Composite film layer and preparation method thereof and light emitting diode

Abstract

The present application relates to the field of display technology, and provides a composite film layer, a preparation method thereof, and a light-emitting diode. The composite film layer provided in the present application includes: at least one metal organic framework material layer and at least one quantum dot layer, the quantum dot layer and the metal organic framework material layer are stacked, the surface of the metal organic framework material layer contains active functional groups, the surface of the quantum dot layer contains cations, and at least part of the active functional groups are connected to at least part of the cations. In this way, the metal organic framework material layer is connected to the quantum dot layer through the active functional groups, so that the quantum dots in the quantum dot layer can be tightly anchored on the surface of the metal organic framework material layer, so that the quantum dot particles are tightly connected, and the quantum dot layer is dense, thereby forming a dense and uniform film layer with high flatness.

Description

Technical Field

[0001] The present application belongs to the field of display technology, and in particular relates to a composite film layer and a preparation method thereof, and a light emitting diode. Background Art

[0002] Quantum dots are a typical nanomaterial, whose radius is usually smaller than or close to the exciton Bohr radius, showing a significant quantum dot confinement effect and unique optical properties, such as long life, narrow emission spectrum, controllable emission wavelength, high quantum yield, excellent monodispersity and strong photothermal stability. With the continuous improvement of the performance of quantum dot materials themselves and the continuous optimization and improvement of other functional layers, the performance of quantum dot light emitting diodes (QLEDs) has been continuously improved, so that the external quantum efficiency of most red, green and blue QLED devices has exceeded 20%, and the life span has basically met the needs of commercial applications.

[0003] The performance of the quantum dot film layer will significantly restrict the performance of the entire light-emitting device, and the preparation method of the quantum dot film layer affects the performance of the quantum dot film layer. Quantum dot materials often have good solution processing properties. The existing method mainly uses a spin coating method to coat the quantum dot solution on the substrate and form a quantum dot film layer after the solvent evaporates. However, after film formation, the connection between the quantum dot particles is not tight, and the film layer is relatively loose. The deposited quantum dots are easily driven by the solvent during the solvent evaporation process to produce local aggregation, or are redissolved and carried away or directly washed away during the solution film formation process of the subsequent film layer, resulting in uneven quantum dot film layer and poor flatness. Summary of the invention

[0004] The purpose of the present application is to provide a composite film layer and a preparation method thereof, aiming to solve the problem that the quantum dots in the quantum dot film layer formed by the existing method are easily driven by volatile solvents to produce local aggregation or are redissolved or directly washed away during the solution-based film formation process of the subsequent film layer, resulting in uneven quantum dot film layer and poor flatness.

[0005] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0006] In a first aspect, the present application provides a composite film layer, comprising at least one metal organic framework material layer and at least one quantum dot layer,

[0007] The quantum dot layer and the metal organic framework material layer are stacked,

[0008] The surface of the metal organic framework material layer contains active functional groups, and the surface of the quantum dot layer contains cations.

[0009] At least part of the reactive functional groups are linked to at least part of the cations.

[0010] In a second aspect, the present application provides a method for preparing a composite film layer, comprising the following steps:

[0011] Providing a first solution formed of a metal organic framework material and a second solution formed of quantum dots;

[0012] The first solution and the second solution are sequentially subjected to film-forming treatment to form at least one metal organic framework material layer and at least one quantum dot layer stacked in layers to obtain the composite film layer.

[0013] The surface of the metal organic framework material layer contains active functional groups, and the surface of the quantum dot layer contains cations.

[0014] At least part of the reactive functional groups are linked to at least part of the cations.

[0015] Preferably, the molar ratio of the metal ion to the organic ligand is 1:(0.5-5).

[0016] Preferably, the organic ligand has a molecular structure as shown in general formula I:

[0017]

[0018] wherein R is selected from alkyl, silane, porphyrinyl, alkenyl, alkynyl, phenylpyridyl, pyrenyl, phenyl or oxazine,

[0019] Ar is selected from benzene or biphenyl,

[0020] X is the active functional group, independently selected from at least one of a carboxyl group, a thiol group, an amino group, a sulfonic acid group and a hydroxyl group,

[0021] n is the number of X, selected from a positive integer between 1 and 4,

[0022] m is a positive integer between 2 and 10.

[0023] Preferably, said n is selected to be 1 or 2; and / or

[0024] The X is selected from carboxyl or thiol; and / or

[0025] The m is selected to be 3-6.

[0026] Preferably, the organic ligand is selected from any one of the following compounds:

[0027]

[0028]

[0029] Preferably, the metal ion is the same as the cation.

[0030] Preferably, the polarity of the quantum dots in the quantum dot layer is opposite to the polarity of the metal organic framework material in the metal organic framework material layer.

[0031] Preferably, the metal organic framework material layer is formed of a water-soluble metal organic framework material, and the quantum dot layer is formed of oil-soluble quantum dots.

[0032] In a third aspect, the present application provides a light-emitting diode, comprising: a light-emitting functional layer, wherein the light-emitting functional layer comprises the aforementioned composite film layer or the composite film layer prepared by the aforementioned preparation method.

[0033] Preferably, the light emitting diode is a QLED.

[0034] The composite film layer provided in the first aspect of the present application includes a metal-organic framework material layer and a quantum dot layer. The quantum dot layer and the metal-organic framework material layer are stacked, and the surface of the metal-organic framework material layer contains active functional groups. The metal-organic framework material layer is connected to the quantum dot layer through the active functional groups, so that the quantum dots in the quantum dot layer can be tightly anchored on the surface of the metal-organic framework material layer, so that the quantum dot particles are tightly connected and the quantum dot layer is dense, thereby forming a composite film layer with dense, uniform film layer and high flatness.

