Quantum dot light emitting device and method of manufacturing the same

Abstract

The present application relates to a kind of quantum dot light emitting device and its preparation method.The quantum dot light emitting layer of the quantum dot light emitting device includes three kinds of quantum dot subunits with different light emitting colors arranged in array, and three kinds of quantum dot subunits all include crosslinking copolymer, which is made by pre-polymer through crosslinking reaction, pre-polymer includes connected repeating unit (see formula I) And end group, end group contains: at least one of cyan group, hydroxyl group, sulfonic acid group, mercapto group, disulfide group, phosphorus group, amino group, carboxyl group, thiocyan group and halogen, the end group is bound together with quantum dot by coordination bond;Ar1It is big π conjugated nitrogen-containing heteroaromatic group, with excellent film-forming property and hole transport capacity, and with low LUMO energy level, can hinder the transmission of anode electron;R9It is crosslinkable group, provides crosslinking basis.The film-forming uniformity of the quantum dot of the present application is good, can maintain the high light emitting efficiency of quantum dot, promote the transmission of hole, improve the balance of carrier.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electroluminescence, in particular to a quantum dot light-emitting device and a preparation method thereof. BACKGROUND

[0002] Display technology has completed a leap after another from the early cathode ray tube (CRT), to liquid crystal display (LCD) in the late 1980s, to plasma panel display (PDP), and to the current mainstream OLED / QLED display.

[0003] Organic light-emitting diode (OLED) has become the mainstream technology in the field of display technology due to its excellent display performance such as self-luminescence, simple structure, ultra-thin, fast response, wide viewing angle, low power consumption, and flexible display. Quantum dot light-emitting diode (QLED) has become a strong competitor of OLED due to its saturated color, adjustable wavelength, and high photoelectric quantum yield.

[0004] The current QLED device has an inorganic quantum dot (QD) layer as the light-emitting layer. Since QD is an inorganic nanoparticle, the film-forming property is poor, and it is easy to penetrate into the gap of other functional film layers in the light-emitting device, thereby reducing the performance of the device. Further, the electron transport layer in the current QLED device generally uses ZnO inorganic oxide, and the hole transport layer is an organic hole transport material (HTM). On the one hand, since the QD light-emitting layer and the ZnO electron transport layer are both inorganic nanoparticles, the film-forming property is not very smooth, and it is easy to penetrate into the gap of the other film-forming layer, thereby becoming a cage of excitons, causing quenching of excitons, and reducing the performance of the device. On the other hand, the electron mobility of ZnO is much greater than the hole mobility of the hole transport layer, and the electron injection barrier from ZnO to the QD layer is smaller than the hole injection barrier from the hole transport layer to the QD layer, which causes imbalance of the carriers in the QD layer, resulting in Russel recombination of the charged QD, and reducing the performance of the device. In addition to ZnO, the electron transport layer prepared from other inorganic oxides also has similar problems.

[0005] In addition, the current industry generally uses inkjet printing (one of the solution methods) to prepare RGB QLED devices. The required R, G, and B three-color quantum dot ink is printed into the corresponding light-emitting unit by inkjet printing on demand, and then the ink is film-formed by a vacuum drying device. This method has the advantages of high resolution and small volume, but it requires high-precision inkjet printing equipment, and the film formation of the ink has a coffee ring effect (thick at the edge and thin in the middle). The prepared device often has a leakage current and insufficient stability. SUMMARY

[0006] Based on this, the purpose of the present application is to provide a quantum dot light-emitting device with uniform quantum dot light-emitting layer film formation.

[0007] The technical solution is as follows:

[0008] A quantum dot light-emitting device comprises:

[0009] A quantum dot light-emitting layer comprises first, second and third quantum dot subunits arranged in an array and having different light-emitting colors, and each of the first, second and third quantum dot subunits independently comprises a crosslinking copolymer;

[0010] The crosslinking copolymer is made of a prepolymer through a crosslinking reaction, the prepolymer comprises connected repeating units and end groups, and the repeating units have a structure shown in formula (I):

[0011]

[0012] * represents a connection site;

[0013] The end groups each occurrence independently contain at least one of a cyano group, a hydroxyl group, a sulfonic acid group, a mercapto group, a disulfide group, a phosphorus group, an amino group, a carboxyl group, a thiocyanate group and a halogen, and the end groups are combined together with the quantum dots through a coordination bond;

[0014] Ar1 is a large pi-conjugated nitrogen-containing heteroaromatic group;

[0015] R9 is a crosslinkable group;

[0016] The crosslinking point of the crosslinking copolymer is a group generated by crosslinking of R9;

[0017] L1 and L2 are independently selected from a single bond, an aryl group with 6 to 20 ring atoms or a heteroaryl group with 5 to 20 ring atoms;

[0018] m and n are independently positive integers, and m / n is 1 to 99.

[0019] The present application also provides a preparation method of the quantum dot light-emitting device as described above, comprising the following steps:

[0020] First, second and third inks are provided, the first ink comprises first quantum dots and the prepolymer combined with the first quantum dots, the second ink comprises second quantum dots and the prepolymer combined with the second quantum dots, and the third ink comprises third quantum dots and the prepolymer combined with the third quantum dots;

[0021] Form a first precursor film layer on the substrate provided with the functional layer by using the first ink, and form the first quantum dot subunit in the first preset area by mask processing, light processing and drying processing;

[0022] Form a second precursor film layer on the substrate provided with the functional layer by using the second ink, and form the second quantum dot subunit in the second preset area by mask processing, light processing and drying processing;

[0023] Form a third precursor film layer on the substrate provided with the functional layer by using the third ink, and form the third quantum dot subunit in the third preset area by mask processing, light processing and drying processing.

[0024] The present application has the following beneficial effects:

[0025] The quantum dot light-emitting device provided by the present application comprises first, second and third quantum dot subunits arranged in an array and having different light-emitting colors, and each of the subunits independently comprises a cross-linked copolymer made from a prepolymer through cross-linking reaction, wherein the prepolymer comprises a terminal group, Ar1 and R9 in structure. The terminal group has strong affinity with the surface of QD and can be tightly combined with the surface layer of QD through coordination bond, and is not easy to fall off, thereby increasing the stability of QD and not affecting the function of quantum dots. The Ar1 is a large π-conjugated nitrogen-containing heteroaromatic group, which has excellent film-forming property and hole transport capacity, and a low LUMO energy level to hinder the transport of anode electrons. The R9 is a cross-linkable group to provide the basis for cross-linking. Through the synergistic cooperation of the three groups, the cross-linked copolymer obtained after cross-linking forms a network with each other, which can significantly improve the film-forming property and compactness of quantum dots, modify the interface performance of quantum dots, and maintain the high light-emitting efficiency of quantum dots. At the same time, the group with hole transport capacity in the cross-linked copolymer can promote the transport of holes and improve the balance of carriers. Further, through the cooperation of subunits of different colors, full-color light-emitting can be realized.

[0026] The preparation method of the quantum dot light-emitting device provided by the present application mainly comprises the steps of preparing ink, applying the ink on a functional layer substrate, and preparing a preset light-emitting subunit in a specific preset area through mask processing, light processing and drying processing. The method is simple to operate, has low requirements on equipment, is high in production efficiency, and is suitable for industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a structure schematic diagram of the quantum dot light-emitting device according to an embodiment of the present application;

[0028] Figure 2 is a structure schematic diagram of the quantum dot light-emitting device according to an embodiment of the present application;

[0029] Figure 3 is a flow chart of a method for preparing a quantum dot light emitting device according to an embodiment of the present application;

[0030] Figure 4 is a schematic diagram of a mask plate used for preparing a red quantum dot sub-unit according to an embodiment of the present application;

[0031] Figure 5 is a schematic diagram of a mask plate used for preparing a green quantum dot sub-unit according to an embodiment of the present application;

[0032] Figure 6 is a schematic diagram of a mask plate used for preparing a blue quantum dot sub-unit according to an embodiment of the present application;

[0033] Figure 7 is a schematic diagram of a quantum dot light emitting layer comprising red quantum dot sub-units, green quantum dot sub-units and blue quantum dot sub-units arranged in an array according to an embodiment of the present application;

[0034] Figure 8 is a flow chart of a method for preparing an upright quantum dot light emitting device according to an embodiment of the present application;

[0035] Figure 9 is a flow chart of a method for preparing an inverted quantum dot light emitting device according to an embodiment of the present application;

[0036] Figure 10 is a schematic diagram of a structure and energy level of a specific electron transport material corresponding to a specific quantum dot sub-unit according to an embodiment of the present application;

[0037] Figure 11 is a 1H NMR spectrum of the prepolymer 1 prepared in Example 1. DETAILED DESCRIPTION

[0038] The present application will be further described by the following non-limiting examples and figures. The present application can be realized in numerous different forms, and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0040] It should be noted that in the description of the present application, for the orientation words, such as the terms "center", "transverse", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation and positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and cannot be understood as limiting the specific protection scope of the present application.

[0041] When describing the positional relationship, unless otherwise specified, when an element such as a layer, a film, or a substrate is referred to as "on" another film layer, it can be directly on the other film layer or there can be an intervening film layer. Further, when a layer is referred to as being "under" another layer, it can be directly under the other layer, or there can be one or more intervening layers. It can also be understood that when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there can be one or more intervening layers.

