CN111725408A - Quantum dot light-emitting diode, preparation method thereof and composite material - Google Patents
Quantum dot light-emitting diode, preparation method thereof and composite material Download PDFInfo
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Abstract
The invention belongs to the technical field of display, and particularly relates to a quantum dot light-emitting diode, a preparation method thereof and a composite material. A quantum dot light-emitting diode comprises an anode, a cathode and a quantum dot light-emitting layer positioned between the anode and the cathode, wherein a hole injection layer composed of nickel oxide is arranged between the anode and the quantum dot light-emitting layer, and a composite material layer is arranged on the surface of the hole injection layer close to the quantum dot light-emitting layer; the composite layer comprises a cross-linker and a polar molecule; the cross-linked substance is formed by cross-linking molecular monomers with hole transmission performance, the polar molecules contain carboxylate radicals and electron-withdrawing radicals, and the carboxylate radicals are combined with the nickel oxide to enable the polar molecules to be directionally grafted on the surface of the hole injection layer.
Description
Technical Field
The invention belongs to the technical field of display, and particularly relates to a quantum dot light-emitting diode, a preparation method thereof and a composite material.
Background art
The Display technology has completed a qualitative leap from the early Cathode Ray Tube (CRT) to the Liquid Crystal Display (LCD) in the middle of 80 years of the 20 th century, the Plasma Display Panel (PDP), the Organic Light Emitting Diode (OLED) and the Quantum Dot Light Emitting Diode (QLED) which are the mainstream at present.
In the conventional QLED device structure, the NiOx film is an oxide material having electron blocking properties among commonly used hole injection materials (HILs), and is expected to be applied to the currently mainstream solution-processed QLED device. The carrier injection barrier of the LED device is determined by the interface energy arrangement, and in the aspect of hole injection, the HIL is generally required to have a surface work function as high as possible so as to realize the alignment with the valence band or HOMO energy level of an adjacent functional layer and achieve the purpose of reducing or eliminating the hole injection barrier. However, the surface work function of a NiOx film in a solution process is generally about 4.86eV without any post-treatment, and for a light emitting material with a relatively deep valence band or HOMO level, an effective ohmic contact cannot be formed when the NiOx film is in contact with the NiOx film, and a large hole injection barrier tends to exist at an interface. In order to increase the surface work function of the NiOx film and reduce the hole injection barrier at the interface, UV-O is commonly adopted at present3Or post-treating the NiOx film by oxygen plasma treatment. After treatment, the surface work function of the NiOx film can be about 5.2eV, and the NiOx film has better hole injection capability in a device, but UV-O3Or the oxygen plasma treatment can cause serious quenching effect on the quantum dot luminescent material while improving the surface work function of the NiOx film, which is fatal to a device such as a QLED with a thinner luminescent layer. Although the insertion of a dielectric layer between the quantum dot and the NiOx film can suppress this quenching effect, a new hole injection barrier is often introduced. More importantly, UV-O3Or NiOx film after oxygen plasma treatmentThe work function of the surface is unstable and can be rapidly and obviously reduced along with the time, and the effect of reducing the hole injection barrier in the device is greatly reduced after a period of time, which is extremely unfavorable for realizing the QLED device with long service life.
In the hole transport material (HTL), in addition to good hole transport performance, solvent resistance is required, and crosslinking is desired to prevent the HTL from being eroded by a quantum dot solvent, thereby forming a good HTL/QD interface and increasing the efficiency and stability of a device.
Therefore, the prior art needs to be improved.
Disclosure of Invention
The invention aims to provide a quantum dot light-emitting diode and a preparation method thereof, and aims to solve the technical problems that the hole injection efficiency and the device performance are influenced due to the fact that the work function of the surface of a nickel oxide hole injection layer in the existing device is low and surface defects exist.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a quantum dot light-emitting diode, which comprises an anode, a cathode and a quantum dot light-emitting layer positioned between the anode and the cathode, wherein a hole injection layer composed of nickel oxide is arranged between the anode and the quantum dot light-emitting layer, and a composite material layer is arranged on the surface of the hole injection layer close to the quantum dot light-emitting layer;
the composite layer comprises a cross-linker and a polar molecule; the cross-linked substance is formed by cross-linking molecular monomers with hole transmission performance, the polar molecules contain carboxylate radicals and electron-withdrawing radicals, and the carboxylate radicals are combined with the nickel oxide to enable the polar molecules to be directionally grafted on the surface of the hole injection layer.