[0035] The second aspect of the present application provides a method for preparing a composite film layer, wherein the first solution contains a metal organic framework material and / or contains metal ions and organic ligands for forming a metal organic framework material, and the metal organic framework material or the organic ligand contains active functional groups, so that the surface of the metal organic framework material layer formed after the film-forming treatment of the first solution contains active functional groups; then, a metal organic framework material layer and a quantum dot layer are formed on the surface of the metal organic framework material layer, so that the quantum dots are anchored on the metal organic framework material layer through the combination of their cations with the active functional groups on the surface of the metal organic framework material layer during film formation, thereby improving the density of the film layer, and preventing the quantum dots from being driven by the volatilized solvent during the film formation process to produce local aggregation and cause uneven quantum dot film layers, which is conducive to forming a dense, uniform, and high-flatness composite film layer. The method is simple and easy to operate.

[0036] The light-emitting diode provided in the third aspect of the present application comprises: a light-emitting functional layer, the light-emitting functional layer comprises the aforementioned composite film layer or the composite film layer prepared by the aforementioned preparation method, the quantum dot layer in the light-emitting functional layer is dense and uniform, has high flatness, and has uniform luminous intensity, and the metal organic framework material layer can promote the timely transmission of carriers to the quantum dot layer, which reduces the accumulation of carriers at the interface of the quantum dot layer to a certain extent, prevents the device voltage from increasing and causing rapid aging and attenuation of the device, thereby further improving the luminescence performance of the device, and thus obtaining a light-emitting diode with high luminescence performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 A schematic diagram of the structure of a composite film layer provided in one embodiment of the present application;

[0039] Figure 2 A schematic diagram of the structure of a composite film layer provided in another embodiment of the present application, wherein Figure 2 The “…” in the figure indicates that multiple unit layers are cycled alternately;

[0040] Figure 3 A flow chart of a method for preparing a composite film layer provided in one embodiment of the present application;

[0041] Figure 4 A schematic diagram of the structure of a light emitting diode provided in one embodiment of the present application;

[0042] Figure 5 A schematic diagram of the structure of a light emitting diode provided in another embodiment of the present application.

[0043] Among them, the reference numerals in the figure are: 31-metal organic framework material layer, 32-quantum dot layer, 1-anode, 21-hole injection layer, 22-hole transport layer, 3-luminescent functional layer, 31-composite film layer, 4-electron transport layer, 5-cathode. DETAILED DESCRIPTION

[0044] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0045] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0046] In a first aspect, the present application provides a composite film layer, such as Figure 1 As shown, the composite film layer includes at least one metal organic framework material layer 31 and at least one quantum dot layer 32. The quantum dot layer 32 and the metal organic framework material layer 31 are stacked. The surface of the metal organic framework material layer 31 contains active functional groups, and the surface of the quantum dot layer 32 contains cations. At least part of the active functional groups are connected to at least part of the cations.

[0047] The composite film layer provided in the embodiment of the present application includes a metal-organic framework material layer and a quantum dot layer. The quantum dot layer and the metal-organic framework material layer are stacked, and the surface of the metal-organic framework material layer contains active functional groups. The metal-organic framework material layer is connected to the quantum dot layer through the active functional groups, so that the quantum dots in the quantum dot layer can be tightly anchored on the surface of the metal-organic framework material layer, so that the quantum dot particles are tightly connected and the quantum dot layer is dense, thereby forming a dense, uniform film layer and a quantum dot layer with high flatness.

[0048] In the present application, "cation" refers to the metal phase on the surface of the quantum dot, which is coordinated and bonded with the metal phase through the active functional group to connect the metal organic framework material layer and the quantum dot layer.

[0049] In some of the embodiments, Figure 2 As shown, the metal organic framework material layer and the quantum dot layer are stacked and combined to form a unit layer, and the composite film layer is formed by alternating at least two light-emitting unit layers. Specifically, the quantum dot layer on each unit layer is arranged on the surface of the metal organic framework material layer away from the quantum dot layer of the previous unit layer. In this way, the adjacent quantum dot layers are spaced by the metal organic framework material layer, the quantum dot spacing is increased, the energy resonance transfer between the quantum dots due to the small quantum dot spacing is avoided, the energy loss is reduced, and the luminescence stability is improved. On the basis of these embodiments, the quantum dot layer is preferably a monomolecular film layer to further increase the quantum dot spacing, reduce the energy loss caused by the energy resonance transfer, and avoid excessive energy loss when the thickness of the light-emitting functional layer is too large. In a further embodiment, the thickness of the metal organic framework material layer is 20-2000nm, and the thickness of the quantum dot layer is 5-20nm. In a specific embodiment, the number of light-emitting unit layers is 2-10, and the number of light-emitting unit layers is controlled within the above range to avoid the composite film layer being too thick or too thin to affect the luminescence performance of the device.

[0050] In the present application, "monomolecule film layer" refers to a film layer having a thickness of only one molecule.

[0051] In some other embodiments, the number of the metal organic framework material layer is one layer, the number of the quantum dot layers is two layers, and the metal organic framework material layer is disposed between the two quantum dot layers.

[0052] In some other embodiments, the number of the metal organic framework material layers is two, the number of the quantum dot layer is one, and the quantum dot layer is disposed between the two metal organic framework material layers.

[0053] Specifically, the metal organic framework material layer is a film layer formed by dense stacking of metal organic framework materials, which is used to anchor the quantum dots in the quantum dot layer and promote carrier transfer to the quantum dot layer to improve the luminescence performance of the device.

[0054] Metal-organic framework materials are a type of composite materials containing metal ions and organic ligands. They use metal ions as coordination centers and are self-assembled by metal ions and organic ligands driven by the coordination force between the metal ions and the active functional groups of the organic ligands.

