Quantum dot patterning method, inverted quantum dot light-emitting diode manufacturing method and inverted quantum dot light-emitting diode

Abstract

The invention relates to a quantum dot patterning method for an inverted quantum dot light-emitting diode, a manufacturing method of the inverted quantum dot light-emitting diode and the inverted quantum dot light-emitting diode. The quantum dot patterning method disclosed by the invention comprises the following steps: treating an oxide electron transport layer by using an organic matter; coating the oxide electron transport layer with a quantum dot film layer; exposing the cross-linked quantum dots; and developing to remove the quantum dot film layer in an unexposed area. According to the method disclosed by the invention, the organic matter monomolecular layer is formed on the oxide electron transport layer by treating the oxide electron transport layer with the organic matter, so that the Van der Waals force between the quantum dots and the oxide electron transport layer is reduced, and the removal effect of residual quantum dots in an unexposed region is obviously enhanced.

Description

Technical Field

[0001] The present disclosure relates to the technical field of inverted quantum dot film preparation, and in particular, to a quantum dot patterning method for an inverted quantum dot light-emitting diode, a method for manufacturing an inverted quantum dot light-emitting diode comprising the method, and an inverted quantum dot light-emitting diode. Background Art

[0002] According to the classical quantum confinement effect, when the geometric radius of a semiconductor nanocrystal is smaller than the exciton Bohr radius of its bulk material, the energy levels of the valence band and conduction band will be discretely distributed, and the properties of the nanocrystal will become size-dependent. Semiconductor nanocrystals with a radius smaller than or close to the exciton Bohr radius are called quantum dots, which are usually 1-10nm in size.

[0003] Due to the quantum confinement effect, quantum dots have excellent luminescence properties such as broadband absorption, narrowband emission, and continuously adjustable peak position. Therefore, quantum dots are expected to be used in lighting and display, photoelectric detection, laser, biomedical imaging and other fields.

[0004] In order to develop integrated devices based on quantum dots, quantum dot patterning is a must. Recent work has shown that photolithography has advantages over other patterning methods in terms of low cost, large scale, simple and efficient patterning of quantum dot films, and is a patterning method that is expected to be widely used in mass production.

[0005] There are some problems with the current photolithography quantum dot patterning process. In the inverted quantum dot light-emitting diode structure, the quantum dots in the unexposed area are difficult to develop and remove due to the electron transport layer, especially the oxide electron transport layer, which hinders the final mass production of quantum dots. In the development process, how to develop and remove the quantum dots in the unexposed area as much as possible without destroying the quantum dot film layer in the exposed area is particularly important for the development of high color purity and wide color gamut display devices.

[0006] Therefore, it is necessary to develop new methods for quantum dot patterning for inverted quantum dot light-emitting devices. Summary of the invention

[0007] The quantum dot lithography patterning process usually includes three main steps: film formation, exposure, and development. The inventors have found through research that the van der Waals attraction between the quantum dots and the substrate ensures that the film layer in the exposed area can be retained on the substrate, but in the non-exposed area, it is also due to the van der Waals attraction between the two that the quantum dots are not easy to separate from the substrate, resulting in residual problems, which affects the color mixing problem of multi-color patterning. Taking the quantum dots on the substrate immersed in the developer as a research model, when the interaction between the quantum dots and the developer is stronger than the interaction between the quantum dots and the substrate, it means that the van der Waals force between the quantum dots and the substrate is overcome, and the quantum dots are engulfed in the developer, achieving the effect of the quantum dots being separated from the substrate. In the inverted quantum dot light-emitting diode structure, the oxide electron transport layer often has a greater polarity, so a stronger van der Waals force will be generated between the electron transport layer and the quantum dots, and the quantum dots are more likely to produce residues on the electron transport layer. Therefore, the inventors believe that one of the key points to solve the residue is how to reduce the van der Waals force between the oxide electron transport layer and the quantum dots. Therefore, the inventors propose that it is possible to achieve this goal by reducing the polarity of the oxide electron transport layer in contact with the quantum dots. When the polarity of the oxide electron transport layer in contact with the quantum dots decreases, the van der Waals force between it and the quantum dots will decrease, which is conducive to achieving the effect of quantum dots detaching from the substrate, so that the surface residue is significantly reduced. Therefore, the inventors proposed a method of using organic matter to treat the oxide electron transport layer, which achieved the effect of developing on the electron transport layer of the inverted quantum dot light-emitting diode structure and removing the quantum dot residue, thereby completing the present invention.

[0008] In one aspect, the present disclosure provides a method for patterning quantum dots for an inverted quantum dot light-emitting diode, comprising the following steps:

[0009] S1, treating the oxide electron transport layer with organic matter;

[0010] S2, coating a quantum dot film layer on the oxide electron transport layer;

[0011] S3, exposure of cross-linked QDs;

[0012] S4, performing development to remove the quantum dot film layer in the unexposed area.

[0013] In some embodiments, in S1, the oxide electron transport layer is treated with an organic solution or an organic atmosphere. In some embodiments, the organic substance contains both an acidic organic group and a hydrophobic organic group.

[0014] In some embodiments, the organic matter is selected from the following structures: R1-COOH, R1-SO3H, R1-SO2H, R1-B(OH)2, R1-P(=O)(OH)2, R2-OH, wherein R1 independently represents an alkyl group, an aromatic group, an ester group, an ether group, an amino group, or an amide group, and R2 represents an aromatic group.

[0015] In some embodiments, the organic matter is selected from R1-COOH, wherein R1 represents a C6-C12 aryl group which is unsubstituted or substituted with a substituent selected from a C1-C12 alkyl group, a C1-C12 alkoxy group, a C6-C12 aryl C1-C4 alkylene group which is unsubstituted or substituted with a substituent selected from a C1-C12 alkyl group, a C1-C12 alkoxy group, or a C3-C11 alkyl group which is unsubstituted or substituted with a substituent selected from a C1-C12 alkoxy group.

