CN109216566B - Composite light emitting layer, QLED device and preparation method thereof - Google Patents

Composite light emitting layer, QLED device and preparation method thereof Download PDF

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CN109216566B
CN109216566B CN201710536591.8A CN201710536591A CN109216566B CN 109216566 B CN109216566 B CN 109216566B CN 201710536591 A CN201710536591 A CN 201710536591A CN 109216566 B CN109216566 B CN 109216566B
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graphene oxide
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CN109216566A (en
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梁柱荣
曹蔚然
刘佳
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TCL Corp
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    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/115—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising active inorganic nanostructures, e.g. luminescent quantum dots
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Abstract

A composite light emitting layer, a QLED device and a preparation method thereof. The invention provides a composite light-emitting layer which is a quantum dot light-emitting layer fixed by three-dimensional graphene and comprises a porous three-dimensional mesh material and quantum dots fixed on the porous three-dimensional mesh material, wherein the porous three-dimensional mesh material contains the three-dimensional graphene and/or three-dimensional graphene oxide.

Description

Composite light emitting layer, QLED device and preparation method thereof
Technical Field
The invention belongs to the technical field of quantum dot light emitting diodes, and particularly relates to a composite light emitting layer, a QLED device and a preparation method thereof.
Background
Quantum dot light-emitting diodes (QLEDs) are the next generation of display and lighting technologies of most interest due to their advantages of self-luminescence, low energy consumption, high color purity, etc.
Currently, in the fabrication technology of QLEDs, the most common and promising production process for large-scale industrialization is a solution film-forming method, particularly a quantum dot light-emitting layer in addition to an electrode and various functional layers in a device. For example, for the deposition method of the quantum dot light emitting layer, most of the solution phase film forming processes at present are to dissolve the quantum dots with functionalized surface ligands in an organic solvent, prepare a quantum dot solution or quantum dot ink, then deposit the substrate or the bottom functional layer by spin coating or printing, then deposit an electron transport layer (such as ZnO) on the quantum dot light emitting layer by the same film forming method, and finally evaporate an electrode to obtain the QLED device. However, because the particle size of the quantum dot is larger than that of common ions or organic micromolecules, and the surface of the quantum dot contains abundant organic ligands, the connection between quantum dot particles after film formation is not tight, the film layer is relatively loose, the deposited quantum dot still has a large chance to be dissolved again and taken away or directly washed away in the film formation process of other subsequent functional layers by a solution method, so that the film layer of the quantum dot is not uniform, the interface defect is larger, and the device is not uniform in light emission. Particularly, the interface between the quantum dot light emitting layer and the ZnO electron transport layer of the electron transport layer prepared by ZnO has important influence on the stability and the light emitting uniformity of the QLED device. Even if a solvent that is difficult to dissolve the quantum dots is used, it is difficult to avoid the process, and because of this, the choice of the subsequent functional layer material is limited by the solvent that can be selected.
Disclosure of Invention
The invention aims to provide a composite light-emitting layer, and aims to solve the problem that quantum dots in a quantum dot light-emitting layer are easily dissolved or washed away by preparation solutions of other functional layers in the existing preparation method of a QLED (quantum light-emitting diode) device, so that the device emits light unevenly.
The invention also aims to provide a QLED device containing the composite luminescent layer and a preparation method thereof.
The composite light-emitting layer is a quantum dot light-emitting layer fixed by three-dimensional graphene, and comprises a porous three-dimensional mesh material and quantum dots fixed on the porous three-dimensional mesh material, wherein the porous three-dimensional mesh material contains the three-dimensional graphene and/or the three-dimensional graphene oxide.
And the QLED device comprises a substrate, an anode, a hole injection layer, a hole transport layer, a luminescent layer, an electron transport layer and a cathode which are sequentially laminated and combined, wherein the luminescent layer is the composite luminescent layer.
Correspondingly, the preparation method of the QLED device comprises the following steps:
providing a substrate, and depositing an anode, a hole injection layer and a hole transport layer on the substrate in sequence;
depositing a porous three-dimensional mesh material on the hole transport layer, depositing a quantum dot layer on the porous three-dimensional mesh material, and combining the porous three-dimensional mesh material with the quantum dot layer to form a composite light-emitting layer, wherein the porous three-dimensional mesh material contains three-dimensional graphene and/or three-dimensional graphene oxide;
and sequentially depositing an electron transport layer and a cathode on the composite light-emitting layer.