In the quantum dot light-emitting diode provided by the invention, a specific composite material layer is arranged on the surface of a hole injection layer consisting of nickel oxide and close to a quantum dot light-emitting layer, and the composite material layer contains: the polymer comprises a cross-linked substance formed by cross-linking molecular monomers with hole transmission performance with each other and polar molecules with carboxylate radical and electron-withdrawing radical. The molecular monomers with the hole transmission performance are mutually crosslinked on the surface of the hole injection layer, so that the interface of nickel oxide can be modified, the surface defect density of the nickel oxide is reduced, and the hole transmission function is realized.
The invention also provides a preparation method of the light-emitting diode with the quantum dots, which comprises the following steps:
providing a substrate;
preparing an anode on the substrate;
preparing a hole injection layer composed of nickel oxide on the anode;
preparing a solution containing molecular monomers and polar molecules, depositing the solution on the hole injection layer, and carrying out annealing treatment to form a composite material layer;
the molecular monomer contains a crosslinking functional group, has hole transmission performance, and contains a carboxylate radical and an electron-withdrawing radical.
The preparation method of the quantum dot light-emitting diode provided by the invention has simple process and low cost, directly deposits solution containing molecular monomer and polar molecule on the surface of a hole injection layer consisting of nickel oxide close to a quantum dot light-emitting layer, and then carries out annealing treatment, in the annealing treatment process, a carboxylate radical in the polar molecule is combined with nickel oxide on the surface of the hole injection layer to ensure that the polar molecule is directionally grafted on the surface of the hole injection layer, and cross-linking functional groups in the molecular monomer are mutually thermally cross-linked to form a cross-linking substance, so that a composite material layer containing the cross-linking substance and the polar molecule is obtained, on one hand, the cross-linking substance can modify the interface of the nickel oxide on the surface of the hole injection layer to reduce the surface defect density of the nickel oxide, on the other hand, the polar molecule forms firm chemical bonding between the carboxylate radical and the nickel oxide and forms electron withdrawing, the work function of the surface of the hole injection layer can be increased, the hole injection barrier from the hole injection layer to the hole transmission layer is reduced, the hole injection efficiency is improved, the injection of holes and electrons is more balanced, and the performance of the finally manufactured device is improved.
Finally, the present invention provides a composite material comprising a cross-linker and a polar molecule; the cross-linking object is formed by cross-linking molecular monomers with hole transmission performance, and the polar molecule contains a carboxylate radical and an electron-withdrawing radical.
The composite material can be used for modifying a nickel oxide film, for example, in a quantum dot light-emitting diode, the composite material is used for modifying the surface of a hole injection layer formed by nickel oxide, which is close to a quantum dot light-emitting layer, on one hand, a cross-linking substance in the composite material can modify the interface of the nickel oxide on the surface of the hole injection layer to reduce the surface defect density of the nickel oxide, on the other hand, polar molecules in the composite material can form firm chemical bonding between a carboxylate radical and the nickel oxide and the electron withdrawing action of an electron withdrawing group, so that the work function of the surface of the hole injection layer can be increased, the hole injection barrier from the hole injection layer to a hole transmission layer is reduced, the hole injection efficiency is improved, the injection of holes and electrons is more balanced, and the performance of a device is improved.
