CN109935715B - Inverted QLED device and preparation method thereof - Google Patents

Inverted QLED device and preparation method thereof Download PDF

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CN109935715B
CN109935715B CN201711353407.2A CN201711353407A CN109935715B CN 109935715 B CN109935715 B CN 109935715B CN 201711353407 A CN201711353407 A CN 201711353407A CN 109935715 B CN109935715 B CN 109935715B
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CN109935715A (en
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曹蔚然
杨一行
向超宇
钱磊
梁柱荣
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TCL Technology Group Co Ltd
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Abstract

The invention provides a preparation method of an inversion type QLED device, which comprises the following steps: providing a cathode and a displacer solution; depositing a quantum dot prefabricated film on the cathode, wherein the quantum dot prefabricated film consists of quantum dots of which the surfaces contain initial ligands, carrying out in-situ ligand exchange on the quantum dot prefabricated film and a replacement ligand in a replacement ligand solution, and replacing the initial ligands with the replacement ligands to obtain a quantum dot light-emitting layer; preparing a hole functional layer on the surface of the quantum dot light-emitting layer, and preparing an anode on the hole functional layer.

Description

Inverted QLED device and preparation method thereof
Technical Field
The invention belongs to the technical field of flat panel display, and particularly relates to an inversion type QLED device and a preparation method thereof.
Background
Quantum dot light-emitting diode (QLED) is a novel light-emitting device, and it adopts Quantum dot materials (QDs) as the luminescent layer, and compared with other luminescent materials, has the advantages that are difficult to compare, such as controllable small-size effect, ultrahigh internal Quantum efficiency, excellent color purity and the like, and has huge application prospect in the future display technology field.
In general, the surface of the quantum dot is connected with an organic ligand by chelating or the like, or connected with an inorganic ligand by forming a chemical bond or the like. The surface ligand of the quantum dot plays a crucial role in the synthesis of the quantum dot, and on one hand, the surface ligand can passivate the defects on the surface of the quantum dot and improve the luminescence property of the quantum dot; on the other hand, the surface ligand can reduce the agglomeration among quantum dots and increase the dispersibility of the quantum dots in a solvent. In a quantum dot light-emitting diode device, the surface ligand can further influence the photoelectric performance of the device, so that the reasonable selection of the ligand on the surface of the quantum dot in the quantum dot film is an important step for improving the light-emitting efficiency of the quantum dot film and the quantum dot light-emitting diode.
Exchanging the ligands on the surface of the quantum dots after the synthesis is currently the more common way. However, this method has certain problems. Firstly, the ligand on the surface of the quantum dot influences the dispersibility of the quantum dot in an organic solvent, so that the dispersibility of the quantum dot may be poor due to the ligand introduced in the ligand exchange process, and particularly for some ligand molecules with short chain length, the problem that the quantum dot cannot be dispersed often occurs, so that a quantum dot film with good uniformity cannot be formed. Secondly, when the ligand exchange is performed directly in solution, the structure and type of the selected ligand are greatly limited, for example, the ligand used for the solution ligand exchange can only be a single coordination ligand, i.e., a cross-linking ligand (2 or more QDs are simultaneously connected) cannot be used, because the quantum dots are connected with each other or connected with each other after the cross-linking ligand is added in the solution, and then aggregated and precipitated. Meanwhile, as the quantum dots in the solution are more, the situation of insufficient ligand exchange is generated. In addition, there are cases where the new ligand used for the replacement cannot be dissolved in the original quantum dot solution, and the selectivity of the ligand is greatly reduced.
On the basis, in the existing mainstream inverted QLED device (the positions of the anode and the cathode are interchanged, and the cathode, the electronic function layer, the quantum dot light-emitting layer, the hole function layer, the hole injection material and the anode are sequentially arranged on the substrate), when the hole transmission layer and the hole injection layer are prepared on the quantum dot light-emitting layer by a solution method, a used solvent can be dissolved again to take away or directly wash away quantum dots in the quantum dot light-emitting layer, so that the quantum dot layer is damaged, the film forming uniformity and the interface performance of the quantum dot light-emitting layer are influenced, the light-emitting uniformity of the inverted QLED device is further influenced, and particularly the quantum dot light-emitting layer prepared by a printing technology.
Disclosure of Invention
The invention aims to provide an inversion type QLED device and a preparation method thereof, and aims to solve the problem that in the preparation process of the existing inversion type QLED device, a solvent of a hole functional layer destroys a quantum dot layer, so that the film forming uniformity and the interface performance of a quantum dot light-emitting layer are influenced.
