Quantum dot ligand, quantum dot, electroluminescent device, preparation method of electroluminescent device and display device
阅读说明：本技术 量子点配体、量子点、电致发光器件及其制备方法、以及显示装置 (Quantum dot ligand, quantum dot, electroluminescent device, preparation method of electroluminescent device and display device ) 是由 眭俊 于 2020-12-31 设计创作，主要内容包括：本发明公开一种量子点配体、量子点、电致发光器件及其制备方法、以及显示装置,所述量子点配体的结构通式为R-1-M-R-2；其中,M用以提供至少两个连接位点,R-1为亲水性基团,R-2用以与量子点的表面形成配位键。本发明提供的量子点配体中至少具有亲水性基团,能够改善量子点发光层的亲水性；当在量子点发光层上制备电子传输层时,可以改善电子传输层墨水在量子点发光层上面的铺展性,也能克服电子传输层颗粒渗透到量子点发光层的间隙中导致激子淬灭的缺陷,从而能够大大提高器件的性能。(The invention discloses a quantum dot ligand, a quantum dot, an electroluminescent device, a preparation method thereof and an electroluminescent deviceThe structural general formula of the quantum dot ligand is R 1 ‑M‑R 2 (ii) a Wherein M is used to provide at least two attachment sites, R 1 Is a hydrophilic group, R 2 For forming coordination bonds with the surface of the quantum dots. The quantum dot ligand provided by the invention at least has hydrophilic groups, so that the hydrophilicity of a quantum dot light-emitting layer can be improved; when the electron transport layer is prepared on the quantum dot light-emitting layer, the spreadability of the ink of the electron transport layer on the quantum dot light-emitting layer can be improved, and the defect of exciton quenching caused by the fact that particles of the electron transport layer permeate into gaps of the quantum dot light-emitting layer can be overcome, so that the performance of the device can be greatly improved.)
1. The quantum dot ligand is characterized in that the structural general formula of the quantum dot ligand is R1-M-R2；
Wherein M is used to provide at least two attachment sites, R1Is a hydrophilic group, R2For forming with the surface of quantum dotsA coordinate bond.
2. The quantum dot ligand of claim 1, wherein R is1Containing one or more of formyl, hydroxyl, carboxyl and amino.
3. The quantum dot ligand of claim 1, wherein R is2Comprising at least one hydrophobe.
4. The quantum dot ligand of claim 1, wherein the quantum dot ligand further comprises a group R3，R3Is linked to M, wherein R3Including triphenylamine, a derivative of triphenylamine, a carbazole group, and a carbazole group-based derivative.
5. The quantum dot ligand of claim 1, wherein in the general structural formula of the quantum dot ligand, M is a nitrogen atom.
6. The quantum dot ligand of claim 1, wherein the quantum dot ligand is a compound having a structure represented by any one of structural formulae (i) to (vi):
7. a quantum dot comprising a quantum dot material and a quantum dot ligand attached to a surface of the quantum dot material, the quantum dot ligand being provided as the quantum dot ligand according to any one of claims 1 to 6.
8. An electroluminescent device, comprising an anode, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer and a cathode, which are sequentially stacked, wherein the electron transport layer is made of a polar material, and the quantum dot light-emitting layer comprises the quantum dot as claimed in claim 7.
9. An electroluminescent device according to claim 8, wherein the electroluminescent device is a quantum dot light emitting diode.
10. A method for preparing an electroluminescent device is characterized by comprising the following steps:
providing an anode on a substrate;
forming a hole injection layer, a hole transport layer, a quantum dot light-emitting layer and an electron transport layer on the anode in sequence by a solution method, wherein the quantum dot light-emitting layer comprises the quantum dot as claimed in claim 7;
a cathode is formed on the electron transport layer.
11. A display device characterized in that it comprises an electroluminescent device as claimed in claim 8 or 9.
Technical Field
The invention relates to the technical field of display devices, in particular to the technical field of electroluminescent devices, and specifically relates to a quantum dot ligand, a quantum dot, an electroluminescent device, a preparation method of the electroluminescent device and a display device.
Background
Quantum dot light emitting diodes (QLEDs) have the advantages of saturated emitted light color and tunable wavelength, and high photoluminescence and electroluminescence quantum yields, and have recently become a strong competitor for OLEDs (organic electroluminescent diodes). The QLED device includes a quantum dot light emitting layer and an electron transport layer, and at present, the quantum dot light emitting layer and the electron transport layer are generally prepared by a solution method.