[0016] In some embodiments, the organic compound is selected from benzoic acid and C4-C6 alkanoic acid substituted with 1-3 methoxy groups.

[0017] In some embodiments, the ligand of the quantum dot is selected from a ligand having a vinyl double bond in the structure. In some embodiments, the ligand is a ligand having an acryloyl or methacryloyl group in the structure, or an unsaturated fatty acid. In some embodiments, the ligand is selected from succinic acid mono-2-(2-methyl-acryloyl)oxyethyl ester and oleic acid.

[0018] In some embodiments, in S4 , the dielectric constant of the solvent of the developer used for developing is less than 10.

[0019] In some embodiments, steps S2 to S4 are repeated multiple times to achieve full-color patterning of the red, green, and blue quantum dot film layer.

[0020] Another aspect of the present disclosure provides a method for manufacturing an inverted quantum dot light-emitting diode, comprising manufacturing a cathode, an oxide electron transport layer, a patterned quantum dot layer and an anode, wherein the patterned quantum dot layer is formed by the method of the present disclosure.

[0021] Another aspect of the present disclosure provides an inverted quantum dot light-emitting diode, comprising a cathode, an oxide electron transport layer, a patterned quantum dot layer and an anode that are stacked, wherein an organic monomolecular layer exists between the patterned quantum dot layer and the oxide electron transport layer.

[0022] In some embodiments, the organic compound contains both an acidic organic group and a hydrophobic organic group. In some embodiments, the organic compound is selected from the following structures: R1-COOH, R1-SO3H, R1-SO2H, R1-B(OH)2, R1-P(=O)(OH)2, R2-OH, wherein R1 independently represents an alkyl group, an aryl group, an ester group, an ether group, an amine group, an amide group, and R2 represents an aryl group.

[0023] In some embodiments, the organic matter is selected from R1-COOH, wherein R1 represents a C6-C12 aryl group which is unsubstituted or substituted with a substituent selected from a C1-C12 alkyl group, a C1-C12 alkoxy group, a C6-C12 aryl C1-C4 alkylene group which is unsubstituted or substituted with a substituent selected from a C1-C12 alkyl group, a C1-C12 alkoxy group, or a C3-C11 alkyl group which is unsubstituted or substituted with a substituent selected from a C1-C12 alkoxy group.

[0024] In some embodiments, the organic compound is selected from benzoic acid and C4-C6 alkanoic acid substituted with 1-3 methoxy groups.

[0025] In some embodiments, the ligand of the quantum dot is selected from a ligand having a vinyl double bond in the structure. In some embodiments, the ligand is a ligand having an acryloyl or methacryloyl group in the structure, or an unsaturated fatty acid. In some embodiments, the ligand is selected from succinic acid mono-2-(2-methyl-acryloyl)oxyethyl ester and oleic acid.

[0026] Beneficial Effects

[0027] In the method disclosed in the present invention, an organic monolayer is formed on the oxide electron transport layer by treating the oxide electron transport layer with organic matter, which is beneficial to reducing the van der Waals force between the quantum dots and the oxide electron transport layer and significantly enhancing the removal effect of residual quantum dots in the unexposed area.

[0028] The method disclosed in the present invention only needs to process the oxide electron transport layer and has no influence on other processes. The method is simple and easy to implement.

[0029] The method disclosed in the present invention can select different ligand molecules specifically for quantum dots of different systems and has universal applicability.

[0030] The method disclosed in the present invention has various treatment methods. A solution method can be used for treatment, such as in Example 1, or a gas atmosphere method can be used for treatment, such as in Example 2. In addition, a treatment method can be selected based on the solubility and boiling point of the specific organic matter (such as carboxylic acid) being treated.

[0031] In the method disclosed in the present invention, the treatment method does not require the addition of other hydrolyzing agents for treatment, and does not produce other compounds, thereby avoiding the damage that the hydrolyzing agent or the produced compounds may cause to the oxide electron transport layer.

[0032] In addition, traditional oxide electron transport layers often have faster transmission speeds than hole transport layers. The imbalance between electron and hole transport speeds will reduce the life of the device. After the oxide electron transport layer is treated with the method disclosed in the present invention, a single molecular layer of organic matter can produce an electron blocking effect, which can reduce the imbalance between electron and hole transport speeds and increase the life of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram showing a comparison of the development effects of the inverted quantum dot lithography patterning method according to the present disclosure and the conventional method.

[0034] Figure 2 The red quantum dot development effect diagram according to Example 1 and Comparative Example 1 is shown.

[0035] Figure 3 The electroluminescence spectra of the quantum dot light emitting diode devices according to Example 1 and Comparative Example 1 are shown.

[0036] Figure 4 The red quantum dot development effect diagram according to Example 2 and Comparative Example 2 is shown.

[0037] Figure 5 The green quantum dot development effect diagram according to Example 3 and Comparative Example 3 is shown. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0039] The words "first", "second" and similar terms used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0040] In the present disclosure, the word "comprise" or its variations, such as "include", "contain", "have", will be understood to include the stated elements, integers or steps, or a combination of elements, integers or steps, but does not exclude the addition of other elements, integers or steps, or a combination of elements, integers or steps.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those of ordinary skill in the art to which the present invention belongs. Although those similar or equivalent to the methods and materials described herein may be used in the practice or testing of the present invention, suitable methods and materials will be described below. In the event of a conflict, this specification (including definitions) shall prevail. In addition, the materials, methods and embodiments are merely illustrative and are not intended to be restrictive.

[0042] “At least one of A, B and C” has the same meaning as “at least one of A, B or C”, and both include the following combinations of A, B and C: only A, only B, only C, a combination of A and B, a combination of A and C, a combination of B and C, and a combination of A, B and C. “A and / or B” includes the following three combinations: only A, only B, and a combination of A and B.

[0043] In the present disclosure, unless otherwise specified, "plurality" means two or more.

[0044] In order to keep the following description of the embodiments of the present disclosure clear and concise, the present disclosure omits detailed descriptions of well-known functions and well-known components.