The invention is realized in this way, and a preparation method of an inversion type QLED device comprises the following steps:
providing a cathode and a displacer solution;
depositing a quantum dot prefabricated film on the cathode, wherein the quantum dot prefabricated film consists of quantum dots of which the surfaces contain initial ligands, carrying out in-situ ligand exchange on the quantum dot prefabricated film and a replacement ligand in a replacement ligand solution, and replacing the initial ligands with the replacement ligands to obtain a quantum dot light-emitting layer;
preparing a hole functional layer on the surface of the quantum dot light-emitting layer, and preparing an anode on the hole functional layer.
And the inversion QLED device comprises a cathode, a quantum dot light-emitting layer, a hole functional layer and an anode which are combined in a laminated mode, wherein the inversion QLED device is prepared by the method.
The preparation method of the inversion type QLED device provided by the invention comprises the steps of depositing a quantum dot prefabricated film, and then replacing an initial ligand on the surface of a quantum dot in the quantum dot prefabricated film with a replacement ligand by adopting in-situ ligand exchange, so that the surface polarity and the surface tension of the quantum dot after film forming are changed, and further, by controlling the polarity of the surface of the quantum dot, a quantum dot light-emitting layer is prevented from being influenced by a solvent of an upper layer cavity functional material solution, so that the preparation of the inversion type device by a full solution method can be realized. Meanwhile, as the arrangement and the position of the quantum dots in the quantum dot prefabricated film are basically fixed, the problem of quantum dot settlement can not occur when in-situ ligand exchange is adopted, so that the selection range of the ligand is expanded, and the solvent selectivity for replacing the ligand is more. In addition, through in-situ ligand exchange, the surface ligands of the quantum dots in the quantum dot light-emitting layer have more selectivity, so that the selectivity of the hole functional material and the dissolving solvent thereof is improved.
The inversion QLED device provided by the invention is prepared by the method, so that the types of hole functional materials of the inversion QLED device, such as hole transport materials, solvents of the hole transport materials and formed ink are not limited any more, and the selection range of the hole functional materials and the ink of the inversion QLED device is expanded.
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.
In the present invention, "strongly polar" and "weakly polar" are relative descriptions indicating the results of comparing the polarity of a certain replacing ligand with that of another replacing ligand, or comparing the polarity of an organic solvent with that of an organic solvent. The opposite polarity refers to the relative strength of the polarity, and is not strictly different between the polarity and the non-polarity.
The embodiment of the invention provides a preparation method of an inversion type QLED device, which comprises the following steps:
s01, providing a cathode and a replacement ligand solution;
s02, depositing a quantum dot prefabricated film on the cathode, wherein the quantum dot prefabricated film is composed of quantum dots of which the surfaces contain initial ligands, performing in-situ ligand exchange on the quantum dot prefabricated film and a replacement ligand in a replacement ligand solution, and replacing the initial ligands with the replacement ligands to obtain a quantum dot light-emitting layer;
s03, preparing a hole functional layer on the surface of the quantum dot light-emitting layer;
s04, preparing an anode on the hole function layer.
According to the preparation method of the inversion type QLED device provided by the embodiment of the invention, the quantum dot prefabricated film is deposited firstly, and then the initial ligand on the surface of the quantum dot in the quantum dot prefabricated film is replaced by the replacement ligand by adopting in-situ ligand exchange, so that the surface polarity and the surface tension of the quantum dot after film forming are changed, and further, by controlling the polarity of the surface of the quantum dot, the quantum dot light-emitting layer is prevented from being influenced by the upper layer cavity functional material solution solvent, so that the preparation of the full-solution inversion type device can be realized. Meanwhile, as the arrangement and the position of the quantum dots in the quantum dot prefabricated film are basically fixed, the problem of quantum dot settlement can not occur when in-situ ligand exchange is adopted, so that the selection range of the ligand is expanded, and the solvent selectivity for replacing the ligand is more. In addition, through in-situ ligand exchange, the surface ligands of the quantum dots in the quantum dot light-emitting layer have more selectivity, so that the selectivity of the hole functional material and the dissolving solvent thereof is improved.
Specifically, in step S01, the cathode may be deposited on the substrate to form a cathode substrate. The substrate is a rigid substrate or a flexible substrate, 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), polyethylene 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.