[0055] In the present application, "self-assembly" refers to the spontaneous organization or aggregation of metal ions and organic ligands into a stable, ordered structure with a regular geometric appearance based on non-covalent bond interactions.

[0056] In some embodiments, the metal organic framework material of the metal organic framework material layer is formed by self-assembly of metal ions and organic ligands.

[0057] In a further embodiment, the organic ligand has a molecular structure as shown in Formula I:

[0058]

[0059] wherein R is selected from alkyl, silane, porphyrinyl, alkenyl, alkynyl, phenylpyridyl, pyrenyl, phenyl or oxazine,

[0060] Ar is selected from benzene or biphenyl,

[0061] X is the active functional group, independently selected from at least one of a carboxyl group, a thiol group, an amino group, a sulfonic acid group and a hydroxyl group,

[0062] n is the number of X, selected from a positive integer between 1 and 4,

[0063] m is a positive integer between 2 and 10.

[0064] The metal organic framework material is formed by self-assembly through the coordination of the active functional group X in the above organic ligand with the metal ion, and some of the active functional groups X that are not coordinated with the metal ion exist on the surface of the metal organic framework material. The active functional group X is combined with the quantum dot metal on the surface of the quantum dot layer, so that the quantum dots in the quantum dot layer can be tightly anchored on the surface of the metal organic framework material layer. At the same time, the above organic ligand has a multi-benzene ring structure. When the composite film layer of the embodiment of the present application is used as the light-emitting functional layer of the light-emitting diode, the above organic ligand can also act as an antenna ligand, promoting the timely transmission of carriers absorbed from the outside to the quantum dot layer, reducing carrier accumulation, and thus improving the luminescence performance of the device.

[0065] More specifically, X is a substituent of Ar, n is the number of X, and in some embodiments, n is 1 or 2.

[0066] The coordination activity of X with metal ions directly affects the formation of metal organic framework materials and the firmness of the quantum dots anchored on the metal organic framework material layer. In some embodiments, X is selected as a carboxyl group or a thiol group. Compared with active functional groups such as amino groups, sulfonic acid groups and hydroxyl groups, carboxyl groups and thiol groups have better coordination activity with metal ions, which can make the quantum dots in the quantum dot layer more firmly anchored on the metal organic framework material layer.

[0067] m is the number of Ar substituted by X. In some embodiments, m is selected to be 3-6.

[0068] In a specific embodiment, the organic ligand is selected from any one of the following compounds:

[0069]

[0070]

[0071] The type and amount of metal ions used to form the metal organic framework material can refer to conventional techniques in the art, so that the metal ions can self-assemble with the above-mentioned organic ligands to form the metal organic framework material.

[0072] In some embodiments, the metal ions are the same as the cations of the quantum dots in the quantum dot layer, so as to better bind the excitons. In a specific embodiment, the quantum dots are core-shell quantum dots, and the metal ions are the same as the cations of the shell material of the quantum dots.

[0073] Based on the above embodiment, the molar ratio of metal ions to organic ligands is 1:(0.5-5). Within this molar ratio range, it can be ensured that the metal ions and organic ligands are fully coordinated to form a metal organic framework material, and at the same time, the quantum dots in the quantum dot layer are anchored on the metal organic framework material layer.

[0074] The quantum dots in the quantum dot layer have good photoelectric properties. When the above composite film layer is used as the light-emitting functional layer of a light-emitting diode, the quantum dot layer serves as the light-emitting layer of the light-emitting functional layer, ensuring that the light-emitting diode has good light-emitting properties.

[0075] The quantum dot material of the quantum dot layer can be selected as a conventional quantum dot material in the art, as long as it does not affect the light-emitting performance of the light-emitting diode. For example, in some embodiments, the quantum dots are selected as II-VI semiconductor quantum dots, III-V semiconductor quantum dots or IV-VI semiconductor quantum dots, wherein II-VI semiconductor quantum dots include but are not limited to CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSe Te, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, etc., III-V semiconductor quantum dots include but are not limited to GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlP As, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaI nNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, etc.; IV-VI group semiconductor quantum dots include but are not limited to SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, SnPbSTe.

[0076] The quantum dots may be selected as oil-soluble quantum dots or water-soluble quantum dots. Preferably, the polarity of the quantum dots in the quantum dot layer is opposite to the polarity of the metal organic framework material in the metal organic framework material layer. At present, the solution method is mainly used to prepare the quantum dot film layer. When the metal organic framework material layer and / or the quantum dot layer are formed by the solution method, the polarities of the two adjacent film layers are adjusted to be opposite, so as to avoid the functional material of the previous film layer being re-dissolved by the solution forming the next film layer, so as to ensure the uniformity and flatness of the film layer. In some embodiments, the quantum dots in the quantum dot layer are oil-soluble quantum dots, and the metal organic framework material of the metal organic framework material layer is a water-soluble metal organic framework material.

[0077] Based on the above technical solution, the second aspect of the embodiment of the present application provides a method for preparing a composite film layer, such as Figure 3 As shown, the following steps are included;

[0078] S01. Providing a first solution and a second solution, wherein the first solution contains a metal organic framework material and / or contains metal ions and organic ligands for forming the metal organic framework material, the metal organic framework material or the organic ligand contains active functional groups, and the second solution contains quantum dots, the quantum dots contain cations, and at least part of the active functional groups can be connected to at least part of the cations;

[0079] S02, performing film-forming treatment on the first solution to form a metal organic framework material layer;

[0080] S03, performing film-forming treatment on the metal organic framework material layer with the second solution to form a quantum dot layer.

