CN109486480B - Hole transport material and quantum dot light-emitting diode - Google Patents

Hole transport material and quantum dot light-emitting diode Download PDF

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CN109486480B
CN109486480B CN201811242098.6A CN201811242098A CN109486480B CN 109486480 B CN109486480 B CN 109486480B CN 201811242098 A CN201811242098 A CN 201811242098A CN 109486480 B CN109486480 B CN 109486480B
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hole transport
quantum dot
transport material
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emitting diode
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CN109486480A (en
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苏文明
刘扬
李宛飞
谢黎明
纪学珍
王邈
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Suzhou Oupuke Display Technology Co ltd
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Abstract

The invention discloses a hole transport material which has the characteristics of deep HOMO, high mobility and high solubility and is suitable for quantum dot light-emitting diodes. The invention also discloses a quantum dot light-emitting diode which has higher efficiency and longer service life. A hole transport material comprises a compound shown as a general formula I,
Figure DDA0001839592830000011
wherein R is1One selected from hydrogen, cyano, trifluoromethyl and sulfonic acid group; r2Is hydrogen or C1-C30 alkyl; r3And R4Independently selected from hydrogen or vinyl, and at least one of which is vinyl.

Description

Hole transport material and quantum dot light-emitting diode
Technical Field
The invention relates to the technical field of photoelectric materials, in particular to a hole transport material and a quantum dot light-emitting diode adopting the hole transport material.
Background
The flat panel display industry is a strategic industry of economic development in China, and Organic Light Emitting Diodes (OLEDs) as a new display industry enter a mass production stage, but the existing commercialized OLEDs are mainly prepared by adopting a vacuum evaporation method, so that the problems of low material utilization rate, poor product yield and high cost exist. The printing display technology is considered to be the inevitable development trend of large-size panel display in the future due to the advantages of high material utilization rate, simple preparation process, large-area large-scale production and the like. The organic light-emitting diode (QLED) has a very narrow emission spectrum, can realize higher color purity and wide color gamut, has relatively low sensitivity to environmental water and oxygen, and can be printed and manufactured by a full solution method to form a light, thin and flexible display device, thereby being of great interest.
In the process of developing a quantum dot light emitting diode (QLED), the mobility of the existing hole transport material (HTL) is more than one order of magnitude different from that of the ZnO electron transport material (ETL), and the injection barrier of holes at the HTL/QDs interface is very high, which causes the charge injection imbalance in the quantum dot light emitting layer, thereby affecting the light emitting efficiency of the QLED; in addition, the HTL/QDs interface has over-high hole injection barrier, can generate serious Joule heat, and the hole transport material has low glass transition temperature and poor thermal stability, which is not favorable for the service life of devices; the erosion damage effect between the film layers in the printing preparation process is not favorable for the stability of the device interface, and the industrial application process of the QLED is severely limited.
Disclosure of Invention
Aiming at the defects and problems in the prior art, the invention aims to provide a hole transport material which has the characteristics of deep HOMO, high mobility and high solubility and is suitable for quantum dot light-emitting diodes. The invention also aims to provide a quantum dot light-emitting diode which has long service life and high efficiency. .
In order to achieve the purpose, the invention adopts the following technical scheme:
a hole transport material comprises a compound shown as a general formula I or a compound shown as a general formula I
Figure BDA0001839592810000021
Wherein R is1One selected from hydrogen, cyano, trifluoromethyl and sulfonic acid group;
R2is hydrogen or C1-C30 alkyl;
R3and R4Independently selected from hydrogen or vinyl, and at least one of which is vinyl.