Preferably, the structural general formula of the replacement ligand in the replacement ligand solution is X1-R-X2Wherein R is a hydrocarbon group or a hydrocarbon group derivative, and X is1Is a functional group cross-linked with the quantum dot, the X2The functional group is used for polarity adjustment, and the crosslinking activity of the X1 and the quantum dot is greater than that of the X2 and the quantum dot (X1 and X2 are different functional groups), so that the anchoring capability of the X1 and the quantum dot is stronger, and X2 is exposed on the outermost surface of a quantum dot ligand shell layer. The embodiment of the invention passes the X1Effecting the attachment of the surface ligands to the quantum dots via the X2The surface polarity of the quantum dots is adjusted, so that the surface polarity and the surface tension of the quantum dot light-emitting layer are changed, the influence of the lower-layer quantum dot light-emitting layer on the upper-layer cavity functional material solution solvent in the preparation process of the inverse QLED device is avoided by controlling the polarity of the quantum dot surface, and the solution preparation of the inverse QLED device can be realized.
Wherein, R is a hydrocarbyl or a hydrocarbyl derivative, and is selected from saturated alkanes, unsaturated alkanes, aromatic hydrocarbons and derivatives thereof containing any organic functional group or no organic functional group, and specifically includes but is not limited to alkanes, alkenes, alkynes, aromatic hydrocarbons, cycloalkanes, halogenated hydrocarbons, alcohols, ethers, phenols, aldehydes, ketones, carboxylic acids, esters and nitrogen-containing compounds.
Preferably, X is1is-SH, -COOH, -NH2、-OH、-NO2、-SO3H. One of phosphine group and phosphate group; preferably, theX2is-COOH, -OH, -CN, -NHCO-CH3、-NH2、-SH、-CHO、-CO-、-COOR、-NO2、-O-、-O-CH3、-CH3One kind of (1).
For the case of adjusting the free active functional group of the quantum dot surface ligand to a polar functional group, it is preferable that when X1 is-SH, X2 is selected from-COOH, -OH, -CN, -NHCO-CH3、-NH2-CHO, -CO-; when X1 is-COOH, X2 is selected from-OH, -NHCO-CH3、-NH2-CHO, -CO-; when X1 is- -CN, X2 is selected from- -NHCO- -CH3、-NH2-CHO, -CO-; when X1 is-OH, X2 is selected from-NHCO-CH3、-NH2-CHO, -CO-; when X1 is-NH 2, X2 is selected from-NHCO-CH3-CHO, -CO-. In the case of adjusting the ligand free active functional group on the surface of the quantum dot to a non-polar or weakly polar functional group, it is preferable that when X1 is-SH, X2 is selected from-COOR, -NO2、-O-、-O-CH3、-CH3(ii) a When X1 is-COOH, X2 is selected from-COOR, -NO2、-O-、-O-CH3、-CH3(ii) a When X1 is-CN, X2 is selected from-COOR, -NO2、-O-、-O-CH3、-CH3(ii) a When X1 is-OH, X2 is selected from-COOR, -NO2、-O-、-O-CH3、-CH3(ii) a When X1 is-NH 2, X2 is selected from-COOR, -NO2、-O-、-O-CH3、-CH3. Of course, the longer the alkyl chain of R in the structure of X1-R-X2, the greater the degree of non-polarity.
As an embodiment, X2is-COOH, -OH, -CN, -NHCO-CH3、-NH2by-SH, -CHO, replacement ligands are understood to be strongly polar ligands, including but not limited to at least one of thioglycolic acid, 3-mercaptopropionic acid, 3-mercaptobutyric acid, 6-mercaptohexanoic acid, mercaptoethylamine, 3-mercaptopropylamine, 4-mercaptobenzoic acid, thioglycerol, 1-trimethylamine ethanethiol, mercaptoaniline, nitroaniline, sulfoaniline, aminobenzoic acid, 4- (diphenylphosphino) benzoic acid.
As another embodiment, X2is-CO-, -COOR, -NO2、-O-、-O-CH3、-CH3By constituted replacement ligand is understood a less polar replacement ligand including, but not limited to, at least one of octylamine, propylamine, hexadecylamine, 4-mercaptoanisole, 1-hydroxy-3-methoxy-propane. Of course, the embodiment of the present invention may also adjust the polarity of the surface ligand by adjusting the carbon chain length of R, and specifically, the longer the carbon chain of R, the lower the polarity of the formed surface ligand is.