Drawings
Fig. 1 is a schematic diagram of a quantum dot light emitting diode structure according to an embodiment of the invention;
fig. 2 is a flowchart of a method for manufacturing a quantum dot light emitting diode according to an embodiment of the invention.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
On one hand, the embodiment of the invention provides a quantum dot light-emitting diode, which comprises an anode, a cathode and a quantum dot light-emitting layer positioned between the anode and the cathode, wherein a hole injection layer composed of nickel oxide is arranged between the anode and the quantum dot light-emitting layer, and a composite material layer is arranged on the surface of the hole injection layer, which is close to the quantum dot light-emitting layer;
the composite layer comprises a cross-linker and a polar molecule; the cross-linked substance is formed by cross-linking molecular monomers with hole transmission performance, the polar molecules contain carboxylate radicals and electron-withdrawing radicals, and the carboxylate radicals are combined with the nickel oxide to enable the polar molecules to be directionally grafted on the surface of the hole injection layer.
The surface work function of a material is determined by the difference between the vacuum level of its surface and the fermi level inside, and is expressed by the following company:
Φ＝EVac-EF
where Φ is the surface work function, EVacRepresents the vacuum level, EFExpressing the fermi level, it can be seen from the above formula that there are two ways to increase the surface work function of a hole injection layer composed of nickel oxide: (1) elevated vacuum level EVac(2) lowering the Fermi level EF. Either or both of these approaches can be added together to increase the surface work function of the hole injection layer.
The embodiment of the invention is based on the first approach, a special composite material layer is arranged on the surface of a hole injection layer consisting of nickel oxide and close to a quantum dot light-emitting layer, and the composite material layer comprises: the polymer comprises a cross-linked substance formed by cross-linking molecular monomers with hole transmission performance with each other and polar molecules with carboxylate radical and electron-withdrawing radical. The molecular monomers with the hole transmission performance are mutually crosslinked on the surface of the hole injection layer, so that the interface of nickel oxide can be modified, the surface defect density of the nickel oxide is reduced, and the hole transmission function is realized.
In one embodiment, the polar molecules in the composite layer are composed of a conjugated group, and a carboxylate group and an electron-withdrawing group bonded to the conjugated group; the intermediate conjugated group structure is beneficial to rearrangement of electron cloud and provides a channel for charge transmission, and specifically, the conjugated group is selected from at least one of benzene ring, naphthyl, anthryl, phenanthryl, carbon-carbon double bond and carbon-carbon triple bond. And the electron-withdrawing group in the polar molecule is selected from tertiary amine positive ions (-N)+R3) Nitro (-NO)2) Trihalomethyl groups such as trifluoromethyl (-CF)3) Trichloromethyl (-CCl)3) Cyano (-CN), sulfonic acid (-SO)3H) And at least one of formyl group (-CHO), acyl group (-COR), carboxyl group (-COOH), etc.
In a preferred embodiment, the polar molecule is selected from at least one of 4-trifluoromethylphenylacetic acid, 4-trifluoromethylbenzoic acid, 3, 5-difluoro-4-trifluoromethylbenzoic acid, 3, 5-bis (trifluoromethyl) benzoic acid, 4-nitrobenzoic acid, 3, 5-difluoro-4-nitrobenzoic acid, 3, 5-bis (nitro) benzoic acid, and 3, 5-bis (trifluoromethyl) -4-nitrobenzoic acid.
In the quantum dot light-emitting diode of the embodiment of the invention, the polar molecules in the composite material layer are strong-polarity small molecular materials which can be grafted to the surface of the nickel oxide hole injection layer in an oriented manner to form a monomolecular layer; the molecular monomer is a small molecular monomer capable of thermal crosslinking, and when the molecular monomer is used as a modification material of nickel oxide, the interface of the nickel oxide can be repaired due to crosslinking, so that the surface defect density of the nickel oxide is reduced, and the molecular monomer has a hole transport property and can be used without an additional hole transport layer material. In one embodiment, the molecular monomer in the composite material layer is synthesized by reacting a molecule (formula i) having the following structure and capable of transporting holes with a molecule (such as trifluorovinyl ether benzoic acid or vinyl benzoic acid) having a crosslinking functional group.
The structural molecule (formula i) capable of transmitting the hole is formed by connecting a methanol group on three carbazolyl groups of 4,4' -tri (carbazole-9-yl) triphenylamine) (namely TCTA), and TCTA-3CH is used in the embodiment of the invention2OH represents.