[0042] In the case of using "include", "have", and "contain" described in this document, it is intended to cover non-exclusive inclusion, unless the explicit limiting term such as "only", "consisting of", etc. is used, another component can also be added.

[0043] In addition, the drawings are not drawn in a 1:1 ratio, and the relative sizes of the elements are only drawn in the drawings by way of example in order to facilitate the understanding of the present application, but are not necessarily drawn in true proportion, and the proportions in the drawings do not constitute a limitation on the present application.

[0044] In the present application, "substituted" means that a hydrogen atom in a substituent is replaced by a substituent. And the term "substituted or unsubstituted" in the present application means that the event or environment described later can occur but does not necessarily occur, and the description includes the case where the event or environment occurs or does not occur. For example, "substituted or unsubstituted aryl" means that the hydrogen atoms on the aryl group can be further substituted or not substituted.

[0045] Further, when the substituents of the present application can be further substituted, they can be substituted with the following groups: 1-10 linear or branched alkyl group, C 1-10 alkoxy group, aryl group having 6 to 20 ring atoms, or heteroaryl group having 5 to 20 ring atoms.

[0046] In the present application, "alkyl" refers to a saturated aliphatic hydrocarbon group, including linear and branched groups. For example, C1-C 10Alkyl refers to an alkyl group containing 1 to 10 carbon atoms. Non-limiting examples include: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, 2-methylbutyl, 3-methylbutyl, n-hexyl, 1-ethyl-2-methylpropyl, 1,1,2-trimethylpropyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 2,2-dimethylbutyl, 1,3-dimethylbutyl, 2-ethylbutyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, and 2,3-dimethylbutyl.

[0047] "Cycloalkyl" refers to a saturated or partially unsaturated monocyclic or polycyclic cyclic hydrocarbon substituent. A 3-10 membered cycloalkyl group refers to a cycloalkyl group comprising 3 to 10 carbon atoms. In one embodiment, a 3-10 membered monocyclic cycloalkyl group is cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cyclohexadienyl, cycloheptyl, cyclohepttrienyl, cyclooctyl, etc.

[0048] Alkoxy groups include -O- (alkyl) and -O- (cycloalkyl). The definitions of alkyl and cycloalkyl are as described above. In one embodiment, the C1-C4 alkoxy group is methoxy, ethoxy, propoxy, butoxy, cyclopropoxy, or cyclobutoxy. The alkoxy group may be optionally substituted or unsubstituted.

[0049] In this invention, "ring atom number" refers to the number of atoms in the ring itself of a structural compound (e.g., monocyclic compound, fused-ring compound, cross-linked compound, carbocyclic compound, heterocyclic compound) obtained by atomic bonding to form a ring. When the ring is substituted by a substituent, the atoms contained in the substituent are not included in the ring-forming atoms. The same applies to the "ring atom number" described below unless otherwise specified. For example, the benzene ring has 6 ring atoms, the naphthalene ring has 10 ring atoms, and the thiophene group has 5 ring atoms.

[0050] "Aryl, aromatic group, or aromatic group" refers to a hydrocarbon group containing at least one aromatic ring. "Heteroaromatic group or heteroaromatic group" refers to an aromatic hydrocarbon group containing at least one heteroatom. The heteroatom is preferably selected from N, O, and S, and particularly preferably from N. A fused-ring aromatic group refers to an aromatic group whose ring can have two or more rings, wherein two carbon atoms are shared by two adjacent rings, i.e., a fused ring. A fused-heterocyclic aromatic group refers to a fused-ring aromatic hydrocarbon group containing at least one heteroatom. For the purposes of this invention, aromatic groups or heteroaromatic groups include not only systems with aromatic rings but also non-aromatic ring systems. Therefore, systems such as pyridine, thiophene, pyrrole, pyrazole, triazole, imidazole, oxazole, oxadiazole, thiazole, tetraazole, pyrazine, pyridazine, pyrimidine, triazine, and carbene are also considered aromatic groups or heterocyclic aromatic groups.

[0051] Further, the aromatic ring in the aromatic group is selected from the group consisting of benzene, naphthalene, anthracene, phenanthrene, benzophenanthrene, pyrene, acenaphthene, fluorene, biphenyl, terphenyl, and derivatives thereof; the heteroaromatic ring in the heteroaromatic group is selected from the group consisting of triazine, pyridine, pyrimidine, imidazole, furan, thiophene, benzofuran, benzothiophene, indole, carbazole, pyrroloimidazole, pyrrolopyrrole, thienopyrrole, thienothiophene, furanopyrrole, furanofuran, thienofuran, benzimidazole, quinoline, isoquinoline, dibenzothiophene, dibenzofuran, carbazole, and derivatives thereof. Further, the aromatic ring in the aromatic group is selected from the group consisting of benzene, naphthalene, or biphenyl; the heteroaromatic ring in the heteroaromatic group is selected from the group consisting of pyridine, pyrimidine, imidazole, triazine, carbazole, triphenylamine, or diphenylamine.

[0052] In the present application, "*" represents a connection site.

[0053] In the present application, the connection line containing "*" interpenetrating in the ring is understood as the general meaning in the art, indicating that the optional connectable positions on the ring can be used as connection sites, for example: indicating that any one of the optional connectable positions X1-X6 on the ring is used as a connection site, indicating that any two of the optional connectable positions X1-X6 on the ring are used as connection sites.

[0054] Crosslinking refers to the process of connecting linear or branched polymer chains into reticular or bulk polymers by covalent bonds. Preferably, in the present application, the crosslinking method is photocrosslinking, which is the process of crosslinking linear polymers to form reticular or bulk polymers by light irradiation.

[0055] In the present application, the composite material refers to a material formed by quantum dots and crosslinked copolymers.

[0056] The technical solutions of the present application are as follows:

[0057] A quantum dot light-emitting device, comprising: a quantum dot light-emitting layer;

[0058] The quantum dot light-emitting layer comprises first, second, and third quantum dot subunits arranged in an array and emitting different colors of light, and each of the first, second, and third quantum dot subunits independently comprises a crosslinked copolymer;

[0059] The crosslinked copolymer is made from a prepolymer through a crosslinking reaction, the prepolymer comprises connected repeating units and end groups, and the repeating units have the structure shown in formula (I):

[0060]

[0061] "*" represents a connection site;

[0062] The end group independently contains at least one of cyano, hydroxyl, sulfonic acid group, mercapto, disulfide, phosphorus group, amino, carboxyl, thiocyanogen and halogen, and the end group is combined with the quantum dot by a coordination bond;

[0063] Ar1 is a large π conjugated nitrogen-containing heteroaromatic group;

[0064] R9 is a crosslinkable group;

[0065] The crosslinking point of the crosslinked copolymer is a group generated by crosslinking of R9;

[0066] L1 and L2 are independently selected from a single bond, an aryl group having 6 to 20 ring atoms, or a heteroaryl group having 5 to 20 ring atoms;

[0067] m and n are independently positive integers, and m / n is 1 to 99.

[0068] The end group can contain other groups such as alkyl, aryl, heteroaryl, etc. in addition to at least one of cyano, hydroxyl, sulfonic acid group, mercapto, disulfide, phosphorus group, amino, carboxyl, thiocyanogen and halogen, and the other groups can be respectively connected to the repeating unit and the above-mentioned cyano, hydroxyl, sulfonic acid group, mercapto, disulfide, phosphorus group, amino, carboxyl, thiocyanogen and halogen groups.

[0069] It can be understood that the crosslinked copolymers contained in the first quantum dot subunit, the second quantum dot subunit and the third quantum dot subunit are independent of each other, and can be the same or different, and for the same reason, each prepolymer for preparing each crosslinked copolymer is independent of each other, and can be the same or different.

[0070] In the present application, the end group has strong affinity with the surface of the QD, can be tightly combined with the surface layer of the QD through a coordination bond, is not easy to fall off, increases the stability of the QD, and does not affect the function of the quantum dot. The Ar1 is a large π conjugated nitrogen-containing heteroaromatic group, has excellent film forming property and hole transport ability, and has a low LUMO energy level to hinder the transmission of anode electrons. R9 is a crosslinking group, which provides the basis for crosslinking. Through the synergistic cooperation of these groups, the crosslinked copolymer is obtained after crosslinking, the molecular chains form a network shape, which can significantly improve the film forming uniformity of the quantum dot, modify the interface performance of the quantum dot, and maintain the high luminous efficiency of the quantum dot. At the same time, the group with hole transport ability in the crosslinked copolymer can promote the transmission of holes and improve the balance of carriers.

[0071] In the present application, the control m / n is 1-99, for example, m / n can be 1, 2, 5, 9, 10, 11, 12, 12.5, 13, 14, 15, 16, 17, 18, 19, 20, 30, 40, 50, 60, 70, 80, 90, 95 or 99, because the crosslinking group is an insulating non-conductive group, and if the content of the crosslinking group is too high, the ability of the QD to transport carriers will be reduced.