[0081] The method for preparing the composite film layer provided in the embodiment of the present application is that the first solution contains a metal organic framework material and / or contains metal ions and organic ligands for forming the metal organic framework material, and the metal organic framework material or the organic ligand contains active functional groups, so that the surface of the metal organic framework material layer formed after the film-forming treatment of the first solution contains active functional groups; then, a metal organic framework material layer and a quantum dot layer are formed on the surface of the metal organic framework material layer, so that the quantum dots are anchored on the metal organic framework material layer through the combination of their cations with the active functional groups on the surface of the metal organic framework material layer during film formation, thereby improving the density of the film layer, and preventing the quantum dots from being driven by the volatilized solvent during the film formation process to produce local aggregation and cause uneven quantum dot film layers, which is conducive to forming a dense, uniform, and high-flatness quantum dot layer. The method is simple and easy to operate.

[0082] The quantum dots, metal organic framework materials, metal ions and organic ligands used to form the metal organic framework materials involved in step S01 are basically the same as the metal organic framework materials and quantum dots described above, and both should have the same types and effects.

[0083] In step S02 , the first solution is subjected to a film-forming treatment to form a metal organic framework material layer, and the surface of the formed metal organic framework material layer contains active functional groups.

[0084] The method for film formation can refer to conventional techniques in the art, for example, a solution method, a magnetron sputtering method and a chemical vapor deposition method are used to deposit a first solution on a substrate and then anneal to form a film layer. The solution method includes but is not limited to a spin coating method, a doctor blade method, an inkjet printing method, etc. The substrate is used as a carrier for film formation, and its type and specific structure can refer to conventional techniques in the art, and can be flexibly adjusted according to the device to be prepared.

[0085] When the solution method is used for film formation, the first solution is in the form of a solution, and the first solution is spin-coated, scraped or ink-jet-printed on the substrate. After the solvent is removed, a metal organic framework material layer can be formed.

[0086] The first solution is used to form a metal organic framework material, and may contain a metal organic framework material, or may contain metal ions and organic ligands used to form a metal organic framework material. When the first solution contains only a metal organic framework material, in the step of subjecting the first solution to film-forming treatment, the metal organic framework material is directly deposited to form a film layer. When the first solution contains metal ions and organic ligands, the metal ions and organic ligands self-assemble to form a metal organic framework material and a metal organic framework material, and are deposited to form a film layer. In some embodiments, the first solution is a mixture of metal ions and organic ligands, and after the step of subjecting the first solution to film-forming treatment, it is heated at 60°C-120°C for 10 minutes to 12 hours to ensure that the metal ions and organic ligands fully react to form a metal organic framework material. In the present application specification, "wet film" refers to a thin film containing a solvent relative to a dry film.

[0087] In a further embodiment, the first solution is prepared by dispersing a metal ion precursor and an organic ligand in a polar solvent, wherein the polar solvent includes but is not limited to methanol, ethanol, acetonitrile, N,N-dimethylformamide and N,N-dimethylacetamide. In addition, the metal ion precursor is used to provide metal ions, including but not limited to halides, nitrates, acetates, etc. corresponding to the metal ions. Preferably, the metal ion is the same as the quantum dot cation. In some embodiments, when the quantum dots are core-shell quantum dots and their outermost shell is ZnS, ZnSe or ZnSeS, the metal ion precursor is selected from at least one of zinc chloride, zinc bromide, zinc iodide and zinc acetate.

[0088] In step S03 , a second solution is subjected to a film-forming process on the metal organic framework material layer to form a quantum dot layer stacked and combined with the metal organic framework material layer.

[0089] When the solution method is used for film formation, the second solution is in the form of a solution, and the second solution is deposited on the metal organic framework material layer. After the solvent is removed, a quantum dot layer can be formed.

[0090] In the step of forming a film of the second solution on the metal-organic framework material layer, quantum dots are deposited on the metal-organic framework material layer and arranged to form a film layer. At the same time, the metal on the surface of the quantum dots coordinates with the active groups on the surface of the metal-organic framework material layer, thereby anchoring the quantum dots on the metal-organic framework material layer.

[0091] In order to obtain a uniform, dense, and highly flat quantum dot layer, the second solution has an opposite polarity to the first solution. In some embodiments, the quantum dots are oil-soluble quantum dots, and the quantum dots are dispersed in a non-polar solvent to obtain the second solution. The non-polar solvent includes, but is not limited to, n-octane, n-hexane, and chloroform.

[0092] In some embodiments, the quantum dot layer and the metal organic framework material layer are stacked and combined to form a unit layer, and the composite film layer is formed by alternately stacking at least two unit layers; in this case, the method for preparing the composite film layer further includes:

[0093] S04, taking the steps of sequentially forming a metal organic framework material layer and forming a quantum dot layer as a repeating unit step, and performing the repeating unit step at least once on the surface of the quantum dot layer.

[0094] Through the above method, adjacent quantum dot layers are separated by metal organic framework material layers, which increases the distance between quantum dots, avoids energy resonance transfer between quantum dots due to too small distance between quantum dots, reduces energy loss, and improves luminescence stability.

[0095] Based on the previous embodiment, the quantum dot layer is a monomolecular film layer.

[0096] On the basis of the previous embodiment, the unit step is repeated 1-9 times on the surface of the quantum dot layer, so that the number of unit layers of the composite film layer formed thereby is 2-10.

[0097] In some embodiments, the preparation method further comprises: subjecting the first solution to film-forming treatment on the quantum dot layer to form a metal organic framework material layer, thereby forming a composite film layer formed by sandwiching the quantum dot layer between the metal organic framework material layers.

[0098] In some embodiments, the step of subjecting the first solution to film-forming treatment includes: subjecting the second solution to film-forming treatment to form a quantum dot layer, and then forming a film of the first solution on the quantum dot layer to form a composite film layer formed by sandwiching a metal organic framework material layer between the quantum dot layers.