In existing QLED devices, the quantum dot light emitting layer includes inorganic quantum dots. Most of the current quantum dots adopt a core-shell structure, an organic ligand is coated outside a shell layer, the commonly used organic ligand is oleic acid, mercaptan and the like, and the whole quantum dot is a relatively symmetrical sphere, so that the whole quantum dot is nonpolar. In the process of preparing the device, according to the orthogonal principle, the whole electron transmission layer is generally arranged to present polarity, so that ink of the electron transmission layer is difficult to spread on the quantum dot light emitting layer, the uniformity of a film layer of the formed electron transmission layer after drying is poor, and the problem of corner defect can occur, so that the overall performance of the QLED device is reduced, and the problems of mixed peaks and the like can be caused during light emitting. In addition, because the quantum dot light-emitting layer and the polar electron transport layer are both inorganic nanoparticles and the mutual film formation is not very smooth, the quantum dot light-emitting layer and the electron transport layer can permeate into the gap formed by the opposite film formation to become trap of excitons, so that the quenching of the excitons is caused, and the performance of the device is reduced.
Disclosure of Invention
The invention mainly aims to provide a quantum dot ligand, a quantum dot, an electroluminescent device, a preparation method of the electroluminescent device and a display device, and aims to solve the problem that the spreadability of an ink film formed by an electronic transmission layer is poor when the electronic transmission layer is prepared on a quantum dot luminescent layer by a solution method at present.
To achieve the above object, the inventionThe quantum dot ligand has a structural general formula of R1-M-R2；
Wherein M is used to provide at least two attachment sites, R1Is a hydrophilic group, R2For forming coordination bonds with the surface of the quantum dots.
Alternatively, R1Including one or more of formyl, hydroxyl, carboxyl and amino.
Alternatively, R2Comprising at least one hydrophobe.
Optionally, the quantum dot ligand further comprises a group R3，R3Is linked to M, wherein R3Including triphenylamine, a derivative of triphenylamine, a carbazole group, and a carbazole group-based derivative.
Optionally, in the structural general formula of the quantum dot ligand, M is a nitrogen atom.
Optionally, the quantum dot ligand is a compound having a structure represented by any one of structural formulae (i) to (vi):
furthermore, the present invention also proposes a quantum dot comprising a quantum dot material and a quantum dot ligand attached to the surface of the quantum dot material, the quantum dot ligand being arranged as the quantum dot ligand as described above.
In addition, the invention also provides an electroluminescent device, which comprises an anode, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer and a cathode which are sequentially stacked, wherein the electron transport layer is made of a polar material, and the quantum dot light-emitting layer comprises the quantum dots.
Optionally, the electroluminescent device is a quantum dot light emitting diode.
In addition, the invention also provides a preparation method of the electroluminescent device, which comprises the following steps:
providing an anode on a substrate;
forming a hole injection layer, a hole transport layer, a quantum dot light-emitting layer and an electron transport layer on the anode in sequence by adopting a solution method, wherein the quantum dot light-emitting layer comprises the quantum dots;
a cathode is formed on the electron transport layer.
Furthermore, the invention also proposes a display device comprising an electroluminescent device as described above.
In the technical scheme provided by the invention, the quantum dot ligand at least has a hydrophilic group, so that the hydrophilicity of the quantum dot luminescent layer can be improved; when the electron transport layer is prepared on the quantum dot light-emitting layer, the spreadability of the ink of the electron transport layer on the quantum dot light-emitting layer can be improved, and the defect of exciton quenching caused by the fact that particles of the electron transport layer permeate into gaps of the quantum dot light-emitting layer can be overcome, so that the performance of the device can be greatly improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a quantum dot light emitting diode according to an embodiment of the present invention.
The reference numbers illustrate:
reference numerals
Name (R)
Reference numerals
Name (R)
10
Substrate
50
Quantum dot light emitting layer
20
Anode
60
Electron transport layer
30
Hole injection layer
70
Cathode electrode
40
Hole transport layer
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially. In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Quantum dot light emitting diodes (QLEDs) have the advantages of saturated emitted light color and tunable wavelength, and high photoluminescence and electroluminescence quantum yields, and have recently become a strong competitor for OLEDs (organic electroluminescent diodes). The QLED device includes a quantum dot light emitting layer and an electron transport layer, and at present, the quantum dot light emitting layer and the electron transport layer are generally prepared by a solution method.
In existing QLED devices, the quantum dot light emitting layer includes inorganic quantum dots. Most of the current quantum dots adopt a core-shell structure, an organic ligand is coated outside a shell layer, the commonly used organic ligand is oleic acid, mercaptan and the like, and the whole quantum dot is a relatively symmetrical sphere, so that the whole quantum dot is nonpolar. In the process of preparing the device, according to the orthogonal principle, the whole electron transmission layer is generally arranged to present polarity, so that ink of the electron transmission layer is difficult to spread on the quantum dot light emitting layer, the uniformity of a film layer of the formed electron transmission layer after drying is poor, and the problem of corner defect can occur, so that the overall performance of the QLED device is reduced, and the problems of mixed peaks and the like can be caused during light emitting. In addition, because the quantum dot light-emitting layer and the polar electron transport layer are both inorganic nanoparticles and the mutual film formation is not very smooth, the quantum dot light-emitting layer and the electron transport layer can permeate into the gap formed by the opposite film formation to become trap of excitons, so that the quenching of the excitons is caused, and the performance of the device is reduced.