As another preferred aspect, R contains a conjugated group. In the embodiment of the invention, because electrons of the conjugated ligand have a delocalization effect, denser molecular accumulation can be formed, effective transmission of charges among molecules is facilitated, and the transmission of carriers is improved in the device, so that the luminous performance of the device is improved. Therefore, the carrier transmission in the quantum dot film is improved, the luminous performance of the device can be correspondingly improved, and the solvent selection range of the subsequent material to be deposited is expanded. However, the steric hindrance of the conjugated ligand is often large, the distance between the quantum dots combined with the conjugated ligand is large, and the transmission effect of carriers between the quantum dots is not ideal, so that the improvement effect of the device performance is limited by simply adopting the conjugated ligand to replace a common ligand. In view of this, the quantum dots are more compact by mutual crosslinking between the conjugated ligands, so that the advantages of the organic ligand are better exerted. However, in a quantum dot thin film formed by respectively crosslinking one quantum dot with an adjacent quantum dot through two crosslinking groups of a conjugated ligand, the crosslinking mode and the type and properties of an intermediate forming a crosslinking structure often cause great difference in carrier transmission, for example, when quantum dots are crosslinked through a long-chain alkane structure, although a quantum dot crosslinked thin film can be formed, the carrier transmission effect of the long-chain alkane is poor, and the carrier transmission performance of the crosslinked thin film is not good. Therefore, in the embodiment of the invention, the plurality of active functional groups are arranged at the chain ends of the conjugated ligands on the surfaces of the quantum dots and are crosslinked with the plurality of active functional groups on the surfaces of the adjacent quantum dots, so that the transmission of carriers can be multi-channel transmission, and meanwhile, the connecting bridges among the quantum dots can play an electron delocalization effect (conjugated ligands), thereby improving the transmission effect of the carriers to a great extent and improving the performance of devices.
It should be understood that the conjugated group of the embodiment of the present invention is a group capable of generating a conjugation effect, and the conjugated group includes, but is not limited to, one or more of pi-pi conjugation, p-pi conjugation, sigma-p conjugation, and p-p conjugation, and the organic unit structure having a conjugation effect includes, but is not limited to, a linear structure and/or a cyclic structure in which double bonds and single bonds are alternately arranged, wherein a triple bond structure may be further included in the structure (in particular, it should be understood that, according to the classical organic chemistry theory, a benzene ring structure is also considered as one of cyclic conjugated structures in which three single carbon-carbon bonds and three double carbon-carbon bonds are alternately connected to each other), wherein the cyclic structure may be an ordered cyclic structure or a heterocyclic structure; specifically, the R contains but is not limited to one or more of benzene ring, -C = C-, -C ≡ C-, -C = O, -N = N-, -C ≡ N, -C = N-group; in particular, the conjugated group may contain a ring structure, wherein the ring structure includes but is not limited to one or more of a benzene ring structure, a phenanthrene structure, a naphthalene structure, an indene structure, a pyrene structure, a benzyl structure, an acenaphthylene structure, a fluorene structure, an anthracene structure, a fluoranthene structure, a benzanthracene structure, a benzopyrene structure, an indenopyrene structure, a dibenzoanthracene structure, a benzoperylene structure, a pyrrole structure, a pyridine structure, a pyridazine structure, a furan structure, a thiophene structure, an indole structure, a porphin structure, a porphyrin structure, a thiazole structure, an imidazole structure, a pyrazine structure, a pyrimidine structure, a quinoline structure, an isoquinoline structure, a pteridine structure, an acridine structure, an oxazole structure, a carbazole structure, a triazole structure, a benzofuran structure, a benzothiophene structure, a benzothiazole structure, a benzoxazole structure, a benzopyrrole structure, and a benzimidazole structure.
Specifically, the replacement ligand is selected from at least one of p-2-mercaptobenzoic acid, 4-aminobenzoic acid, 4-hydroxybenzoic acid, p-sulfobenzoic acid, p-nitrobenzoic acid, 4-mercaptoaniline, 4-hydroxyaniline, 4-cyanoaniline, 4-mercaptostyrene acid, 4-hydroxystyrenic acid, 2- (4-hydroxyphenyl) pyridine, 2-chloro-5-cyanothiazole, 2-amino-3-cyanothiophene and 3-amino-5-mercapto-1, 2, 4-triazole.