[0045] The present disclosure relates to a method for patterning quantum dots for an inverted quantum dot light emitting diode, a method for manufacturing an inverted quantum dot light emitting diode comprising the method, an inverted quantum dot light emitting diode, and an optoelectronic device.

[0046] Quantum dot patterning method

[0047] The present disclosure provides a method for patterning quantum dots of an inverted quantum dot light-emitting diode, wherein the inverted quantum dot light-emitting diode comprises a cathode, an oxide electron transport layer, a quantum dot layer, and an anode that are stacked, and the method comprises the following steps:

[0048] S1, treating the oxide electron transport layer with organic matter;

[0049] S2, coating a quantum dot film layer on the oxide electron transport layer;

[0050] S3, exposure of cross-linked QDs;

[0051] S4, performing development to remove the quantum dot film layer in the unexposed area.

[0052] The above steps are described in detail below.

[0053] S1: Monolayer organic treatment of oxide electron transport layer

[0054] In step S1 , an organic layer, preferably a monomolecular layer, may be formed on the oxide electron transport layer by treating the oxide electron transport layer with an organic material.

[0055] As mentioned above, the van der Waals attraction between the quantum dots and the substrate ensures that the film layer in the exposed area can be retained on the substrate, but in the non-exposed area, the van der Waals attraction between the two causes the quantum dots to be difficult to separate from the substrate, resulting in a residue problem, which affects the color mixing problem of multi-color patterning. In the upright quantum dot light-emitting diode structure, the quantum dot layer is prepared after the hole transport layer (whose material is usually an organic molecule). Since the polarity of the hole transport layer is weak, the van der Waals force between the hole transport layer and the quantum dots is weak. After development, the quantum dots are not easy to produce residues on the hole transport layer, so the color mixing problem caused by quantum dot residues is less likely to occur in the upright quantum dot light-emitting diode structure. In the inverted quantum dot light-emitting diode structure, the quantum dot layer is prepared after the electron transport layer (which is usually an inorganic oxide). The oxide electron transport layer often has a greater polarity, so a stronger van der Waals force will be generated between the electron transport layer and the quantum dots.

[0056] The present invention discloses that in the process of preparing an inverted quantum dot light-emitting diode, an organic monolayer can be formed on the oxide electron transport layer by treating the oxide electron transport layer with an organic substance, thereby reducing the polarity of the surface of the oxide electron transport layer and correspondingly reducing the van der Waals force between the electron transport layer and the quantum dots.

[0057] Figure 1 A schematic diagram showing the comparison of the development effects of the inverted quantum dot lithography patterning method according to the present disclosure and the conventional method. Figure 1 As shown, in the traditional development process, after ultraviolet exposure and good solvent development, quantum dots are likely to remain on the electron transport layer, resulting in color mixing problems; while according to the disclosed method, the oxide electron transport layer is first treated with organic matter to form a monomolecular layer, and then ultraviolet exposure and good solvent development are performed, so the quantum dots on the electron transport layer are easily removed, reducing or eliminating the quantum dot residues, thereby reducing or eliminating the color mixing problem.

[0058] Specifically, the oxide electron transport layer can be an electron transport layer formed of any suitable oxide without particular limitation. In some embodiments, the oxide can be selected from ZnO, SnO2, ZnMgO, ZnAlO, ZnGaO or TiO2, but is not limited thereto. More particularly, the oxide is ZnO.

[0059] Specifically, there is no particular limitation on the method of treating the oxide electron transport layer with an organic substance, as long as the two are in contact and an organic layer can be formed on the oxide electron transport layer without causing damage to the product structure. In some embodiments, the oxide electron transport layer can be treated with an organic substance or a solution thereof. For example, the oxide electron transport layer is immersed in an organic substance or a solution thereof, and then dried to form an organic layer on the oxide electron transport layer. In other embodiments, the oxide electron transport layer can be treated with an organic atmosphere. For example, the oxide electron transport layer is placed in an organic vapor and then dried to form an organic layer on the oxide electron transport layer. In addition, the treatment method can be selected according to the solubility, boiling point, etc. of the specific organic substance (such as carboxylic acid) being treated. Therefore, the method of treating the oxide electron transport layer with an organic substance of the present invention is not limited thereto.

[0060] Specifically, the organic matter contains both an acidic organic group and a hydrophobic organic group. Thus, the acidic organic group at one end of the organic matter can be connected to the oxide electron transport layer, for example, by forming a covalent bond, a coordination bond, a hydrogen bond, etc. with the oxide, while the hydrophobic organic group at the other end faces away from the oxide electron transport layer, thereby reducing the polarity of the oxide electron transport layer surface, which is conducive to the removal of quantum dots.

[0061] In some embodiments, the acidic organic group includes, but is not limited to, a carboxyl group, a sulfonic acid group, a sulfinic acid group, a phenolic hydroxyl group, a boric acid group, a phosphoric acid group, etc. The use of these acidic organic groups is conducive to connecting one end of the organic matter to the oxide electron transport layer. On the one hand, the metal element in the oxide can form a coordination bond with the acidic organic group, and on the other hand, there are usually hydroxyl groups on the surface of the oxide, which can form covalent bonds, hydrogen bonds, etc. with the acidic organic group, thereby connecting to the organic matter.

[0062] In some embodiments, the hydrophobic organic group may include, but is not limited to, hydrocarbon groups, aromatic groups, ester groups, ether groups, amine groups, amide groups, etc. The use of these hydrophobic organic groups is conducive to forming a hydrophobic surface on the surface of the oxide electron transport layer, reducing the polarity of the surface of the oxide electron transport layer, and weakening the van der Waals force between the quantum dots and the oxide electron transport layer, thereby facilitating the removal of quantum dots in the non-exposed cross-linked area and reducing the residue of quantum dots on the electron transport layer.

