The synthesis of MOF materials typically involves renewable metals and organic resources, and their porous nature helps to improve the efficiency of material use.

[0042] The study of MOF materials is an interdisciplinary field involving multiple disciplines such as chemistry, materials science, physics, and engineering. Their unique properties and potential applications are constantly being explored and developed.

[0043] Specifically, the applications of MOF materials in light-emitting devices:

[0044] As the light-emitting layer of light-emitting diodes: MOF materials are used to develop novel light-emitting diodes due to their unique optical properties. For example, white light emission can be achieved by combining the red emission of Eu-MOF with the blue, green, and yellow emission of metal halide perovskites; in addition, OX-2MOF has been tested as a potential electroluminescent material, contributing to the examples of electroluminescent MOFs.

[0045] As optical display materials, MOF materials can be used to prepare high-efficiency optical display materials due to their advantages such as high light transmittance, chemical stability, porosity and tunability.

[0046] As light-emitting detectors and sensors: MOF materials can be used to prepare highly sensitive optical sensors, enabling efficient conversion and storage of light, electricity, and magnetic energy; in addition, some MOF materials, such as photochromic Ln-MOFs, have potential applications in luminescent devices, including next-generation diode materials, optical and magnetic sensors, and ratio thermometers.

[0047] As electrochromic display devices: The electrochromic properties of MOF materials can be utilized to develop pixels for intelligent displays. For example, intelligent display pixels can be achieved by doping electrochromic guest molecules into MOF patterns.

[0048] As a photonic sensor: 2D diffraction gratings constructed using MOF materials can be used for gas sensing, which further expands the application of MOF materials in the field of photonic sensors.

[0049] As a flexible electronic device, flexible organic field-effect transistor (OFET) technology has shown broad prospects for application in fields such as flexible displays and flexible sensors due to its advantages such as foldability, light weight, and low manufacturing cost.

[0050] Based on the background technology described above, embodiments of this application provide a composite thin film, which aims to reduce the electron injection barrier of the composite thin film, thereby improving the carrier transport efficiency of the composite thin film.

[0051] Please see Figure 1 As shown, this application provides a composite film, including a first film 1 and a second film 2 stacked together, wherein the second film 2 is disposed on the first film 1.

[0052] In some embodiments, the first thin film comprises a MOF material and an electron transport material, wherein the conductivity of the MOF material is greater than or equal to 5 × 10⁻⁶. -3 S / m; In this embodiment, the conductivity of the first thin film 1 is greater than or equal to 10. - 4 S / m, the electron affinity of the first thin film 1 is less than or equal to 3.2 eV.

[0053] In some embodiments, the electron affinity of the second thin film 2 is greater than or equal to 4.7 eV.

[0054] The composite thin film provided in this application includes a first thin film and a second thin film stacked together. The first thin film is made of a high-conductivity MOF material and an electron transport material. The high conductivity of the MOF material improves the conductivity of the first thin film, thereby reducing the resistance within the first thin film and lowering the electron injection barrier between the first and second thin films. At the same time, the addition of the electron transport material assists in electron injection. Furthermore, the second thin film with high electron affinity promotes charge separation within the composite thin film, which is beneficial for the separation of electrons and holes, thereby improving both electron and hole injection efficiency. Furthermore, by setting the electron affinity of the first thin film 1, the electron injection barrier is reduced, thereby further improving the electron injection efficiency of the composite thin film. Since the first thin film 1 contains MOF material with high conductivity, the first thin film 1 has high conductivity, which is beneficial to reducing the electron injection barrier between the first thin film 1 and the second thin film 2 and reducing the resistance of the composite thin film, thus further improving the electron injection efficiency of the composite thin film. By setting the second thin film 2 with high electron affinity, charge separation within the composite thin film can be promoted, which is beneficial to the separation of electrons and holes, thereby improving the electron injection efficiency and hole injection efficiency. In summary, this application improves the carrier injection efficiency of the composite thin film by setting the first thin film 1 and the second thin film 2.

[0055] In some embodiments, the MOF material comprises cations and halide anions, wherein the cations have the following general structural formula:

[0056]

[0057] Wherein, R1 and R2 are each independently selected from one or more of substituted or unsubstituted C2-C10 alkenyl, C6-C30 aryl, and C5-C30 heteroaryl groups; R3 is selected from substituted or unsubstituted H, D, C1-C6 alkyl, C2-C10 alkenyl, C6-C30 aryl, and C5-C30 heteroaryl groups, wherein the heteroatom is selected from one or more of N, O, and S, the number of heteroatoms is less than or equal to 5, and the substituent is selected from halogen, hydroxyl, nitro, cyano, amino, amidine, hydrazine, hydrazone, carboxyl or its salt, sulfonyl or its salt, etc. One or more of the following: phosphoryl group or its salt, C1-C30 alkyl group, alkenyl group not exceeding C30, alkynyl group not exceeding C30, C6-C30 aryl group, C7-C20 aralkyl group, C2-C20 heteroaryl group, or C3-30 heteroaryl group; wherein R1 is cyclic with R2, and R1, R2, and C=N together constitute a heteroaryl group with 5-30 ring atoms; wherein R2 is cyclic with R3 or not cyclic; wherein X is selected from C atoms or N atoms; wherein L is selected from a single bond, an arylene group with 6-30 ring atoms, or a heteroarylene group with 5-30 ring atoms; wherein M is Os 2+ Or Ru 2+ n≥5; Halogen anions are selected from one or more of Cl, Br, and I.

[0058] In this embodiment, the cyclic formation of R1 and R2, and the cyclic formation of R2 and R3, protect the phenanthroline structure in the MOF material and improve the structural stability of the MOF material.

[0059] In this embodiment, M is Os complexed with two bipyridines. 2+ Ions, wherein bipyridine has the following general structural formula:

[0060]

[0061] Among them, Os 2+ The ion complexes with one of the two N atoms in the general structural formula of bipyridine described above.