In the embodiment of the invention, by selecting X2 with a large polarity difference with the material polarity of the hole transport layer, according to the difference of the polarities of the displacement ligands, a solvent with opposite (or large difference) polarity can be selectively selected as a solvent of a hole functional material to realize the polarity conversion of adjacent material layers, so that the problem that in the preparation process, when a hole functional layer solution of a next layer is configured, due to similar and compatible polarities, quantum dots of a lower layer are dissolved or washed away, and the performance of a quantum dot film is influenced, can be avoided.
In one embodiment, when the material of the hole transport layer is a strongly polar organic material, X2 in the replacing ligand of the replacing ligand solution is a weakly polar or nonpolar functional group selected from the group consisting of-CO-, -COOR, -NO2、-O-、-O-CH3、-CH3At least one of (1).
In another embodiment, when the material of the hole transport layer is a weakly polar organic material, X2 is a strongly polar functional group selected from-COOH, -OH, -CN, -NHCO-CH, and the substitution ligand of the substitution ligand solution3、-NH2At least one of, -SH, -CHO.
In still another embodiment, when the material of the hole transport layer is an inorganic compound, X2 in the replacing ligand of the replacing ligand solution is a weakly polar or nonpolar functional group selected from the group consisting of-CO-, -COOR, -NO2、-O-、-O-CH3、-CH3At least one of (1).
In the embodiment of the present invention, the replacing ligand solution may be a combination of a strongly polar ligand and a strongly polar solvent (the replacing ligand is a strongly polar ligand), or a combination of a weakly polar ligand and a weakly polar solvent (the replacing ligand is a weakly polar ligand), depending on the quantum dot thin film for performing in-situ ligand exchange. Specifically, the solvent of the replacement ligand solution is an organic solvent, and the organic solvent includes, but is not limited to, one or a mixture of more of saturated hydrocarbon, unsaturated hydrocarbon, aromatic hydrocarbon, alcohol solvent, ether solvent, ketone solvent, nitrile solvent, ester solvent, and derivatives thereof. Wherein the organic solvent includes, but is not limited to, at least one of hexane, toluene, xylene, ethylbenzene, dichloromethane, chloroform, propanol, isopropanol, phenetole, acetonitrile, diethylamine, triethylamine, aniline, pyridine, picoline, ethylenediamine, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, hexamethylphosphoramide.
The cathode is selected from one of a metal material and a carbon material, wherein the metal material includes but is not limited to Al, Ag, Cu, Mo, Au or an alloy thereof; the carbon material includes, but is not limited to, one or more of graphite, carbon nanotubes, graphene, carbon fibers.
In the step S02, the initial ligands on the surface of the quantum dots in the quantum dot pre-fabricated film include, but are not limited to, one or more of tetradecene, hexadecene, octadecene, octadecylamine, octadecenoic acid, trioctylamine, trioctylphosphine, octadecylphosphonic acid, 9-octadecenylamine, and mercaptoundecanoic acid.
In the embodiment of the invention, the quantum dots in the quantum dot prefabricated film are 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. Specifically, the II-VI compound (semiconductor material) includes CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, PbS, PbSe, PbTe, but is not limited thereto, and may also be other binary, ternary, or quaternary II-VI compounds; nanocrystals of III-V compounds (semiconductor materials) include, but are not limited to, GaP, GaAs, InP, InAs, but are not limited to, and may also be other binary, ternary, or quaternary III-V compounds.
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 =2, the inorganic metal halide octahedron MX6 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-。
The in-situ ligand exchange between the quantum dot preformed film and the replacement ligand in the replacement ligand solution can be realized by soaking the quantum dot preformed film in the replacement ligand solution, but is not limited thereto. And through in-situ ligand replacement, ligand exchange is carried out between the initial ligand in the quantum dot prefabricated film and the replacement ligand in the replacement ligand solution, so that the quantum dot light-emitting film with the surface of the quantum dot connected with the replacement ligand is formed.
Further, after the ligand exchange is finished, the method also comprises the step of removing the replaced original ligand. The cleaning method can be to clean the initial ligand remained on the surface of the quantum dot light-emitting film by using a solvent, or to place the prepared quantum dot light-emitting film in a vacuum device, and to remove the initial ligand on the surface of the quantum dot light-emitting film by regulating the pressure and temperature of a vacuum chamber (the ligand with loose structure or not participating in coordination in the quantum dot film is removed by vacuumizing, and a more stable quantum dot layer is finally obtained).