In view of the above, the present invention provides a quantum dot ligand, wherein the structural general formula of the quantum dot ligand is R1-M-R2(ii) a Wherein M is used to provide at least two attachment sites, R1Is a hydrophilic group, R2For forming coordination bonds with the surface of the quantum dots.
In the technical scheme provided by the invention, the quantum dot ligand at least has a hydrophilic group, so that the hydrophilicity of the quantum dot luminescent layer 50 can be improved; when the electron transport layer 60 is prepared on the quantum dot light-emitting layer 50, the spreadability of the ink of the electron transport layer 60 on the quantum dot light-emitting layer 50 can be improved, so that the mutual film formation of the quantum dot light-emitting layer 50 and the electron transport layer 60 is smoother, exciton quenching caused by permeation of particles of the electron transport layer 60 into film forming gaps of the quantum dot light-emitting layer 50 is avoided, and the performance of the device can be greatly improved.
Wherein R is1May be any group having hydrophilic properties, specifically, the R1Comprises formyl (-CHO), hydroxyl (-OH), carboxyl (-COOH) and amino (-NH)2) One or more of (a). R2Can form coordinate bonds with the surface of the quantum dots so as to tightly combine quantum dot ligands with the quantum dots, specifically, R2Containing at least one mercapto group, e.g. R2Can be-CH2SH or-CH (SH)2The SH has strong affinity with the surface of the quantum dot and can be precisely combined with the quantum dot, so that the ligand of the quantum dot is not easy to fall off, and the stability of the quantum dot can be enhanced.
M as a linking structure to be R1And R2Sufficient attachment sites are provided so that M has at least two attachment sites, and in particular, M may be a nitrogen atom, in which case the present quantum dot ligand has the general structural formula shown in formula (1) below:
when M is a nitrogen atom, the synthesis difficulty of the quantum dot ligand is greatly reduced, and the stability of the quantum dot ligand is enhanced.
In addition, the quantum dot ligand can also comprise a third group R3，R3And M is connected, and based on the connection, the quantum dot ligand has the structural general formula shown in the following structural formula (2):
when M is a nitrogen atom, the quantum dot ligand has a structural general formula shown in the following structural formula (3):
wherein R is3Including triphenylamine, a derivative of triphenylamine, a carbazole group, and a carbazole group-based derivative. Specifically, the derivative of triphenylamine may be mono-or polysubstituted products of triphenylamine, such as halogen substituted products, amine substituted products, alkyl substituted products, etc.; likewise, the carbazole group-based derivative may be a mono-or polysubstituted structure having a carbazole skeleton, such as a group represented by the following structural formula (4):
triphenylamine, a derivative of triphenylamine, a carbazole group, and a carbazole group-based derivative can improve the film formation uniformity of the quantum dot light-emitting layer 50, have a strong hole transport ability, can promote hole transport, and have a low LUMO that can hinder electron transport, thereby being able to achieve a carrier balance effect. Meanwhile, under the condition of having three groups, the three groups have synergistic effect, and the performance and the stability of the device can be greatly improved.
Specifically designed, the quantum dot ligand includes, but is not limited to, compounds designed to have a structure as shown in any one of structural formulae (i) to (vi):
based on the structure of the quantum dot ligand, the following steps can be performed during actual preparation:
step S10, providing A-R1Wherein, a comprises M with two attachment sites;
step S20, introducing R at one of the connection sites of M2And obtaining the quantum dot ligand.
In particular, may have R1The compound of (1) as a starting material, introducing R to the linking site of M2. In specific practice, R2Can be introduced according to R2The specific structural design of (A) is realized by adopting a conventional synthesis method. With M as nitrogen atom, R2is-CH (SH)2For example, NH may be used2-R1Mixing with carbon disulfide at equal ratio, and heating at 80 deg.C to obtain R1-NH-CH(SH)2。
In one embodiment, M has at least three connecting sites, and the quantum dot ligand to be synthesized has a structure shown in a structural general formula (2), and in this case, R is selected as the preparation method of the quantum dot ligand3-M. Specifically, the preparation method of the quantum dot ligand comprises the following steps:
step S11, providing R3-M；
Step S12, at R3-introduction of R at another of said linking sites of M in M1To obtain R3-M-R1Wherein, said R3-M-R1Namely A-R1；
Step S20, introducing R at one of the connection sites of M2And obtaining the quantum dot ligand.