[0063] Specifically, the organic compound can be selected from the following structures: R1-COOH, R1-SO3H, R1-SO2H, R1-B(OH)2, R1-P(=O)(OH)2, R2-OH,

[0064] in,

[0065] R1 independently represents, but is not limited to, an alkyl group, an aryl group, an ester group, an ether group, an amine group, an amide group, etc.

[0066] R2 represents, but is not limited to, an aryl group.

[0067] In particular, the alkyl group may be a substituted or unsubstituted C3-C12 alkyl group or C3-C8 alkyl group, and the substituted substituent may be selected from C1-C12 alkoxy, C6-C12 aryl and C6-C12 aryl substituted by C1-C12 alkyl or C1-C12 alkoxy, in particular may be selected from C1-C6 alkoxy, C6-C10 aryl and C6-C10 aryl substituted by C1-C6 alkyl or C1-C6 alkoxy, more in particular may be selected from C1-C4 alkoxy, phenyl and phenyl substituted by C1-C6 alkyl or C1-C6 alkoxy.

[0068] The aryl group can be a substituted or unsubstituted C6-C12 aryl or C6-C10 aryl or phenyl group, and the substituted substituent refers to a substituent selected from C1-C12 alkyl (e.g. C1-C8 alkyl, C1-C6 alkyl, C1-C4 alkyl), C1-C12 alkoxy (e.g. C1-C8 alkoxy, C1-C6 alkoxy, C1-C4 alkoxy), R'C(=O)OR"-, R'OC(=O)R"-, R'OR"-, R'NHR"-, (R')2NR"-, R'C(=O)NR"-, R'NC(=O)R"-.

[0069] The ester group may be R'C(=O)OR" or -R'OC(=O)R"-.

[0070] The ether group may be R'OR"-.

[0071] The amino group may be R'NHR"- or (R')2NR"-.

[0072] The amide group may be R'C(=O)NR"- or R'NC(=O)R"-.

[0073] The above R' is independently selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C5-C12 cycloalkyl, substituted or unsubstituted C6-C12 aryl, preferably substituted or unsubstituted C2-C8 alkyl, substituted or unsubstituted C5-C8 cycloalkyl, substituted or unsubstituted C6-C10 aryl, preferably substituted or unsubstituted C2-C6 alkyl, substituted or unsubstituted C5-C6 cycloalkyl, substituted or unsubstituted phenyl The substituted substituent may be selected from C1-C12 alkoxy, C6-C12 aryl and C6-C12 aryl substituted by C1-C12 alkyl or C1-C12 alkoxy, in particular may be selected from C1-C6 alkoxy, C6-C10 aryl and C6-C10 aryl substituted by C1-C6 alkyl or C1-C6 alkoxy, more in particular may be selected from C1-C4 alkoxy, phenyl and phenyl substituted by C1-C4 alkyl or C1-C4 alkoxy.

[0074] The above R" is independently selected from non-existence, C1-C12 alkylene, C5-C12 cycloalkylene, C6-C12 arylene or a combination thereof at each occurrence, preferably selected from non-existence, C1-C8 alkylene, C5-C8 cycloalkylene, C6-C10 arylene or a combination thereof, more preferably selected from non-existence, C1-C6 alkylene, C5-C6 cycloalkylene, phenylene or a combination thereof.

[0075] In some embodiments, the organic compound is represented by R1-COOH, wherein R1 represents a C6-C12 aryl group which is unsubstituted or substituted by a substituent selected from C1-C12 alkyl (e.g., C1-C8 alkyl, C1-C6 alkyl, C1-C4 alkyl), C1-C12 alkoxy (e.g., C1-C8 alkoxy, C1-C6 alkoxy, C1-C4 alkoxy), a C6-C12 aryl group which is unsubstituted or substituted by a substituent selected from C1-C12 alkyl (e.g., C1-C8 alkyl, C1-C6 alkyl, C1-C4 alkyl), C1-C12 alkoxy (e.g., C1-C8 alkoxy, C1-C6 alkoxy, C1-C4 alkoxy) R1 represents a C6-C12 arylC1-C4 alkylene group substituted with a substituent selected from C1-C8 alkoxy (e.g. C1-C8 alkoxy, C1-C6 alkoxy, C1-C4 alkoxy), or a C3-C11 alkyl group which is unsubstituted or substituted with a substituent selected from C1-C12 alkoxy (e.g. C1-C8 alkoxy, C1-C6 alkoxy, C1-C4 alkoxy), in particular, R1 represents a phenyl group or a C3-C7 alkyl group which is unsubstituted or substituted with a substituent selected from C1-C12 alkoxy (e.g. C1-C8 alkoxy, C1-C6 alkoxy, C1-C4 alkoxy).

[0076] In some embodiments, the organic compound is selected from benzoic acid and C4-C6 alkanoic acid substituted with 1-3 methoxy groups, in particular p-methoxybenzoic acid, 3,4,5-trimethoxybenzoic acid and isobutyric acid.

[0077] In the present disclosure, a numerical range such as "C1-C12" means that the group may have 1-12 carbon atoms, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms.

[0078] In the present disclosure, "alkyl" may include straight or branched chain alkyl. Unsubstituted alkyl may be a "saturated alkyl group" without any double or triple bonds. Examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl and hexyl.

[0079] In the present disclosure, "alkoxy" means RO-, wherein R represents the above-mentioned alkyl group.

[0080] In the present disclosure, cycloalkyl refers to a group derived from a saturated cyclic carbon chain structure. The cycloalkyl may be substituted or unsubstituted. Examples of cycloalkyl include, but are not limited to, cyclopentyl, cyclohexyl, adamantyl, norbornyl, etc.