In one embodiment, the cross-linked material is formed by cross-linking molecular monomers containing cross-linking functional groups, and the cross-linking functional groups are selected from trifluorovinyl groups or vinyl groups. Specifically, the structural formula of the molecular monomer is shown as the following formula I or formula II, namely, the cross-linked product is formed by mutually cross-linking the molecular monomers shown as the following formula I or formula II:
when the crosslinking functionality is selected from the group consisting of trifluorovinyl groups, the crosslinker is of formula III:
in the crosslinked material of the formula III, the trifluorovinyl group may be crosslinked all the time.
When the crosslinking functional group is a vinyl group, the crosslinking compound has the following structural formula IV:
in the crosslinked material of formula IV, the vinyl group may be crosslinked all the time.
The molecular sheetThe body is composed of TCTA-3CH capable of transporting holes2OH and molecules with crosslinking functional groups, wherein the molecules with the crosslinking functional groups are trifluorovinyl ether benzoic acid, vinyl benzoic acid and the like, and when the molecules are 3-fluorovinyl ether benzoic acid, the molecular structure of the synthesized molecular monomer is the formula I: the 3-fluorovinyl group can be crosslinked by heating, the double bond of the 3-fluorovinyl group is opened so as to be combined with the adjacent 3-fluorovinyl group, and the crosslinked partial molecular structure is as follows:
further, in the composite material layer in the quantum dot light emitting diode, the mass range of the polar molecule and the cross-linked substance may be any ratio, and the object of the present invention can be solved as long as the polar molecule and the molecular monomer are present in the composite material layer, and the mass ratio of the polar molecule and the cross-linked substance may be (0.01: 1) to (1: 0.01).
Further, the thickness of the composite material layer is 10-30 nm; and/or an electronic function layer is arranged between the cathode and the quantum dot light-emitting layer; and a hole transport layer is arranged between the material layer and the quantum dot light-emitting layer.
Another aspect of the present invention provides a method for manufacturing a light emitting diode with quantum dots, as shown in fig. 2, including the following steps:
s01: providing a substrate;
s02: preparing an anode on the substrate;
s03: preparing a hole injection layer composed of nickel oxide on the anode;
s04: preparing a solution containing molecular monomers and polar molecules, depositing the solution on the hole injection layer, and carrying out annealing treatment to form a composite material layer;
the molecular monomer contains a crosslinking functional group, has hole transmission performance, and contains a carboxylate radical and an electron-withdrawing radical.
The preparation method of the quantum dot light-emitting diode provided by the embodiment of the invention has simple process and low cost, directly deposits solution containing molecular monomer and polar molecule on the surface of a hole injection layer consisting of nickel oxide close to a quantum dot light-emitting layer, then carries out annealing treatment, in the annealing treatment process, carboxylate radical in the polar molecule is combined with nickel oxide on the surface of the hole injection layer to ensure that the polar molecule is directionally grafted on the surface of the hole injection layer, and crosslinking functional groups in the molecular monomer are mutually thermally crosslinked to form a crosslinking object, thus obtaining a composite material layer containing the crosslinking object and the polar molecule, on one hand, the crosslinking object can modify the interface of the nickel oxide on the surface of the hole injection layer to reduce the surface defect density of the nickel oxide, on the other hand, the polar molecule forms firm chemical bonding between the carboxylate radical and the nickel oxide and the electron withdrawing action of an electron withdrawing group, the work function of the surface of the hole injection layer can be increased, the hole injection barrier from the hole injection layer to the hole transmission layer is reduced, the hole injection efficiency is improved, the injection of holes and electrons is more balanced, and the performance of the finally manufactured device is improved.
In the above preparation method, when the solution containing the molecular monomer and the polar molecule is prepared, the molecular monomer and the polar molecule are selected as described in detail above, for example, the molecular monomer is selected from the molecular monomers represented by formula I or formula II, and the polar molecule is selected from at least one of 4-trifluoromethylphenylacetic acid, 4-trifluoromethylbenzoic acid, 3, 5-difluoro-4-trifluoromethylbenzoic acid, 3, 5-bis (trifluoromethyl) benzoic acid, 4-nitrobenzoic acid, 3, 5-difluoro-4-nitrobenzoic acid, 3, 5-bis (nitro) benzoic acid, and 3, 5-bis (trifluoromethyl) -4-nitrobenzoic acid; the role and kind of molecular monomers and polar molecules have been elaborated above.