This example uses R3-M is the starting material to which R is introduced1Reintroducing R2The three groups are well prevented from connecting wrong sites or being damaged in the reaction process. Wherein R is3the-M is a substance which is generally available and has been synthesized by a mature method, can be directly obtained from a commercially available channel or the like, and can be synthesized by itself. In specific practice, R1、R2Can be introduced according to R1And R2The specific structural design of (A) is realized by adopting a conventional synthesis method. With M as nitrogen atom, R1Is formyl, R2is-CH (SH)2For example, the following steps are carried out: can be substituted by R3-M is mixed with formic acid and heated for dehydration reaction to obtain R3-NH-CHO; then R is put3-NH-CHO is mixed with carbon disulphide in equal proportions and heated at 80 ℃ to allow the formation of R3-N(CHO)-CH(SH)2。
Based on the above quantum dot ligand, the present invention also provides a quantum dot, comprising a quantum dot material and a quantum dot ligand attached to the surface of the quantum dot material, wherein the quantum dot ligand is configured as the quantum dot ligand described above. Because the quantum dot ligand at least has hydrophilic groups, the quantum dot luminescent layer 50 is printed by the quantum dots of which the surfaces are connected with the quantum dot ligand, so that the hydrophilicity of the quantum dot luminescent layer 50 can be well improved; when the electron transport layer is prepared on the quantum dot light emitting layer, the spreadability of the ink of the electron transport layer 60 on the quantum dot light emitting layer 50 can be improved, and the defect of exciton quenching caused by the fact that particles of the electron transport layer 60 penetrate into gaps of the quantum dot light emitting layer 50 can be overcome, so that the performance of the device can be greatly improved.
The quantum dot material is of a core-shell structure and comprises one or more of II-VI compounds, III-V compounds, II-V compounds, III-VI compounds, IV-VI compounds, I-III-VI compounds, II-IV-VI compounds or IV elementary substances. Specifically, the core material includes, but is not limited to, at least one selected from the group consisting of CdSe, CdS, ZnSe, ZnS, CdTe, CdZnS, CdZnSe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdSeSTe, ZnSeTe, CdZnSeTe, InP, InAs, InAsP, and the shell material includes, but is not limited to, at least one selected from the group consisting of CdS, ZnSe, ZnS, CdSeS, and ZnSeS.
In actual preparation, the quantum dot ligand can be connected to the surface of the quantum dot material in a ligand exchange mode to obtain the quantum dot provided by the invention. Specifically, the preparation method of the quantum dot comprises the following steps:
adding the quantum dot ligand into a quantum dot solution with the surface connected with an oil-soluble organic ligand, mixing to enable ligand exchange to occur, and separating to obtain the quantum dots.
With R2is-CH (SH)2For example, the reaction sequence for ligand exchange is as follows:
in the embodiment, quantum dots with oil-soluble organic ligands (such as oleic acid, oleylamine, octyl mercaptan and the like) connected to the surfaces are dispersed in a first solvent (such as toluene) to form a quantum dot solution; dispersing a quantum dot ligand in a first solvent (e.g., toluene) to form a quantum dot ligand solution; uniformly mixing the quantum dot ligand solution and the quantum dot solution, and tightly combining the quantum dot ligand and the surface sites of the quantum dots so as to gradually replace the oil-soluble organic ligand and complete ligand exchange; and after ligand exchange is finished, separating to obtain the quantum dots with the surface connected with the quantum dot ligands. Among them, the first solvent may be a common non-polar solvent.
In addition, the present invention further provides an electroluminescent device, which includes an anode 20, a hole injection layer 30, a hole transport layer 40, a quantum dot light emitting layer 50, an electron transport layer 60, and a cathode 70, which are sequentially stacked, wherein the quantum dot light emitting layer 50 includes the quantum dot as described above, the quantum dot includes a quantum dot material and a quantum dot ligand connected to a surface of the quantum dot material, and a specific structure of the quantum dot ligand refers to the above embodiments; the electron transport layer 60 is made of a polar material, for example, the electron transport layer 60 may be made of zinc oxide, barium oxide, titanium oxide, or the like. Since the electroluminescent device provided by the invention adopts all technical solutions of all embodiments of the quantum dot ligand, at least all beneficial effects brought by the technical solutions of the embodiments are achieved, and no further description is given here.
Further, the electroluminescent device is preferably a quantum dot light emitting diode (QLED). Fig. 1 illustrates an embodiment of a quantum dot light emitting diode. Referring to fig. 1, the quantum dot light emitting diode includes a substrate 10, an anode 20, a hole injection layer 30, a hole transport layer 40, a quantum dot light emitting layer 50, an electron transport layer 60, and a cathode 70, which are sequentially stacked. The substrate 10 may be made of glass, PI film, or the like; the anode 20 may be made of high work function metal and metal oxide such as ITO, IZO, Au, etc.; the hole injection layer 30 comprises PEDOT, PSS and NiOx，WO3CuPc, HATCN, m-MTDATA, F4-TCQN or MoO3(ii) a The hole transport layer 40 is made of TPD, poly-TPD, PVK, CBP, NPB, TCTA, mCP, TAPC, or TFB; the quantum dot light-emitting layer 50 includes the above quantum dots; the electron transport layer 60 is made of zinc oxide, barium oxide or titanium oxide; the cathode 70 may be made of Al, Ag, MgAg alloy, or the like.