In the general formula I, 4,4'-N, N' -dicarbazole biphenyl (CBP) is a hole transport functional unit, R1Regulation of HOMO energy level, R, for strongly electron-withdrawing groups2Adjusting solubility and surface energy after film formation, R3And R4Is a thermal crosslinking functional unit and realizes the solvent resistance after film forming and crosslinking. The invention provides deep HOMO cross-linked hole transport materials useful for QLEDs. The hole transport material contains a CBP rigid plane structure, a flexible alkyl chain and an ethylene group, and is directly hinged through a simple heating mode, so that a non-erosion functional hole transport layer structure film layer is formed. The planar structures are relatively orderly stacked and arranged under the heat treatment condition, and the mobility is improved by 1-10000 times. The hole transport material has application in printed QLEDs displays, white light illumination.
The compound shown in the general formula I is a micromolecule precursor with a determined structure, has solvent resistance after being heated and crosslinked without a catalyst, has a deep HOMO energy level, can realize high-efficiency injection of hole carrier to a quantum dot light-emitting layer when being used for a QLED device, has high mobility, and has the advantages of high light-emitting efficiency, long service life of the device and low driving voltage of a quantum dot light-emitting device prepared from the hole transport layer prepared from the crosslinkable compound.
Preferably, the hole transport material is one or more of the following compound 1, compound 2, compound 3 and compound 4,
Figure BDA0001839592810000031
the invention also adopts the following technical scheme:
a quantum dot light emitting diode comprising a layer of hole transporting material formed from a hole transporting material as described above. The hole transport material is a deep HOMO energy level cross-linked organic micromolecule with high hole mobility, is prepared into a film by spin coating or printing, and is subjected to cross-linking between bonds through simple heating post-treatment to form a solvent-resistant hole transport layer film. The CBP structure in the hole transport material has high hole migration characteristic, the rigid plane biphenyl skeleton of the CBP structure is easy to introduce strong electron-withdrawing groups, and deeper HOMO energy level can be realized, so that hole injection barriers at HTL/QDs interfaces are further reduced, charge injection balance of QLED devices is realized, ethylene double bonds are easy to heat and crosslink to form a stable hole transport layer, and 100% solvent resistance and high interface stability can be realized.
Further, the hole transport material layer is formed by crosslinking the hole transport material.
Further, it is characterized in that the hole transport material contains a 4,4'-N, N' -dicarbazole biphenyl rigid planar structure, a flexible alkyl chain and a vinyl group which are crosslinked by heating.
Preferably, the 4,4'-N, N' -dicarbazole biphenyl rigid planar structures are in an ordered stacking arrangement upon heating.
Further, the hole transport material layer is formed by forming a film of the hole transport material and then heating the film to crosslink sufficiently.
Further, the hole transport material is prepared into a solution and then is subjected to spin coating or printing film forming, and a film layer has a retention of more than 99% after heating and crosslinking.
Further, the quantum dot light emitting diode includes a functional layer formed on the hole transport material layer.
By adopting the technical scheme, compared with the prior art, the invention has the following advantages:
the vinyl group of the hole transport material is used as a heat crosslinking group, the conjugated plane rigid structure CBP is used as a hole transport unit, the strong electron-absorbing group regulates and controls the interface hole injection barrier, the planar structure improves the compactness of the film, the mobility is greatly improved, and therefore the crosslinked hole transport layer has high hole transport and hole injection performance and strong interface stability, and the efficiency and the service life of the quantum dot light-emitting diode device are greatly improved.
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In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without inventive labor.
Figure 1 shows the HNMR spectrum of compound 1;
fig. 2 shows a graph of absorption spectra of a hole transport material compound 1 for a quantum dot electroluminescent device after cross-linking before and after elution with toluene, chlorobenzene, n-tridecane, tetrahydronaphthalene and indane solvents, respectively, according to an exemplary embodiment of the present invention;
fig. 3 shows a graph of absorption spectra of hole transport material compound 2 for quantum dot electroluminescent devices after cross-linking before and after elution with toluene, chlorobenzene, n-tridecane, tetrahydronaphthalene and indane solvents, respectively, according to an exemplary embodiment of the present invention;
fig. 4 shows a graph of absorption spectra of a hole transport material compound 3 for a quantum dot electroluminescent device after cross-linking before and after elution with toluene, chlorobenzene, n-tridecane, tetrahydronaphthalene and indane solvents, respectively, according to an exemplary embodiment of the present invention;
fig. 5 shows a graph of absorption spectra of a hole transport material compound 4 for a quantum dot electroluminescent device after cross-linking before and after elution with toluene, chlorobenzene, n-tridecane, tetrahydronaphthalene and indane solvents, respectively, according to an exemplary embodiment of the present invention;
fig. 6 shows the surface roughness of the film after crosslinking of the hole transport material compound 1 for quantum dot electroluminescent devices according to an exemplary embodiment of the present invention before and after n-octane cleaning.