[0099] Based on the above technical solution, a third aspect of an embodiment of the present application provides a light-emitting diode, comprising: a light-emitting functional layer, wherein the light-emitting functional layer comprises the aforementioned composite film layer or the composite film layer prepared by the above preparation method.

[0100] The light-emitting diode provided in the third aspect of the present application comprises: a light-emitting functional layer, the light-emitting functional layer comprises the aforementioned composite film layer or the composite film layer prepared by the aforementioned preparation method, the quantum dot layer in the light-emitting functional layer is dense and uniform, has high flatness, and has uniform luminous intensity, and the metal organic framework material layer can promote the timely transmission of carriers to the quantum dot layer, which reduces the accumulation of carriers at the interface of the quantum dot layer to a certain extent, prevents the device voltage from increasing and causing rapid aging and attenuation of the device, thereby further improving the luminescence performance of the device, and thus obtaining a light-emitting diode with high luminescence performance.

[0101] like Figure 4 As shown, a light-emitting diode provided in an embodiment of the present application includes: a bottom electrode 1 and a top electrode 5 arranged opposite to each other, and a light-emitting functional layer 3 stacked and combined between the bottom electrode 1 and the top electrode 5, and the light-emitting functional layer 3 includes the aforementioned composite film layer or the composite film layer prepared by the aforementioned preparation method.

[0102] In the light emitting diode, when the composite film layer is formed by stacking at least two of the unit layers, the quantum dot layer is arranged on the surface of the metal organic framework material layer facing away from the bottom electrode.

[0103] The specific structure of the light-emitting diode of the present application can refer to the conventional technology in the field. In some embodiments, the light-emitting diode is a positive structure, and the anode is connected to the substrate as the bottom electrode; in some embodiments, the light-emitting diode is an inverted structure, and the cathode is connected to the substrate as the bottom electrode.

[0104] In the present application, the light-emitting functional layer refers to a composite functional film layer including a light-emitting layer. In addition to the composite film layer, the light-emitting functional layer may also include a hole functional layer such as a hole injection layer, a hole transport layer and a hole blocking layer, or an electron functional layer such as an electron injection layer, an electron transport layer and an electron blocking layer.

[0105] In some embodiments, the light-emitting functional layer further includes a first functional layer and / or a second functional layer, the first functional layer is disposed between the bottom electrode and the composite film layer, and the second functional layer is disposed between the composite film layer and the top electrode.

[0106] In a further embodiment, the bottom electrode is an anode, the top electrode is a cathode, the first functional layer is a hole injection layer and a hole transport layer stacked and bonded on the anode in sequence, and the second functional layer is an electron transport layer stacked and bonded on the composite film layer; or

[0107] The bottom electrode is a cathode, the top electrode is an anode, the first functional layer is an electron transport layer stacked on the cathode, and the second functional layer is a hole transport layer and a hole injection layer stacked in sequence on the composite film layer.

[0108] In a specific embodiment, Figure 5 As shown, the light-emitting diode includes: an anode 1, a hole injection layer 21, a hole transport layer 22, a composite film layer 31, an electron transport layer 4 and a cathode 5, wherein the anode 1 is connected to the substrate as a bottom electrode, the hole injection layer 21 is arranged between the anode 1 and the composite film layer 31, the hole transport layer 22 is arranged between the hole injection layer 21 and the composite film layer 31, and the electron transport layer 4 is arranged between the composite film layer 31 and the cathode 5.

[0109] In the light emitting diode, the materials and thicknesses of the anode, the hole injection layer, the hole transport layer, the electron transport layer and the cathode may refer to conventional techniques in the art.

[0110] The substrate connected to the bottom electrode includes a rigid substrate and a flexible substrate. In some embodiments, the substrate is selected from at least one of glass, silicon wafer, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyamide and polyether sulfone.

[0111] The anode includes a conductive metal and / or a conductive metal oxide. The conductive metal includes but is not limited to nickel, platinum, vanadium, chromium, copper, zinc and gold or their alloys. The conductive metal oxide includes but is not limited to zinc oxide, indium oxide, tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO), fluorine-doped tin oxide, etc.

[0112] The material of the hole injection layer is selected as a material with good hole injection performance, including but not limited to poly (3,4-ethylenedioxythiophene) - polystyrene sulfonic acid (PEDOT:PSS), copper phthalocyanine (CuPc), 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinone-dimethane (F4-TCNQ), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HATCN), doped or undoped transition metal oxides, doped or undoped metal sulfur compounds, etc.; wherein, transition metal oxides include but are not limited to MoO3, VO2, WO3, CuO, etc., and metal sulfur compounds include but are not limited to MoS2, MoSe2, WS2, WSe2, CuS, etc. The thickness of the hole injection layer is preferably 10-150nm.

[0113] The material of the hole transport layer is an organic material with good hole transport ability, including but not limited to poly (9,9-dioctylfluorene-co-N-(4-butylphenyl) diphenylamine) (TFB), polyvinyl carbazole (PVK), poly (N,N'-bis (4-butylphenyl)-N,N'-bis (phenyl) benzidine) (Poly-TPD), poly (9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine) (PFB), 4,4',4"-triphenylene glycol (TFB), poly (4,4',4"-triphenylene glycol) ...PB), poly (4,4',4"-triphenylene glycol) (TPB), poly (4, (Carbazole-9-yl) triphenylamine (TCTA), 4,4'-di(9-carbazole) biphenyl (CBP), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), doped graphene, undoped graphene, C60, etc. The thickness of the hole transport layer is preferably 10-150 nm.

[0114] The material of the electron transport layer is selected from materials with good electron transport properties, including but not limited to ZnO, TiO2, Alq3, SnO, ZrO, AlZnO, ZnSnO, BCP, TAZ, PBD, TPBI, Bphen, CsCO3, etc. The thickness of the electron transport layer is preferably 10-100 nm.