The invention further provides a preparation method of the quantum dot electroluminescent device, which comprises the following steps:
step S100 of providing an anode 20 on a substrate 10;
step S101, sequentially forming a hole injection layer 30, a hole transport layer 40, a quantum dot light emitting layer 50, and an electron transport layer 60 on the anode 20 by using a solution method, wherein the quantum dot light emitting layer 50 includes the quantum dots as described above;
step S102, a cathode 70 is formed on the electron transport layer 60.
In this embodiment, a solution method is selected to sequentially prepare the hole injection layer 30, the hole transport layer 40, the quantum dot light emitting layer 50, and the electron transport layer 60, and since the ink used for printing the quantum dot light emitting layer 50 contains the quantum dots described above, the quantum dots include quantum dot materials and quantum dot ligands connected to the surfaces of the quantum dot materials, and the specific structure of the quantum dot ligands refers to the above embodiments, the film forming property and the spreading property of the electron transport layer 60 on the quantum dot light emitting layer 50 are improved, and thus the performance of the device is greatly improved.
In practice, the solution method has various realization forms, such as spin coating, doctor blade coating, ink-jet printing, etc., and can be self-adjusted according to the actual process requirements.
In addition, the present invention further provides a display apparatus, where the display apparatus includes the electroluminescent device, where the electroluminescent device includes an anode 20, a hole injection layer 30, a hole transport layer 40, a quantum dot light emitting layer 50, an electron transport layer 60, and a cathode 70, which are sequentially stacked, where the quantum dot light emitting layer 50 includes the quantum dot described above, the quantum dot includes a quantum dot material and a quantum dot ligand connected to a surface of the quantum dot material, and a specific structure of the quantum dot ligand refers to the above embodiments.
The technical solutions of the present invention are further described in detail below with reference to specific examples and drawings, it should be understood that the following examples are merely illustrative of the present invention and are not intended to limit the present invention.
Example 1
The structural formula of the quantum dot ligand in the embodiment is as follows:
the preparation method comprises the following steps:
(1) mixing 4-amino triphenylamine and formic acid according to a molar ratio of 1:1, adding into a flask, heating for dehydration for 0.5h, cooling, and filtering out crystals; the crystals were dissolved in toluene to give a 4-formylamino triphenylamine solution. The reaction formula is as follows:
(2) and adding carbon disulfide into the 4-formylamino triphenylamine solution, and heating at 80 ℃ for 12h to obtain the quantum dot ligand. Wherein the molar ratio of the added carbon disulfide to the 4-formylamino triphenylamine contained in the 4-formylamino triphenylamine solution is 1: 1.
The preparation method of the quantum dot comprises the following steps:
and (3) respectively dispersing the quantum dot ligand prepared in the step (2) and the CdSe @ ZnS green quantum dot with the oleic acid ligand in toluene, mixing, stirring at room temperature for 24 hours, and separating out lower-layer solids to obtain the quantum dot with the quantum dot ligand connected to the surface. And dissolving the quantum dots into chloroform to form the quantum dot ink for later use.
The preparation method of the quantum dot light-emitting diode QLED comprises the following steps:
the structure of the QLED is shown in fig. 1, and includes a substrate 10, an anode 20, a hole injection layer 30, a hole transport layer 40, a quantum dot light emitting layer 50, an electron transport layer 60, and a cathode 70, which are sequentially disposed from bottom to top. Specifically, a glass substrate 10 is adopted, and an ITO anode 20 is prepared on the glass substrate 10; ink-jet printing a hole injection layer 30 on an ITO anode 20 by adopting PEDOT (Poly ethylene glycol Ether-Co-Ltd.), drying to form a film, and annealing at 150 ℃ for 20min to obtain a film with the thickness of 45 nm; performing ink-jet printing on the hole transport layer 40 on the hole injection layer 30 by using TFB ink, performing vacuum drying to form a film, and then annealing at 230 ℃ for 30min to obtain a film with the thickness of 25 nm; taking the quantum dot printing ink prepared above, printing a quantum dot light-emitting layer 50 on the hole transport layer 40 by ink-jet printing, and annealing at 100 ℃ for 10min after vacuum drying and film forming, wherein the thickness is 20 nm; the ZnO ink is printed on the quantum dot light-emitting layer 50 through ink-jet to form an electron transmission layer 60, and after the electron transmission layer is dried in vacuum to form a film, the film is annealed for 15min at 120 ℃ and the thickness is 40 nm; evaporating aluminum on the electron transport layer 60 to form a cathode 70 with a thickness of 150 nm; and packaging to obtain the quantum dot light-emitting diode.