[0062] Furthermore, based on the general structural formula described above, the cations of MOF materials are further explained:

[0063] In some embodiments, the cation in the MOF material is selected from one or more of the following structural formulas a to d, wherein in formulas a to d, 50 ≤ n ≤ 1000, and n is an integer; R4 in formula a is selected from H atoms, D atoms, alkyl groups of 1 to 8 carbon atoms, aryl groups of 6 to 30 carbon atoms, and heteroaryl groups of 5 to 30 carbon atoms; R5 and R6 in formula b are each independently selected from H atoms, D atoms, alkyl groups of 1 to 8 carbon atoms, aryl groups of 6 to 30 carbon atoms, and heteroaryl groups of 5 to 30 carbon atoms each time they appear:

[0064]

[0065]

[0066] In this embodiment, L can be selected from one or more of the following structures:

[0067]

[0068] Based on the general structural formula described above, in this embodiment, the anion of the MOF material is selected from bromide ions, and the cation of the MOF material is selected from one or more of the following formulas (1) to (24):

[0069]

[0070]

[0071]

[0072]

[0073]

[0074] In some embodiments, the mass-average molecular weight of the MOF material is 10000≤Mv≤200000. Specifically, the mass-average molecular weight of the MOF material can be set to 10000, 20000, 50000, 100000, 150000, or 200000.

[0075] In some embodiments, in the thin film 1, the mass ratio of the MOF material to the electron transport material is 5:1 to 1:5. Specifically, the mass ratio of the MOF material to the electron transport material can be set to any one of 5:1, 2:1, 1:1, 1:5 or a range between any two values.

[0076] This embodiment of the application sets the mass ratio of the MOF material to the electron transport material in the first thin film 1. By adding the MOF material, the conductivity of the composite first thin film 1 is increased, which reduces the resistance within the first thin film 1 and lowers the electron injection barrier between the first thin film 1 and the second thin film 2. At the same time, the addition of the electron transport material assists in achieving electron injection. Through the combination of the MOF material and the electron transport material, the electron injection efficiency of the first thin film 1 is improved.

[0077] In some embodiments, the electron transport material is selected from one or more of the following: quinoxaline compounds, imidazole compounds, triazine compounds, fluorene compounds, hydroxyquinoline compounds, phosphonooxide compounds, oxazole compounds, isoxazole compounds, borane compounds, pyridine compounds, benzimidazole compounds, acridine compounds, and phenanthroline compounds.

[0078] In some embodiments, the electron transport material may be selected from TV-TmPY (reference doi:10.1021 / acsphotonics.6b00882), B2PYMPM (CAS number 1266181-51-4), B4PYMPM (CAS number 1030380-51-8), B3PYPPM (CAS number 1382639-67-9), B4PYPPyPM (CAS number 1382639-70-4), B4P YPPM (CAS No. 1097652-83-9), Tm3PyP26PyB (CAS No. 1492917-78-8), TPyQB (CAS No. 1350742-68-5), TmPyPB (CAS No. 921205-03-0), BP4mPy (CAS No. 1009033-94-6), BmPyPhB (CAS No. 1030380-38-1), T3PyTRZ (CAS No. 27038) 50-25-1), 3P-T2T (CAS No. 352196-01-1), TPM-TAZ (CAS No. 1874199-82-2), HNBphen (CAS No. 923972-84-3), DBimiBphen (CAS No. 1447848-17-0), Bpy-OXD (CAS No. 866117-19-3), Bpy-TP2 (CAS No. 1394813-58-1), BIPO (CA S (CAS number 1426143-77-2), DPPS (CAS number 1152162-74-7), 3TPYMB (CAS number 929203-02-1), 2,4,6-tris(3-([2,3'-bipyridin]-6-yl)phenyl)-1,3,5-triazine, Tris(quinoline)chromium(III)complex (CAS number 27313-32-0), 1,3,4-Oxadiazole-based One or more of the following materials (CAS No. 519-73-3), DPFO (CAS No. 32598-51-3), Alq3 (CAS No. 72624-73-6), Isoxazole-based organic semiconductors (CAS No. 881818-07-1), Boron-dipyrromethene (BODIPY) derivatives (CAS No. 24059-98-5), Acridine orange (CAS No. 650-69-9), and N-Phenylphthalimide (CAS No. 119-84-6).

[0079] In some embodiments, the thickness of the first film 1 is 10 to 50 nm. Optionally, the thickness of the first film 1 can be set to 40 nm to 50 nm.

[0080] By adjusting the thickness of the first thin film 1, the embodiments of this application can reduce the resistance of the first thin film 1, thereby improving the electron injection efficiency of the first thin film 1.

[0081] In some embodiments, the second thin film 2 is a deep electron acceptor thin film, and the material of the second thin film 2 is selected from one or more of MoO3 nanoparticles, WO3 nanoparticles, molybdenum ethoxide, tungsten ethoxide, phosphomolybdic acid, phosphotungstic acid, ammonium metavanadate, ammonium metatungstate, ammonium molybdate, HATCN, F6TCNQ, CN6-CP, and NDP-9.

[0082] In some embodiments, the thickness of the second film 2 is 10-50 nm, and optionally, the thickness of the second film 2 can be set to 30 nm-40 nm.

[0083] In this embodiment, by setting the thickness of the second thin film 2, the electron injection barrier and electron injection efficiency of the second thin film 2 are adjusted, so as to avoid the electron injection efficiency being affected by the film being too thick.

[0084] Based on the composite film described above, this application also provides a method for preparing the composite film as described above.

[0085] Please see Figure 2 As shown, in some embodiments, the method for preparing the composite film includes the following steps:

[0086] Step S100: A first solution containing MOF material and electron transport material is provided, and the first solution is deposited to form a first thin film;

[0087] In this embodiment, the electrical conductivity of the MOF material is greater than or equal to 5 × 10⁻⁶. -3 The conductivity of the first thin film is greater than or equal to 10⁻⁴ S / m, and the electron affinity of the first thin film is less than or equal to 3.2 eV.

[0088] Step S200: Provide a second solution, deposit the second solution on the first film to form a second film, and obtain the composite film;

[0089] In this embodiment, the second thin film 2 is a deep electron acceptor film, and the electron affinity of the second thin film is greater than or equal to 4.7 eV.