The composite luminescent layer provided by the invention comprises a porous three-dimensional mesh material and quantum dots fixed on the porous three-dimensional mesh material, wherein the porous three-dimensional mesh material contains three-dimensional graphene and/or three-dimensional graphene oxide. On one hand, the three-dimensional graphene and the three-dimensional graphene oxide can play a role of a support in a film forming process, assist in film forming of quantum dots, and effectively avoid the problems of uneven device luminescence, low luminescence performance, poor device stability and the like caused by agglomeration, incomplete coverage and the like of the quantum dots. On the other hand, the three-dimensional porous network structure provided by the three-dimensional graphene and the three-dimensional graphene oxide can provide a large amount of gaps, and the quantum dots are embedded into the three-dimensional network structure, so that the quantum dots are tightly fixed, the quantum dots are prevented from being washed away by other solutions in the subsequent film forming process of the functional layer or falling off in the film forming process, the film forming quality of the quantum dots is remarkably improved, and the light emitting uniformity and the light emitting efficiency of the device are effectively improved. In addition, because the quantum dots are tightly combined in the porous three-dimensional mesh material, the selection requirement of a solvent during the deposition of a subsequent functional layer is reduced, namely, the selectivity of the subsequent functional layer and the solvent thereof is improved, and the structural design flexibility of the QLED device is improved.
The QLED device provided by the invention contains the composite luminescent layer. Because the quantum dots in the composite light-emitting layer are fixed on the porous three-dimensional mesh material, not only can the agglomeration of the quantum dots be effectively avoided, but also when other functional layers are deposited on the composite light-emitting layer by adopting a solution method, the corrosion of a prepared solvent to the quantum dot layer can be effectively avoided, and the quantum dots are prevented from being dissolved or washed away. In conclusion, the QLED device provided by the invention has the advantages that the light-emitting uniformity, the film stability, the light-emitting efficiency and the service life are improved.
According to the preparation method of the QLED device, the porous three-dimensional mesh material is deposited before the quantum dot layer is deposited. The quantum dots are fixed by the porous three-dimensional mesh material, so that the quantum dots are prevented from being dissolved or washed away by a preparation solvent in the subsequent preparation process of the functional layer, the film forming uniformity of the quantum dots is improved, and further, the light emitting uniformity, the film stability, the light emitting efficiency and the service life of a QLED device are improved.
Drawings
Fig. 1 is a schematic structural diagram of a QLED device provided in an embodiment of the present invention.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The embodiment of the invention provides a composite light-emitting layer which is a quantum dot light-emitting layer fixed by three-dimensional graphene and comprises a porous three-dimensional mesh material and quantum dots fixed on the porous three-dimensional mesh material, wherein the porous three-dimensional mesh material contains the three-dimensional graphene and/or three-dimensional graphene oxide.
Specifically, the porous three-dimensional mesh material comprises three-dimensional graphene and/or three-dimensional graphene oxide. Here, the porous three-dimensional network material may be three-dimensional graphene or three-dimensional graphene oxide alone, or may be a mixed material of three-dimensional graphene and three-dimensional graphene oxide. However, it should be understood that the composition of the porous three-dimensional mesh material is not limited to three-dimensional graphene and/or three-dimensional graphene oxide, and may include other carbon materials other than three-dimensional graphene and/or three-dimensional graphene oxide. Preferably, the porous three-dimensional network material further contains at least one of carbon nanotubes, fullerenes, and carbon fibers. That is, the porous three-dimensional mesh material may be a composite material composed of three-dimensional graphene and at least one of carbon nanotubes, fullerenes and carbon fibers, or may be a composite material composed of three-dimensional graphene oxide and at least one of carbon nanotubes, fullerenes and carbon fibers. Because the three-dimensional graphene and/or the three-dimensional graphene oxide in the porous three-dimensional mesh material can provide a large number of pores, the quantum dots can be embedded into a void structure and fixed on the porous three-dimensional mesh material, so that the anchoring of the quantum dots is realized. When the porous three-dimensional mesh material comprises three-dimensional graphene oxide, as the surface of the three-dimensional graphene oxide contains a large number of electron-rich groups, the electron-rich groups are combined with the quantum dots through electrostatic adsorption; on the other hand, the electron-rich group is bonded to a chemical bond formed by the dipole effect of metal cation vacancies on the surface of the quantum dot. When the porous three-dimensional mesh material comprises the three-dimensional graphene-carbon nanotube composite material, the carbon nanotubes are inserted in the three-dimensional graphene, so that the quantum dots can be better fixed in the composite material.