In the preparation method, the temperature of the annealing treatment is 150-200 ℃; and/or the time of the annealing treatment is 20-60 min. In one embodiment, the step of annealing comprises: first annealing, cleaning with solvent (such as ethanol), and then performing second annealing; wherein, the first annealing temperature and the second annealing temperature can be 150-: the first annealing time is 15-35min, and the second annealing time can be 5-25 min.
In the preparation method, the quantum dot light-emitting layer is a commonly used quantum dot, such as one or more of II-VI compound, III-V compound, II-V compound, III-VI compound, IV-VI compound, I-III-VI compound, II-IV-VI compound or IV simple substance; the Electron Transport Layer (ETL) is ZnO, BaO, TiO2 and the like; the cathode is a common cathode material, such as Al, Ag, MgAg alloy and the like.
Finally, the embodiment of the invention also provides a composite material, which comprises a cross-linking substance and polar molecules; the cross-linking object is formed by cross-linking molecular monomers with hole transmission performance, and the polar molecule contains a carboxylate radical and an electron-withdrawing radical.
The composite material can be used for modifying a nickel oxide film, for example, in a quantum dot light-emitting diode, the composite material is used for modifying the surface of a hole injection layer formed by nickel oxide, which is close to a quantum dot light-emitting layer, on one hand, a cross-linking substance in the composite material can modify the interface of the nickel oxide on the surface of the hole injection layer, so that the surface defect density of the nickel oxide is reduced, on the other hand, polar molecules in the composite material can form firm chemical bonding between a carboxylate radical and the nickel oxide and the electron withdrawing effect of an electron-withdrawing group, so that the work function of the surface of the hole injection layer can be increased, the hole injection barrier from the hole injection layer to the hole transmission layer is reduced, the hole injection efficiency is improved, the injection of holes and electrons is more balanced, and.
The role and kind of the above-mentioned cross-linker and polar molecule have been described in detail above. For example, the polar molecule is composed of a conjugated group selected from at least one of a benzene ring, a naphthyl group, an anthryl group, a phenanthryl group, a carbon-carbon double bond and a carbon-carbon triple bond, and a carboxylate group and an electron-withdrawing group bonded to the conjugated group selected from at least one of a tertiary amine cation, a nitro group, a trihalomethyl group, a cyano group, a sulfonic group, a formyl group, an acyl group and a carboxyl group; specifically, the polar molecule is selected from at least one of 4-trifluoromethylphenylacetic acid, 4-trifluoromethylbenzoic acid, 3, 5-difluoro-4-trifluoromethylbenzoic acid, 3, 5-bis (trifluoromethyl) benzoic acid, 4-nitrobenzoic acid, 3, 5-difluoro-4-nitrobenzoic acid, 3, 5-bis (nitro) benzoic acid, and 3, 5-bis (trifluoromethyl) -4-nitrobenzoic acid. The crosslinking matter is formed by mutually crosslinking molecular monomers containing crosslinking functional groups, and the crosslinking functional groups are selected from trifluorovinyl or vinyl. Specifically, the cross-linked product is formed by cross-linking molecular monomers shown in formula I or formula II with each other.
The invention is described in further detail with reference to a part of the test results, which are described in detail below with reference to specific examples.
Example 1
A schematic structural diagram of a QLED light emitting device in this embodiment is shown in fig. 1, and the QLED light emitting device includes a substrate, an anode disposed on the substrate, a hole injection layer disposed on the anode, a material layer disposed on the hole injection layer, a quantum dot light emitting layer disposed on the material layer, an electron transport layer disposed on the quantum dot light emitting layer, a cathode disposed on the electron transport layer, and an encapsulation layer disposed between the anode and the cathode.