[0072] In one embodiment, the end group is selected from at least one of cyano, alkyl mercapto, aryl mercapto, disulfide, amino, carboxyl, thiocyanate, halogen and phosphine group. Such end groups have stronger binding force with the metal atoms on the surface of the quantum dots. Further, the end group is selected from at least one of benzene thiol, 1,2-benzene thiol, 1,3-benzene thiol, 1,4-benzene thiol, thio propionic acid, thiocyanate and halogen. In addition to having strong affinity with the surface of the QD, it can also reduce the Fermi level of the QD, thereby making the LUMO and HOMO levels of the QD shallower, and the ability of aromatic mercaptan, carboxylic acid, thiocyanate ion, halogen ion to change the QD energy level decreases in turn. After being combined with aromatic mercaptan, the LUMO and HOMO levels of the QD are the shallowest, which is beneficial to the injection of holes.

[0073] In one embodiment, Ar1 is selected from any of the groups represented by (A-1)-(A-4):

[0074]

[0075] wherein:

[0076] X and Y1 are independently N or CR1;

[0077] Y2 is independently selected from NR2, O, S, CR3R4;

[0078] R1-R4 are independently selected from hydrogen atom, deuterium atom, alkyl group having 1-10 C atoms, alkoxy group having 1-10 C atoms, aryl group having 6-20 ring atoms or heteroaryl group having 5-20 ring atoms;

[0079] (A-1)-(A-4) contains at least one N.

[0080] The groups represented by (A-1)-(A-4) have a rigid structure, good thermal stability and film-forming property, which can further enhance the film-forming property and hole transport ability of the quantum dot composite material of the present application.

[0081] In one embodiment, R1-R4 are independently selected from methyl, ethyl, tert-butyl, phenyl, biphenyl, terphenyl, naphthyl, pyridyl, triazine, pyrimidine and pyrazine.

[0082] In one embodiment, Ar1 is selected from one of the following groups:

[0083]

[0084] The N-containing heteroaryl group described above can increase the conjugation degree of the compound, lower the LUMO, and thus improve the hole transport ability.

[0085] Further, Ar1 is selected from one of the following groups:

[0086]

[0087] It can be understood that the temperature of thermal crosslinking is high, and the end group is less heat-resistant, especially the thiol group in the end group. Compared with thermal crosslinking, the application uses a photo-crosslinking group as a crosslinking group, and the stability of each group is better. After crosslinking, the effect of improving the uniformity of the quantum dot film is better, and finally the quenching of metal oxides (such as ZnO) on QD excitons can be greatly reduced.

[0088] In one embodiment, R9 is selected from at least one of an azido group and a ketone carbonyl group. The use of these photosensitive groups can improve the crosslinking effect and improve the film forming property of the quantum dots.

[0089] In one embodiment, the ketone carbonyl group is a benzophenone group.

[0090] In one embodiment, L1 and L2 are independently selected from a single bond or one of the following groups (B-1) to (B-7):

[0091]

[0092] In which:

[0093] X1 and Y3 are independently N or CR5;

[0094] Y4 is independently selected from NR6, CR7R8;

[0095] R5-R8 are independently selected from a hydrogen atom, a deuterium atom, an alkyl group having 1 to 10 C atoms, an alkoxy group having 1 to 10 C atoms, an aryl group having 6 to 20 ring atoms, or a heteroaryl group having 5 to 20 ring atoms.

[0096] In one embodiment, L1 and L2 are independently selected from a single bond or one of the following groups:

[0097]

[0098] The following lists the structures of the prepolymer according to the application, but is not limited thereto:

[0099]

[0100]

[0101] In one embodiment, the method for preparing the prepolymer of the present application comprises the following steps:

[0102] providing a compound containing L1 and Ar1, reacting it with a vinyl compound to prepare a monomer;

[0103] providing a monomer;

[0104] mixing a monomer, a monomer, an initiator and a chain transfer agent containing a terminal group, and copolymerization occurs.

[0105] In one embodiment, the crosslinked copolymer comprises at least one structure represented by formula (II) or formula (III):

[0106]

[0107] The crosslinking degree of the crosslinked copolymer is 10-100. Further, the crosslinking degree of the crosslinked copolymer is 10-30. The suitable crosslinking degree can improve the uniformity of quantum dot film formation, and also can keep the ability of QD to transport carriers at a relatively good level.

[0108] In one embodiment, the crosslinked copolymer of the present application comprises at least one structure represented by any one of formula (C-1)-(C-4) for each occurrence, respectively:

[0109]

[0110] The quantum dots in the present application are quantum dot light emitting materials with core-shell structure, such as one or more of group II-VI compounds, group III-V compounds, group II-V compounds, group III-VI compounds, group IV-VI compounds, group I-III-VI compounds, group II-IV-VI compounds or group IV single element, the core material can be but is not limited to at least one selected from CdSe, CdS, ZnSe, ZnS, CdTe, CdZnS, CdZnSe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdSeSTe, ZnSeSTe, CdZnSeSTe, InP, InAs, InAsP, and the shell material can be but is not limited to at least one selected from CdS, ZnSe, ZnS, CdSeS and ZnSeS. With such quantum dots, higher light emitting performance is achieved.

[0111] In one embodiment, the red quantum dots are CdSe / ZnSe; the green quantum dots are CdSe / ZnS; and the blue quantum dots are selected from ZnCdS / ZnS. Understandably, quantum dots can be adjusted in size to control the wavelength, and the same kind of quantum dots can emit red, blue or green light or other colors of light by adjusting their size.

[0112] In one embodiment, the first quantum dot subunit is a red quantum dot subunit, the second quantum dot subunit is a green quantum dot subunit, and the third quantum dot subunit is a blue quantum dot subunit. By combining quantum dot subunits of multiple light-emitting colors, a full-color device effect can be adjusted.

[0113] In one embodiment, the quantum dot light-emitting device further comprises:

[0114] Oppositely arranged cathode and anode, the quantum dot light-emitting layer is arranged between the cathode and the anode;

[0115] An electron transport layer, the electron transport layer is arranged between the quantum dot light-emitting layer and the cathode, and the electron transport layer comprises an electron transport material;

[0116] In the electron transport layer, the LUMO energy level of the electron transport material corresponding to the red quantum dot subunit is > 4.1 eV, and the LUMO energy level of the electron transport material corresponding to the blue quantum dot subunit and the green quantum dot subunit is independently 3 eV-4.1 eV

[0117] Since the film uniformity of the cross-linked modified quantum dot composite material is significantly improved, the interface performance of the quantum dot light-emitting layer and the electron transport layer can be modified, the exciton quenching of the electron transport layer to the quantum dot light-emitting layer is greatly reduced, the high quantum light-emitting efficiency of the quantum dot light-emitting layer is maintained, and based on the group with hole transport ability in the quantum dot light-emitting layer, the transmission and injection of holes can be promoted, the balance of carriers is improved, and thus the performance and stability of the device are improved. Further, by arranging corresponding electron transport layer materials in the red quantum dot subunit, the green quantum dot subunit and the blue quantum dot subunit, the best energy level matching of RGB three colors can be achieved, so the best electron injection efficiency of RGB three colors can be achieved, and the best RGB QLED device can be obtained. As shown in Figure 10 .

[0118] In one embodiment, the electron transport material corresponding to the red quantum dot subunit is selected from at least one of zinc oxide (ZnO), tin dioxide (SnO2), zinc tin oxide (SnZnO) and zinc magnesium oxide (MgZnO);

[0119] The electron transport materials corresponding to the blue quantum dot unit and the green quantum dot unit are each independently selected from at least one of zirconium dioxide (ZrO2) and titanium dioxide (TiO2).

[0120] In one embodiment, the anode material is optionally, but not limited to, high work function metals and their metal oxides such as ITO, IZO, and Au.

[0121] In one embodiment, the cathode material is at least one of conductive carbon material, metallic material and transparent conductive oxide material, wherein the conductive carbon material includes, but is not limited to, doped or undoped carbon nanotubes, doped or undoped graphene, doped or undoped graphene oxide, C60, graphite, carbon fiber, porous carbon; the metallic material includes, but is not limited to, aluminum, silver, gold, calcium, barium, magnesium or alloys thereof; and the transparent conductive oxide includes, but is not limited to, ITO, FTO, ATO, AZO, IZO, IZTO, IGTO.

[0122] In one embodiment, the quantum dot light-emitting device further includes a hole injection layer and a hole transport layer, wherein the hole injection layer is disposed between the anode and the quantum dot light-emitting layer, and the hole transport layer is disposed between the hole injection layer and the quantum dot light-emitting layer.

[0123] Based on the different structures of quantum dot light-emitting devices, quantum dot light-emitting devices can be divided into upright structures and inverted structures.

[0124] As one implementation method, when the quantum dot light-emitting device is in an upright structure, such as Figure 1 As shown, the quantum dot light-emitting device includes an anode 102, a hole injection layer 103, a hole transport layer 104, a quantum dot light-emitting layer 105, an electron transport layer 106, and a cathode 107 sequentially stacked on a substrate 101. The quantum dot light-emitting layer 105 contains red quantum dot units (RQD), green quantum dot units (GQD), and blue quantum dot units (BQD) arranged in an array as described in this invention.