[0090] The composite film preparation method provided in this application involves sequentially depositing a first film and a second film using a solution method to obtain the composite film. The preparation method is simple and has high preparation efficiency. At the same time, the composite film prepared by the preparation method of this application has good charge separation capability and good carrier injection efficiency.

[0091] In some embodiments, the first solution is prepared by the following steps:

[0092] We provide MOF materials and electron transport materials;

[0093] In this embodiment, the MOF material comprises cations and halide anions, wherein the cations have the following general structural formula:

[0094]

[0095] Wherein, R1 and R2 form a ring, and R1, R2, and C=N together constitute a heteroaryl group with 5 to 30 ring atoms; R2 and R3 may form a ring or not; X is selected from either C or N atoms; L is selected from a single bond, an arylene group with 6 to 30 ring atoms, or a heteroarylene group with 5 to 30 ring atoms; R1, R2, and R3 are unsubstituted or substituted by halogen atoms, hydroxyl, nitro, cyano, amino, amido, hydrazine, hydrazone, carboxyl or its salt, sulfonyl or its salt, phosphoryl or its salt, C1 to C30 alkyl, alkenyl not exceeding C30, alkynyl not exceeding C30, C6 to C30 aryl, C7 to C20 aralkyl, C2 to C20 heteroaryl, or C3 to C30 heteroaryl; M is an Os group that coordinates with the nitrogen atom on the heteroaryl group. 2+ Or Ru 2+ n≥5; Halogen anions are selected from one or more of Cl, Br, and I.

[0096] The electron transport material is selected from one or more of the following: quinoxaline compounds, imidazole compounds, triazine compounds, fluorene compounds, hydroxyquinoline compounds, phosphonates, oxazole compounds, isoxazole compounds, borane compounds, pyridine compounds, benzimidazole compounds, acridine compounds, and phenanthroline compounds. Optionally, the electron transport material includes TV-TmPY, B2PYMPM, B4PYMPM, B3PYPPM, B4PYPPyPM, B4PYPPM, Tm3PyP26PyB, TPyQB, TmPyPB, BP4mPy, and BmP. One or more of the following: yPhB, T3PyTRZ, 3P-T2T, TPM-TAZ, HNBphen, DBimiBphen, Bpy-OXD, Bpy-TP2, BIPO, DPPS, 3TPYMB, 2,4,6-tris(3-([2,3'-bipyridine]-6-yl)phenyl)-1,3,5-triazine, Tris(quinoline)chromium(III)complex, 1,3,4-Oxadiazole-based materials, DPFO, Alq3, Isoxazole-based organic semiconductors, Boron-dipyrromethene(BODIPY)derivatives, Acridine orange, and N-Phenylphthalimide.

[0097] In an inert gas atmosphere, the MOF material and the electron transport material are dispersed in a dispersant at a set mass ratio to obtain the first solution;

[0098] In this embodiment, the inert gas atmosphere can be selected from nitrogen, helium, neon, or argon.

[0099] The set mass ratio is 5:1 to 1:5. Specifically, the set mass ratio can be set to any one of 5:1, 2:1, 1:1, 1:5 or a range formed between any two values.

[0100] The dispersant is selected from one or more of alcohol solvents, ether solvents, and ketone solvents. The alcohol solvent is selected from one or more of ethanol, isopropanol, n-butanol, 2-butanol, cyclohexanol, ethylene glycol, glycerol, butanediol, pentanediol, n-hexanol, heptanol, and thiols. The thiols are selected from ethylene glycol di-3-mercaptopropionate, ethylene glycol dimercaptoacetate, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), and pentaerythritol. Tetra(2-mercaptoacetate), 1,6-hexanedithiol, 1,3-propanedithiol, 1,2-ethylenedithiol, and polyethylene glycol dithiols containing 1-10 ethylene glycol repeating units; ether solvents are selected from one or more of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, and ethylene glycol di-n-butyl ether; ketone solvents are selected from one or more of cyclohexanone, cyclopentanone, and isophorone.

[0101] The first solution prepared by the first solution preparation method provided in this application improves the conductivity of the first thin film by adding MOF material in a set mass ratio, thereby reducing the resistance within the first thin film and lowering the electron injection barrier between the first and second functions; adding electron transport material in a set mass ratio assists in achieving electron injection; and the combination of MOF material and electron transport material improves the electron injection efficiency of the first thin film prepared from the first solution.

[0102] Based on the composite thin film and the method for preparing the composite thin film as described above, this application also provides a light-emitting device, wherein the light-emitting device is a stacked light-emitting device.

[0103] Please see Figure 3 As shown, in some embodiments, this application provides a light-emitting device, which includes an anode 100 and a cathode 500 disposed opposite to each other, and at least two layers of light-emitting units stacked between the anode 100 and the cathode 500.

[0104] Furthermore, the light-emitting device also includes an intermediate layer 300 disposed between two adjacent light-emitting units, wherein the intermediate layer 300 is a composite film as described above or prepared by the composite film preparation method described above.

[0105] In this embodiment, the light-emitting device includes two light-emitting units, namely a first light-emitting unit 200 disposed near the anode 100 and a second light-emitting unit 400 disposed near the cathode 500, and the intermediate layer 300 is located between the first light-emitting unit 200 and the second light-emitting unit 400.

[0106] In this embodiment, the light-emitting device is an upright light-emitting device. The first light-emitting unit 200 includes a first hole injection layer 201, a first hole transport layer 202, a first light-emitting layer 203, and a first electron transport layer 204 stacked sequentially from bottom to top. The second light-emitting unit 400 includes a second hole injection layer 401, a second hole transport layer 402, a second light-emitting layer 403, and a second electron transport layer 404 stacked sequentially from bottom to top. Optionally, the light-emitting device includes an anode 100, a first hole injection layer 201, a first hole transport layer 202, a first light-emitting layer 203, a first electron transport layer 204, an intermediate layer 300, a second hole injection layer 401, a second hole transport layer 402, a second light-emitting layer 402, a second electron transport layer 404, and a cathode 500 stacked sequentially from bottom to top. The intermediate layer 300 includes the composite thin film described above.