[0115] The cathode can be selected as a single metal or its alloy, including but not limited to at least one of magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin, lead, cesium, and barium; or, the cathode is selected as a multilayer structure material, including but not limited to alkali metal halides, alkaline earth metal halides, alkali metal oxides, etc.; or, the cathode is selected as a combination of a multilayer structure material and a metal layer, and the metal layer is selected as an alkaline earth metal and / or a Group 13 metal, including but not limited to LiF / Al, LiO2 / Al, LiF / Ca, Liq / Al, and BaF2 / Ca, etc.

[0116] In order to enable those skilled in the art to clearly understand the above implementation details and operations of the present invention, and to significantly demonstrate the improved performance of a composite film layer and a preparation method thereof and a light-emitting diode in an embodiment of the present invention, the implementation of the present invention is illustrated by way of examples below.

[0117] Example 1

[0118] This embodiment provides a composite film layer, wherein a light-emitting layer is constructed using a metal organic framework material and quantum dots, wherein the metal organic framework material is self-assembled in a solution by zinc chloride and 4'-[4,6-di(4'-carboxyl[1,1'-biphenyl]-4-yl)-1,3,5-triazine-2-yl]-[1,1'-biphenyl]-4-carboxylic acid, and the quantum dots are CdZnSe / ZnSe / ZnS. The preparation method of the light-emitting diode specifically comprises the following steps:

[0119] 1) CdZnSe / ZnSe / ZnS quantum dots with a peak wavelength of 528 nm, a peak width of 21 nm, and a quantum yield of 80% were selected and added to n-octane to prepare a quantum dot solution with a mass concentration of 10 mg / mL.

[0120] 2) Add zinc chloride and 4'-[4,6-di(4'-carboxy[1,1'-biphenyl]-4-yl)-1,3,5-triazine-2-yl]-[1,1'-biphenyl]-4-carboxylic acid to ethanol, and stir until completely dissolved to obtain a mixed solution.

[0121] 3) depositing the mixed solution prepared in step 2) on the substrate, and heating it at 100° C. for 60 min to form a metal organic framework material layer; then, spin coating the quantum dot solution prepared in step 1) on the metal organic framework material layer at a spin coating speed of 5000 rpm to obtain a quantum dot layer.

[0122] 4) Repeat steps 2) and 3) for 5 times to obtain a composite film layer.

[0123] Among them, the molecular structure of 4'-[4,6-di(4'-carboxy[1,1'-biphenyl]-4-yl)-1,3,5-triazine-2-yl]-[1,1'-biphenyl]-4-carboxylic acid is:

[0124]

[0125] Example 2

[0126] This embodiment provides a composite film layer, and its preparation method is basically the same as that of Embodiment 1, except that: in step 2), zinc chloride and 1,4-bis(2',6,'-dicarboxyphenyl-4'-pyridine)benzene are added to methanol and stirred until completely dissolved to obtain a mixed solution.

[0127] Among them, the molecular structure of 1,4-bis(2',6'-dicarboxyphenyl-4'-pyridine)benzene is:

[0128]

[0129] Example 3

[0130] This embodiment provides a composite film layer, and its preparation method is basically the same as that of embodiment 1, except that: in step 2), zinc chloride and 1,2,3,4,5,6-hexa(4″-carboxybiphenyl)benzene are added to methanol and stirred until completely dissolved to obtain a mixed solution.

[0131] Among them, the molecular structure of 1,2,3,4,5,6-hexa(4″-carboxybiphenyl)benzene is:

[0132]

[0133] Example 4

[0134] This embodiment provides a composite film layer, wherein a light-emitting layer is constructed using a metal organic framework material and quantum dots, wherein the metal organic framework material is self-assembled in a solution by cadmium chloride and 4'-[4,6-di(4'-carboxyl[1,1'-biphenyl]-4-yl)-1,3,5-triazine-2-yl]-[1,1'-biphenyl]-4-carboxylic acid, and the quantum dots are CdSe / ZnSe / ZnS. The preparation method of the light-emitting diode specifically comprises the following steps:

[0135] 1) CdSe / ZnSe / ZnS quantum dots with a peak wavelength of 532 nm, a peak width of 19 nm, and a quantum yield of 86% were selected and added to n-octane to prepare a quantum dot solution with a mass concentration of 10 mg / mL.

[0136] 2) Add cadmium chloride and 4'-[4,6-di(4'-carboxy[1,1'-biphenyl]-4-yl)-1,3,5-triazine-2-yl]-[1,1'-biphenyl]-4-carboxylic acid to a mixed solvent of acetonitrile and ethanol, and stir until completely dissolved to obtain a mixed solution.

[0137] 3) depositing the mixed solution prepared in step 2) on the substrate, and heating it at 100° C. for 60 min to form a metal organic framework material layer; then, spin coating the quantum dot solution prepared in step 1) on the metal organic framework material layer at a spin coating speed of 5500 rpm to obtain a quantum dot layer.

[0138] 4) Repeat steps 2) and 3) for 5 times to obtain a composite film layer.

[0139] Among them, the molecular structure of 4'-[4,6-di(4'-carboxy[1,1'-biphenyl]-4-yl)-1,3,5-triazine-2-yl]-[1,1'-biphenyl]-4-carboxylic acid is:

[0140] Example 5

[0141] This embodiment provides a composite film layer, and its preparation method is basically the same as that of Example 4, except that: in step 2), cadmium chloride and 1,4-bis(2',6,'-dicarboxyphenyl-4'-pyridine)benzene are added to a mixed solvent of acetonitrile and ethanol, and stirred until completely dissolved to obtain a mixed solution.