[0081] In the present disclosure, aryl refers to an optional functional group or substituent derived from an aromatic carbocyclic ring. Aryl can be a monocyclic aryl (e.g., phenyl) or a polycyclic aryl. In other words, aryl can be a monocyclic aryl, a condensed ring aryl, two or more monocyclic aryl groups connected by carbon-carbon bond conjugation, a monocyclic aryl and a condensed ring aryl connected by carbon-carbon bond conjugation, and two or more condensed ring aryl groups connected by carbon-carbon bond conjugation. That is, unless otherwise specified, two or more aromatic groups connected by carbon-carbon bond conjugation can also be regarded as aryl of the present disclosure. Wherein, condensed ring aryl can, for example, include bicyclic condensed aryl (e.g., naphthyl), tricyclic condensed aryl (e.g., phenanthrenyl, fluorenyl, anthracenyl), etc. For example, in the present disclosure, biphenyl, terphenyl, etc. are aryl. Examples of aryl can include, but are not limited to, phenyl, naphthyl, fluorenyl, anthracenyl, phenanthrenyl, biphenyl, etc. In the present disclosure, biphenyl can be understood as an aryl substituted by phenyl, or as an unsubstituted aryl.

[0082] In the method disclosed in the present invention, the treatment method does not require the addition of other hydrolyzing agents for treatment, and does not produce other compounds, thereby avoiding the damage to the oxide electron transport layer caused by the hydrolyzing agent or the produced compounds.

[0083] S2, coating a quantum dot film layer on the oxide electron transport layer

[0084] In step S2, a quantum dot film layer is coated on the oxide electron transport layer.

[0085] There is no particular limitation on the method of coating quantum dots on the oxide electron transport layer to form a quantum dot film layer, and any suitable coating method in the relevant field can be used. In some embodiments, the quantum dot film layer can be coated on the oxide electron transport layer by spin coating.

[0086] The quantum dots include a quantum dot body and a quantum dot ligand.

[0087] There is no particular limitation on the quantum dot body, and any suitable quantum dots in the relevant field can be adopted. In some embodiments, the quantum dot body is selected from II-VI group quantum dots such as CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgSe, HgTe, HgS, Hg x Cd 1-x Te, Hg x Cd 1-x S, Hg x Cd 1-x Se, Hg x Zn 1-x Te, Cd x Zn 1-x Se, Cd x Zn 1-x S, where 0 < x < 1; III-V group quantum dots such as InP, InAs, InSb, GaAs, GaP, GaN, GaSb, InN, InSb, AlP, AlN, AlAs; VI-VI group quantum dots such as PbS, PbSe, PbTe; quantum dots with a core-shell structure such as CdSe@ZnS, CdSe@CdS, InP@ZnS, CdTe@CdSe, CdSe@ZnTe, ZnTe@CdSe, ZnSe@CdS, and Cd 1-x Zn x S@ZnS; ABX3-type perovskite quantum dots, where A is one or more of CH3NH3 + , NH2CH=NH2, Cs + , B is one or two of Pb 2+ , Sn 2+ , X is one or more of Cl - , Br - , I - , such as CH3NH3PbBr3, CH3NH3PbCl3, CH3NH3PbI3, CsPbBr3, CsPbCl3, CsPbI3; or other quantum dots such as CuInS2, CuInSe2, AgInS2, however, the present invention is not limited thereto.

[0088] The quantum dot ligand is a crosslinking group connected to the quantum dot body. There is no particular limitation on the quantum dot ligand, as long as the crosslinking group can crosslink when irradiated with ultraviolet light, so that the quantum dots in the ultraviolet-irradiated area are crosslinked into a whole.

[0089] In an embodiment, the quantum dot ligand is selected from a ligand having a vinyl double bond in the structure. In some embodiments, the ligand is a ligand having an acryloyl or methacryloyl group in the structure, or an unsaturated fatty acid. In some embodiments, the ligand is selected from succinic acid mono-2-(2-methyl-acryloyl)oxyethyl ester and oleic acid.

[0090] S3, Exposure of cross-linked quantum dots

[0091] In step S3, exposure is performed to cross-link the quantum dots.

[0092] There is no particular limitation on the method of exposing the quantum dots to UV light for cross-linking, and any suitable exposure method in the related art may be used.

[0093] In some embodiments, the quantum dot film layer may be irradiated with a laser under the shielding of a mask plate, so that the quantum dots in the exposed area (also referred to as the laser irradiated area) are cross-linked, while the quantum dots in the unexposed and unirradiated area (also referred to as the laser unirradiated area) are not cross-linked, thereby forming a cross-linked area and an uncross-linked area. Since the uncross-linked area and the cross-linked area have different solubilities in the developer, the quantum dots in the uncross-linked area can be dissolved in the developer, while the quantum dots in the cross-linked area are insoluble in the developer, so the uncross-linked area can be selectively removed during the development process, thereby forming a patterned quantum dot layer.

[0094] S4, developing to remove the quantum dot film layer in the unexposed area

[0095] In step S4 , development is performed to remove the quantum dot film layer in the unexposed area, thereby forming a patterned quantum dot layer.

[0096] There is no particular limitation on the solvent of the developer used for development, and it can be appropriately selected according to the polarity and solubility of the ligands on the quantum dots used. Usually, the solvent of the quantum dot solution can be selected as the solvent of the developer.

[0097] In some embodiments, in S4, the dielectric constant of the solvent of the developer used for development is not greater than 10, preferably not greater than 9.5, more preferably not greater than 9, such as 8, 7, 6, 5, etc.

[0098] In some embodiments, the solvent is selected from toluene, chlorobenzene, n-hexane, n-octane, n-heptane, cyclohexane, dichloromethane, chloroform and tetrahydrofuran.

[0099] The above steps S2 to S4 can be a patterning production process for a quantum dot film layer that emits one light color. If multiple quantum dots emitting different light colors are required, steps S2 to S4 can be repeated multiple times to achieve full-color patterning of red, green and blue quantum dot film layers. For example, it is necessary to produce a quantum dot film layer having a red light-emitting portion that emits red light, a green light-emitting portion that emits green light, and a blue light-emitting portion that emits blue light. When producing the red light-emitting portion, steps S2-S4 can be used to achieve this. When producing the green light-emitting portion, steps S2 to S4 can be performed again. When producing the blue light-emitting portion, steps S2 to S4 can be performed again. Of course, the corresponding patterned areas in different light-emitting portions emitting different light colors may be different.