Preferably, the method further comprises preparing an electronic function layer between the cathode and the quantum dot light emitting layer, wherein the electronic function layer comprises at least one of an electron injection layer and an electron transport layer. Wherein the electron transport layer is selected from materials with electron transport property, preferably inorganic materials or organic materials with electron transport property, and the inorganic materials include but are not limited to n-type ZnO, TiO2、SnO2、Ta2O3、AlZnO、ZnSnO、InSnO、Ca、Ba、CsF、LiF、Cs2CO3At least one of; the organic material includes, but is not limited to, Alq3TPBi, BCP, BPhen, PBD, TAZ, OXD-7, 3TPYMB, BP4mPy, TmPyPB, BmPyPhB, TQB.
In step S03, the hole function layer is preferably deposited by a solution processing method, so as to improve the film thickness uniformity of the hole function layer, thereby providing the hole function layer with excellent stability. Specifically, the preparation method of the hole functional layer comprises the following steps: and providing a hole functional material solution, depositing the hole functional material solution on the surface of the quantum dot light-emitting layer, and preparing a hole functional layer through annealing treatment.
Wherein, the solvent of the hole functional material solution comprises a strong polar solvent or a weak polar solvent, when the replacement ligand on the surface of the quantum dot light emitting layer is a strong polar ligand, the solvent of the hole functional material solution is preferably a weak polar solvent, including but not limited to one or more of hexane, cyclohexane, heptane, n-octane, isooctane, isopentane, pentane, methylpentane, ethylpentane, cyclopentane, methylcyclopentane, ethylcyclopentane, benzene, toluene, xylene, ethylbenzene, carbon disulfide, carbon tetrachloride, dichloromethane, dichloroethane, chlorobutane, dibromomethane, bromopropane, iodomethane, diphenyl ether, trichloroethylene, n-butyl ether, disulfide, isopropyl ether, dimethyl carbonate, trioctylamine, methyl ethyl ketone, tributylamine, tetrahydrofuran, chlorobenzene; when the replacement ligand on the surface of the quantum dot light-emitting layer is a weak polar ligand, the solvent of the hole functional material solution is preferably a strong polar solvent, including but not limited to methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, amyl alcohol, isoamyl alcohol, tert-amyl alcohol, cyclohexanol, octanol, benzyl alcohol, ethylene glycol, phenol, o-cresol, diethyl ether, anisole, phenetole, diphenyl ether, ethylene glycol dimethyl ether, propylene glycol methyl ether, ethylene glycol diethyl ether, hydroxyethyl ethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, acetaldehyde, benzaldehyde, acetone, butanone, cyclohexanone, acetophenone, formic acid, acetic acid, ethyl acetate, diethyl oxalate, diethyl malonate, propyl acetate, methyl propyl ester, butyl acetate, methyl amyl acetate, nitrobenzene, acetonitrile, diethylamine, triethylamine, aniline, pyridine, diethyl oxalate, methyl propyl ester, butyl acetate, methyl amyl acetate, nitrobenzene, acetonitrile, diethylamine, triethylamine, aniline, pyridine, At least one of picoline, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, hexamethylphosphoramide, carbon disulfide, methyl sulfide, ethyl sulfide, dimethyl sulfoxide, mercaptan, ethanethiol, and methoxytetrahydrofuran.
Specifically, the hole function layer includes at least one of a hole transport layer and a hole injection layer.
Wherein the hole injection layer is selected from organic materials having hole injection capability. The hole injection material for preparing the hole injection layer 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), transition metal oxide, and transition metal chalcogenide compound. 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.
The hole transport layer is selected from organic materials having hole transport capability 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 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 the step S04, the anode is selected from one of doped metal oxides, including but not limited to 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). The anode can also be a composite electrode with a transparent metal oxide containing a metal interlayer, wherein the transparent metal oxide can 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/TiO2。
In the embodiment of the present invention, the deposition methods of the anode, the cathode, the hole injection layer, the hole transport layer, the electron injection layer, and the quantum dot prefabricated film may be implemented by a chemical method or a physical method, wherein the chemical method includes, but is not limited to, one or more of a chemical vapor deposition method, a continuous ion layer adsorption and reaction method, an anodic oxidation method, an electrodeposition method, and a coprecipitation method; the physical method includes but is not limited to physical coating method or solution processing method, wherein the solution processing method includes but is not limited to spin coating method, printing method, blade coating method, dip-coating method, soaking method, spray coating method, roll coating method, casting method, slit coating method, strip coating method; physical coating methods include, but are not limited to, one or more of thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion coating, physical vapor deposition, atomic layer deposition, pulsed laser deposition.