[0107] In some embodiments, the composite film includes a first film 1 and a second film 2, wherein the first film 1 is located on the side closer to the anode 100 and the second film 2 is located on the side closer to the cathode 500.

[0108] In this embodiment, the first thin film 1 is disposed on the first electron transport layer 204, and the second thin film 2 is located between the first thin film 1 and the second hole injection layer 401.

[0109] The light-emitting device provided in this embodiment uses the aforementioned composite thin film as an intermediate layer 300. By stacking the first thin film 1 and the second thin film 2, the resistance of the composite thin film and the electron injection barrier are reduced, thereby improving the electron injection efficiency from the intermediate layer 300 to the first light-emitting unit 200. Furthermore, by setting the electron affinity of the first thin film 1, the electron injection barrier is reduced, thereby improving the electron injection efficiency of the composite thin film. Since the first thin film 1 is made of a high-conductivity MOF material and an electron transport material, the high conductivity of the first thin film 1 is beneficial for reducing the electron injection barrier between the first thin film 1 and the first light-emitting unit 200. The electron injection barrier between the two thin films 2 and the reduced resistance of the composite thin film further improve the electron injection efficiency of the intermediate layer 300 to the first light-emitting unit 200. By setting the second thin film 2 with high electron affinity, charge separation within the composite thin film can be promoted, which is beneficial for the separation of electrons and holes, thereby improving the electron injection efficiency of the intermediate layer 300 to the first light-emitting unit 200 and the hole injection efficiency of the intermediate layer 300 to the second light-emitting unit 400. In summary, this application improves the carrier injection efficiency of the intermediate layer 300 to the light-emitting units on both sides by setting the first thin film 1 and the second thin film 2.

[0110] In some embodiments, the materials of the anode 100 and / or cathode 500 include one or more of metals, carbon materials, and metal oxides. The metals include one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, Yb, and Mg. The carbon materials include one or more of graphite, carbon nanotubes, graphene, and carbon fibers. The metal oxides include doped or undoped metal oxides, including one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO, or composite electrodes consisting of metal sandwiched between doped or undoped transparent metal oxides. The composite electrodes include one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2.

[0111] The materials of the first hole injection layer 201 and / or the second hole injection layer 401 and / or the first hole transport layer 202 and / or the second hole transport layer 402 include one or more of TFB, CuPc, PVK, Poly-TPD, PFB, DNTPD, TCATA, TCCA, CBP, TPD, NPB, NPD, PEDOT:PSS, TAPC, MCC, F4-TCNQ, HATCN, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, polyaniline, transition metal oxides, transition metal sulfides, transition metal tin compounds, doped graphene, undoped graphene, and C60.

[0112] The first light-emitting layer 203 and / or the second light-emitting layer 403 are quantum dot light-emitting layers or organic light-emitting layers; wherein, the material of the quantum dot light-emitting layer includes one or more of single-structure quantum dots and core-shell structure quantum dots, the material of the single-structure quantum dots, the core material of the core-shell structure quantum dots, and the shell material of the core-shell structure quantum dots are respectively selected from one or more of group II-VI compounds, group IV-VI compounds, group III-V compounds, and group I-III-VI compounds, and the shell of the core-shell structure quantum dots includes one or more layers; wherein, group II-VI compounds include, but are not limited to, CdS, CdSe, CdTe, ZnS, ZnSe, ZnO ... nTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, Cd One or more of HgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe and HgZnSTe, group IV-VI The compounds include, but are not limited to, one or more of SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, and SnPbSTe. III-V group compounds include, but are not limited to, GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, and Al One or more of NP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, and InAlPSb, and group I-III-VI compounds including but not limited to one or more of CuInS2, CuInSe2, and AgInS2;The organic light-emitting layer is made of one or more of the following materials: 4,4'-bis(N-carbazole)-1,1'-biphenyl:tris[2-(p-tolyl)pyridine-C2,N)iridium(III), 4,4',4”-tris(carbazole-9-yl)triphenylamine:tris[2-(p-tolyl)pyridine-C2,N)iridium, diaromatic anthracene derivatives, stilbene aromatic derivatives, pyrene derivatives, fluorene derivatives, TBPe fluorescent materials, TTPX fluorescent materials, TBRb fluorescent materials and DBP fluorescent materials, polyacetylene and its derivatives, poly(p-phenylene) and its derivatives, polythiophene and its derivatives, and polyfluorene and its derivatives.

[0113] The first electron transport layer 204 and / or the second electron transport layer 404 comprise inorganic or organic materials; wherein the inorganic material is selected from one or more of the following: doped or undoped zinc oxide, barium oxide, aluminum oxide, nickel oxide, titanium oxide, tin oxide, tantalum oxide, zirconium oxide, nickel oxide, lithium titanium oxide, zinc aluminum oxide, zinc manganese oxide, zinc tin oxide, zinc lithium oxide, indium tin oxide, cadmium sulfide, zinc sulfide, molybdenum sulfide, tungsten sulfide, copper sulfide, zinc tin sulfide, indium phosphide, gallium phosphide, copper indium sulfide, copper gallium sulfide, and barium titanate; and the doped elements include one or more of aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, and gadolinium; and the organic material is selected from one or more of the following: quinoxaline compounds, imidazole compounds, triazine compounds, fluorene-containing compounds, hydroxyquinoline compounds, and phosphine oxide compounds.

[0114] This application also provides a display device, which includes the above-described light-emitting device.

[0115] The display device can be any electronic product with display function, including but not limited to smartphones, tablets, laptops, digital cameras, digital camcorders, smart wearable devices, smart weighing scales, in-vehicle displays, televisions, or e-book readers. Among them, smart wearable devices can be, for example, smart bracelets, smartwatches, virtual reality (VR) headsets, etc.

[0116] The present application will be specifically described below through specific embodiments. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.