[0100] Method for making quantum dot light-emitting diode

[0101] Another aspect of the present disclosure provides a method for manufacturing an inverted quantum dot light-emitting diode, comprising manufacturing a cathode, an oxide electron transport layer (ETL), a patterned quantum dot layer and an anode, wherein the patterned quantum dot layer is formed by the method of the present disclosure.

[0102] There is no particular limitation on the structure of the inverted quantum dot light-emitting diode, and any suitable structure in the relevant field can be adopted. The quantum dot light-emitting device may further include: a substrate, an electron injection layer (EIL), a hole blocking layer (HBL), an electron blocking layer, a hole transport layer (HTL), a hole injection layer (HIL), a cap layer (CPL), a LiF layer, and an encapsulation layer, etc., but the present invention is not limited thereto.

[0103] Except that the patterned quantum dot layer is formed by the method disclosed above, there is no particular limitation on the specific structure, material composition and preparation method of the substrate, cathode, oxide electron transport layer, electron injection layer, hole blocking layer, electron blocking layer, hole transport layer, hole injection layer, anode, cap layer, LiF layer and encapsulation layer, and any suitable process in the relevant field can be used. The present disclosure does not involve improvements to these components, so these components are not described in detail to avoid blurring the main technical ideas of the present disclosure.

[0104] Quantum dot light emitting diodes

[0105] Another aspect of the present disclosure provides an inverted quantum dot light-emitting diode, comprising a cathode, an oxide electron transport layer, a patterned quantum dot layer and an anode that are stacked, wherein an organic monomolecular layer exists between the patterned quantum dot layer and the oxide electron transport layer.

[0106] The descriptions of organic matter, quantum dots, and oxides are the same as before and will not be repeated here.

[0107] In some embodiments, the patterned quantum dot layer is formed by the method of the present disclosure. In other words, the inverted quantum dot light emitting diode described in the present disclosure is prepared by the method of preparing the inverted quantum dot light emitting diode according to the present disclosure.

[0108] There is no particular limitation on the structure of the inverted quantum dot light-emitting diode, and any suitable structure in the relevant field can be adopted. The quantum dot light-emitting device may also include: a substrate, an electron injection layer (EIL), a hole blocking layer (HBL), an electron blocking layer, a hole transport layer (HTL), a hole injection layer (HIL), a cap layer (CPL), a LiF layer, and an encapsulation layer, etc. One or more, but the present invention is not limited thereto. Those skilled in the art can select a suitable inverted quantum dot light-emitting diode structure as needed, and prepare it with reference to a suitable process in the relevant field.

[0109] In one embodiment, the inverted quantum dot light-emitting device includes: a substrate, a cathode arranged on the substrate, an electron injection layer located on the side of the cathode facing away from the substrate, an oxide electron transport layer located on the side of the electron injection layer facing away from the substrate, a quantum dot layer located on the side of the oxide electron transport layer facing away from the substrate, a hole transport layer located on the side of the quantum dot layer facing away from the substrate, a hole injection layer located on the side of the hole transport layer facing away from the substrate, and an anode located on the side of the hole injection layer facing away from the substrate. In another embodiment, the inverted quantum dot light-emitting device includes: a substrate, a cathode arranged on the substrate, an electron injection layer located on the side of the cathode facing away from the substrate, an oxide electron transport layer located on the side of the electron injection layer facing away from the substrate, a hole blocking layer located on the side of the oxide electron transport layer facing away from the substrate, a quantum dot layer located on the side of the hole blocking layer facing away from the substrate, an electron blocking layer located on the side of the quantum dot layer facing away from the substrate, a hole transport layer located on the side of the electron blocking layer facing away from the substrate, a hole injection layer located on the side of the hole transport layer facing away from the substrate, and an anode located on the side of the hole injection layer facing away from the substrate.

[0110] The inverted quantum dot light-emitting diode can be used to prepare optoelectronic devices. The optoelectronic devices can be applied to the fields of lighting and display, photoelectric detection, laser, biomedical imaging, etc.

[0111] There is no particular limitation on the optoelectronic device, as long as it includes the above-mentioned inverted quantum dot light-emitting diode disclosed in the present invention. The optoelectronic device may be a lamp, a display device, a photodetector, etc., but is not limited thereto. In particular, the display device may be: a mobile phone, a tablet computer, a television, a monitor, a laptop computer, a digital photo frame, a navigator, a smart watch, a fitness wristband, a personal digital assistant, or any other product or component with a display function. Other essential components of optoelectronic devices such as lamps, display devices, photodetectors, etc. should be understood by those of ordinary skill in the art, and will not be elaborated here, nor should they be used as limitations on the present invention.

[0112] Example

[0113] In order to objectively evaluate the technical effects of the embodiments of the present disclosure, the technical solutions provided by the present disclosure will be described in detail and exemplarily through embodiments below. These embodiments are provided so that the present disclosure will be more comprehensive and complete, and the concepts of the exemplary embodiments are fully conveyed to those skilled in the art. The features, structures or characteristics described in these exemplary embodiments can be combined in one or more embodiments in any suitable manner, so that they can be implemented in various forms, and therefore should not be understood as being limited to the examples set forth herein. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by those of ordinary skill in the art are within the scope of protection of the present disclosure.

[0114] Reagents and instruments

[0115] The quantum dots were purchased from Xingshuo, the ligand was oleic acid, and they were cadmium selenide core-shell quantum dots.

[0116] The quantum dots modified with mono-2-(2-methyl-acryloyl)oxyethyl succinate (MMES) were prepared as follows: the quantum dots purchased from Xingshuo were used for the solution ligand exchange method to prepare the quantum dots modified with MMES. The specific operation was as follows: MMES was added to the quantum dot solution of crude oil acid ligand (n-octane solvent), and stirred for about 1 hour, the quantum dots were separated by centrifugation, and washed with PMA, and redissolved in PMA.

