KR20140121957A - Blue Phophorescene Compounds and Organic Light Emitting Diode Device using the same - Google Patents

Abstract

A blue phosphorescent compound according to an embodiment of the present invention can be represented by chemical formula 1. In chemical formula 1, X is any one selected from a carbazole group, an alpha-carboline group, a beta-carboline group, a gamma-carboline group, a florene group, a silicon group, a phenyl group, a pyridine group, and substituents thereof.

Description

TECHNICAL FIELD [0001] The present invention relates to a blue phosphorescent compound and an organic electroluminescent device using the blue phosphorescent compound and organic light emitting diode device using the same.

The present invention relates to a blue phosphorescent compound and an organic electroluminescent device using the same.

One of the new flat panel display devices, the organic electroluminescent device, is a self-emitting type and has a better viewing angle and contrast ratio than a liquid crystal display device (LCD), and it does not require a separate backlight, It is advantageous. In addition, it is possible to drive the DC low voltage, has a high response speed, and is especially advantageous in terms of manufacturing cost.

The organic electroluminescent device can be formed by sequentially laminating an anode, a hole injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, an electron injecting layer and a cathode sequentially. At this time, excitons are formed in the light emitting layer by recombination of electrons and holes injected from both electrodes, and fluorescence in singlet excitons and phosphorescence in triplet excitons are involved.

In recent years, the material of the light emitting layer is changing from fluorescence to phosphorescence. This is because, in the case of a fluorescent material, only about 25% of the excitons formed in the light emitting layer are used to make light, and 75% of the triplet is mostly lost to heat, while the phosphorescent material has a light emitting mechanism to be.

Briefly examining the light-emitting process of the phosphorescent device, holes injected from the anode and electrons injected from the cathode meet at the host material of the light-emitting layer. Of course, in some cases, holes and electrons may be encountered directly in the dopant, but in general, a large amount of the host material is encountered because of the high concentration of the host material. At this time, a single-termed exciton formed in the host is energy-transferred to the single or triplet of the dopant, and the triplet exciton is transferred to the triplet of the dopant.

First, the exciton transited to a single term of the dopant is transited to the triplet of the dopant through inter system crossing, so that the primary terminus of all the excitons is the triplet level of the dopant. The excitons thus formed transition to a ground state and emit light. When the triplet energies of the hole transporting layer or the electron transporting layer adjacent to the upper and lower portions of the light emitting layer are smaller than the triplet energy of the dopant, reverse energy transfer occurs between the dopant and the host layer. Accordingly, the triplet energy of the hole / electron transport layer as well as the host material of the light emitting layer plays a very important role in the phosphorescent device.

For effective energy transfer from the host to the dopant, the triplet energy of the host must be greater than the triplet energy of the dopant. However, the most widely used CBP has a triplet energy of 2.6 eV, so that when the well-known Firpic phosphorescent dopant is used, reverse energy (endothermic) transition occurs from the host to the dopant and the efficiency decreases. In addition, even when an iridium phosphide dopant (FCNIr (3,5-difluoro-4-cyanophenyl) pyridine) having high color purity is used, energy transfer is still not smooth.

Therefore, there is a desperate need to develop a novel phosphor having a high triplet energy and excellent thermal stability.

An object of the present invention is to provide a highly efficient organic electroluminescent device using a novel blue phosphorescent compound as a host in a light emitting layer of an organic electroluminescent device.

According to one aspect of the present invention, a blue phosphorescent compound is represented by the following general formula (1).

[Chemical Formula 1]

In Formula 1,

X is at least one selected from the group consisting of a carbazole group, an alpha-carboline group, a beta-carboline group, a gamma-carboline group, a fluorene group, (Silicon) group, a phenyl group, a pyridine group, and a substituent thereof.

According to the present invention, a novel blue phosphorescent compound having a high triple energy of 2.9 eV or more and excellent thermal stability is prepared and formed as a host of a light emitting layer of an organic electroluminescent device, thereby facilitating energy transfer in the light emitting layer, There is an advantage that the luminous efficiency can be improved.

1 is a view illustrating an organic electroluminescent device according to an embodiment of the present invention; And
FIGS. 2 and 3 are graphs showing the UV absorption spectrum of the material of Example 1 of the present invention and the material of Comparative Example 3 and the PL spectrum measured at a low temperature (77 K).

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, well-known functions or constructions are not described in detail to avoid unnecessarily obscuring the subject matter of the present invention.

1 is a view illustrating an organic electroluminescent device according to an embodiment of the present invention.

1, an organic electroluminescent device 100 according to an embodiment of the present invention includes an anode 110, a hole injecting layer 120, a hole transporting layer 130, a light emitting layer 140, A cathode 150, an electron injection layer 160, and a cathode 170.