[0117] Composite Thin Film Example 1

[0118] Step (1): Provide a substrate;

[0119] Step (2) provides MOF material and TV-TmPY, wherein the MOF material comprises a cation and a bromide anion, and the structural formula of the cation is as follows:

[0120]

[0121] The mass-average molecular weight of the MOF material is 100,000. For detailed information on the preparation method of the MOF material, please refer to the following reference: doi:10.1021 / jp0109325;

[0122] Step (3): 2 mg of MOF material and 1 mg of TV-TmPY were dispersed in 0.3 ml of butanol at room temperature (25 °C) and under a nitrogen atmosphere, and stirred for 0.5 h to obtain the first solution;

[0123] Step 4: Spin-coat the first solution onto the substrate, bake it at 120°C for 30 min in a nitrogen atmosphere to form a first film with a thickness of 50 nm;

[0124] Step (5) provides a second solution, wherein the second solution is formed by dissolving phosphomolybdic acid in acetonitrile, spin-coating the second solution onto the first film, and baking at 80°C for 5 min to form a second film with a thickness of 30 nm, thereby obtaining the composite film.

[0125] Composite film Example 2

[0126] The difference between this embodiment and the composite film embodiment 1 is that in step (3), 1 mg of MOF material and 1 mg of TV-TmPY are dispersed in 0.3 ml of butanol at room temperature (25°C) and in a nitrogen atmosphere, and stirred for 0.5 h to obtain the first solution.

[0127] Composite film Example 3

[0128] The difference between this embodiment and the composite film embodiment 1 is that in step (3), 5 mg of MOF material and 1 mg of TV-TmPY are dispersed in 0.3 ml of butanol at room temperature (25°C) and in a nitrogen atmosphere, and stirred for 0.5 h to obtain the first solution.

[0129] Composite film Example 4

[0130] The difference between this embodiment and the composite film embodiment 1 is that in step (3), 1 mg of MOF material and 5 mg of TV-TmPY are dispersed in 0.3 ml of butanol at room temperature (25°C) and in a nitrogen atmosphere, and stirred for 0.5 h to obtain the first solution.

[0131] Composite film Example 5

[0132] The difference between this embodiment and the composite film embodiment 1 is that the structural formula of the MOF material in step (2) is as follows:

[0133]

[0134] The mass-average molecular weight of the MOF material is 100,000. For detailed information on the preparation method of the MOF material, please refer to the following reference: doi:10.1021 / jp0109325.

[0135] Composite film Example 6

[0136] The difference between this embodiment and the composite film embodiment 1 is that the structural formula of the MOF material in step (2) is as follows:

[0137]

[0138] The mass-average molecular weight of the MOF material is 100,000. For detailed information on the preparation method of the MOF material, please refer to the following reference: doi:10.1021 / jp0109325.

[0139] Composite film Example 7

[0140] The difference between this embodiment and the composite film embodiment 1 is that in step (5), the second solution is formed by dissolving MoO3 nanoparticles in acetonitrile, wherein the particle size of the MoO3 nanoparticles is 5 nm.

[0141] Composite film comparative example 1

[0142] Step (1): Provide a substrate;

[0143] Step (2) provides MOF material and TV-TmPY, wherein the structural formula of the MOF material is as follows:

[0144]

[0145] The mass-average molecular weight of the MOF material is 100,000. For detailed information on the preparation method of the MOF material, please refer to the following reference: doi:10.1021 / jp0109325;

[0146] Step (3): 2 mg of MOF material and 1 mg of TV-TmPY material were dispersed in 3 ml of butanol at room temperature (25 °C) and under a nitrogen atmosphere, and stirred for 0.5 h to obtain the first solution.

[0147] Step 4: Spin-coat the first solution onto the substrate, bake it in a nitrogen atmosphere at 120°C for 30 min to form a first thin film with a thickness of 50 nm, and obtain the composite film.

[0148] Composite film comparative example 2

[0149] Step (1): Provide a substrate;

[0150] Step (2): A second solution is provided, wherein the second solution is formed by dissolving phosphomolybdic acid in acetonitrile. The second solution is spin-coated onto the substrate and baked at 80°C for 5 min to form a second film with a thickness of 30 nm, thereby obtaining the composite film.

[0151] The composite films prepared in Examples 1-7, Comparative Examples 1 and 2 were used as intermediate layers to fabricate test devices. The electron injection capability of each test device was tested, and the results are shown in Table 1. (The structure of the test device is: ITO / intermediate layer / cathode)

[0152] The electron injection capability test is performed by testing the IV properties of the composite thin film, wherein the test device operates at a current density of 10 mA / cm². 2 The driving voltage at that time was recorded.

[0153] Drive voltage (V) Composite Thin Film Example 1 2.1 Composite film Example 2 2.9 Composite film Example 3 2.0 Composite film Example 4 3.7 Composite film Example 5 2.1 Composite film Example 6 2.1 Composite film Example 7 2.0 Composite film comparative example 1 1.9 Composite film comparative example 2 7.4

[0154] Table 1

[0155] Based on the test results of composite thin film Examples 1-7 and Composite Thin Film Comparative Example 2, it can be seen that the driving voltage of the test devices prepared in Composite Thin Film Examples 1-7 is lower than that of the test device prepared in Composite Thin Film Comparative Example 2.

[0156] Based on the test results of Composite Thin Film Example 1, Composite Thin Film Examples 5-7 and Composite Thin Film Comparative Example 1, it can be seen that the driving voltage of the test device in Composite Thin Film Example 1 and Composite Thin Film Examples 5-7 is basically the same as the driving voltage of the test device in Composite Thin Film Comparative Example 1.

[0157] According to the test results of composite thin film Examples 1 to 4, it can be seen that as the mass ratio of MOF material in the first thin film increases, the driving voltage gradually decreases.

[0158] Therefore, it can be seen that setting a composite film including a first film and a second film can reduce the voltage of the test device. However, as the mass ratio of MOF material in the first film increases, the driving voltage gradually decreases. Therefore, it can be seen that the composite film includes a first film and a second film, and by increasing the mass ratio of MOF material, the conductivity in the composite film can be increased and the resistance in the composite film can be reduced. In addition, the second film does not affect the conductivity of the first film.