Fig. 7 shows the change in film thickness of the thin film before and after crosslinking of the hole transport material compound 1 for quantum dot electroluminescent device according to an exemplary embodiment of the present invention.
Fig. 8 shows a luminance-current efficiency graph and a luminance-power efficiency graph of a red quantum dot light emitting diode device formed using a hole transport material (compound 1) for a quantum dot electroluminescent device according to an exemplary embodiment of the present invention and TFB, Poly-TPD, PVK;
fig. 9 shows a luminance-external quantum efficiency graph of a red quantum dot light emitting diode device formed using a hole transport material (compound 1) for a quantum dot electroluminescent device according to an exemplary embodiment of the present invention and TFB, Poly-TPD, PVK.
Fig. 10 shows a luminance-current efficiency graph of an inkjet printed red quantum dot light emitting diode device formed using a hole transport material (compound 1) for a quantum dot electroluminescent device according to an exemplary embodiment of the present invention.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the advantages and features of the invention may be more readily understood by those skilled in the art.
Example 1: synthesis of Compound 1
3 equivalents of starting material 2 (Ph)3PCH3Br, hereinafter abbreviated as SM-2) was dissolved in an appropriate amount of Tetrahydrofuran (THF), nitrogen was substituted 3 times, 3 equivalents of base (NaOH) was slowly added, and the reaction was carried out for two hours to form a yellow solution. Then 1 equivalent of starting material 1 (shown as SM-1 in scheme 1) was weighed into an appropriate amount of THF, and added dropwise thereto under nitrogen protection at room temperatureThe reaction was stirred overnight in the above solution. Pouring the reaction solution after the reaction into water to terminate the reaction, extracting by dichloromethane, drying to remove water, spin-drying the solvent, and purifying by taking a mixed solvent of petroleum ether and dichloromethane as a mobile phase column chromatography to obtain a target product 1, wherein the yield is as follows: 65%, elemental analysis: c, 89.55%; h, 5.20%; n, 5.27% (found); c, 89.52%; h, 5.26%; n, 5.22% (C)71H56N2O2Theoretical), the hydrogen spectrum is shown in fig. 1.
Scheme 1:
Figure BDA0001839592810000061
example 2: synthesis of Compound 2
3 equivalents of starting material 2(SM-2) were dissolved in an appropriate amount of THF, replaced with nitrogen 3 times, and 3 equivalents of base (lithium diisopropylamide, LDA) were slowly added and reacted for two hours to form a yellow solution. Then 1 equivalent of starting material 3 (shown as SM-3 in scheme 2) was weighed into an appropriate amount of THF, added dropwise to the above solution at room temperature under nitrogen protection, and stirred overnight. Pouring the reaction solution after the reaction into water to terminate the reaction, extracting by dichloromethane, drying to remove water, spin-drying the solvent, and purifying by taking a mixed solvent of petroleum ether and dichloromethane as a mobile phase column chromatography to obtain a target product 2, wherein the yield is as follows: 85%, elemental analysis: c, 85.95%; h, 4.40%; n, 9.57% (found); c, 85.98%; h, 4.47%; n, 9.55% (C)71H56N2O2Theoretical value).