Further preferably, the three-dimensional graphene oxide contains electron-rich functional groups including, but not limited to, -OH, -COOH, -NH2、-NH-、-SH、-CN、-SO3H、-SOOH、-NO2、-CONH2At least one of, -CONH-, -COCl, -CO-, -CHO, -Cl and-Br. The electron-rich functional groups can provide electrons, and chemical bonding is formed between the electron-rich functional groups and the quantum dots through the dipole effect of metal cation vacancies on the surfaces of the quantum dots.
In the composite light-emitting layer provided by the embodiment of the invention, the mass ratio of the total amount of the three-dimensional graphene and the three-dimensional graphene oxide to the quantum dots is 0.5-120: 1, so that the composite light-emitting layer has good light-emitting efficiency while the quantum dots are effectively anchored. If the content of the three-dimensional graphene and the three-dimensional graphene oxide is higher, the composite light-emitting layer is too thick, so that exciton recombination is difficult, and the light-emitting efficiency of the device is reduced; if the content of the three-dimensional graphene and the three-dimensional graphene oxide is low, the quantum dots cannot be anchored in the porous network structure sufficiently.
The composite light-emitting layer provided by the embodiment of the invention comprises a porous three-dimensional mesh material and quantum dots fixed on the porous three-dimensional mesh material, wherein the porous three-dimensional mesh material contains three-dimensional graphene and/or three-dimensional graphene oxide. On one hand, the three-dimensional graphene and the three-dimensional graphene oxide can play a role of a support in a film forming process, assist in film forming of quantum dots, and effectively avoid the problems of uneven device luminescence, low luminescence performance, poor device stability and the like caused by agglomeration, incomplete coverage and the like of the quantum dots. On the other hand, the three-dimensional porous network structure provided by the three-dimensional graphene and the three-dimensional graphene oxide can provide a large amount of gaps, and the quantum dots are embedded into the three-dimensional network structure, so that the quantum dots are tightly fixed, the quantum dots are prevented from being washed away by other solutions in the subsequent film forming process of the functional layer or falling off in the film forming process, the film forming quality of the quantum dots is remarkably improved, and the light emitting uniformity and the light emitting efficiency of the device are effectively improved. In addition, because the quantum dots are tightly combined in the porous three-dimensional mesh material, the selection requirement of a solvent during the deposition of a subsequent functional layer is reduced, namely, the selectivity of the subsequent functional layer and the solvent thereof is improved, and the structural design flexibility of the QLED device is improved.
And, with reference to fig. 1, an embodiment of the present invention provides a QLED device, including a substrate 1, an anode 2, a hole injection layer 3, a hole transport layer 4, a light emitting layer 5, an electron transport layer 6, and a cathode 7, which are sequentially stacked and combined, where the light emitting layer is the above-mentioned composite light emitting layer.
Specifically, the selection of the substrate 1 is not strictly limited, and may be a rigid substrate or a flexible substrate. Wherein the rigid substrate includes, but is not limited to, one or more of glass, metal foil; the flexible substrate includes, but is not limited to, one or more of polyethylene terephthalate (PET), ethylene terephthalate (PEN), Polyetheretherketone (PEEK), Polystyrene (PS), Polyethersulfone (PES), Polycarbonate (PC), Polyarylate (PAT), Polyarylate (PAR), Polyimide (PI), polyvinyl chloride (PV), Polyethylene (PE), polyvinylpyrrolidone (PVP), textile fibers.
The anode 2 may be selected from anode materials conventional in the field of QLEDs. As an implementation case, the anode 2 is a doped metal oxide including, but not limited to, one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), magnesium-doped zinc oxide (MZO), and aluminum-doped magnesium oxide (AMO). As another implementation, the anode 2 is a composite electrode containing a transparent metal oxide and a metal interlayer, wherein the transparent metal oxide may be a doped transparent metal oxide or an undoped transparent metal oxide. The composite electrode includes but is not limited to AZO/Ag/AZO, AZO/Al/AZO, ITO/Ag/ITO, ITO/Al/ITO, ZnO/Ag/ZnO, ZnO/Al/ZnO, TiO2/Ag/TiO2、TiO2/Al/TiO2、ZnS/Ag/ZnS、ZnS/Al/ZnS、TiO2/Ag/TiO2、TiO2/Al/TiO2One or more of (a).