The anode 110 may be any one selected from indium tin oxide (ITO), indium zinc oxide (IZO), and zinc oxide (ZnO). When the anode 110 is a reflective electrode, the anode 110 may have a reflective layer made of any one of aluminum (Al), silver (Ag), and nickel (Ni) under the layer made of any one of ITO, IZO, .

The hole injection layer 120 may function to smoothly inject holes from the anode 110 into the light emitting layer 140. The hole injection layer 120 may be formed of cupper phthalocyanine (CuPc), poly (3,4) -ethylenedioxythiophene (PEDOT) polyaniline and NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine). However, the present invention is not limited thereto.

The thickness of the hole injection layer 120 may be 1 to 150 nm. If the thickness of the hole injection layer 120 is 1 nm or more, the hole injection characteristics can be prevented from being degraded. If the thickness is 150 nm or less, the thickness of the hole injection layer 120 is too thick, There is an advantage that it is possible to prevent the drive voltage from rising.

The hole transport layer 130 plays a role of facilitating the transport of holes and may be formed by using NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine), TPD (N, N'- N, N'-bis- (phenyl) -benzidine), s-TAD, and MTDATA (4,4 ' But the spirit of the present invention is not limited thereto.

The thickness of the hole transport layer 130 may be 1 to 150 nm. If the thickness of the hole transport layer 130 is 5 nm or more, it is possible to prevent the hole transport property from being degraded. If the thickness is 150 nm or less, the thickness of the hole transport layer 130 is too thick, There is an advantage that the driving voltage can be prevented from rising.

The light emitting layer 140 may be formed of a material that emits red, green, and blue light, and may be formed using phosphorescent or fluorescent materials. Hereinafter, a phosphorescent material emitting blue light will be described in detail in one embodiment of the present invention.

The light emitting layer 140 of the present invention may include a host and a dopant.

At this time, the host of the present invention is composed of a blue phosphorescent compound represented by the following formula (1).

[Chemical Formula 1]

In Formula 1, X represents a carbazole group, an alpha-carboline group, a beta-carboline group, a gamma-carboline group, fluorene a fluorine group, a silicon group, a phenyl group, a pyridine group and substituents thereof.

Here, the substituent of X may be any one selected from the group consisting of C1 to C6 aryl groups, C1 to C6 alkyl groups, and C1 to C12 heteroaryl groups.

The substituent of X may be any one selected from the following substances.

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Accordingly, the material of Formula 1 may be any one selected from the following materials.

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In the case of the dopant mixed into the host in the light emitting layer 140 of the present invention, it may be an iridium compound such as FCNIr or FIrpic. In addition, the light emitting layer 140 of the present invention may contain 0.1 to 20% by weight of the dopant relative to 100% by weight of the host.

The electron transport layer 150 serves to smooth the transport of electrons and may be at least one selected from Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq and SAlq. The idea is not limited to this.

The thickness of the electron transport layer 150 may be 1 to 50 nm. If the thickness of the electron transporting layer 150 is 1 nm or more, the electron transporting property can be prevented from being degraded. If the thickness is 50 nm or less, the thickness of the electron transporting layer 150 is too thick, There is an advantage that the driving voltage can be prevented from rising.

The electron injection layer 160 serves to smoothly inject electrons and may use Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq or SAlq, Are not limited thereto.

The thickness of the electron injection layer 160 may be 1 to 50 nm. If the thickness of the electron injection layer 160 is 1 nm or more, there is an advantage that the electron injection characteristics can be prevented from being degraded. If the thickness is 50 nm or less, the thickness of the electron injection layer 160 is too thick, There is an advantage that it is possible to prevent the drive voltage from rising.

The cathode 170 is an electron injection electrode and may be made of magnesium (Mg), calcium (Ca), aluminum (Al), silver (Ag), or an alloy thereof having a low work function. Here, when the organic electroluminescent device is a front or both-side light emitting structure, the cathode 170 may be formed to have a thickness thin enough to transmit light, and when the organic electroluminescent device is a back light emitting structure, It can be formed thick enough.

Hereinafter, the synthesis examples of the blue phosphorescent compound of the present invention and the characteristics of the compounds will be described in detail in Synthesis Examples and Examples below. However, the following examples are illustrative of the present invention, but the present invention is not limited to the following examples.

Synthetic example

1) Preparation of dibenzo [b, d] furan-2-yl (phenyl) methanone (dibenzo [b, d] furan-2-yl (phenyl) methanone)

Dibenzofurane (5 g, 29.7 mmol) was dissolved in dimethyl chloride (10 ml) in a 250 ml two-necked flask and benzoyl chloride, aluminum trichloride ) (0.90 g, 6.76 mmol) were dissolved and mixed at room temperature for 10 minutes. Subsequently, the mixture was stirred at room temperature for 2 hours and then 1M HCl solution was added thereto. The mixture was extracted with ether, dried with magnesium sulfate, and distilled under reduced pressure to remove the solvent. After precipitation, 1.5 g (80% .