Scheme 2:
Figure BDA0001839592810000071
example 3: synthesis of Compound 3
3 equivalents of starting material 2(SM-2) were dissolved in an appropriate amount of THF, purged with nitrogen 3 times, and slowly added 3 equivalents of base (n-butyllithium, BuLi) and reacted for two hours to form a yellow solution. Then 1 equivalent of starting material 4 (shown as SM-4 in scheme 3) was weighed out and dissolvedThe mixture is added into the solution dropwise in a proper amount of THF under the protection of nitrogen at room temperature, and the reaction is stirred overnight. Pouring the reaction solution after the reaction into water to terminate the reaction, extracting by dichloromethane, drying to remove water, spin-drying the solvent, and purifying by taking a mixed solvent of petroleum ether and dichloromethane as a mobile phase column chromatography to obtain a target product 3, wherein the yield is as follows: 80%, elemental analysis: c, 74.95%; h, 3.91%; n, 4.17% (found); c, 74.99%; h, 3.90%; n, 4.16% (C)71H56N2O2Theoretical value).
Scheme 3:
Figure BDA0001839592810000072
example 4: synthesis of Compound 4
3 equivalents of 2(SM-2) starting material are dissolved in an appropriate amount of THF, nitrogen is replaced 3 times, and 3 equivalents of base (sodium tert-butoxide, Bu) are slowly addedtONa), reacted for two hours to form a yellow solution. Then 1 equivalent of starting material 5 (shown as SM-5 in the synthetic route) was weighed into an appropriate amount of THF, added dropwise to the above solution at room temperature under nitrogen protection, and stirred for reaction overnight. Pouring the reaction solution after the reaction into water to terminate the reaction, extracting by dichloromethane, drying to remove water, spin-drying the solvent, and purifying by taking a mixed solvent of petroleum ether and dichloromethane as a mobile phase column chromatography to obtain a target product 2, wherein the yield is as follows: 95%, elemental analysis: c, 68.95%; h, 4.01%; n, 4.07% (found); c, 68.95%; h, 4.05%; n, 4.02% (C)71H56N2O2Theoretical value).
Scheme 4:
Figure BDA0001839592810000081
example 5: investigation of solvent etching resistance of Compounds 1 to 4
Fig. 2 to 5 respectively show graphs of absorption spectra of a hole transport material (compounds 1 to 4) for a quantum dot electroluminescent device after cross-linking, respectively before and after elution with toluene, chlorobenzene, n-tridecane, tetrahydronaphthalene, and indane solvents, according to an exemplary embodiment of the present invention.
The corrosion resistance of compounds 1 to 4 after crosslinking curing against commonly used organic solvents was investigated. The ultraviolet-visible absorption spectrum with high sensitivity is adopted to study the change of the crosslinked and cured film before and after being rinsed by the solvent, so that whether the material is corroded by the solvent can be clearly judged. The specific implementation process comprises the following steps: the material was formulated into a solution and spin coated on quartz glass. The crosslinking curing conditions were thermal crosslinking at 230 ℃ for 30 minutes in a glove box. The solvents for washing are toluene, chlorobenzene, n-tridecane, tetrahydronaphthalene and indane, the results of which are shown in fig. 2 to 5.
As shown in fig. 2 to 5, the absorption curves are well overlapped before and after rinsing, which illustrates that after the hole transport material for the quantum dot electroluminescent device according to the exemplary embodiment of the present invention is crosslinked, the film layers are respectively washed with toluene, chlorobenzene, n-tridecane, tetrahydronaphthalene, and indane solvents, the film layers of 4 samples are intact and have no damage, and the absorption spectra are unchanged before and after washing, which indicates that the film layers of the present invention have excellent solvent resistance, and the results are shown in fig. 2 to 5.
Example 6: film-Forming Properties of Compound 1-4
Fig. 6 shows the surface roughness of the film after crosslinking of the hole transport material compound 1 for quantum dot electroluminescent devices according to an exemplary embodiment of the present invention before and after n-octane cleaning.