In the embodiment of the present invention, the hole injection layer 3 is selected from organic materials having a hole injection capability.The hole injection material for preparing the hole injection layer 3 includes, but is not limited to, one or more of poly (3, 4-ethylenedioxythiophene) -polystyrenesulfonic acid (PEDOT: PSS), copper phthalocyanine (CuPc), 2,3,5, 6-tetrafluoro-7, 7',8,8' -tetracyanoquinodimethane (F4-TCNQ), 2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-Hexaazatriphenylene (HATCN), doped or undoped transition metal oxides, and doped or undoped metal chalcogenide compounds. Wherein the transition metal oxide includes, but is not limited to, MoO3、VO2、WO3、CrO3At least one of CuO and CuO; the metal chalcogenide compounds include but are not limited to MoS2、MoSe2、WS2、WSe2And CuS.
In the present invention, as an example, the hole transport layer 4 is selected from organic materials having a hole transport ability, including but not limited to poly (9, 9-dioctylfluorene-CO-N- (4-butylphenyl) diphenylamine) (TFB), Polyvinylcarbazole (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 ″ -tris (carbazol-9-yl) triphenylamine (TCTA), 4' -bis (9-Carbazole) Biphenyl (CBP), N '-diphenyl-N, N' -bis (3-methylphenyl) -1,1 '-biphenyl-4, 4' -diamine (TPD), N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine (NPB), doped graphene, undoped graphene, C60. As another example, the hole transport layer 4 is selected from inorganic materials having hole transport capability, including but not limited to doped or undoped MoO3、VO2、WO3、CrO3、CuO、MoS2、MoSe2、WS2、WSe2And CuS.
In an embodiment of the invention, the light emitting layer 5 is the composite light emitting layer. Specifically, the composite light-emitting layer is a quantum dot light-emitting layer fixed by three-dimensional graphene, and comprises a porous three-dimensional mesh material and quantum dots fixed on the porous three-dimensional mesh material, wherein the porous three-dimensional mesh material contains three-dimensional graphene and/or three-dimensional graphene oxide. The porous three-dimensional mesh material comprises three-dimensional graphene and/or three-dimensional graphene oxide, a large number of pores can be provided, and the quantum dots can be embedded into a gap structure and fixed on the porous three-dimensional mesh material, so that the quantum dots can be tightly combined on the porous three-dimensional mesh material and are not easy to fall off, the film forming quality of the light emitting layer 5 is improved, and the light emitting uniformity and the light emitting efficiency of the QLED device are improved.
Specifically, the porous three-dimensional mesh material is at least one of three-dimensional graphene, three-dimensional graphene oxide and a three-dimensional graphene-carbon nanotube composite material. Further, the three-dimensional graphene oxide contains electron-rich functional groups, and the electron-rich functional groups include but are not limited to-OH, -COOH and-NH2、-NH-、-SH、-CN、-SO3H、-SOOH、-NO2、-CONH2At least one of, -CONH-, -COCl, -CO-, -CHO, -Cl and-Br.
The quantum dots in the quantum dot layer can be one or more of II-VI compounds, III-V compounds, II-V compounds, III-VI compounds, IV-VI compounds, I-III-VI compounds, II-IV-VI compounds or IV elementary substances.