The embodiment of the invention also provides an inversion QLED device, which comprises a cathode, a quantum dot light-emitting layer, a hole functional layer and an anode which are combined in a laminated mode, wherein the inversion QLED device is prepared by the method.
The inversion QLED device provided by the embodiment of the invention is prepared by the method, so that the types of hole functional materials of the inversion QLED device, such as hole transport materials, solvents of the hole transport materials and formed ink, are not limited any more, and the selection range of the hole functional materials and the ink of the inversion QLED device is expanded.
Specifically, the inverted 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.
The packaging mode of the inversion type QLED device may be partial packaging, full packaging, or no packaging, and the embodiment of the present invention is not limited strictly.
The embodiment of the invention also provides a printed quantum dot display screen which comprises the inverse QLED device.
The following description will be given with reference to specific examples.
Example 1
A preparation method of an inversion structure quantum dot light-emitting diode comprises the following steps:
providing a cathode; dissolving 3-mercaptopropionic acid in ethanol to prepare a replacement ligand solution;
printing a CdSe quantum dot prefabricated film on a cathode, immersing the quantum dot prefabricated film into the ligand replacement solution, taking out after immersing for 10min, transferring the quantum dot prefabricated film into a vacuum chamber, adjusting the vacuum degree to 10Pa and maintaining for 30min, removing the ligand and the solvent which are not coordinated in the quantum dot light-emitting layer, and preparing the CdSe quantum dot light-emitting layer;
and printing a hole functional layer on the CdSe quantum dot light-emitting layer, and finally evaporating an anode to obtain the quantum dot light-emitting diode with the inverse structure.
Example 2
A preparation method of an inversion structure quantum dot light-emitting diode comprises the following steps:
providing a cathode; dissolving 3-mercaptopropionic acid in ethanol to prepare a replacement ligand solution;
sequentially printing a ZnO electronic transmission layer and a CdSe quantum dot prefabricated film on an ITO cathode, immersing the quantum dot prefabricated film into the ligand replacement solution, taking out after immersing for 10min, transferring the quantum dot prefabricated film into a vacuum chamber, adjusting the vacuum degree to 10Pa and maintaining for 30min, removing the ligand and the solvent which are not coordinated in the quantum dot light-emitting layer, and preparing the CdSe quantum dot light-emitting layer;
and printing a TFB hole transport layer and a PEDOT (Poly ethylene glycol ether ketone) (PSS) hole injection layer on the CdSe quantum dot light emitting layer, and finally evaporating an Al cathode to obtain the quantum dot light emitting diode with the full-solution-method inverse structure.
Example 3
A preparation method of an inversion structure quantum dot light-emitting diode comprises the following steps:
providing a cathode; dissolving 3-mercaptopropionic acid and isophthalic acid in ethanol to prepare a replacement ligand solution;
sequentially printing a ZnO electronic transmission layer and a CdSe quantum dot prefabricated film on an ITO cathode, immersing the quantum dot prefabricated film into the ligand replacement solution, taking out after immersing for 10min, transferring the quantum dot prefabricated film into a vacuum chamber, adjusting the vacuum degree to 10Pa and maintaining for 30min, removing the ligand and the solvent which are not coordinated in the quantum dot light-emitting layer, and preparing the CdSe quantum dot light-emitting layer;
and printing a TFB hole transport layer and a PEDOT (Poly ethylene glycol ether ketone) (PSS) hole injection layer on the CdSe quantum dot light emitting layer, and finally evaporating an Al cathode to obtain the quantum dot light emitting diode with the full-solution-method inverse structure.
Example 4
A preparation method of an inversion structure quantum dot light-emitting diode comprises the following steps:
providing a cathode; dissolving isophthalic acid in ethanol to prepare a replacement ligand solution;
sequentially printing a ZnO electronic transmission layer and a CdSe quantum dot prefabricated film on an ITO cathode, immersing the quantum dot prefabricated film into the ligand replacement solution, taking out after immersing for 10min, transferring the quantum dot prefabricated film into a vacuum chamber, adjusting the vacuum degree to 10Pa and maintaining for 30min, removing the ligand and the solvent which are not coordinated in the quantum dot light-emitting layer, and preparing the CdSe quantum dot light-emitting layer;
and printing a TFB hole transport layer and a PEDOT (Poly ethylene glycol ether ketone) (PSS) hole injection layer on the CdSe quantum dot light emitting layer, and finally evaporating an Al cathode to obtain the quantum dot light emitting diode with the full-solution-method inverse structure.