The surface roughness of compound 1 was characterized after crosslinking to form a film and before and after washing with a solvent. AFM tests show that the surface roughness (Rq) of the crosslinked compound 1 film before and after cleaning is respectively 0.53nm and 0.74nm, which are both lower than 1nm, and the hole transport material (HTL) layer has good film forming quality. The results are shown in fig. 6.
Similarly, the film-forming properties of compounds 2, 3 and 4 were tested and found to have surface roughness (Rq) of 0.82nm, 0.93nm and 0.76nm, respectively, after n-octane washing, all indicating good film-forming properties.
Example 7: study of electrochemical Properties of Compounds 1 to 4
The HOMO energy level of the film after the compound 1-4 is crosslinked is determined by adopting Ultraviolet Photoelectron Spectroscopy (UPS). Specifically, the compounds 1-4 are prepared into solutions respectively, then spin-coated on a conductive silicon electrode, and crosslinked and cured at 230 ℃ for 30 minutes. The HOMO levels of the HTL films of compounds 1-4 were-6.2 eV, -6.4eV, -6.5eV, -6.3eV, respectively, indicating that they had deep HOMO levels. The deep HOMO energy level enables holes to be injected into the quantum dot light emitting layer more easily, and carrier injection in the quantum dot light emitting layer is balanced. Table 1 shows work functions and HOMO levels of films after crosslinking of hole transport materials (compounds 1 to 4) for quantum dot electroluminescent devices according to exemplary embodiments of the present invention.
TABLE 1 surface work function and HOMO energy levels of Compounds 1-4
HTL Work function (eV) HOMO(eV)
Compound 1 -3.8 -6.2
Compound 2 -4.2 -6.4
Compound 3 -4.3 -6.5
Compound 4 -4.0 -6.3
Example 8: study of hole mobility Properties of Compound 1
The film after the compound 1 is crosslinked is used for measuring the hole mobility (mu) by preparing an organic field effect transistor device (OFET) with a bottom contact-bottom grid (bottom-gate) structureh-OFET). Specific embodiment with n++-Si/HfO2The substrate is used as a grid electrode, the Au electrode is used as a source electrode and a drain electrode, the compound 1 is dissolved in chlorobenzene, the concentration is 5mg/mL, and the compound is deposited in a dropping mode in the channel regions of the source electrode and the drain electrode. And then, under the protection of nitrogen, carrying out thermal annealing treatment at 230 ℃ for 30 minutes to form an active conductive layer. migration rate test was conducted in room temperature air. The crosslinked compound 1 film shows quite high hole mobility which reaches 4.9 multiplied by 10-2cm-2V · S. Is a conventional hole transport material TFB (1X 10)-2cm-2/(V·S))、 PVK(2.5×10-6cm-2V · S)) 1 to 10000 times the mobility. So that the injection of holes and electrons into the quantum dot light-emitting layer is more matched.
Example 9: study of film Density of Compound 1
Fig. 7 shows the film thickness change of the hole transport material compound 1 before and after crosslinking for a quantum dot electroluminescent device according to an exemplary embodiment of the present invention.
The film thickness before and after crosslinking of the compound 1 film was measured by means of a step-meter (AlphaStep profiler) model Veeo Dektak 150. Specifically, Compound 1 was dissolved in chlorobenzene at a concentration of 20mg/mL and spin-coated on an ITO glass substrate. Annealing at 100 ℃ for 20 minutes under the protection of nitrogen, measuring the thickness of the film before crosslinking, performing thermal annealing treatment at 230 ℃ for 30 minutes, and measuring the thickness of the film after crosslinking. Statistically, the average shrinkage of the crosslinked compound 1 film was 22% greater than that before crosslinking. The crosslinked compound 1 film is more compact, and planar molecules are easy to orderly accumulate, thereby being beneficial to improving the mobility.