A glass substrate is used in this embodiment;
in this example, the anode was made of ITO, 150 nm. Taking out the ITO, firstly removing large particle dust on the surface by using a nitrogen gun, then sequentially ultrasonically cleaning for 15min by using a detergent, ultrapure water and isopropanol, finally quickly blow-drying the surface by using a high-purity nitrogen gun, and drying for later use;
preparing a hole injection layer on an anode, in the embodiment, a nickel oxide solution is coated on the anode by spin coating, and after a film is formed by vacuum drying, annealing is carried out for 15min at 120 ℃ and the thickness is 60 nm;
preparing a composite material layer on the hole injection layer (nickel oxide), comprising the steps of:
(1) preparing a molecular monomer solution:
firstly preparing TCTA-3CH2OH：
The first step is as follows: preparation of TCTA-3CHO, 10.97g of N' N-dimethylformamide are added dropwise at 0 ℃ to 3.78g of phosphorus oxychloride, stirred for 2h, afterAdding into TCTA solution (TCTA: 2.22g dissolved in dichloromethane/dichloroethane mixed solvent) at room temperature, refluxing the mixture overnight, pouring into 150ml of ice water, slowly adding NaOAc to adjust pH to 7, extracting the aqueous layer with dichloromethane, combining the remaining organic layers, and adding Na2SO4The mixture was dried, the solvent was removed by rotary evaporation, and the mixture was purified using dichloromethane/ethyl acetate (1:1) as a washing solution to give TCTA-3CHO as a yellow solid.
The second step is that: preparation of TCTA-3CH2OH, taking 126mg of NaBH at room temperature4Slowly adding into TCTA-3CHO solution (TCTA-3CHO solution: 457mg TCTA-3CHO is dissolved in 10ml mixed solvent of tetrahydrofuran and 10ml ethanol), stirring for 24 hr, removing solvent by rotary evaporation, washing with ethyl acetate, and purifying to obtain TCTA-3CH2OH yellow solid.
Then preparing a molecular monomer solution capable of thermal crosslinking: 117mg of TCTA-3CH were taken2OH, 107mg of trifluorovinyl ether benzoic acid (molecules with crosslinking functional groups), 26mg of 4-dimethylaminopyridine are dissolved in 30ml of dichloromethane, then an activating reagent 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride is added, stirring reaction is carried out for 20h at room temperature [ hydroxyl and carboxyl carry out esterification reaction to generate molecular monomer shown in formula I ], then the solvent is evaporated under negative pressure to obtain solid powder, the obtained solid is redissolved in dichloromethane, washed by deionized water, and Na is used for washing2SO4After drying, repeatedly washing with n-hexane for 5 times, and dissolving in ethanol to obtain molecular monomer solution with concentration of 6.8mg/ml for use.
(1) Preparing a polar molecule solution:
the 3, 5-bis (trifluoromethyl) benzoic acid (polar molecule) is adopted, and the molecular structure is as follows:
3, 5-bis (trifluoromethyl) benzoic acid was dissolved in an ethanol solvent to obtain a 3, 5-bis (trifluoromethyl) benzoic acid solution having a concentration of 10 mg/ml.
In this implementationIn the example, the prepared 3, 5-bis (trifluoromethyl) benzoic acid solution and the prepared small molecule monomer solution are mixed according to the volume ratio of 1:1 mixing, spin-coating on the surface of the hole injection layer, vacuum drying to form a film, and heating to 180 deg.C to N2Annealing for 30min under atmosphere, spin-coating with ethanol solvent to remove uncoordinated 3, 5-bis (trifluoromethyl) benzoic acid, repeating the spin-coating with ethanol solvent for 6 times, and performing N-spin-coating at 180 deg.C2Annealing for 20min in the atmosphere to obtain a composite material layer with the thickness of 20nm, combining adjacent 3-fluoroethylene groups after annealing to generate a cross-linked substance shown in a formula (III), and obtaining the composite material of the cross-linked substance and coordinated 3, 5-bis (trifluoromethyl) benzoic acid, namely the composite material layer;
in this embodiment, CdSe/CdS/ZnS red light quantum dot ink is spin-coated on the interface modification layer, vacuum-dried to form a film, and N is 120 deg.C2Annealing for 10min under atmosphere, with thickness of 30 nm;
preparing an electron transport layer on a quantum dot light emitting layer, in the embodiment, ZnO is adopted as an electron transport layer material, ZnO solution is coated on the quantum dot light emitting layer in a spinning mode, after vacuum drying and film forming, N is carried out at 120 DEG C2Annealing for 15min under atmosphere, with thickness of 40 nm;
preparing a cathode on the electron transport layer, and in the embodiment, evaporating Al on the electron transport layer; the thickness is 150 nm;
and packaging all functional layers between the anode and the cathode through UV frame glue and a drying sheet to obtain a complete device.