[0159] Example 1 of light-emitting device

[0160] Step (1): Provide an ITO anode substrate, clean it, and then treat it under UV conditions for 15 minutes;

[0161] Step (2): Print PEDOT:PSS solution onto the anode by inkjet printing. After drying into a film, bake at 150°C in air for 20 minutes to form a first hole injection layer with a thickness of 45 nm.

[0162] Step (3): Print TFB solution onto the first hole injection layer by inkjet printing. After drying to form a film, bake at 180°C for 60 minutes in a nitrogen atmosphere to form a 20nm thick first hole transport layer.

[0163] Step 4: Spin-coat polymer material F8BT onto the first hole transport layer, dry it to form a film, and then bake it at 130°C for 10 minutes to form a 60nm thick first light-emitting layer.

[0164] Step 5: LiF is deposited onto a substrate by vapor deposition to form the first light-emitting layer, forming a first electron transport layer with a thickness of 1 nm.

[0165] Step 6: Using the preparation method of the composite thin film in Example 1, an 80 nm thick intermediate layer is formed on the first electron transport layer. The intermediate layer includes a 50 nm thick first thin film and a 30 nm thick second thin film stacked together.

[0166] Step 7: Print PEDOT:PSS solution onto the intermediate layer by inkjet printing, dry it into a film, and bake it at 150°C in air for 20 minutes to form a second hole injection layer with a thickness of 45nm.

[0167] Step 8: Inkjet print TFB solution onto the second hole injection layer, dry it to form a film, and then bake it at 180°C for 60 minutes in a nitrogen atmosphere to form a 20nm thick second hole transport layer.

[0168] Step 9: Spin-coat polymer material F8BT onto the second hole transport layer, dry it to form a film, and then bake it at 130°C for 10 minutes to form a 60nm thick second light-emitting layer.

[0169] Step 10: LiF is deposited onto the substrate by vapor deposition to form a second light-emitting layer, forming a second electron transport layer with a thickness of 1 nm.

[0170] Step 11: Al is deposited onto the second electron transport layer by vapor deposition to form a cathode with a wavelength of 100 nm.

[0171] Example 2 of light-emitting device

[0172] The difference between this embodiment and the first embodiment of the light-emitting device is that, in step 6, an 80 nm thick intermediate layer is formed on the first electron transport layer using the preparation method of the upper composite thin film embodiment 2. The intermediate layer includes a 50 nm thick first thin film and a 30 nm thick second thin film stacked together.

[0173] Example 3 of light-emitting device

[0174] The difference between this embodiment and the light-emitting device embodiment 1 is that, in step 6, an 80 nm thick intermediate layer is formed on the first electron transport layer using the preparation method of the upper composite thin film embodiment 3. The intermediate layer includes a 50 nm thick first thin film and a 30 nm thick second thin film stacked together.

[0175] Example 4 of light-emitting device

[0176] The difference between this embodiment and the light-emitting device embodiment 1 is that, in step 6, an 80 nm thick intermediate layer is formed on the first electron transport layer using the preparation method of the upper composite thin film embodiment 4. The intermediate layer includes a 50 nm thick first thin film and a 30 nm thick second thin film stacked together.

[0177] Example 5 of light-emitting device

[0178] The difference between this embodiment and the light-emitting device embodiment 1 is that, in step 6, an 80 nm thick intermediate layer is formed on the first electron transport layer using the preparation method of the upper composite thin film embodiment 5. The intermediate layer includes a 50 nm thick first thin film and a 30 nm thick second thin film stacked together.

[0179] Example 6 of light-emitting device

[0180] The difference between this embodiment and the light-emitting device embodiment 1 is that, in step 6, an 80 nm thick intermediate layer is formed on the first electron transport layer using the preparation method of the upper composite thin film embodiment 6. The intermediate layer includes a 50 nm thick first thin film and a 30 nm thick second thin film stacked together.

[0181] Example 7 of light-emitting device

[0182] The difference between this embodiment and the light-emitting device embodiment 1 is that, in step 6, an 80 nm thick intermediate layer is formed on the first electron transport layer using the preparation method of the upper composite thin film embodiment 7. The intermediate layer includes a 50 nm thick first thin film and a 30 nm thick second thin film stacked together.

[0183] Comparative Example 1 of Light Emitting Devices

[0184] The difference between this embodiment and embodiment 1 of the light-emitting device is that, in step 6, a 50 nm thick intermediate layer is formed on the first electron transport layer using the preparation method of comparative example 1 of the upper composite thin film, and the intermediate layer includes the first thin film.

[0185] Comparative Example 2 of Light Emitting Devices

[0186] The difference between this embodiment and embodiment 1 of the light-emitting device is that, in step 6, a 30 nm thick intermediate layer is formed on the first electron transport layer using the preparation method of comparative example 2 of the upper composite thin film, and the intermediate layer includes a second thin film.

[0187] The driving voltage, current efficiency, and working life of the light-emitting devices prepared in Examples 1 to 7, Comparative Examples 1 and 2 were tested respectively. The test results are shown in Table 2.

[0188] The performance (driving voltage, current efficiency) of the light-emitting device is tested using an IVL (Inductively Coupled Light) instrument, specifically at a current density of 10 mA / cm². 2 The voltage at which the device is tested is used as the driving voltage evaluation index, and the current efficiency when the brightness of the device is 1000 nits is used as the current efficiency evaluation index. The working life of the device is measured using a life aging device, and the time when the brightness of the light-emitting device decays to 95% under constant current conditions from an initial brightness of 1000 nits is used as the working life evaluation index.

[0189]

[0190]

[0191] Table 2

[0192] Based on the test results of Examples 1-7 and Comparative Example 2, it can be seen that the driving voltage of the light-emitting devices prepared in Examples 1-7 is lower than that of the light-emitting device prepared in Comparative Example 2, the current efficiency of the light-emitting devices prepared in Examples 1-7 is higher than that of the light-emitting device prepared in Comparative Example 2, and the working life of the light-emitting devices prepared in Examples 1-7 is longer than that of the light-emitting device prepared in Comparative Example 2.

[0193] Based on the test results of Examples 1 to 7 and Comparative Example 1, it can be seen that the working life of the light-emitting devices prepared in Examples 1 to 7 is longer than that of the light-emitting device prepared in Comparative Example 1.