As a preferred implementation, the quantum dots are doped or undoped inorganic perovskite type semiconductors, and/or organic-inorganic hybrid perovskite type semiconductors. Specifically, the structural general formula of the inorganic perovskite type semiconductor is AMX3Wherein A is Cs+Ion, M is a divalent metal cation, including but not limited to Pb2+、Sn2+、Cu2+、Ni2+、Cd2+、Cr2+、Mn2+、Co2+、Fe2+、Ge2+、Yb2+、Eu2+X is a halide anion, including but not limited to Cl-、Br-、I-. The structural general formula of the organic-inorganic hybrid perovskite type semiconductor is BMX3Wherein B is an organic amine cation including but not limited to CH3(CH2)n-2NH3 +(n.gtoreq.2) or NH3(CH2)nNH3 2+(n.gtoreq.2). When n is 2, the inorganic metal halideOctahedron MX of compound6 4-The metal cations M are positioned in the center of a halogen octahedron through connection in a roof sharing mode, and the organic amine cations B are filled in gaps among the octahedrons to form an infinitely extending three-dimensional structure; inorganic metal halide octahedra MX linked in a coterminous manner when n > 26 4-The organic amine cation bilayer (protonated monoamine) or the organic amine cation monolayer (protonated diamine) is inserted between the layers, and the organic layer and the inorganic layer are overlapped with each other to form a stable two-dimensional layered structure; m is a divalent metal cation including, but not limited to, Pb2+、Sn2+、Cu2+、Ni2+、Cd2+、Cr2+、Mn2+、Co2+、Fe2+、Ge2+、Yb2+、Eu2+X is a halide anion, including but not limited to Cl-、Br-、I-。
In the embodiment of the present invention, the electron transport layer 6 is selected from materials having electron transport properties, preferably metal oxides having electron transport properties, including but not limited to n-type ZnO, TiO2、SnO、Ta2O3、AlZnO、ZnSnO、InSnO、Alq3、Ca、Ba、CsF、LiF、CsCO3At least one of (1).
In the embodiment of the present invention, the cathode 7 is one or more of various conductive carbon materials, conductive metal oxide materials, and metal materials. Wherein the conductive carbon material includes, but is not limited to, doped or undoped carbon nanotubes, doped or undoped graphene oxide, C60, graphite, carbon fibers, porous carbon, or mixtures thereof; the conductive metal oxide material includes, but is not limited to, ITO, FTO, ATO, AZO, or mixtures thereof; the metal material includes, but is not limited to, Al, Ag, Cu, Mo, Au, or an alloy thereof. Wherein, the metal material has a form including, but not limited to, nanospheres, nanowires, nanorods, nanocones, hollow nanospheres, or a mixture thereof. Specifically, the cathode 7 is preferably Ag or Al.
Further preferably, the QLED device according to the embodiment of the present invention further includes an interface modification layer, where the interface modification layer is at least one of an electron blocking layer, a hole blocking layer, an electrode modification layer, and an isolation protection layer.
Of course, it should be understood that the QLED device of the embodiment of the present invention may be a positive-type QLED device, and may also be an inverted-type QLED device. The packaging mode of the QLED device may be partially packaged, fully packaged, or unpackaged, and the embodiments of the present invention are not limited strictly.
The QLED device provided by the embodiment of the invention contains the composite light-emitting layer. Because the quantum dots in the composite light-emitting layer are fixed on the porous three-dimensional mesh material, not only can the agglomeration of the quantum dots be effectively avoided, but also when other functional layers are deposited on the composite light-emitting layer by adopting a solution method, the corrosion of a prepared solvent to the quantum dot layer can be effectively avoided, and the quantum dots are prevented from being dissolved or washed away. In summary, the QLED device provided by the embodiment of the invention has the advantages that the light-emitting uniformity, the film stability, the light-emitting efficiency and the service life are improved.
Correspondingly, the embodiment of the invention also provides a preparation method of the QLED device, which comprises the following steps:
s01, providing a substrate, and depositing an anode, a hole injection layer and a hole transport layer on the substrate in sequence;
s02, depositing a porous three-dimensional mesh material on the hole transport layer, depositing a quantum dot layer on the porous three-dimensional mesh material, and combining the porous three-dimensional mesh material with the quantum dot layer to form a composite light-emitting layer, wherein the porous three-dimensional mesh material contains three-dimensional graphene and/or three-dimensional graphene oxide;
and S03, sequentially depositing an electron transport layer and a cathode on the composite light-emitting layer.
Specifically, in the step S01, the selection of the substrate, the anode, the hole injection layer, and the hole transport layer is as described above, and for the sake of brevity, the detailed description thereof is omitted here. The deposition of each layer can be carried out by conventional methods, such as chemical or physical methods. Wherein, the chemical method comprises one or more of but not limited to chemical vapor deposition method, continuous ion layer adsorption and reaction method, anodic oxidation method, electrolytic deposition method and coprecipitation method; the physical method includes, but is not limited to, one or more of spin coating, printing, knife coating, dip coating, dipping, spraying, roll coating, casting, slit coating, bar coating, thermal evaporation, electron beam evaporation, magnetron sputtering, multi-arc ion coating, physical vapor deposition, atomic layer deposition, and pulsed laser deposition. Preferably, an anode is evaporated on the substrate, and a hole injection layer and a hole transport layer are sequentially deposited on the anode by a solution processing method.