[0125] As another implementation method, when the quantum dot light-emitting device has an inverted structure, such as Figure 2 As shown, the quantum dot light-emitting device includes a cathode 202, an electron transport layer 203, a quantum dot light-emitting layer 204, a hole transport layer 205, a hole injection layer 206, and an anode 207, which are sequentially stacked on a substrate 201. The quantum dot light-emitting layer 204 contains red, green, and blue quantum dot units arranged in an array as described in this invention.

[0126] In one embodiment, the material for preparing the hole injection layer of the normal and / or inverted quantum dot light-emitting device includes, but is not limited to, PEDOT:PSS, NiOx, WO3, CuPc, HATCN, m-MTDATA, F4-TCQN and MoO3.

[0127] In one embodiment, the material for preparing the hole transport layer of the normal and / or inverted quantum dot light-emitting device includes, but is not limited to, TPD, poly-TPD, PVK, CBP, NPB, TCTA, mCP, TAPC and TFB.

[0128] In one embodiment, the substrate for preparing the normal and / or inverted quantum dot light-emitting device is a rigid substrate such as glass, or a flexible substrate such as a PI film.

[0129] In one embodiment, the thickness of the anode of the normal and / or inverted quantum dot light-emitting device is 10-200 nm.

[0130] In one embodiment, the thickness of the hole injection layer of the normal and / or inverted quantum dot light-emitting device is 10-100 nm.

[0131] In one embodiment, the thickness of the hole transport layer of the normal and / or inverted quantum dot light-emitting device is 10-100 nm.

[0132] In one embodiment, the thickness of the quantum dot light-emitting layer of the normal and / or inverted quantum dot light-emitting device is 10-100 nm.

[0133] In one embodiment, the thickness of the electron transport layer of the normal and / or inverted quantum dot light-emitting device is 10-100 nm.

[0134] In one embodiment, the thickness of the cathode of the normal and / or inverted quantum dot light-emitting device is 50-200 nm.

[0135] In one embodiment, the quantum dot light-emitting device of the present application is a QLED device.

[0136] The present application also provides a preparation method of the quantum dot light-emitting device as described above, referring to Figure 3 , comprising the following steps:

[0137] The first ink, the second ink and the third ink are provided respectively, the first ink includes the first quantum dot and the prepolymer combined with the first quantum dot, the second ink includes the second quantum dot and the prepolymer combined with the second quantum dot, and the third ink includes the third quantum dot and the prepolymer combined with the third quantum dot;

[0138] The first ink is used to form a first precursor film layer on a substrate provided with a functional layer, and through mask processing, light processing and drying processing, the first quantum dot sub-unit is formed in a first preset area;

[0139] The second ink is used to form a second precursor film layer on a substrate provided with a functional layer, and through mask processing, light processing and drying processing, the second quantum dot sub-unit is formed in a second preset area;

[0140] The third ink is used to form a third precursor film layer on a substrate provided with a functional layer, and through mask processing, light processing and drying processing, the third quantum dot sub-unit is formed in a third preset area.

[0141] In one embodiment, the functional layer is any one of an anode, a cathode, an electron transport layer, an electron blocking layer, a hole transport layer and a hole blocking layer.

[0142] In one embodiment, the first ink, the second ink or the third ink can be applied on the functional layer in a coating, inkjet printing or spin coating manner, which can form a film in the whole plane efficiently and quickly. In particular, since the prepolymer of the present application has excellent film-forming property, the inkjet printing manner can be used without using high-precision printing equipment, and even if the inkjet printing manner is used, the coffee ring phenomenon can be avoided.

[0143] In one embodiment, the mask plate used in each mask processing has light leakage holes arranged in an array. Understandably, in the first mask processing, the position exposed by the light leakage hole corresponds to the first quantum dot sub-unit formed in the area, and the prepolymer contained in the position is crosslinked by light to form a crosslinked copolymer. In the second mask processing, the position exposed by the light leakage hole corresponds to the second quantum dot sub-unit formed in the area, and the prepolymer contained in the position is crosslinked by light to form a crosslinked copolymer. In the third mask processing, the position exposed by the light leakage hole corresponds to the first quantum dot sub-unit formed in the area, and the prepolymer contained in the position is crosslinked by light to form a crosslinked copolymer.

[0144] Understandably, the shape of the light-emitting quantum dot sub-unit (the first light-emitting quantum dot sub-unit, the second light-emitting quantum dot sub-unit and the third light-emitting quantum dot sub-unit) is related to the shape of the light leakage hole and the ultraviolet light irradiation angle, and various shapes of light-emitting quantum dot sub-units can be obtained by changing the shape of the light leakage hole or the ultraviolet light irradiation angle. In the present application, as long as the light-emitting quantum dot sub-unit can be arranged in an array, there is no special requirement for its shape.

[0145] In one embodiment, the wavelength of the light source used in each of the light irradiation processes is 254 nm to 400 nm. The wavelength range is selected according to the type of the photocrosslinking group.

[0146] It is understood that the first ink, the second ink and the third ink also contain a solvent. Preferably, the solvent is photodegradable, has a low swelling effect on the crosslinked copolymer obtained after photocrosslinking of the prepolymer, and is easy to remove. In one embodiment, the solvent in the first ink, the second ink and the third ink is chloroform.

[0147] In one embodiment, after each drying process, a step of cleaning the precursor film layer with a good solvent of the prepolymer is further included. Since the product after crosslinking is insoluble in the solvent, the precursor film layer is cleaned with the good solvent of the prepolymer, and the uncrosslinked prepolymer is removed, leaving the arrayed quantum dot subunits in the quantum dot light-emitting layer. Preferably, the good solvent of the prepolymer is selected from at least one of toluene, n-octane, n-hexane, dimethyl anisole and dihydroinden.

[0148] In one embodiment, the first ink is prepared as follows:

[0149] The first transition ligand and the first quantum dots are dissolved in a first solvent to prepare a first mixture;

[0150] The first prepolymer is dissolved in the first solvent to prepare a second mixture;

[0151] The first mixture and the second mixture are mixed to undergo a ligand exchange reaction, and the first prepolymer and the first quantum dots form a first light-emitting intermediate (a first metal-organic complex intermediate);

[0152] The first light-emitting intermediate is dissolved in a second solvent to obtain the first ink.

[0153] In one embodiment, the first transition ligand is selected from at least one of oleic acid, octyl mercaptan and trioctylphosphine.

[0154] The solvent used to dissolve the first prepolymer has good solubility for the prepolymer, which is more conducive to the ligand exchange reaction.

[0155] In one embodiment, the first solvent is selected from at least one of toluene, n-octane, n-hexane, dimethyl anisole and dihydroinden, and the second solvent is chloroform.

[0156] In one embodiment, the second ink is prepared as follows:

[0157] The second transition ligand and the second quantum dots are dissolved in a third solvent to prepare a third mixture;

[0158] The second prepolymer is dissolved in the third solvent to prepare a fourth mixture;

[0159] The third mixture and the fourth mixture are mixed to cause a ligand exchange reaction, and the second prepolymer forms a second luminescent intermediate (a second metal organic complex intermediate) with the second quantum dots;

[0160] The second luminescent intermediate is dissolved in a fourth solvent to prepare the second ink.

[0161] In one embodiment, the second transition ligand is at least one selected from the group consisting of oleic acid, octanethiol and trioctylphosphine.

[0162] The solvent used to dissolve the second prepolymer has good solubility for the prepolymer, and is more conducive to the ligand exchange reaction.

[0163] In one embodiment, the third solvent is at least one selected from the group consisting of toluene, n-octane, n-hexane, dimethyl anisole and dihydroindene; and the fourth solvent is chloroform.

[0164] In one embodiment, the third ink is prepared as follows:

[0165] The third transition ligand and the third quantum dots are dissolved in a fifth solvent to prepare a fifth mixture;

[0166] The third prepolymer is dissolved in the fifth solvent to prepare a sixth mixture;

[0167] The fifth mixture and the sixth mixture are mixed to cause a ligand exchange reaction, and the third prepolymer forms a third luminescent intermediate (a third metal organic complex intermediate) with the third quantum dots;

[0168] The third luminescent intermediate is dissolved in a sixth solvent to prepare the third ink.

[0169] In one embodiment, the third transition ligand is at least one selected from the group consisting of oleic acid, octanethiol and trioctylphosphine.

[0170] The solvent used to dissolve the third prepolymer has good solubility for the prepolymer, and is more conducive to the ligand exchange reaction.

[0171] In one embodiment, the fifth solvent is at least one selected from the group consisting of toluene, n-octane, n-hexane, dimethyl anisole and dihydroindene; and the sixth solvent is chloroform.