The device provided in this example was modified by spin-coating a composite material layer on the surface of the hole injection layer made of nickel oxide, where the composite material layer contains a cross-linked product formed by cross-linking molecular monomers shown in formula I and 3, 5-bis (trifluoromethyl) benzoic acid. The molecular monomer capable of being crosslinked has hole transmission performance, and the formed crosslinking material is a crosslinked hole transmission material, so that the corrosion of a quantum dot solvent to the crosslinking material can be prevented, the interface performance of the surface of a hole injection layer consisting of nickel oxide can be improved, the defect density of the surface of the hole injection layer is reduced, and the performance of a device is improved; 3, 5-bis (trifluoromethyl) benzylOne end of the acid molecule contains carboxyl (-COOH), and the other end contains two trifluoromethyl (-CH)3) And the middle parts are connected through benzene rings with conjugated structures. The carboxyl can form a firm chemical bond with nickel oxide, a monomolecular layer is formed on the surface of a hole injection layer consisting of nickel oxide through oriented grafting, an electron-withdrawing group (trifluoromethyl) at the other end of the molecule is consistent to the outside, a positive dipole is formed on the surface of the hole injection layer under the attraction effect of the trifluoromethyl on electrons, so that the work function of the surface of the hole injection layer is increased, and the benzene ring with the middle conjugated structure is favorable for rearranging electron clouds and provides a channel for charge transmission. By increasing the surface work function of the hole injection layer, the hole injection barrier from the hole injection layer to the composite material layer is reduced, the hole injection efficiency is improved, the injection of holes and electrons is more balanced, and the performance of the device is improved.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A quantum dot light-emitting diode comprises an anode, a cathode and a quantum dot light-emitting layer positioned between the anode and the cathode, and is characterized in that a hole injection layer composed of nickel oxide is arranged between the anode and the quantum dot light-emitting layer, and a composite material layer is arranged on the surface of the hole injection layer close to the quantum dot light-emitting layer;
the composite layer comprises a cross-linker and a polar molecule; the cross-linked substance is formed by cross-linking molecular monomers with hole transmission performance, the polar molecules contain carboxylate radicals and electron-withdrawing radicals, and the carboxylate radicals are combined with the nickel oxide to enable the polar molecules to be directionally grafted on the surface of the hole injection layer.
2. The quantum dot light-emitting diode of claim 1, wherein the polar molecule is composed of a conjugated group, and a carboxylate group and an electron-withdrawing group bonded to the conjugated group; and/or the presence of a gas in the gas,
the crosslinking matter is formed by mutually crosslinking molecular monomers containing crosslinking functional groups, and the crosslinking functional groups are selected from trifluorovinyl or vinyl.
3. The qd-led of claim 2, wherein the conjugated groups in the polar molecule are selected from at least one of benzene ring, naphthyl, anthryl, phenanthryl, carbon-carbon double bond and carbon-carbon triple bond; and/or the presence of a gas in the gas,
the electron-withdrawing group in the polar molecule is selected from at least one of tertiary amine positive ions, nitryl, trihalomethyl, cyano, sulfonic acid groups, formyl, acyl and carboxyl.