In the step S02, a porous three-dimensional network material is deposited on the hole transport layer, and the three-dimensional network material may be selected in various ways. Specifically, the porous three-dimensional mesh material may be a porous three-dimensional mesh material composed of graphene and/or graphene oxide, or may be a composite material composed of graphene and/or graphene oxide and another carbon material.
As a specific example, the porous three-dimensional mesh material is three-dimensional graphene and/or three-dimensional graphene oxide, and the method for depositing the porous three-dimensional mesh material on the hole transport layer comprises:
dispersing three-dimensional graphene and/or three-dimensional graphene oxide in a solvent to prepare a porous three-dimensional mesh material solution; the porous three-dimensional network material solution is then deposited on the hole transport layer by solution processing.
As another specific example, the porous three-dimensional network material is a three-dimensional porous composite material formed by at least one of three-dimensional graphene and three-dimensional graphene oxide and at least one of carbon nanotubes, fullerenes and carbon fibers, and the method for depositing the porous three-dimensional network material on the hole transport layer is as follows:
dispersing at least one of three-dimensional graphene and three-dimensional graphene oxide in a solvent to prepare a first solution, and depositing the first solution on the hole transport layer by a solution processing method to form the three-dimensional graphene and/or the three-dimensional graphene oxide layer; and then depositing at least one of carbon nano tube, fullerene and carbon fiber on the three-dimensional graphene and/or the three-dimensional graphene oxide layer by a solution processing method to form a three-dimensional porous composite structure layer.
As another specific example, the porous three-dimensional network material is a three-dimensional porous composite material formed by at least one of three-dimensional graphene and three-dimensional graphene oxide and at least one of carbon nanotubes, fullerenes and carbon fibers, and the method for depositing the porous three-dimensional network material on the hole transport layer is as follows:
dispersing at least one of three-dimensional graphene and three-dimensional graphene oxide and at least one of carbon nano tube, fullerene and carbon fiber in a solvent to prepare a mixed solution; and then depositing the mixed solution on the hole transport layer by a solution processing method to form a three-dimensional porous composite structure layer.
In the above embodiments, the solution processing method includes, but is not limited to, spin coating, printing, blade coating, dip-draw method, dipping method, spray coating, roll coating, casting method, slit coating, and bar coating.
And a quantum dot layer is deposited on the porous three-dimensional mesh material, the quantum dots are embedded into the porous three-dimensional mesh material through three-dimensional pores, so that the quantum dots are fixed, the deposited quantum dot layer and the porous three-dimensional mesh material are combined to form a composite luminescent layer, the film forming property of the luminescent layer is improved, and the luminescent uniformity and the device stability of the QLED device are further improved.
In the above step S03, the method of sequentially depositing the electron transport layer and the cathode on the composite light emitting layer may refer to the deposition method of each layer in step S02. Preferably, an electron transport layer is deposited on the composite light-emitting layer by a solution processing method, and then a cathode is evaporated to obtain the QLED device.
Furthermore, an interface modification layer can be deposited according to the performance requirements of the device, wherein the interface modification layer is at least one of an electron blocking layer, a hole blocking layer, an electrode modification layer and an isolation protection layer.
According to the preparation method of the QLED device, the porous three-dimensional mesh material is deposited before the quantum dot layer is deposited. The quantum dots are fixed by the porous three-dimensional mesh material, so that the quantum dots are prevented from being dissolved or washed away by a preparation solvent in the subsequent preparation process of the functional layer, the film forming uniformity of the quantum dots is improved, and further, the light emitting uniformity, the film stability, the light emitting efficiency and the service life of a QLED device are improved.
The following description will be given with reference to specific examples.
Example 1
A preparation method of a QLED device is characterized by comprising the following steps:
s11, providing ITO conductive glass, and spin-coating PEDOT on the ITO conductive glass, wherein a PSS film is used as a hole injection layer, and a TFB layer is spin-coated on the hole injection layer and used as a hole transport layer;
s12, spinning and coating a graphene dispersion liquid on the hole transport layer to form a three-dimensional porous graphene layer; spin-coating a CdSe/ZnS quantum dot light-emitting layer on the three-dimensional porous graphene layer to form a composite light-emitting layer;
s13, coating ZnO on the composite light emitting layer in a spin mode to serve as an electron transmission layer, and evaporating an Al cathode layer on the electron transmission layer to obtain the quantum dot light emitting diode.