[0172] In one of the embodiments, the present application first uses ligands mature in the industry as transition ligands to ensure the stability of quantum dots, and then forms a pre-polymer in the present application and quantum dots into a structurally stable metal organic complex intermediate through ligand exchange; then applies it on a plane by coating or spin coating or inkjet printing, which can form a film on the entire plane, efficient and fast; then cleverly uses a mask containing light leakage holes arranged in an array and a UV crosslinking reaction to make the UV light pass through the light leakage holes, and the light-illuminated luminescent intermediate undergoes a photo-crosslinking reaction, and after photo-crosslinking, it forms a network with each other, to obtain a luminescent quantum dot subunit with excellent film-forming property. Since it is a crosslinked product, it will not dissolve in a solvent (anti-solvent), and the un-illuminated luminescent intermediate film layer can be removed by dissolving in a solvent, and only the crosslinked quantum dot composite material is retained. By repeating the above operation of preparing a luminescent quantum dot subunit, red, green and blue light quantum dot subunits arranged in an array can be prepared, and the display of the arrayed quantum dot light-emitting device is realized by the cooperation of red, green and blue light.

[0173] In one of the embodiments, the present application provides a preparation method of a quantum dot light-emitting device, which comprises the step of preparing a quantum dot light-emitting layer, and the preparation of the quantum dot light-emitting layer comprises the following steps:

[0174] The first transition ligand and the red light quantum dots are dissolved in a first solvent to prepare a first mixture;

[0175] The first pre-polymer is dissolved in a first solvent to prepare a second mixture;

[0176] The first mixture and the second mixture are mixed to undergo a ligand exchange reaction, and the first pre-polymer and the red light quantum dots form a red light intermediate;

[0177] The red light intermediate is dissolved in a second solvent to prepare a red light intermediate ink;

[0178] The red light intermediate ink is applied on the plane of the functional layer by coating or spin coating, and dried to form a red light intermediate film layer;

[0179] A first mask containing light leakage holes arranged in an array is placed above the red light intermediate film layer (see Figure 4 ), and a first UV light is used to irradiate the first mask and the red light intermediate film layer, and the red light intermediate subjected to the light irradiation undergoes a photo-crosslinking reaction to prepare a red light crosslinked modified quantum dot composite material as a red light quantum dot subunit;

[0180] The first solvent is used to dissolve and remove the red light intermediate film layer not subjected to the light irradiation;

[0181] The second transition ligand and the green quantum dots are dissolved in a third solvent to prepare a third mixture;

[0182] The second prepolymer is dissolved in a third solvent to prepare a fourth mixture;

[0183] The third mixture and the fourth mixture are mixed to cause a ligand exchange reaction, and the second prepolymer and the green quantum dots form a green intermediate;

[0184] The green intermediate is dissolved in a fourth solvent to prepare a green intermediate ink;

[0185] The green intermediate ink is applied on the plane of the functional layer by coating or spin coating, and is dried to form a green intermediate film layer;

[0186] A second mask plate (see Figure 5 ) containing light leakage holes arranged in an array is placed above the green intermediate film layer, and the second mask plate and the green intermediate film layer are irradiated with a second ultraviolet light, and the green intermediate subjected to the irradiation undergoes a photocrosslinking reaction to prepare a green photocrosslinking modified quantum dot composite material as a green quantum dot subunit;

[0187] The green intermediate film layer not subjected to the irradiation is removed by using a third solvent for dissolution;

[0188] A third transition ligand and blue quantum dots are dissolved in a fifth solvent to prepare a fifth mixture;

[0189] A third prepolymer is dissolved in a first solvent to prepare a sixth mixture;

[0190] The fifth mixture and the sixth mixture are mixed, and the third prepolymer and the blue quantum dots form a blue intermediate;

[0191] The blue intermediate is dissolved in a sixth solvent to prepare a blue intermediate ink;

[0192] The blue intermediate ink is applied on the plane of the functional layer by coating or spin coating, and is dried to form a blue intermediate film layer;

[0193] A third mask plate (see Figure 6 ) containing light leakage holes arranged in an array is placed above the blue film layer, and the third mask plate and the blue intermediate film layer are irradiated with a third ultraviolet light, and the blue intermediate subjected to the irradiation undergoes a photocrosslinking reaction to prepare a blue photocrosslinking modified quantum dot composite material as a blue quantum dot subunit;

[0194] The blue intermediate film layer not subjected to the irradiation is removed by using a fifth solvent for dissolution.

[0195] SeeFigure 7 The quantum dot light-emitting layer of the present application comprises red quantum dot subunits, green quantum dot subunits and blue quantum dot subunits arranged in an array.

[0196] When the quantum dot light-emitting device of the present application is a device of a normal structure, the preparation method thereof is described as follows: Figure 8 The preparation method comprises the following steps:

[0197] A substrate is provided, and an anode is prepared on the substrate;

[0198] A hole injection layer is prepared on the anode;

[0199] A hole transport layer is prepared on the hole injection layer;

[0200] A quantum dot light-emitting layer comprising red quantum dot subunits, green quantum dot subunits and blue quantum dot subunits arranged in an array is prepared on the hole transport layer by using the method for preparing a quantum dot light-emitting layer of the present application;

[0201] An electron transport layer is prepared on the quantum dot light-emitting layer;

[0202] A cathode is prepared on the electron transport layer.

[0203] In one embodiment, the anode is prepared by magnetron sputtering or purchased directly as an ITO substrate, and ITO is used as the anode; the hole injection layer, the hole transport layer, the quantum dot light-emitting layer and the electron transport layer in the quantum dot light-emitting device of the normal structure are prepared by a solution method or a vapor deposition method, the solution method comprises coating or spin coating, and the vapor deposition method is an evaporation method; the cathode in the quantum dot light-emitting device of the normal structure is prepared by a vapor deposition method, such as an evaporation method.

[0204] In one embodiment, the preparation method of the quantum dot light-emitting device of the normal structure comprises the following steps:

[0205] A substrate is provided, and an anode is prepared on the substrate;

[0206] A hole injection layer is prepared on the anode by spin coating;

[0207] A hole transport layer is prepared on the hole injection layer by spin coating;

[0208] A quantum dot light-emitting layer comprising red quantum dot subunits, green quantum dot subunits and blue quantum dot subunits arranged in an array is prepared on the hole transport layer by using the method for preparing a quantum dot light-emitting layer of the present application;

[0209] An electron transport layer is prepared on the quantum dot light-emitting layer by spin coating;

[0210] A cathode is prepared on the electron transport layer by evaporation, and a quantum dot light-emitting device of a normal structure is obtained.

[0211] The present application also provides a preparation method of the quantum dot light-emitting device with the inverted structure, referring to Figure 9 , comprising the following steps:

[0212] providing a substrate, and evaporating a cathode on the substrate;

[0213] preparing an electron transport layer on the cathode by spin coating;

[0214] preparing a quantum dot light-emitting layer containing red quantum dot sub-units, green quantum dot sub-units and blue quantum dot sub-units arranged in an array on the electron transport layer by the method for preparing a quantum dot light-emitting layer according to the present application;

[0215] preparing a hole transport layer on the quantum dot light-emitting layer by spin coating;

[0216] preparing a hole injection layer on the hole transport layer by spin coating;

[0217] preparing an anode on the hole injection layer by magnetron sputtering.

[0218] In one embodiment, the hole injection layer, the hole transport layer, the quantum dot light-emitting layer and the electron transport layer in the quantum dot light-emitting device with the inverted structure are prepared by a solution method or a gas phase deposition method, the solution method including coating or spin coating, and the gas phase deposition method being an evaporation method; the cathode in the quantum dot light-emitting device with the inverted structure is prepared by a gas phase deposition method, such as an evaporation method.

[0219] In one embodiment, the preparation method of the quantum dot light-emitting device with the inverted structure comprises the following steps:

[0220] providing a substrate, and evaporating a cathode on the substrate;

[0221] preparing an electron transport layer on the cathode by spin coating;

[0222] preparing a quantum dot light-emitting layer containing red quantum dot sub-units, green quantum dot sub-units and blue quantum dot sub-units arranged in an array on the electron transport layer by the method for preparing a quantum dot light-emitting layer according to the present application;

[0223] preparing a hole transport layer on the quantum dot light-emitting layer by spin coating;

[0224] preparing a hole injection layer on the hole transport layer by spin coating;

[0225] preparing an anode on the hole injection layer by magnetron sputtering, to obtain the quantum dot light-emitting device with the inverted structure. Specific embodiments

[0227] Embodiment 1

[0228] The embodiment provides a normal QLED device and a preparation method thereof. Figure 1 As shown in a structural schematic diagram of the normal QLED device: a substrate 101, an anode 102, a hole injection layer 103, a hole transport layer 104, a QD light-emitting layer 105, an electron transport layer 106 and a cathode 107 are sequentially arranged from bottom to top.