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 (3)

1. A preparation method of an inversion type QLED device is characterized by comprising the following steps:
providing a cathode and a displacer solution;
depositing a quantum dot prefabricated film on the cathode, wherein the quantum dot prefabricated film is made of quantum dots of which the surfaces contain initial ligands, carrying out in-situ ligand exchange on the quantum dot prefabricated film and a replacement ligand in a replacement ligand solution, and replacing the initial ligands with the replacement ligands to obtain a quantum dot light-emitting layer;
preparing a hole functional layer on the surface of the quantum dot light-emitting layer by a solution processing method;
preparing an anode on the hole-functional layer,
wherein the replacement ligand is selected from octylamine, propylamine, hexadecylamine, 4-mercaptoanisole, 1-hydroxy-3-methoxy-propane, mercaptoglycerol, 1-trimethylamine ethanethiol, mercaptoaniline, nitroaniline, sulfoaniline, aminobenzoic acid, 4- (diphenylphosphino) benzoic acid, 4-aminobenzoic acid, 4-hydroxybenzoic acid, p-sulfobenzoic acid, p-nitrobenzoic acid, 4-mercaptoaniline, 4-hydroxyaniline, 4-cyanoaniline, 4-mercaptostyrene acid, 4-hydroxystyrenic acid, 2- (4-hydroxyphenyl) pyridine, 2-chloro-5-cyanothiazole, 2-amino-3-cyanothiophene, 3-amino-5-mercapto-1, at least one of 2, 4-triazole,
when the replacement ligand is selected from at least one of octylamine, propylamine, hexadecylamine, 4-mercaptoanisole, and 1-hydroxy-3-methoxy-propane, the solvent for preparing the solution of hole functional material of the hole functional layer is selected from methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, amyl alcohol, isoamyl alcohol, tert-amyl alcohol, cyclohexanol, octanol, benzyl alcohol, ethylene glycol, phenol, o-cresol, diethyl ether, anisole, phenetole, diphenyl ether, ethylene glycol dimethyl ether, propylene glycol methyl ether, ethylene glycol diethyl ether, hydroxyethyl diethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, acetaldehyde, benzaldehyde, acetone, butanone, cyclohexanone, acetophenone, formic acid, acetic acid, ethyl acetate, diethyl oxalate, diethyl malonate, propyl acetate, methyl propyl ester, butyl acetate, ethyl acetate, diethyl oxalate, diethyl acetate, propyl acetate, methyl propyl ester, butyl acetate, and the like, At least one of methyl amyl acetate, nitrobenzene, acetonitrile, diethylamine, triethylamine, aniline, pyridine, picoline, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, hexamethylphosphoramide, carbon disulfide, methyl sulfide, ethyl sulfide, dimethyl sulfoxide, mercaptan, ethanethiol, methoxytetrahydrofuran, and
when the substitution ligand is selected from at least one of thioglycerol, 1-trimethylamine ethanethiol, mercaptoaniline, nitroaniline, sulfoaniline, aminobenzoic acid, 4- (diphenylphosphino) benzoic acid, the hole functional material solution for preparing the hole functional layer is selected from one or more of hexane, cyclohexane, heptane, n-octane, isooctane, isopentane, pentane, methylpentane, ethylpentane, cyclopentane, methylcyclopentane, ethylcyclopentane, benzene, toluene, xylene, ethylbenzene, carbon disulfide, carbon tetrachloride, dichloromethane, dichloroethane, chlorobutane, dibromomethane, bromopropane, iodomethane, diphenyl ether, trichloroethylene, n-butyl ether, disulfide, isopropyl ether, dimethyl carbonate, trioctylamine, methyl ethyl ketone, tributylamine, tetrahydrofuran, chlorobenzene.
2. The method of claim 1, wherein the in-situ ligand exchange between the quantum dot pre-fabricated film and the displacer in the displacer solution is performed by: and soaking the quantum dot prefabricated film in the replacement ligand solution to perform in-situ ligand exchange.
3. An inverted QLED device comprising a cathode, a quantum dot light emitting layer, a hole functional layer, and an anode in stacked combination, wherein the inverted QLED device is prepared by the method of any of claims 1-2.
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