It should be understood that embodiment 1 of the present invention is only an example, and does not represent the actual protection scope of the technical solution of the present invention. The choice of materials, the structure of the layers of the embodiments of the invention and their preferred aspects can all be selected under the circumstances shown herein.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. The composite light-emitting layer is a quantum dot light-emitting layer with three-dimensional graphene fixed, and comprises a porous three-dimensional mesh material and quantum dots fixed on the porous three-dimensional mesh material, wherein the porous three-dimensional mesh material contains three-dimensional graphene oxide, the three-dimensional graphene oxide contains an electron-rich functional group, and the electron-rich functional group and the quantum dots are bonded through electrostatic adsorption while forming chemical bonds.
2. The composite light-emitting layer according to claim 1, wherein the porous three-dimensional network material further contains at least one of carbon nanotubes, fullerenes, and carbon fibers.
3. The composite light emitting layer of claim 2, wherein the electron rich functional group comprises-OH, -COOH, -NH2、-NH-、-SH、-CN、-SO3H、-SOOH、-NO2、-CONH2At least one of, -CONH-, -COCl, -CO-, -CHO, -Cl and-Br.
4. The composite light-emitting layer according to any one of claims 1 to 3, wherein a mass ratio of the three-dimensional graphene oxide to the quantum dots is 0.5 to 120: 1.
5. A QLED device comprising a substrate, an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode, which are sequentially stacked and combined, wherein the light-emitting layer is the composite light-emitting layer according to any one of claims 1 to 4.
6. The QLED device of claim 5, further comprising an interface modification layer, wherein the interface modification layer is at least one of an electron blocking layer, a hole blocking layer, an electrode modification layer, and an isolation protection layer.
7. A preparation method of a QLED device is characterized by comprising the following steps:
providing a substrate, and depositing an anode, a hole injection layer and a hole transport layer on the substrate in sequence;
depositing a porous three-dimensional mesh material on the hole transport layer, depositing a quantum dot layer on the porous three-dimensional mesh material, and combining the porous three-dimensional mesh material with the quantum dot layer to form a composite light-emitting layer, wherein the porous three-dimensional mesh material contains three-dimensional graphene oxide, the three-dimensional graphene oxide contains an electron-rich functional group, and the electron-rich functional group is combined with the quantum dot through electrostatic adsorption; the electron-rich functional group and the quantum dot form chemical bond combination;
and sequentially depositing an electron transport layer and a cathode on the composite light-emitting layer.
8. The method of fabricating the QLED device of claim 7, wherein the porous three-dimensional network material is three-dimensional graphene oxide, and the method of depositing the porous three-dimensional network material on the hole transport layer comprises:
dispersing three-dimensional graphene oxide in a solvent to prepare a porous three-dimensional mesh material solution; the porous three-dimensional network material solution is then deposited on the hole transport layer by solution processing.
9. The method of claim 7, wherein the porous three-dimensional network material is a three-dimensional porous composite material formed by three-dimensional graphene oxide and at least one of carbon nanotubes, fullerenes and carbon fibers, and the porous three-dimensional network material is deposited on the hole transport layer by:
dispersing three-dimensional graphene oxide in a solvent to prepare a first solution, and depositing the first solution on the hole transport layer by a solution processing method to form a three-dimensional graphene oxide layer; and then depositing at least one of carbon nano tube, fullerene and carbon fiber on the three-dimensional graphene oxide layer by a solution processing method to form a three-dimensional porous composite structure layer.
10. The method of claim 7, wherein the porous three-dimensional network material is a three-dimensional porous composite material formed by three-dimensional graphene oxide and at least one of carbon nanotubes, fullerenes and carbon fibers, and the porous three-dimensional network material is deposited on the hole transport layer by:
dispersing three-dimensional graphene oxide and at least one of carbon nano tube, fullerene and carbon fiber in a solvent to prepare a mixed solution; and then depositing the mixed solution on the hole transport layer by a solution processing method to form a three-dimensional porous composite structure layer.
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