Example 10: red light quantum dot electroluminescent device
Fig. 8 shows a luminance-current efficiency graph and a luminance-power efficiency graph of a red quantum dot light emitting diode device formed using the hole transport material (compound 1) for a quantum dot electroluminescent device according to an exemplary embodiment of the present invention and TFB, Poly-TPD, PVK. Fig. 9 shows a luminance-external quantum efficiency graph of a red quantum dot light emitting diode device formed using a hole transport material (compound 1) for a quantum dot electroluminescent device according to an exemplary embodiment of the present invention and TFB, Poly-TPD, PVK.
The red light quantum dot light-emitting diode device is manufactured according to the following method: PSS, annealing and drying to form the anode modification layer PEDOT, and then manufacturing the hole transport layer. In the class-4 quantum dot light-emitting diode device manufactured in this embodiment, the hole transport layers of the class-4 device are respectively spin-on compounds 1, TFB, Poly-TPD, and PVK; wherein the crosslinking condition of the compound 1 is that the temperature is 230 ℃ for 30 minutes, and the spin coating hole transport material ink is 10mg/mL chlorobenzene solution; spin-coating a red light quantum dot light-emitting layer (624nm) with 15mg/ml of n-octane dispersed, and annealing and drying at 100 ℃ for 20 minutes; spin-coating 25mg/mL ethanol-dispersed ZnO solution, and annealing and drying at 100 ℃ for 20 minutes; finally at 5X 10-4And forming the aluminum electrode by adopting a vacuum evaporation method under the vacuum condition of Pa. The structure of the formed 4-type red light quantum dot light-emitting diode device is as follows: ITO/PEDOT PSS (30 nm)/Compound 1(35nm)/QDs (30nm)/ZnO (50nm)/Al (100nm), ITO/PEDOT PSS (30nm)/TFB (35nm)/QDs (30nm)/ZnO (50nm)/Al (100nm), ITO/PEDOT PSS (30nm)/Poly-TPD (35nm)/QDs (30nm)/ZnO (50nm)/Al (100nm), ITO/PEDOT PSS (30nm)/PVK (35nm)/QDs (30nm)/ZnO (50nm)/Al (100 nm). The power supply was tested using the KEITHLEY 2400 system and was tested using the PR655 spectrometer. The test was performed in an atmospheric environment without a packaging process, and the results of the test are shown in fig. 7 to 8.
Based on a method similar to the method, the compound 1 is used as a hole transport material to prepare a red light quantum dot light-emitting diode device, and the efficiency of the device is found to be superior to that of TFB, Poly-TPD and PVK traditional hole transport materials, the driving voltage is equivalent to that of standard parts, and the deviceAt 100--2Compared with TFB, Poly-TPD and PVK devices, the intrinsic thin film transistor has lower efficiency roll-off and device stability. And the lifetime of the compound 1 devices is longer than that of the reference devices. The detection data of the device prepared by using the red light quantum dots as the luminescent layer are shown in table 2:
table 2 red QLED device test data for compound 1 and conventional HTL
Figure BDA0001839592810000111
Example 11: ink-jet printing quantum dot electroluminescent device
Fig. 10 shows a luminance-current efficiency graph of an inkjet printed red quantum dot light emitting diode device formed using a hole transport material (compound 1) for a quantum dot electroluminescent device according to an exemplary embodiment of the present invention.
The ink-jet printing red light quantum dot light-emitting diode device is manufactured according to the following method:
(1) PSS is formed as an anode modification layer, annealing and drying are carried out, then the compound 1 is subjected to spin coating or ink-jet printing to be used as a hole transport layer, and the crosslinking condition of the compound 1 is 230 ℃ for 30 minutes. Wherein the spin-coating compound 1 ink is a chlorobenzene solution, and the ink formula of the ink-jet printing compound 1 is prepared from a mixed solution of indan and n-butylbenzene;
(2) the red light quantum dot luminescent layer (624nm) is coated by spin coating or ink-jet printing, and is annealed and dried for 20 minutes at 100 ℃. The spin-coating quantum dot ink is an n-octane dispersion solution, and the inkjet printing quantum dot ink is prepared from a chlorobenzene and n-tetradecane mixed solution;
(3) spin-coating 25mg/mL ethanol-dispersed ZnO solution, and annealing and drying at 100 ℃ for 20 minutes;
(4) finally at 5X 10-4And forming the aluminum electrode by adopting a vacuum evaporation method under the vacuum condition of Pa.