[0142] Among them, the molecular structure of 1,4-bis(2',6'-dicarboxyphenyl-4'-pyridine)benzene is:

[0143]

[0144] Example 6

[0145] This embodiment provides a composite film layer, and its preparation method is basically the same as that of Embodiment 4, except that: in step 2), cadmium chloride and 1,2,3,4,5,6-hexa(4″-carboxybiphenyl)benzene are added to a mixed solvent of ethanol and acetonitrile, and stirred until completely dissolved to obtain a mixed solution.

[0146] Among them, the molecular structure of 1,2,3,4,5,6-hexa(4″-carboxybiphenyl)benzene is:

[0147]

[0148] Example 7

[0149] This embodiment provides a light-emitting diode, and its preparation method includes: depositing an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode on a substrate in sequence. The substrate is a glass substrate; the bottom electrode is ITO with a thickness of 100 nm; the hole injection layer is PEDOT:PSS with a thickness of 40 nm; the hole transport layer is TFB with a thickness of 100 nm; the electron transport layer is ZnO with a thickness of 40 nm; the top electrode is Al with a thickness of 50 nm; and the light-emitting layer is the composite film layer prepared in Example 1 with a thickness of 100 nm.

[0150] Example 8

[0151] This embodiment provides a light-emitting diode, and its preparation method includes: depositing an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode on a substrate in sequence. The substrate is a glass substrate; the bottom electrode is ITO with a thickness of 100 nm; the hole injection layer is PEDOT:PSS with a thickness of 40 nm; the hole transport layer is TFB with a thickness of 100 nm; the electron transport layer is ZnO with a thickness of 40 nm; the top electrode is Al with a thickness of 50 nm; and the light-emitting layer is the composite film layer prepared in Example 2 with a thickness of 100 nm.

[0152] Example 9

[0153] This embodiment provides a light-emitting diode, and its preparation method includes: depositing an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode on a substrate in sequence. The substrate is a glass substrate; the bottom electrode is ITO with a thickness of 100 nm; the hole injection layer is PEDOT:PSS with a thickness of 40 nm; the hole transport layer is TFB with a thickness of 100 nm; the electron transport layer is ZnO with a thickness of 40 nm; the top electrode is Al with a thickness of 50 nm; and the light-emitting layer is the composite film layer prepared in Example 3 with a thickness of 100 nm.

[0154] Example 10

[0155] This embodiment provides a light-emitting diode, and its preparation method includes: depositing an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode on a substrate in sequence. The substrate is a glass substrate; the bottom electrode is ITO with a thickness of 100 nm; the hole injection layer is PEDOT:PSS with a thickness of 40 nm; the hole transport layer is TFB with a thickness of 100 nm; the electron transport layer is ZnO with a thickness of 40 nm; the top electrode is Al with a thickness of 50 nm; and the light-emitting layer is the composite film layer prepared in Example 4 with a thickness of 100 nm.

[0156] Embodiment 11

[0157] This embodiment provides a light-emitting diode, and its preparation method includes: depositing an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode on a substrate in sequence. The substrate is a glass substrate; the bottom electrode is ITO with a thickness of 100 nm; the hole injection layer is PEDOT:PSS with a thickness of 40 nm; the hole transport layer is TFB with a thickness of 100 nm; the electron transport layer is ZnO with a thickness of 40 nm; the top electrode is Al with a thickness of 50 nm; and the light-emitting layer is the composite film layer prepared in Example 5 with a thickness of 100 nm.

[0158] Example 12

[0159] This embodiment provides a light-emitting diode, and its preparation method includes: depositing an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode on a substrate in sequence. The substrate is a glass substrate; the bottom electrode is ITO with a thickness of 100 nm; the hole injection layer is PEDOT:PSS with a thickness of 40 nm; the hole transport layer is TFB with a thickness of 100 nm; the electron transport layer is ZnO with a thickness of 40 nm; the top electrode is Al with a thickness of 50 nm; and the light-emitting layer is the composite film layer prepared in Example 6 with a thickness of 100 nm.

[0160] Comparative Example 1

[0161] This embodiment provides a film layer, and the preparation method thereof specifically includes the following steps:

[0162] 1) CdZnSe / ZnSe / ZnS quantum dots with a peak wavelength of 528 nm, a peak width of 21 nm, and a quantum yield of 80% were selected and added to n-octane to prepare a quantum dot solution with a mass concentration of 10 mg / mL.

[0163] 2) Spin coating the quantum dot solution prepared in step 1) on the substrate at a spin coating speed of 5000 rpm.

[0164] Comparative Example 2

[0165] This embodiment provides a film layer, and the preparation method thereof specifically includes the following steps:

[0166] 1) CdSe / ZnSe / ZnS quantum dots with a peak wavelength of 532 nm, a peak width of 19 nm, and a quantum yield of 86% were selected and added to n-octane to prepare a quantum dot solution with a mass concentration of 10 mg / mL.

[0167] 2) Spin coating the quantum dot solution prepared in step 1) on the substrate at a spin coating speed of 5500 rpm.

[0168] Comparative Example 3

[0169] This comparative example provides a light-emitting diode, and its preparation method includes: depositing an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode on a substrate in sequence. The substrate is a glass substrate; the bottom electrode is ITO with a thickness of 100 nm; the hole injection layer is PEDOT:PSS with a thickness of 40 nm; the hole transport layer is TFB with a thickness of 100 nm; the electron transport layer is ZnO with a thickness of 40 nm; the top electrode is Al with a thickness of 50 nm; and the light-emitting layer is the film layer prepared in comparative example 1 with a thickness of 100 nm.