[0194] According to the test results of embodiments 1 to 4 of the light-emitting device, as the mass ratio of the electron transport material in the first thin film increases, the driving voltage increases, and the current efficiency and working life decrease.

[0195] In summary, the composite thin film provided in this application, through the stacking of the first and second thin films, reduces the resistance and electron injection barrier of the composite thin film, thereby improving the electron injection efficiency. Furthermore, by adjusting the mass ratio of MOF material to electron transport material in the first thin film, the electron injection barrier is lowered, improving the electron injection efficiency and conductivity of the composite thin film. This is beneficial for reducing the electron injection barrier between the first and second thin films and lowering the resistance of the composite thin film, thus improving the electron injection efficiency. By further setting a second thin film with high electron affinity, charge separation within the composite thin film can be promoted, which is beneficial for the separation of electrons and holes, thereby improving both electron and hole injection efficiency.

[0196] Obviously, the embodiments described above are only some embodiments of this application, not all embodiments. The accompanying drawings show preferred embodiments of this application, but do not limit the patent scope of this application. This application can be implemented in many different forms; rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this application's specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the scope of patent protection of this application.

Claims

1. A composite film, characterized in that, Includes a first film and a second film stacked together; The first thin film comprises a MOF material and an electron transport material, wherein the conductivity of the MOF material is greater than or equal to 5 × 10⁻⁶. -3 S / m; The electron affinity of the second thin film is greater than or equal to 4.7 eV.

2. The composite film according to claim 1, characterized in that, The MOF material comprises cations and halide anions, wherein the cations have the following general structural formula: R1 and R2 are each independently selected from one or more of substituted or unsubstituted C2-C10 alkenyl, C6-C30 aryl, and C5-C30 heteroaryl groups; R3 is selected from substituted or unsubstituted H, D, C1-C6 alkyl, C2-C10 alkenyl, C6-C30 aryl, and C5-C30 heteroaryl groups, wherein the heteroatom is selected from one or more of N, O, and S, the number of heteroatoms is less than or equal to 5, and the substituent is selected from halogen, hydroxyl, and nitro groups. One or more of the following: cyano, amino, amido, hydrazine, hydrazone, carboxyl or its salt, sulfonyl or its salt, phosphoryl or its salt, C1-C30 alkyl, alkenyl not exceeding C30, alkynyl not exceeding C30, C6-C30 aryl, C7-C20 aralkyl, C2-C20 heteroaryl, or C3-30 heteroaryl; wherein R1 is cyclic with R2, and R1, R2, and C=N together constitute a heteroaryl group with 5-30 ring atoms; wherein R2 is cyclic with R3 or not cyclic; X is selected from either C or N atoms; L is selected from single bonds, arylene groups with 6 to 30 ring atoms, or heteroarylene groups with 5 to 30 ring atoms; M is Os 2+ Or Ru 2+ ; n≥5； The halogen anion is selected from one or more of Cl, Br, and I.

3. The composite film according to claim 2, characterized in that, The cations in the MOF material are selected from one or more of the following structural formulas a to d, wherein... In equations a to d, 50 ≤ n ≤ 1000, and n is an integer; In formula a, R4 is selected from H atoms, D atoms, alkyl groups with 1 to 8 carbon atoms, aryl groups with 6 to 30 carbon atoms, and heteroaryl groups with 5 to 30 carbon atoms; In formula b, R5 and R6 are each independently selected from H atoms, D atoms, alkyl groups with 1 to 8 carbon atoms, aryl groups with 6 to 30 carbon atoms, and heteroaryl groups with 5 to 30 carbon atoms.

4. The composite film according to claim 3, characterized in that, The cations in the MOF material are selected from one or more of the following formulas (1) to (24):

5. The composite film according to any one of claims 2 to 4, characterized in that, The mass-average molecular weight of the MOF material is 10000≤Mv≤200000.

6. The composite film according to claim 1, characterized in that, In the first thin film, the mass ratio of the MOF material to the electron transport material is 5:1 to 1:5; and / or, The electron transport material is selected from one or more of the following: quinoxaline compounds, imidazole compounds, triazine compounds, fluorene compounds, hydroxyquinoline compounds, phosphonates, oxazole compounds, isoxazole compounds, borane compounds, pyridine compounds, benzimidazole compounds, acridine compounds, and phenanthroline compounds. Optionally, the electron transport material includes TV-TmPY, B2PYMPM, B4PYMPM, B3PYPPM, B4PYPPyPM, B4PYPPM, Tm3PyP26PyB, and TPyQB. One or more of the following: TmPyPB, BP4mPy, BmPyPhB, T3PyTRZ, 3P-T2T, TPM-TAZ, HNBphen, DBimiBphen, Bpy-OXD, Bpy-TP2, BIPO, DPPS, 3TPYMB, 2,4,6-tris(3-([2,3'-bipyridinyl]-6-yl)phenyl)-1,3,5-triazine, Tris(quinoline)chromium(III)complex, 1,3,4-Oxadiazole-based materials, DPFO, Alq3, Isoxazole-based organic semiconductors, Boron-dipyrromethene(BODIPY)derivatives, Acridine orange, N-Phenylphthalimide; and / or, The material of the second thin film is selected from one or more of MoO3 nanoparticles, WO3 nanoparticles, molybdenum ethoxide, tungsten ethoxide, phosphomolybdic acid, phosphotungstic acid, ammonium metavanadate, ammonium metatungstate, ammonium molybdate, HATCN, F6TCNQ, CN6-CP, and NDP-9; and / or, The thickness of the first thin film is 10 nm to 50 nm, optionally, the thickness of the first thin film is 40 nm to 50 nm; and / or, The thickness of the second thin film is 10 nm to 50 nm, optionally, the thickness of the second thin film is 30 nm to 40 nm and / or, The conductivity of the first thin film is greater than or equal to 10. -4 S / m; and / or, The electron affinity of the first thin film is less than or equal to 3.2 eV.