[0229] (1) Preparation of the anode:

[0230] An ITO anode with a thickness of 150 nm is prepared on a glass substrate by magnetron sputtering;

[0231] (2) Preparation of the hole injection layer:

[0232] A water-soluble conductive polymer PEDOT is spin-coated on the anode, and after being dried into a film, annealing is performed at 150 DEG C for 20 min to obtain the hole injection layer with a thickness of 45 nm;

[0233] (3) Preparation of the hole transport layer:

[0234] TFB ink is spin-coated on the hole injection layer, and after being vacuum-dried into a film, annealing is performed at 230 DEG C for 30 min to obtain the hole transport layer with a thickness of 25 nm;

[0235] (4) Preparation of the quantum dot light-emitting layer:

[0236] i) Synthesis of monomer TPA, Chinese name: 4-(N,N-diphenylamino)styrene, and the reaction formula is as follows:

[0237]

[0238] The specific synthesis process is as follows: 15 g of triphenylmethyl phosphonium iodide (Mepph3l) is dissolved in 100 ml of anhydrous tetrahydrofuran in a nitrogen glove box, then poured into a flask, then 3 g of potassium tert-butoxide (t-BuOK) is added, stirred for 10 min, and then 5 g of 4-(N,N-diphenylamino) benzaldehyde is added. After reaction at room temperature for 24 h, the filtrate is washed with deionized water:dichloromethane equal to 1:1 (volume ratio), and then dried with anhydrous sodium sulfate to obtain a crude product TPA, and then purified by dichloromethane silica gel column chromatography to obtain purified TPA;

[0239] ii) Synthesis of intermediate 1, and the reaction formula is as follows:

[0240]

[0241] The specific synthesis process is as follows: 1g of monomer TPA and 28.12mg of monomer 4-chloromethylstyrene were added to a flask, and then 27.19mg of chain transfer agent 2-cyanopropyl-2-ol dithiobenzoate (CPBD), 1.97mg of initiator azobisisobutyronitrile (AIBN), and 3ml of solvent 1,4-dioxane were added to the flask. The reaction was carried out at 90℃ for 24h under an argon atmosphere. The mixture was filtered, the filter cake was washed with methanol, and dried to obtain intermediate 1, with m = 95 and n = 5.

[0242] iii) Synthesize intermediate 2, the reaction formula is as follows:

[0243]

[0244] The specific synthesis process is as follows: 6 mg of intermediate 1 is dissolved in 10 ml of n-octane, then 24 mg of hexylamine is added, the reaction is carried out at room temperature for 1 h, filtered, the filter cake is washed with methanol, and dried to obtain intermediate 2.

[0245] iv) Synthesize prepolymer 1, the reaction formula is as follows:

[0246]

[0247] The specific synthesis process is as follows: 6 mg of intermediate 2 was dissolved in 10 ml of n-octane, then 24 mg of NaN3 was added, and the mixture was reacted at room temperature for 1 h. After filtration, the filter cake was washed with methanol and dried to obtain prepolymer 1. Its proton NMR spectrum is shown below. Figure 11 As shown, by Figure 11 It can be seen that the target prepolymer 1 was successfully synthesized in this embodiment.

[0248] v) Ligand exchange to prepare intermediates of red, green, and blue light-emitting organometallic complexes:

[0249] Prepolymer 1 was dissolved in toluene and divided into three portions, namely, a first ligand solution, a second ligand solution, and a third ligand solution;

[0250] Using oleic acid as a transition ligand, oleic acid and CdSe / ZnSe red quantum dots were mixed in toluene to prepare a CdSe / ZnSe red quantum dot solution with oleic acid ligands. Similarly, using oleic acid as a transition ligand, oleic acid and CdSe / ZnS green quantum dots were mixed in toluene to prepare a CdSe / ZnS green quantum dot solution with oleic acid ligands. Likewise, using oleic acid as a transition ligand, oleic acid and ZnCdS / ZnS blue quantum dots were mixed in toluene to prepare a ZnCdS / ZnS blue quantum dot solution with oleic acid ligands.

[0251] The CdSe / ZnSe red quantum dot solution with oleic acid ligand was added to the first ligand solution at room temperature, and stirred for 24 h for ligand exchange, and then separated by layering. The supernatant was separated from the lower solid to obtain a solid red light metal organic complex intermediate.

[0252] Similarly, the CdSe / ZnS green quantum dot solution with oleic acid ligand was added to the second ligand solution, stirred for 24 h for ligand exchange, and then separated by layering. The supernatant was separated from the lower solid to obtain a solid green light metal organic complex intermediate.

[0253] Similarly, the ZnCdS / ZnS blue quantum dot solution with oleic acid ligand was added to the third ligand solution, stirred for 24 h for ligand exchange, and then separated by layering. The supernatant was separated from the lower solid to obtain a solid red light metal organic complex intermediate.

[0254] vi) Photocrosslinking to prepare a quantum dot light-emitting layer containing red, green and blue quantum dot subunits arranged in an array:

[0255] The solid red light metal organic complex intermediate was dissolved in chloroform to obtain a red intermediate ink, which was applied to the hole transport layer by spin coating, vacuum dried to form a red intermediate film, and then a first mask plate containing light leakage holes arranged in an array was added to the red intermediate film (see Figure 4 ). Subsequently, the red intermediate film was irradiated with ultraviolet light of 254 nm for 5 min to cause photocrosslinking of the red intermediate film exposed to the ultraviolet light. Then, the red intermediate film not exposed to the ultraviolet light was removed by toluene cleaning to obtain an arrayed RQD. Finally, the RQD was annealed at 100°C for 10 min, and the thickness of the RQD was 15 nm. The photocrosslinking group is -N3, and the specific photocrosslinking reaction is:

[0256]

[0257] The solid green light metal organic complex intermediate was dissolved in chloroform to obtain a green intermediate ink, which was applied to the hole transport layer by spin coating, and the RQD was also covered. Vacuum drying formed a green intermediate film, and then a second mask plate containing light leakage holes arranged in an array was added to the green intermediate film (see Figure 5), and then the green light intermediate film is irradiated with ultraviolet light of a wavelength of 254 nm for 5 min to cause the green light intermediate subjected to the ultraviolet light irradiation to undergo a photocrosslinking reaction, and then the green light intermediate not subjected to the ultraviolet light irradiation is cleaned away with toluene to obtain an arrayed GQD with the RQD exposed, and then annealing is performed at 100 ℃ for 10 min, and finally a GQD with a thickness of 15 nm is obtained. Since the prepolymer used in this embodiment is the same and the photocrosslinking reaction is also the same, no further description is given here.

[0258] The solid blue light metal organic complex intermediate is dissolved in chloroform to obtain a blue light intermediate ink, which is applied on the hole transport layer by spin coating, and the RQD and the GQD are also covered, vacuum drying to form a blue light intermediate film, and then a third mask plate (see Figure 6 ) containing a light leakage hole arranged in an array is added on the blue light intermediate film, and then the blue light intermediate film is irradiated with ultraviolet light of a wavelength of 254 nm for 5 min to cause the blue light intermediate subjected to the ultraviolet light irradiation to undergo a photocrosslinking reaction, and then the blue light intermediate not subjected to the ultraviolet light irradiation is cleaned away with toluene to obtain an arrayed BQD with the RQD and the GQD exposed, and then annealing is performed at 100 ℃ for 10 min, and finally a GQD with a thickness of 15 nm is obtained. Since the prepolymer used in this embodiment is the same and the photocrosslinking reaction is also the same, no further description is given here.

[0259] The film layer containing the above red light quantum dot subunit, green light quantum dot subunit and blue light quantum dot subunit arranged in an array is used as a quantum dot light emitting layer.

[0260] (5) Preparation of an electron transport layer:

[0261] ZnO ink is spin coated on the quantum dot light emitting layer, vacuum drying to form a film, and then annealing is performed at 120 ℃ for 15 min to obtain an electron transport layer with a thickness of 40 nm;

[0262] (6) Preparation of a cathode:

[0263] Al is evaporated on the electron transport layer to obtain a cathode with a thickness of 150 nm;

[0264] (7) Packaging, and finally a QLED device is obtained.

[0265] Example 2

[0266] This embodiment provides a QLED device and a preparation method thereof. A structural schematic diagram of the QLED device is shown in Figure 1 from bottom to top, a substrate 101, an anode 102, a hole injection layer 103, a hole transport layer 104, a QD light emitting layer 105, an electron transport layer 106 and a cathode 107.

[0267] The steps of preparing the anode (1), the hole injection layer (2), and the hole transport layer (3) are the same as those of Example 1.

[0268] (4) Preparation of the quantum dot light-emitting layer:

[0269] i) Synthesis of monomer TPA, Chinese name: 4-(N,N-diphenylamino)styrene, reaction formula as follows:

[0270]

[0271] The specific synthesis process is as follows: 15 g of triphenylmethyl phosphonium iodide (Mepph3l) is dissolved in 100 ml of anhydrous tetrahydrofuran in a nitrogen glove box, then poured into a flask, followed by the addition of 3 g of potassium tert-butoxide (t-BuOK), stirred for 10 min, and then 5 g of 4-(N,N-diphenylamino) benzaldehyde is added. After reacting at room temperature for 24 h, it is filtered and washed with deionized water: dichloromethane in a volume ratio of 1:1, and then dried with anhydrous sodium sulfate to obtain the crude product TPA, which is then purified by silica gel column chromatography with dichloromethane to obtain purified TPA;

[0272] ii) Synthesis of intermediate 1, reaction formula as follows:

[0273]

[0274] The specific synthesis process is as follows: 1 g of monomer TPA and 28.12 mg of monomer 4-chloromethylstyrene are added to a flask, 27.19 mg of chain transfer agent 2-cyanopropyl-2-ol dithiobenzoate (CPBD) is added to the flask as a solvent, 1.97 mg of initiator azobisisobutyronitrile (AIBN) and 3 ml of solvent 1,4-dioxane are added, and the mixture is reacted at 90°C for 24 h under an argon atmosphere. After suction filtration, the filter cake is washed with methanol and dried to obtain intermediate 1, m is 95, and n is 5.