Example 2
The structural formula of the quantum dot ligand in the embodiment is as follows:
the preparation method comprises the following steps:
(1) reacting 9- (4-aminophenyl) carbazole hydrochloride (C)18H15ClN2) Mixing with formic acid according to the molar ratio of 1:1, adding into a flask, heating for dehydration for 0.5h, cooling, and filtering out crystals; the crystals were dissolved in toluene to give a 9- (4-formylaminophenyl) carbazole solution. The reaction formula is as follows:
(2) and adding carbon disulfide into the 9- (4-formylaminophenyl) carbazole solution, and heating at 80 ℃ for 12h to obtain the quantum dot ligand. Wherein the molar ratio of the added carbon disulfide to the 9- (4-formylaminophenyl) carbazole in the 9- (4-formylaminophenyl) carbazole solution is 1: 1.
The preparation method of the quantum dot comprises the following steps:
and respectively dissolving the quantum dot ligand and the CdSe @ ZnS green quantum dot with the oleic acid ligand in toluene, mixing, stirring at room temperature for 24 hours, and separating out lower-layer solids to obtain the quantum dot with the quantum dot ligand connected to the surface.
And dissolving the solid into chloroform to form the quantum dot ink for later use.
The preparation method of the quantum dot light-emitting diode QLED comprises the following steps:
the structure of the QLED is shown in fig. 1, and includes a substrate 10, an anode 20, a hole injection layer 30, a hole transport layer 40, a quantum dot light emitting layer 50, an electron transport layer 60, and a cathode 70, which are sequentially disposed from bottom to top. Specifically, a glass substrate 10 is adopted, and an ITO anode 20 is prepared on the glass substrate 10; ink-jet printing a hole injection layer 30 on an ITO anode 20 by adopting PEDOT (Poly ethylene glycol Ether-Co-Ltd.), drying to form a film, and annealing at 150 ℃ for 20min to obtain a film with the thickness of 45 nm; performing ink-jet printing on the hole transport layer 40 on the hole injection layer 30 by using TFB ink, performing vacuum drying to form a film, and then annealing at 230 ℃ for 30min to obtain a film with the thickness of 25 nm; taking the quantum dot printing ink prepared above, printing a quantum dot light-emitting layer 50 on the hole transport layer 40 by ink-jet printing, and annealing at 100 ℃ for 10min after vacuum drying and film forming, wherein the thickness is 20 nm; the ZnO ink is printed on the quantum dot light-emitting layer 50 through ink-jet to form an electron transmission layer 60, and after the electron transmission layer is dried in vacuum to form a film, the film is annealed for 15min at 120 ℃ and the thickness is 40 nm; evaporating aluminum on the electron transport layer 60 to form a cathode 70 with a thickness of 150 nm; and packaging to obtain the quantum dot light-emitting diode.
Example 3
The structural formula of the quantum dot ligand in the embodiment is as follows:
the preparation method comprises the following steps:
(1) reacting 9- (4-aminophenyl) carbazole hydrochloride (C)18H15ClN2) Mixing with formic acid according to the molar ratio of 1:1, adding into a flask, heating for dehydration for 0.5h, cooling, and filtering out crystals; the crystals were dissolved in toluene to give a 9- (4-formylaminophenyl) carbazole solution.
Adding silver diammine hydroxide with the same molar mass into a 9- (4-formylaminophenyl) carbazole solution, heating for 5h at 60 ℃, cooling, and filtering out crystals; and dissolving the crystal in toluene to obtain a 9- (4-carboxyl aminophenyl) carbazole solution.
(2) And adding carbon disulfide into the 9- (4-carboxyl aminophenyl) carbazole solution, and heating at 80 ℃ for 12h to obtain the quantum dot ligand. Wherein the molar ratio of the added carbon disulfide to the 9- (4-carboxyl aminophenyl) carbazole in the 9- (4-carboxyl aminophenyl) carbazole solution is 1: 1.
The preparation method of the quantum dot comprises the following steps:
and respectively dissolving the quantum dot ligand and the CdSe @ ZnS green quantum dot with the oleic acid ligand in toluene, mixing, stirring at room temperature for 24 hours, and separating out lower-layer solids to obtain the quantum dot with the quantum dot ligand connected to the surface.
And dissolving the solid into chloroform to form the quantum dot ink for later use.
Example 4
The structural formula of the quantum dot ligand in the embodiment is as follows:
the preparation method comprises the following steps:
(1) mixing 4-amino triphenylamine and ethanolamine according to a molar ratio of 1:1, adding the mixture into a flask, heating and dehydrating for 0.5h, cooling, and filtering out crystals; the crystals were dissolved in toluene to give a solution of 4-ethylaminotriphenylamine.
(2) And adding carbon disulfide into the 4-ethylamine amino triphenylamine solution, and heating at 80 ℃ for 12h to obtain the quantum dot ligand. Wherein, the molar ratio of the added carbon disulfide to the 4-carboxyl amino triphenylamine contained in the 4-carboxyl amino triphenylamine solution is 1: 1.