7. A method for preparing a composite thin film, characterized in that, Includes the following steps: A first solution comprising MOF material and electron transport material is provided, and the first solution is deposited to form a first thin film; A second solution is provided, and the second solution is deposited on the first film to form a second film, thereby obtaining the composite film.

8. The method for preparing the composite thin film according to claim 7, characterized in that, The first solution is prepared by the following steps: We provide MOF materials and electron transport materials; In an inert gas atmosphere, the MOF material and the electron transport material are dispersed in a dispersant at a set mass ratio to obtain the first solution.

9. The method for preparing the composite thin film according to claim 8, characterized in that, The set mass ratio is 5:1 to 1:5; and / or, The dispersant is selected from one or more of alcohol solvents, ether solvents, and ketone solvents. The alcohol solvent is selected from one or more of ethanol, isopropanol, n-butanol, 2-butanol, cyclohexanol, ethylene glycol, glycerol, butanediol, pentanediol, n-hexanol, heptanol, and thiols. The thiols are selected from ethylene glycol di-3-mercaptopropionate, ethylene glycol dimercaptoacetate, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), and pentaerythritol. Tetra(2-mercaptoacetate), 1,6-hexanedithiol, 1,3-propanedithiol, 1,2-ethylenedithiol, and polyethylene glycol dithiols containing 1-10 ethylene glycol repeating units; ether solvents are selected from one or more of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, and ethylene glycol di-n-butyl ether; ketone solvents are selected from one or more of cyclohexanone, cyclopentanone, and isophorone.

10. A light-emitting device, characterized in that, It includes an anode and a cathode arranged opposite to each other, and at least two layers of light-emitting units stacked between the anode and the cathode; The light-emitting device further includes an intermediate layer disposed between two adjacent light-emitting units, wherein the intermediate layer is the composite film according to any one of claims 1 to 6 or is prepared by the method of preparing the composite film according to any one of claims 7 to 9.

11. The light-emitting device according to claim 10, characterized in that, The composite film includes a first film and a second film, wherein the first film is located near the anode and the second film is located near the cathode.

12. The light-emitting device according to claim 10, characterized in that, The light-emitting unit includes a stacked hole functional layer, a light-emitting layer, and an electronic functional layer; The anode and / or cathode materials include one or more of metals, carbon materials, and metal oxides. The metals include one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, Yb, and Mg. The carbon materials include one or more of graphite, carbon nanotubes, graphene, and carbon fibers. The metal oxides include doped or undoped metal oxides, including one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO, or composite electrodes consisting of metal sandwiched between doped or undoped transparent metal oxides. These composite electrodes include one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2; and / or... The hole functional layer includes a hole transport layer and / or a hole injection layer, wherein the material of the hole transport layer and / or hole injection layer includes one or more of the following: TFB, CuPc, PVK, Poly-TPD, PFB, DNTPD, TCATA, TCCA, CBP, TPD, NPB, NPD, PEDOT:PSS, TAPC, MCC, F4-TCNQ, HATCN, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, polyaniline, transition metal oxides, transition metal sulfides, transition metal tin compounds, doped graphene, undoped graphene, and C60; and / or, The light-emitting layer is a quantum dot light-emitting layer or an organic light-emitting layer; wherein, the material of the quantum dot light-emitting layer includes one or more of single-structure quantum dots and core-shell structure quantum dots, the material of the single-structure quantum dots, the core material of the core-shell structure quantum dots, and the shell material of the core-shell structure quantum dots are respectively selected from one or more of group II-VI compounds, group IV-VI compounds, group III-V compounds, and group I-III-VI compounds, and the shell of the core-shell structure quantum dots includes one or more layers; wherein, group II-VI compounds include, but are not limited to, CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, and Hg. One or more of Se, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, and HgZnSTe, and group IV-VI compounds include, but are not limited to, those... One or more of SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, and SnPbSTe, and III-V compounds including but not limited to GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, and A One or more of the following compounds: lNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, and InAlPSb; and group I-III-VI compounds, including but not limited to one or more of CuInS2, CuInSe2, and AgInS2.The organic light-emitting layer is made of one or more of the following materials: 4,4'-bis(N-carbazole)-1,1'-biphenyl:tris[2-(p-tolyl)pyridine-C2,N)iridium (II), 4,4',4”-tris(carbazole-9-yl)triphenylamine:tris[2-(p-tolyl)pyridine-C2,N)iridium, diaromatic anthracene derivatives, stilbene aromatic derivatives, pyrene derivatives, fluorene derivatives, TBPe fluorescent materials, TTPX fluorescent materials, TBRb fluorescent materials and DBP fluorescent materials, polyacetylene and its derivatives, poly(p-phenylene) and its derivatives, polythiophene and its derivatives, and polyfluorene and its derivatives; and / or, The electronic functional layer includes an electron transport layer and / or an electron injection layer, wherein the electron transport layer and / or electron injection layer comprises inorganic or organic materials; wherein the inorganic material is selected from one or more of the following: doped or undoped zinc oxide, barium oxide, aluminum oxide, nickel oxide, titanium oxide, tin oxide, tantalum oxide, zirconium oxide, nickel oxide, lithium titanium oxide, zinc aluminum oxide, zinc manganese oxide, zinc tin oxide, zinc lithium oxide, indium tin oxide, cadmium sulfide, zinc sulfide, molybdenum sulfide, tungsten sulfide, copper sulfide, zinc tin sulfide, indium phosphide, gallium phosphide, copper indium sulfide, copper gallium sulfide, and barium titanate; and the doped elements include one or more of aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, and gadolinium; and the organic material is selected from one or more of the following: quinoxaline compounds, imidazole compounds, triazine compounds, fluorene-containing compounds, hydroxyquinoline compounds, and phosphine oxide compounds.

13. The light-emitting device according to claim 10, characterized in that, The light-emitting device is a positive light-emitting device, and the light-emitting device includes an anode, a first hole injection layer, a first hole transport layer, a first light-emitting layer, a first electron transport layer, an intermediate layer, a second hole injection layer, a second hole transport layer, a second light-emitting layer, a second electron transport layer, and a cathode, which are stacked sequentially from bottom to top. The intermediate layer includes the composite thin film according to any one of claims 1 to 6.

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

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