[0170] Comparative Example 4

[0171] This comparative example provides a light-emitting diode, and its preparation method includes: depositing an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode on a substrate in sequence. Wherein, the substrate is a glass substrate; the bottom electrode is ITO with a thickness of 100nm; the hole injection layer is PEDOT:PSS with a thickness of 40nm; the hole transport layer is TFB with a thickness of 100nm; the electron transport layer is ZnO with a thickness of 40nm; the top electrode is Al with a thickness of 50nm; the light-emitting layer is the film layer prepared in comparative example 2 with a thickness of 100nm.

[0172] The composite film layers of Examples 1-6 and the film layers prepared in Comparative Examples 1-2 were tested for quantum yield. The quantum yield of the film samples was tested using the photoluminescence quantum yield accessory on an Edinburgh FLS980 fluorescence spectrometer, and the results in Table 1 were obtained.

[0173] Table 1

[0174] Quantum yield Quantum yield Example 1 50％ Example 4 63％ Example 2 46％ Example 5 58％ Example 3 43％ Example 6 53％ Comparative Example 1 Comparative Example 2

[0175] The light-emitting diodes prepared in Examples 7-12 were taken and the external quantum dot efficiency (EQE) of each light-emitting diode was tested using an EQE optical testing instrument. The test results are shown in Table 2.

[0176] Among them, the ratio of the number of electron-hole pairs injected into the quantum dots to the number of emitted photons, the unit is %, which is an important parameter to measure the quality of electroluminescent devices. The specific calculation formula of EQE is as follows:

[0177]

[0178] Where η e is the light output coupling efficiency, η r is the ratio of the number of recombined carriers to the number of injected carriers, χ is the ratio of the number of photon-generating excitons to the total number of excitons, K R is the radiation process rate, K NR is the rate of the non-radiative process.

[0179] Table 2

[0180] EQE(%) EQE(%) Example 7 13.5 Example 10 15.3 Example 8 12.1 Embodiment 11 14.2 Example 9 11.9 Example 12 13.8 Comparative Example 3 7.8 Comparative Example 4 8.9

[0181] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A composite film layer, characterized in that: It comprises a metal organic framework material layer and a quantum dot layer, wherein the metal organic framework material layer and the quantum dot layer are stacked and combined to form a unit layer, the composite film layer is formed by alternately stacking at least two of the unit layers, and the quantum dot layer on each unit layer is arranged on the surface of the metal organic framework material layer away from the quantum dot layer of the previous unit layer; The quantum dot layer and the metal organic framework material layer are stacked. The surface of the metal organic framework material layer contains active functional groups, the surface of the quantum dot layer contains cations, and at least part of the active functional groups are connected to at least part of the cations; The polarity of the quantum dots in the quantum dot layer is opposite to the polarity of the metal organic framework material in the metal organic framework material layer; the metal organic framework material in the metal organic framework material layer is self-assembled by metal ions and organic ligands, and the organic ligands have a molecular structure as shown in general formula I: wherein R is selected from alkyl, silane, porphyrinyl, alkenyl, alkynyl, phenylpyridyl, pyrenyl, phenyl or oxazine, Ar is selected from benzene or biphenyl, X is the active functional group, independently selected from at least one of a carboxyl group, a thiol group, an amino group, a sulfonic acid group and a hydroxyl group, n is the number of X, selected from a positive integer between 1 and 4, m is a positive integer between 2 and 10; The metal ion is the same as the cation.

2. The composite film layer according to claim 1, characterized in that The molar ratio of the metal ion to the organic ligand is 1:(0.5-5).

3. The composite film layer according to claim 2, characterized in that: n is selected as 1 or 2, and / or X is selected from carboxyl or thiol, and / or m is selected from 3-6.

4. The composite film layer according to claim 3, characterized in that: The organic ligand is selected from any one of the following compounds:

5. The composite film layer according to any one of claims 1 to 4, characterized in that: The number of the metal organic framework material layer is one layer, the number of the quantum dot layers is two layers, and the metal organic framework material layer is arranged between the two quantum dot layers, or The number of the metal organic framework material layers is two, the number of the quantum dot layer is one, and the quantum dot layer is arranged between the two metal organic framework material layers.

6. A method for preparing a composite film layer, characterized in that: The following steps are involved: Providing a first solution formed of a metal organic framework material and a second solution formed of quantum dots; The first solution and the second solution are sequentially subjected to film-forming treatment to form a stacked metal organic framework material layer and a quantum dot layer, wherein the steps of sequentially forming the metal organic framework material layer and the quantum dot layer are a repeating unit step, and the unit step is repeated at least once on the surface of the quantum dot layer to obtain the composite film layer. The metal organic framework material layer and the quantum dot layer are stacked and combined to form a unit layer, the composite film layer is formed by alternating at least two of the unit layers, the quantum dot layer on each unit layer is arranged on the surface of the metal organic framework material layer away from the quantum dot layer of the previous unit layer, the surface of the metal organic framework material layer contains active functional groups, and the surface of the quantum dot layer contains cations. At least part of the active functional groups are linked to at least part of the cations; The polarity of the quantum dots is opposite to that of the metal organic framework material; the metal organic framework material is self-assembled from metal ions and organic ligands, and the organic ligands have a molecular structure as shown in general formula I: wherein R is selected from alkyl, silane, porphyrinyl, alkenyl, alkynyl, phenylpyridyl, pyrenyl, phenyl or oxazine, Ar is selected from benzene or biphenyl, X is the active functional group, independently selected from at least one of a carboxyl group, a thiol group, an amino group, a sulfonic acid group and a hydroxyl group, n is the number of X, selected from a positive integer between 1 and 4, m is a positive integer between 2 and 10; The metal ion is the same as the cation.

7. A light emitting diode, characterized in that: It comprises a light-emitting functional layer, wherein the light-emitting functional layer comprises the composite film layer according to any one of claims 1 to 5.

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