The preparation method of the quantum dot comprises the following steps:
and respectively dissolving the quantum dot ligand and the CdSe @ ZnS green quantum dot with the oleic acid ligand in toluene, mixing, stirring at room temperature for 24 hours, and separating out lower-layer solids to obtain the quantum dot with the quantum dot ligand connected to the surface.
And dissolving the solid into chloroform to form the quantum dot ink for later use.
The preparation method of the quantum dot light-emitting diode QLED comprises the following steps:
the structure of the QLED is shown in fig. 1, and includes a substrate 10, an anode 20, a hole injection layer 30, a hole transport layer 40, a quantum dot light emitting layer 50, an electron transport layer 60, and a cathode 70, which are sequentially disposed from bottom to top. Specifically, a glass substrate 10 is adopted, and an ITO anode 20 is prepared on the glass substrate 10; ink-jet printing a hole injection layer 30 on an ITO anode 20 by adopting PEDOT (Poly ethylene glycol Ether-Co-Ltd.), drying to form a film, and annealing at 150 ℃ for 20min to obtain a film with the thickness of 45 nm; performing ink-jet printing on the hole transport layer 40 on the hole injection layer 30 by using TFB ink, performing vacuum drying to form a film, and then annealing at 230 ℃ for 30min to obtain a film with the thickness of 25 nm; taking the quantum dot printing ink prepared above, printing a quantum dot light-emitting layer 50 on the hole transport layer 40 by ink-jet printing, and annealing at 100 ℃ for 10min after vacuum drying and film forming, wherein the thickness is 20 nm; the ZnO ink is printed on the quantum dot light-emitting layer 50 through ink-jet to form an electron transmission layer 60, and after the electron transmission layer is dried in vacuum to form a film, the film is annealed for 15min at 120 ℃ and the thickness is 40 nm; evaporating aluminum on the electron transport layer 60 to form a cathode 70 with a thickness of 150 nm; and packaging to obtain the quantum dot light-emitting diode.
Example 5
The structural formula of the quantum dot ligand in the embodiment is as follows:
the preparation method comprises the following steps:
(1) mixing 4-amino triphenylamine and formic acid according to a molar ratio of 1:1, adding into a flask, heating for dehydration for 0.5h, cooling, and filtering out crystals; the crystals were dissolved in toluene to give a 4-formylamino triphenylamine solution. Adding silver diammine hydroxide with the same molar mass into the 4-formylamino triphenylamine solution, heating for 5h at 60 ℃, cooling, and filtering out crystals; the crystals were dissolved in toluene to give a 4-carboxyamidotriphenylamine solution.
(2) And adding carbon disulfide into the 4-carboxyl amino triphenylamine solution, and heating at 80 ℃ for 12h to obtain the quantum dot ligand. Wherein, the molar ratio of the added carbon disulfide to the 4-carboxyl amino triphenylamine contained in the 4-carboxyl amino triphenylamine solution is 1: 1.
The preparation method of the quantum dot comprises the following steps:
and respectively dissolving the quantum dot ligand and the CdSe @ ZnS green quantum dot with the oleic acid ligand in toluene, mixing, stirring at room temperature for 24 hours, and separating out lower-layer solids to obtain the quantum dot with the quantum dot ligand connected to the surface.
And dissolving the solid into chloroform to form the quantum dot ink for later use.
The preparation method of the quantum dot light-emitting diode QLED comprises the following steps:
the structure of the QLED is shown in fig. 1, and includes a substrate 10, an anode 20, a hole injection layer 30, a hole transport layer 40, a quantum dot light emitting layer 50, an electron transport layer 60, and a cathode 70, which are sequentially disposed from bottom to top. Specifically, a glass substrate 10 is adopted, and an ITO anode 20 is prepared on the glass substrate 10; ink-jet printing a hole injection layer 30 on an ITO anode 20 by adopting PEDOT (Poly ethylene glycol Ether-Co-Ltd.), drying to form a film, and annealing at 150 ℃ for 20min to obtain a film with the thickness of 45 nm; performing ink-jet printing on the hole transport layer 40 on the hole injection layer 30 by using TFB ink, performing vacuum drying to form a film, and then annealing at 230 ℃ for 30min to obtain a film with the thickness of 25 nm; taking the quantum dot printing ink prepared above, printing a quantum dot light-emitting layer 50 on the hole transport layer 40 by ink-jet printing, and annealing at 100 ℃ for 10min after vacuum drying and film forming, wherein the thickness is 20 nm; the ZnO ink is printed on the quantum dot light-emitting layer 50 through ink-jet to form an electron transmission layer 60, and after the electron transmission layer is dried in vacuum to form a film, the film is annealed for 15min at 120 ℃ and the thickness is 40 nm; evaporating aluminum on the electron transport layer 60 to form a cathode 70 with a thickness of 150 nm; and packaging to obtain the quantum dot light-emitting diode.