4. The quantum dot light-emitting diode of claim 1, wherein the polar molecule is selected from at least one of 4-trifluoromethylphenylacetic acid, 4-trifluoromethylbenzoic acid, 3, 5-difluoro-4-trifluoromethylbenzoic acid, 3, 5-bis (trifluoromethyl) benzoic acid, 4-nitrobenzoic acid, 3, 5-difluoro-4-nitrobenzoic acid, 3, 5-bis (nitro) benzoic acid, and 3, 5-bis (trifluoromethyl) -4-nitrobenzoic acid; and/or the presence of a gas in the gas,
the cross-linked substance is formed by cross-linking molecular monomers shown in the following formula I or formula II:
5. the qd-led of any one of claims 1 to 4, wherein the thickness of the composite material layer is 10 nm to 30 nm; and/or the presence of a gas in the gas,
an electronic function layer is arranged between the cathode and the quantum dot light-emitting layer; and/or the presence of a gas in the gas,
and a hole transport layer is arranged between the composite material layer and the quantum dot light-emitting layer.
6. A preparation method of a light-emitting diode with quantum dots is characterized by comprising the following steps:
providing a substrate;
preparing an anode on the substrate;
preparing a hole injection layer composed of nickel oxide on the anode;
preparing a solution containing molecular monomers and polar molecules, depositing the solution on the hole injection layer, and carrying out annealing treatment to form a composite material layer;
the molecular monomer contains a crosslinking functional group, has hole transmission performance, and contains a carboxylate radical and an electron-withdrawing radical.
7. The method of manufacturing of claim 6, wherein the step of annealing comprises: firstly, carrying out first annealing, cleaning by using a solvent, and then carrying out second annealing; and/or the presence of a gas in the gas,
the temperature of the annealing treatment is 150-200 ℃; and/or the presence of a gas in the gas,
the time of the annealing treatment is 20-60 min.
8. A composite material, wherein the composite material comprises a cross-linker and a polar molecule; the cross-linking object is formed by cross-linking molecular monomers with hole transmission performance, and the polar molecule contains a carboxylate radical and an electron-withdrawing radical.
9. The composite of claim 8, wherein the polar molecule is composed of a conjugated group selected from at least one of a benzene ring, a naphthalene group, an anthracene group, a phenanthrene group, a carbon-carbon double bond and a carbon-carbon triple bond, and a carboxylate group and an electron withdrawing group bonded to the conjugated group selected from at least one of a tertiary amine cation, a nitro group, a trihalomethyl group, a cyano group, a sulfonic acid group, a formyl group, an acyl group and a carboxyl group; and/or the presence of a gas in the gas,
the crosslinking matter is formed by mutually crosslinking molecular monomers containing crosslinking functional groups, and the crosslinking functional groups are selected from trifluorovinyl or vinyl.
10. The composite of claim 8, wherein the polar molecule is selected from at least one of 4-trifluoromethylphenylacetic acid, 4-trifluoromethylbenzoic acid, 3, 5-difluoro-4-trifluoromethylbenzoic acid, 3, 5-bis (trifluoromethyl) benzoic acid, 4-nitrobenzoic acid, 3, 5-difluoro-4-nitrobenzoic acid, 3, 5-bis (nitro) benzoic acid, and 3, 5-bis (trifluoromethyl) -4-nitrobenzoic acid; and/or the presence of a gas in the gas,
the cross-linked substance is formed by cross-linking molecular monomers shown in the following formula I or formula II:
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| CN112599690A (en) * | 2020-12-14 | 2021-04-02 | 广东聚华印刷显示技术有限公司 | White light QLED device, display device and preparation method |
| CN114497401A (en) * | 2020-11-13 | 2022-05-13 | 夏普株式会社 | Light emitting device and light emitting structure |
| CN115769387A (en) * | 2020-10-28 | 2023-03-07 | 京东方科技集团股份有限公司 | Hole transport material, quantum dot light-emitting device, manufacturing method of quantum dot light-emitting device and display device |
| WO2024192734A1 (en) * | 2023-03-22 | 2024-09-26 | 京东方科技集团股份有限公司 | Quantum dot film layer patterning method and quantum dot light-emitting device |
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