[0275] iii) Synthesis of intermediate 2, reaction formula as follows:

[0276]

[0277] The specific synthesis process is as follows: 6 mg of intermediate 1 is dissolved in 10 ml of n-octane, 24 mg of hexylamine is added, and the mixture is reacted at room temperature for 1 h. After suction filtration, the filter cake is washed with methanol and dried to obtain intermediate 2.

[0278] iv) Synthesis of prepolymer 2, reaction formula as follows:

[0279]

[0280] The specific synthesis process is: 6 mg of intermediate 2 is dissolved in 10 ml of n-octane, 24 mg of NaN3 is added, and the reaction is carried out at room temperature for 1 h, the filter cake is washed with methanol, and the product is dried to obtain the prepolymer 1.

[0281] 6 mg of prepolymer 1 is dissolved in n-octane, 24 mg of 4-bromothiophenol is added, and the reaction is carried out at 120°C for 1 h to obtain the prepolymer 2.

[0282] v) ligand exchange to prepare red, green and blue metal organic complex intermediates:

[0283] The prepolymer 2 is dissolved in toluene and divided into three parts, which are the first ligand solution, the second ligand solution and the third ligand solution;

[0284] With oleic acid as a transition ligand, the oleic acid and CdSe / ZnSe red quantum dots are mixed in toluene to prepare a CdSe / ZnSe red quantum dot solution with an oleic acid ligand. Similarly, with oleic acid as a transition ligand, the oleic acid and CdSe / ZnS green quantum dots are mixed in toluene to prepare a CdSe / ZnS green quantum dot solution with an oleic acid ligand. Similarly, with oleic acid as a transition ligand, the oleic acid and ZnCdS / ZnS blue quantum dots are mixed in toluene to prepare a ZnCdS / ZnS blue quantum dot solution with an oleic acid ligand;

[0285] At room temperature, the CdSe / ZnSe red quantum dot solution with an oleic acid ligand is added to the first ligand solution, and the ligand exchange is carried out by stirring for 24 h. After standing and layering, the upper clear liquid is separated from the lower solid to obtain a solid red metal organic complex intermediate.

[0286] Similarly, the CdSe / ZnS green quantum dot solution with an oleic acid ligand is added to the second ligand solution, and the ligand exchange is carried out by stirring for 24 h. After standing and layering, the upper clear liquid is separated from the lower solid to obtain a solid green metal organic complex intermediate.

[0287] Similarly, the ZnCdS / ZnS blue quantum dot solution with an oleic acid ligand is added to the third ligand solution, and the ligand exchange is carried out by stirring for 24 h. After standing and layering, the upper clear liquid is separated from the lower solid to obtain a solid red metal organic complex intermediate.

[0288] vi) photo-crosslinking to prepare a quantum dot light-emitting layer containing red, green and blue quantum dot subunits arranged in an array:

[0289] The solid red metal organic complex intermediate is dissolved in chloroform to obtain a red intermediate ink, which is applied on the hole transport layer by spin coating, vacuum dried to form a red intermediate film, and a first mask plate containing light leakage holes arranged in an array is added on the red intermediate film (seeFigure 4 ), and then the red intermediate film is irradiated with ultraviolet light of 254 nm for 5 min to make the red intermediate subjected to the ultraviolet light to undergo a photo-crosslinking reaction, and then the red intermediate not subjected to the ultraviolet light is cleaned away with toluene to obtain arrayed RQDs, and then the RQDs are annealed at 100°C for 10 min. The thickness of the finally prepared RQDs is 15 nm. The photo-crosslinking group is -N3, and the specific crosslinking reaction is as follows:

[0290]

[0291] The solid green intermediate metal organic complex intermediate is dissolved in chloroform to obtain green intermediate ink, which is applied on the hole transport layer by spin coating, and the RQDs are also covered, vacuum drying to form a green intermediate film, and then a second mask plate containing arrayed light leakage holes is added on the green intermediate film (see Figure 5 ), and then the green intermediate film is irradiated with ultraviolet light of 254 nm for 5 min to make the green intermediate subjected to the ultraviolet light to undergo a photo-crosslinking reaction, and then the green intermediate not subjected to the ultraviolet light is cleaned away with toluene to obtain arrayed GQDs, and the RQDs are exposed, and then the GQDs are annealed at 100°C for 10 min. The thickness of the finally prepared GQDs is 15 nm. Since the prepolymer used in this embodiment is the same, the photo-crosslinking reaction is also the same, which will not be described here.

[0292] The solid blue intermediate metal organic complex intermediate is dissolved in chloroform to obtain blue intermediate ink, which is applied on the hole transport layer by spin coating, and the RQDs and GQDs are also covered, vacuum drying to form a blue intermediate film, and then a third mask plate containing arrayed light leakage holes is added on the blue intermediate film (see Figure 6 ), and then the blue intermediate film is irradiated with ultraviolet light of 254 nm for 5 min to make the blue intermediate subjected to the ultraviolet light to undergo a photo-crosslinking reaction, and then the blue intermediate not subjected to the ultraviolet light is cleaned away with toluene to obtain arrayed BQDs, and the RQDs and GQDs are exposed, and then the BQDs are annealed at 100°C for 10 min. The thickness of the finally prepared GQDs is 15 nm. Since the prepolymer used in this embodiment is the same, the photo-crosslinking reaction is also the same, which will not be described here.

[0293] The film layer containing the above arrayed red quantum dot subunits, green quantum dot subunits and blue quantum dot subunits is used as a quantum dot light-emitting layer.

[0294] (5) Preparation of an electron transport layer:

[0295] The ZnO ink is spin-coated on the quantum dot light-emitting layer, vacuum dried to form a film, and then annealed at 120°C for 15 min to prepare an electron transport layer with a thickness of 40 nm.

[0296] (6) Preparation of a cathode:

[0297] Al is evaporated on the electron transport layer to prepare a cathode with a thickness of 150 nm.

[0298] (7) Packaging to prepare a top-emitting QLED device.

[0299] Example 3

[0300] This example provides a top-emitting QLED device and a preparation method thereof. A structural schematic diagram of the top-emitting QLED device is shown in FIG. 1. Figure 1 The substrate 101, the anode 102, the hole injection layer 103, the hole transport layer 104, the QD light-emitting layer 105, the electron transport layer 106, and the cathode 107 are sequentially arranged from bottom to top.

[0301] Steps (1) to (4) for preparing the anode, the hole injection layer, the hole transport layer, and the quantum dot light-emitting layer are the same as those in Example 1.

[0302] (5) Preparation of an electron transport layer:

[0303] The ZnO ink is inkjet-printed on the region corresponding to the red quantum dot unit, vacuum dried to form a film, and then annealed at 120°C for 15 min. The TiO2 ink is inkjet-printed on the regions corresponding to the green quantum dot unit and the blue quantum dot unit, vacuum dried to form a film, and then annealed at 120°C for 15 min. An electron transport layer containing ZnO and TiO2 is prepared, with a thickness of 40 nm.

[0304] (6) Preparation of a cathode:

[0305] Al is evaporated on the electron transport layer to prepare a cathode with a thickness of 150 nm.

[0306] (7) Packaging to prepare a top-emitting QLED device.

[0307] Comparative Example 1

[0308] This example provides a top-emitting QLED device. A structural schematic diagram of the top-emitting QLED device is shown in FIG. 1. Figure 4 The substrate 101, the anode 102, the hole injection layer 103, the hole transport layer 104, the QD light-emitting layer 105, the electron transport layer 106, and the cathode 107 are sequentially arranged from bottom to top.

[0309] (1) Preparation of an anode:

[0310] The ITO anode with a thickness of 150 nm is prepared on the glass substrate by magnetron sputtering;

[0311] (2) Preparation of a hole injection layer:

[0312] The water-soluble conductive polymer PEDOT is inkjet printed on the anode, and after drying into a film, annealing at 150℃ for 20 min, the hole injection layer with a thickness of 45 nm is prepared;

[0313] (3) Preparation of a hole transport layer:

[0314] The TFB ink is inkjet printed on the hole injection layer, and after vacuum drying into a film, annealing at 230℃ for 30 min, the hole transport layer with a thickness of 25 nm is prepared;

[0315] (4) Preparation of a quantum dot light-emitting layer:

[0316] The CdSe / ZnSe red quantum dot solution with an oleic acid ligand is prepared by mixing oleic acid and CdSe / ZnSe red quantum dots in toluene. The CdSe / ZnSe red quantum dot solution with an oleic acid ligand is applied to the hole transport layer by inkjet printing, and after vacuum drying into a film, annealing at 100℃ for 10 min, the red quantum dot light-emitting layer with a thickness of 15 nm is prepared.

[0317] The CdSe / ZnS green quantum dot solution with an oleic acid ligand is prepared by mixing oleic acid and CdSe / ZnS quantum dots in toluene. The CdSe / ZnS green quantum dot solution with an oleic acid ligand is applied to the hole transport layer by inkjet printing, and after vacuum drying into a film, annealing at 100℃ for 10 min, the green quantum dot light-emitting layer with a thickness of 15 nm is prepared.