Example 6
The structural formula of the quantum dot ligand in the embodiment is as follows:
and respectively dissolving the quantum dot ligand and the CdSe @ ZnS green quantum dot with the oleic acid ligand in toluene, mixing, stirring at room temperature for 24 hours, and separating out lower-layer solids to obtain the quantum dot with the quantum dot ligand connected to the surface.
And dissolving the solid into chloroform to form the quantum dot ink for later use.
The preparation method of the quantum dot light-emitting diode QLED comprises the following steps:
the structure of the QLED is shown in fig. 1, and includes a substrate 10, an anode 20, a hole injection layer 30, a hole transport layer 40, a quantum dot light emitting layer 50, an electron transport layer 60, and a cathode 70, which are sequentially disposed from bottom to top. Specifically, a glass substrate 10 is adopted, and an ITO anode 20 is prepared on the glass substrate 10; ink-jet printing a hole injection layer 30 on an ITO anode 20 by adopting PEDOT (Poly ethylene glycol Ether-Co-Ltd.), drying to form a film, and annealing at 150 ℃ for 20min to obtain a film with the thickness of 45 nm; performing ink-jet printing on the hole transport layer 40 on the hole injection layer 30 by using TFB ink, performing vacuum drying to form a film, and then annealing at 230 ℃ for 30min to obtain a film with the thickness of 25 nm; taking the quantum dot printing ink prepared above, printing a quantum dot light-emitting layer 50 on the hole transport layer 40 by ink-jet printing, and annealing at 100 ℃ for 10min after vacuum drying and film forming, wherein the thickness is 20 nm; the ZnO ink is printed on the quantum dot light-emitting layer 50 through ink-jet to form an electron transmission layer 60, and after the electron transmission layer is dried in vacuum to form a film, the film is annealed for 15min at 120 ℃ and the thickness is 40 nm; evaporating aluminum on the electron transport layer 60 to form a cathode 70 with a thickness of 150 nm; and packaging to obtain the quantum dot light-emitting diode.
Example 7
The structural formula of the quantum dot ligand in the embodiment is as follows:
and respectively dissolving the quantum dot ligand and the CdSe @ ZnS green quantum dot with the oleic acid ligand in toluene, mixing, stirring at room temperature for 24 hours, and separating out lower-layer solids to obtain the quantum dot with the quantum dot ligand connected to the surface.
And dissolving the solid into chloroform to form the quantum dot ink for later use.
The preparation method of the quantum dot light-emitting diode QLED comprises the following steps:
the structure of the QLED is shown in fig. 1, and includes a substrate 10, an anode 20, a hole injection layer 30, a hole transport layer 40, a quantum dot light emitting layer 50, an electron transport layer 60, and a cathode 70, which are sequentially disposed from bottom to top. Specifically, a glass substrate 10 is adopted, and an ITO anode 20 is prepared on the glass substrate 10; ink-jet printing a hole injection layer 30 on an ITO anode 20 by adopting PEDOT (Poly ethylene glycol Ether-Co-Ltd.), drying to form a film, and annealing at 150 ℃ for 20min to obtain a film with the thickness of 45 nm; performing ink-jet printing on the hole transport layer 40 on the hole injection layer 30 by using TFB ink, performing vacuum drying to form a film, and then annealing at 230 ℃ for 30min to obtain a film with the thickness of 25 nm; taking the quantum dot printing ink prepared above, printing a quantum dot light-emitting layer 50 on the hole transport layer 40 by ink-jet printing, and annealing at 100 ℃ for 10min after vacuum drying and film forming, wherein the thickness is 20 nm; the ZnO ink is printed on the quantum dot light-emitting layer 50 through ink-jet to form an electron transmission layer 60, and after the electron transmission layer is dried in vacuum to form a film, the film is annealed for 15min at 120 ℃ and the thickness is 40 nm; evaporating aluminum on the electron transport layer 60 to form a cathode 70 with a thickness of 150 nm; and packaging to obtain the quantum dot light-emitting diode.
Comparative example 1
This comparative example provides a QLED having a structure shown in fig. 1, and the other settings were the same as in example 1 except that the quantum dots used in the quantum dot light-emitting layer 50 were CdSe @ ZnS green quantum dots with an oleic acid ligand.
The QLED devices of each example and comparative example 1 were tested for external quantum efficiency, current efficiency, and lifetime ([email protected]), respectively, and the results are shown in table 1 below (in table 1, lifetime is the time taken for luminance to decrease from 1000nit to 80% in the case of constant current):
TABLE 1 QLED Performance test
As can be seen from the test results in table 1, when the quantum dot ligand provided by the embodiment of the invention is used as a material for preparing a quantum light emitting layer of a QLED, the prepared QLED has better external quantum efficiency, higher current efficiency and longer lifetime.
The above is only a preferred embodiment of the present invention, and it is not intended to limit the scope of the invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall be included in the scope of the present invention.
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