The structure of the formed red light quantum dot light-emitting diode device is as follows: ITO/PEDOT PSS (30 nm)/Compound 1(35nm)/QDs (30nm)/ZnO (50nm)/Al (100 nm). The four prepared device processes are respectively as follows:
device 1: HTL (spin-on)/QDs (spin-on)
Device 2: HTL (spin coating)/QDs (printing)
Device 3: HTL (printing)/QDs (spin coating)
Device 4: HTL (print)/QDs (print)
The printed layer was prepared using a DMP2831 ink jet printer, the power supply was tested using a KEITHLEY 2400 system, and the test was performed using a PR655 spectrometer. The test was performed in an atmospheric environment without a packaging process, and the results of the test are shown in fig. 9.
Based on the novel HTL/QDs double-layer ink-jet printing red light quantum dot light-emitting diode device prepared by the method, the maximum current efficiency of the device is found to reach 87.5% of the performance of a full-spin coating device. The detection data of the device prepared by using the red light quantum dots as the luminescent layer are shown in table 3:
TABLE 3 ink-jet printing red light QLED device and spin-coating device detection data
Figure BDA0001839592810000121
In summary, unlike the conventional hole transport material, the hole transport material for the quantum dot electroluminescent device according to the exemplary embodiment of the present invention has the characteristic of being capable of being cross-linked and cured, and can effectively reduce or prevent the erosion of the upper layer to the lower organic functional layer in the process of preparing the quantum dot electroluminescent device by the solution method; the material has a deep HOMO energy level, so that the hole injection barrier of an HTL/QDs interface is further reduced, and the charge injection balance of a QLED device is easier to realize; due to the fact that molecules are more tightly stacked after crosslinking and curing, charge transmission is more effective, mobility is obviously improved, and performance of the device is further improved; the performance of the double-layer ink-jet printing red-light quantum dot device realizes 87.5% of the performance of the full-spin coating device, and lays a beneficial foundation for the subsequent preparation of high-performance full-printing quantum dot devices.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and are preferred embodiments, which are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention. All equivalent changes or modifications made according to the present invention should be covered within the protection scope of the present invention.

Claims (6)

1. A quantum dot light-emitting diode comprises a hole transport material layer, and is characterized in that the hole transport material layer is formed by crosslinking hole transport materials, the hole transport materials comprise compounds shown as a general formula I,
Figure FDA0003242598550000011
wherein R is1One selected from hydrogen, cyano, trifluoromethyl and sulfonic acid group;
R2is hydrogen or C1-C30 alkyl;
R3and R4Independently selected from hydrogen or vinyl, and at least one of which is vinyl.
2. The quantum dot light-emitting diode of claim 1, wherein the hole transport material comprises a 4,4'-N, N' -dicarbazole biphenyl rigid planar structure, a flexible alkyl chain, and a vinyl group that are crosslinked by heating.
3. The qd-led of claim 2, wherein the 4,4'-N, N' -dicarbazole biphenyl rigid planar structures are in an orderly stacked arrangement upon heating.
4. The quantum dot light-emitting diode of claim 1, wherein the hole transport material layer is formed by forming a film of the hole transport material and heating the film to crosslink the film sufficiently.
5. The quantum dot light-emitting diode of claim 1, wherein the quantum dot light-emitting diode comprises a functional layer formed on the hole transport material layer.
6. The quantum dot light-emitting diode of claim 1, wherein the hole transport material is a combination of one or more of compound 1, compound 2, compound 3, compound 4,
Figure FDA0003242598550000012
Figure FDA0003242598550000021
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