[0117] NPB: N,N'-diphenyl-N,N'-di(1-naphthyl)-1,1'-biphenyl-4,4'-diamine

[0118] Preparation of Sol-gel zinc oxide (75 mg / ml) solution: Mix 740 mg of zinc acetate dihydrate, 76.5 mg of aluminum acetate, 229 mg of ethanolamine, and 4.6 g of 2-methoxyethanol to obtain 5 ml of Sol-gel zinc oxide solution.

[0119] Example 1 Quantum dot development after zinc oxide treatment using p-methoxybenzoic acid

[0120] After spin coating the sol-gel zinc oxide (75 mg / ml) solution on the ITO, it was heated on a 300°C hot plate for 5 minutes to prepare the zinc oxide electron transport layer, and the zinc oxide on the electrode part (i.e., the surrounding part of the substrate) was erased (so that there was no zinc oxide layer in the surrounding part and only the central part had ZnO), and then the subsequent device preparation was carried out. Then, it was soaked in an isopropanol solution of 1% p-methoxybenzoic acid for five minutes, dried, and then spin coated with red quantum dots (cadmium selenide core-shell quantum dots, with a luminescence peak position of about 630 nm) modified with succinic acid mono-2-(2-methyl-acryloyl)oxyethyl ester (MMES) (25 mg / mL, 2000 rpm, 40 s), and then developed with a propylene glycol monomethyl ether acetate (PMA) solution containing 2% MMES to obtain a patterned quantum dot layer.

[0121] Comparative Example 1 Quantum dot development of zinc oxide without using p-methoxybenzoic acid to treat

[0122] A patterned quantum dot layer was obtained in the same manner as in Example 1, except that the 1% by mass p-methoxybenzoic acid isopropanol solution was not used for treatment.

[0123] Experimental Example 1

[0124] The quantum dots are illuminated by ultraviolet light (365nm wavelength) of the same power to emit light. The quantum dots will generate red light after being excited by ultraviolet light. The quantum dot layers prepared in Example 1 and Comparative Example 1 are respectively verified for luminescence. The results are shown in FIG. Figure 2 .

[0125] Figure 2 In the figure, A shows the result of the quantum dot layer prepared in Comparative Example 1 (only the central part has ZnO, and the zinc oxide electron transport layer is not treated with p-methoxybenzoic acid), and there is significant red residue on the zinc oxide electron transport layer in the central part, and B shows the result of the quantum dot layer prepared in Example 1 (only the central part has ZnO, and the zinc oxide electron transport layer is treated with p-methoxybenzoic acid), and the red residue on the zinc oxide electron transport layer in the central part is significantly reduced after development.

[0126] Experimental Example 2

[0127] Based on the quantum dot layer substrate prepared in Example 1 and Comparative Example 1, a blue quantum dot film, a hole transport material layer and an electrode material layer were further prepared to make a quantum dot light-emitting diode device, and the residual situation was verified by electroluminescence.

[0128] In this experiment, 20mg / ml blue light quantum dots (purchased from Xingshuo, oleic acid ligand, cadmium selenide core-shell quantum dots, luminescence peak position around 470nm) were first spin-coated at a speed of 3000rpm for 40s. Then the hole transport layer was evaporated. In this experiment, 60nm of NPB was evaporated; 10nm of molybdenum trioxide was evaporated; and finally, the electrode was evaporated, which was 100nm of aluminum electrode.

[0129] Electroluminescence spectra such as Figure 3 See Figure 3 , wherein the quantum dot light-emitting diode device prepared using the untreated quantum dot layer substrate of comparative example 1 has obvious red light emission, while the quantum dot light-emitting diode device prepared using the treated quantum dot layer substrate according to example 1 of the present invention has significantly reduced red light emission and significantly improved color coordinates from (0.239, 0.101) to (0.145, 0.057).

[0130] Example 2: Quantum dot development after zinc oxide treatment using isobutyric acid gas atmosphere

[0131] A 10% isobutyric acid isopropanol solution is prepared and placed in an inverted glass cover. Since isobutyric acid is volatile, the glass cover will be filled with an isobutyric acid atmosphere.

[0132] After spin coating the sol-gel zinc oxide (75 mg / ml) solution on the ITO, the substrate was heated on a 300°C hot plate for 5 minutes to prepare a zinc oxide electron transport layer (the zinc oxide of the electrode part was not erased here), and then the substrate after the ZnO film was prepared was placed in the above-mentioned glass cover, but not in contact with the isopropanol solution of isobutyric acid, thereby treating the ZnO film in an isobutyric acid atmosphere. After one hour of treatment, the substrate was dried.

[0133] Then, red quantum dots (purchased from Xingshuo, oleic acid ligands, soluble in n-octane, cadmium selenide core-shell quantum dots, with a luminescence peak position at around 630 nm) were spin-coated (25 mg / mL, 2000 rpm, 40 s), and finally developed with n-octane to obtain a patterned quantum dot layer.

[0134] Comparative Example 2: Quantum dot development of zinc oxide without using isobutyric acid gas atmosphere

[0135] A patterned quantum dot layer was obtained in the same manner as in Example 2 except that the isobutyric acid atmosphere was not used for treatment.

[0136] Experimental Example 3

[0137] The quantum dots are illuminated by ultraviolet light (365nm wavelength) of the same power to emit light. The quantum dots will generate red light after being excited by ultraviolet light. The quantum dot layers prepared in Example 2 and Comparative Example 2 are respectively verified for luminescence. The results are shown in FIG. Figure 4 .

[0138] Figure 4 In the figure, A shows the result of the quantum dot layer prepared in comparative example 2 (the zinc oxide electron transport layer was not treated with an isobutyric acid atmosphere), and there was significant red residue. B shows the result of the quantum dot layer prepared in example 2 (the zinc oxide electron transport layer was treated with an isobutyric acid atmosphere), and the red residue was significantly reduced after development.