[0318] The ZnCdS / ZnS blue quantum dot solution with an oleic acid ligand is prepared by mixing oleic acid and ZnCdS / ZnS blue quantum dots in toluene. The ZnCdS / ZnS blue quantum dot solution with an oleic acid ligand is applied to the hole transport layer by inkjet printing, and after vacuum drying into a film, annealing at 100℃ for 10 min, the blue quantum dot light-emitting layer with a thickness of 15 nm is prepared.

[0319] (5) Preparation of an electron transport layer:

[0320] The ZnO ink is inkjet printed on the quantum dot light-emitting layer, and after vacuum drying into a film, annealing at 120℃ for 15 min, the electron transport layer with a thickness of 40 nm is prepared;

[0321] (6) Preparation of a cathode:

[0322] Al is evaporated on the electron transport layer to prepare the cathode with a thickness of 150 nm.

[0323] (7) encapsulation, to prepare a QLED device in normal position.

[0324] 2. Performance test:

[0325] Performance evaluation of QLED device

[0326] The brightness of the tested device as a function of current or voltage, and the lifetime of the device, the lifetime being measured as T80@1000nit, which is the time taken for the brightness to decay to 800nit from the initial brightness of 1000nit.

[0327] Taking red light emission as an example, the external quantum efficiency, current efficiency and external quantum efficiency are shown in Table 1.

[0328] Table 1

[0329] Example 1 Example 2 Example 3 Comparative Example 1 External quantum efficiency (%) 16.7 18.2 19.4 12.3 Current efficiency (cd / A) 64.5 71.6 76.9 47.8 T80@1000 nit (h) 3628 4107 4463 1451

[0330] As can be seen from Table 1, compared with Comparative Example 1, the external quantum and current efficiency of the device prepared in Example 1 of the present application can be increased by about 1.35 times, and the lifetime can be increased by about 2.5 times, and the stability of the device is greatly improved; the external quantum efficiency of the device prepared in Example 2 of the present application can be increased by about 1.48 times, the current efficiency can be increased by about 1.5 times, and the lifetime can be increased by about 2.83 times, and the stability of the device is also greatly improved; the external quantum efficiency of the device prepared in Example 3 of the present application can be increased by about 1.57 times, the current efficiency can be increased by about 1.61 times, and the lifetime can be increased by about 3.07 times, and the stability of the device is also greatly improved. This is mainly due to the fact that the uniformity of QD film in Examples 1 to 3 is greatly improved compared with Comparative Example 1, and the improvement in film formation can improve the stability of the device by reducing the leakage current and interface defects of the device. In addition, the end group of Example 2 contains thiophenol, which not only has strong affinity with the surface of QD, but also can reduce the Fermi level of QD, so as to make the LUMO and HOMO energy levels of QD shallow, which is beneficial to the injection of holes. Example 3 realizes the best energy level matching of RGB three colors by setting corresponding electron transport layer materials in the red light quantum dot subunit, green light quantum dot subunit and blue light quantum dot subunit, thereby improving the electron injection efficiency.

[0331] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, however, as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present disclosure.

[0332] The above embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but should not be understood as a limitation on the patent scope of the present application. It should be noted that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims and drawings.

Claims

1. A quantum dot light emitting device, comprising: The quantum dot light-emitting device comprises: a quantum dot light-emitting layer, the quantum dot light-emitting layer comprising first, second and third quantum dot sub-units arranged in an array and emitting different light colors, each of the first, second and third quantum dot sub-units independently comprising a crosslinked copolymer; wherein the crosslinked copolymer is made from a prepolymer through a crosslinking reaction, the prepolymer comprising a linking repeat unit and a terminal group, the repeat unit having a structure shown in formula (I): * represents a linking site; the terminal group, at each occurrence, independently contains at least one of a cyano group, an alkyl mercapto group, an aryl mercapto group, a disulfide group, a carboxyl group, a thiocyanate group, an amino group, a halogen and a phosphine group, and the terminal group is bound together with the quantum dot through a coordination bond; R9 is a crosslinkable group; the crosslinking point of the crosslinked copolymer is a group generated by crosslinking of R9; L1 is a single bond, and L2 is selected from a single bond, an aryl group having 6 to 20 ring atoms or a heteroaryl group having 5 to 20 ring atoms; m and n are each independently a positive integer, and m / n is 1 to 99; Ar1 is selected from any one of groups (A-1) to (A-4): wherein: X and Y1 are each independently N or CR1; Y2 is each independently selected from NR2, O, S, CR3R4; R1 to R4 are each independently selected from a hydrogen atom, a deuterium atom, an alkyl group having 1 to 10 C atoms, an alkoxy group having 1 to 10 C atoms, an aryl group having 6 to 20 ring atoms or a heteroaryl group having 5 to 20 ring atoms; (A-1) to (A-4) each contain at least one N.

2. The quantum dot light emitting device of claim 1, wherein, the crosslinked copolymer contains at least one structure shown in formula (II) or formula (III): the crosslinking degree of the crosslinked copolymer is 10 to 100.

3. The quantum dot light emitting device of claim 1, wherein, L2 is selected from a single bond or any one of groups (B-1) to (B-7): wherein: X1 and Y3 are each independently N or CR5; Y4 is each independently selected from NR6, CR7R8; R5 to R8 are each independently selected from a hydrogen atom, a deuterium atom, an alkyl group having 1 to 10 C atoms, an alkoxy group having 1 to 10 C atoms, an aryl group having 6 to 20 ring atoms or a heteroaryl group having 5 to 20 ring atoms.

4. The quantum dot light emitting device of claim 1, wherein, R9 is selected from at least one of an azido group and a ketone carbonyl group.

5. The quantum dot light emitting device of claim 1, wherein, each occurrence of the prepolymer independently has a structure shown below:

6. The quantum dot light emitting device of claim 5, wherein, each occurrence of the crosslinked copolymer independently contains at least one structure shown in any one of formulae (C-1) to (C-4):

7. The quantum dot light emitting device of any one of claims 1 to 5, wherein, the first quantum dot sub-unit is a red light quantum dot sub-unit, the second quantum dot sub-unit is a green light quantum dot sub-unit, and the third quantum dot sub-unit is a blue light quantum dot sub-unit.

8. The quantum dot light emitting device of claim 7, wherein, The quantum dot light-emitting device further comprises: oppositely arranged cathode and anode, the quantum dot light-emitting layer being arranged between the cathode and the anode; an electron transport layer, the electron transport layer being arranged between the quantum dot light-emitting layer and the cathode, and the electron transport layer comprising an electron transport material; The LUMO energy level of the electron transport material corresponding to the red quantum dot subunit in the electron transport layer is >4.1 eV, and the LUMO energy level of the electron transport material corresponding to the blue quantum dot subunit and the green quantum dot subunit is independently 3 eV-4.1 eV.

9. The quantum dot light emitting device of claim 8, wherein, The electron transport material corresponding to the red quantum dot subunit is selected from at least one of zinc oxide, tin dioxide, zinc tin oxide, and zinc magnesium oxide; and / or The electron transport material corresponding to the blue quantum dot subunit and the green quantum dot subunit is independently selected from at least one of zirconium dioxide and titanium dioxide; and / or The quantum dots contained in the first quantum dot subunit, the second quantum dot subunit, and the third quantum dot subunit are independently selected from at least one of quantum dot light-emitting materials with a core-shell structure, and the core material is selected from at least one of CdSe, CdS, ZnSe, ZnS, CdTe, CdZnS, CdZnSe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdSeSTe, ZnSeSTe, and CdZnSeSTe, and the shell material is selected from at least one of CdS, ZnSe, ZnS, CdSeS, and ZnSeS.

10. A method of fabricating a quantum dot light emitting device as claimed in any one of claims 1 to 9, characterized in that, It comprises: The first ink, the second ink, and the third ink are provided respectively, the first ink comprises first quantum dots and the prepolymer combined with the first quantum dots, the second ink comprises second quantum dots and the prepolymer combined with the second quantum dots, and the third ink comprises third quantum dots and the prepolymer combined with the third quantum dots; The first precursor film layer is formed on the substrate provided with the functional layer by using the first ink, and the first quantum dot subunit is formed in the first preset area by mask processing, light processing, and drying processing; The second precursor film layer is formed on the substrate provided with the functional layer by using the second ink, and the second quantum dot subunit is formed in the second preset area by mask processing, light processing, and drying processing; The third precursor film layer is formed on the substrate provided with the functional layer by using the third ink, and the third quantum dot subunit is formed in the third preset area by mask processing, light processing, and drying processing.

11. The method for fabricating a quantum dot light-emitting device according to claim 10, characterized in that, The mask plate used in each mask processing has light leakage holes arranged in an array; and / or The wavelength of the light source used in each light processing is 254 nm-400 nm.

12. The preparation method of the quantum dot light-emitting device according to claim 11, wherein The first ink, the second ink, and the third ink further comprise a solvent; The solvent in the first ink, the second ink, and the third ink is chloroform.

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