[0139] Example 3

[0140] A zinc oxide film was prepared on ITO by sputtering. The preparation method was as follows: the sputtering power was 100 W, the sputtering time was 900 s, and the thickness of the prepared zinc oxide film was 40 nm.

[0141] After the ZnO film was prepared, the substrate was soaked in a 1% mass fraction of 3,4,5-trimethoxybenzoic acid isopropanol solution for five minutes and then dried. Green quantum dots (purchased from Xingshuo, oleic acid ligands, soluble in n-octane, cadmium selenide core-shell quantum dots, luminescence peak position around 530nm) were spin-coated (20mg / ml, 3000rpm, 40s). Then, n-octane was used for development to obtain a patterned quantum dot layer.

[0142] Comparative Example 3

[0143] A patterned quantum dot layer was obtained in the same manner as in Example 3 except that the isopropanol solution of 3,4,5-trimethoxybenzoic acid was not used for the immersion treatment.

[0144] Experimental Example 4

[0145] When the quantum dots are excited by ultraviolet light (365 nm wavelength) of the same power, they will emit green light. The quantum dot layers prepared in Example 3 and Comparative Example 3 are respectively verified for luminescence. The results are shown in FIG. Figure 5 .

[0146] Figure 5 In the figure, A shows the result of the quantum dot layer prepared in comparative example 3 (the zinc oxide electron transport layer is not treated with 3,4,5-trimethoxybenzoic acid), and there is significant green residue, and B shows the result of the quantum dot layer prepared in embodiment 3 (the zinc oxide electron transport layer is treated with 3,4,5-trimethoxybenzoic acid), and the green residue is significantly reduced after treatment.

[0147] Although the present disclosure has been described above, the contents described are only embodiments adopted to facilitate understanding of the present disclosure and are not intended to limit the present disclosure. Any person skilled in the art may make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in the present disclosure, but the scope of patent protection of this application shall still be subject to the scope defined in the attached claims.

Claims

1. A method for patterning quantum dots for an inverted quantum dot light emitting diode, comprising the following steps: S1, treating the oxide electron transport layer with organic matter; S2, coating a quantum dot film layer on the oxide electron transport layer; S3, exposure of cross-linked QDs; S4, performing development to remove the quantum dot film layer in the unexposed area.

2. The method according to claim 1, characterized in that In S1, the oxide electron transport layer is treated with an organic solution or an organic atmosphere.

3. The method according to claim 1, characterized in that In S1, the organic matter contains both an acidic organic group and a hydrophobic organic group.

4. The method according to claim 3, characterized in that: The organic matter is selected from the following structures: R1-COOH, R1-SO3H, R1-SO2H, R1-B(OH)2, R1-P(=O)(OH)2, R2-OH, in, R1 each independently represents an alkyl group, an aryl group, an ester group, an ether group, an amine group, or an amide group, R2 represents an aryl group.

5. The method according to claim 1, characterized in that The organic matter is selected from R1-COOH, wherein R1 represents a C6-C12 aryl group which is unsubstituted or substituted with a substituent selected from C1-C12 alkyl and C1-C12 alkoxy, a C6-C12 aryl C1-C4 alkylene group which is unsubstituted or substituted with a substituent selected from C1-C12 alkyl and C1-C12 alkoxy, or a C3-C11 alkyl group which is unsubstituted or substituted with a substituent selected from C1-C12 alkoxy.

6. The method according to claim 1, characterized in that The organic compound is selected from benzoic acid and C4-C6 alkanoic acid substituted by 1-3 methoxy groups.

7. The method according to claim 1, characterized in that The ligands of the quantum dots are selected from ligands having vinyl double bonds in their structures.

8. The method according to claim 7, characterized in that The ligand is a ligand having an acryloyl group or a methacryloyl group in its structure, or is an unsaturated fatty acid.

9. The method according to claim 7, characterized in that: The ligand is selected from succinic acid mono-2-(2-methyl-acryloyl)oxyethyl ester and oleic acid.

10. The method according to claim 1, characterized in that In S4, the dielectric constant of the solvent of the developer used for development is less than 10.

11. The method according to claim 1, characterized in that: In some embodiments, steps S2 to S4 are repeated multiple times to achieve full-color patterning of the red, green, and blue quantum dot film layer.

12. A method for manufacturing an inverted quantum dot light-emitting diode, comprising manufacturing a cathode, an oxide electron transport layer, a patterned quantum dot layer and an anode, wherein the patterned quantum dot layer is formed by the method according to any one of claims 1 to 11.

13. An inverted quantum dot light-emitting diode, comprising a cathode, an oxide electron transport layer, a patterned quantum dot layer and an anode arranged in a stacked manner, wherein an organic monomolecular layer exists between the patterned quantum dot layer and the oxide electron transport layer.

14. The inverted quantum dot light emitting diode according to claim 13, characterized in that: The organic matter contains both an acidic organic group and a hydrophobic organic group.

15. The inverted quantum dot light emitting diode according to claim 13, characterized in that: The organic matter is selected from the following structures: R1-COOH, R1-SO3H, R1-SO2H, R1-B(OH)2, R1-P(=O)(OH)2, R2-OH, in, R1 each independently represents an alkyl group, an aryl group, an ester group, an ether group, an amine group, or an amide group, R2 represents an aryl group.

16. The inverted quantum dot light emitting diode according to claim 13, characterized in that: The organic matter is selected from R1-COOH, wherein R1 represents a C6-C12 aryl group which is unsubstituted or substituted with a substituent selected from C1-C12 alkyl and C1-C12 alkoxy, a C6-C12 aryl C1-C4 alkylene group which is unsubstituted or substituted with a substituent selected from C1-C12 alkyl and C1-C12 alkoxy, or a C3-C11 alkyl group which is unsubstituted or substituted with a substituent selected from C1-C12 alkoxy.

17. The inverted quantum dot light emitting diode according to claim 13, characterized in that: The organic compound is selected from benzoic acid and C4-C6 alkanoic acid substituted by 1-3 methoxy groups.

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