Preparation of 2) (8-iodo-dibenzo [b, d] furan-2-yl (phenyl) methanone (8-Iododibenzo [b, d] furan-2-yl) (phenyl) methanone)

250mL 2-dibenzo necked flask [b, d] furan-2-yl (phenyl) methanone (3.0g, 11.02 mmol) (dibenzo [b, d] furan-2-yl) (phenyl) methanone), iodine iodine (1.4 g, 5.51 mmol), periodic acid (1.26 g, 5.51 mmol), acetic acid (100 ml), DI water (20 ml) and sulfuric acid (0.2 ml) After stirring at 60 占 폚 for 10 hours, the temperature was lowered to room temperature, and stirring was further continued for 16 hours. Subsequently, the precipitated solid was filtered, extracted with toluene, distilled under reduced pressure to remove the solvent, and precipitated to obtain 2.75 g (62.6%) of a white solid.

3) 8 (8-iodo-dibenzo [bd] furan-2-yl) -8-phenyl-indole -8H- [3,2,1- de] acridine (8- (8-iododibenzo [b , d ] furan-2-yl) -8-phenyl-8H-indole [3,2,1-de] acridine

50 ml of THF was added to 9- (2-bromophenyl) -9H-carbazole (2.23 g, 6.91 mmol) in a 250 ml two-necked flask and cooled to -78 ° C And then 4.53 ml of n-BuLi (1.6 M in hexane) was added slowly. After 1 hour passed, the 8-iodo-dibenzo [bd] furan-2-yl) (phenyl) methanone ((8-iododibenzo [b, d] furan-2-yl) (phenyl) methanone) (2.75g, 6.91 mmol) was slowly added thereto again, and after 30 minutes, the temperature was raised to RT, followed by stirring overnight. Next, the organic layer was extracted with ethyl acetate, and the solvent was removed by distillation under reduced pressure to obtain a wax form. In a 250 ml two-necked flask, a wax-like substance was dissolved in acetic acid ( 50 ml) and HCl, and the mixture was stirred under reflux. After completion of the reaction, distilled water was added to filter the resulting solid to obtain 0.9 g (20.9%) of a white solid.

Dibenzo [ b, d ] furan-2-yl) -8-phenyl-8H-indolo [3,2,1-de] acryle Preparation of 8- (8- (9H-carbazol-9-yl) dibenzo [ b, d ] furan-2-yl) -8-phenyl-8H-indolo [3,2,1-

8-iododibenzo [b, d] furan-2-yl) -8-phenyl-8H-indolo [3,2,1-de] 2-yl) -8-phenyl-8H-indolo [3,2,1-de] acridine (0.9 g, 1.44 mmol), carbazole (0.24 g, 1.44 mmol), CuI (82.0 mg, 0.433 mmol), K ₃ PO ₄ (610 mg, 2.88 mmol), trans-1,2-dicyclohexane-diamine (49.7 mg , 0.433 mmol) were dissolved in 50 ml of 1,4-dioxane. Subsequently, the reaction mixture was refluxed for 24 hours. After completion of the reaction, the solvent was distilled off under reduced pressure, and the residue was subjected to column chromatography using methylene chloride and hexane to obtain 0.5 g (52%) of a white solid.

The UV absorption spectrum of carbazole biphenyl (CBP) and 1,3-bis (carbazol-9-yl), which are conventional phosphorescent compounds, and the low temperature (77K ) Were measured and shown in FIG. 2 and FIG. 3. The results are summarized in Table 1 below.

[ CBP ]

[ mCP ]

matter HOMO ^a
level( eV ) LUMO
level( eV ) Band gap
energy( eV ) ^b E _T
( eV ) ^C Tg
(° C) Comparative Example 1 CBP - 6.0 - 2.5 3.5 2.6 - Comparative Example 2 mCP - 5.9 - 2.5 3.4 2.95 65 Example 1 Formula 1 - 5.71 - 2.31 3.4 2.99 131 Comparative Example 3 (2) - 5.3 - 1.9 3.4 2.98 98

a) Measurement result by CV (Cyclic Voltammetry).

b) the result of measurement at the absorption onset.

c) The maximum PL value of the 2-methyl THF solution (transition at 77 K).

Referring to Table 1, FIG. 2 and FIG. 3, it was confirmed that the triplet energy (E _T ) of Example 1 prepared according to the present invention was higher than Comparative Example 1 (2.6). It was also confirmed that the thermal stability (Tg) of Example 1 produced according to the present invention was higher than that of Comparative Example 2 (65) and Comparative Example 3 (98).

As described above, the phosphorescent compound according to an embodiment of the present invention and the organic electroluminescent device including the phosphorescent compound according to the present invention can produce a novel phosphorescent compound having high triplet energy and excellent thermal stability, As a host, the energy transfer in the light emitting layer is facilitated, and as a result, the light emitting efficiency can be improved.

Accordingly, the present invention provides a novel blue phosphorescent compound having a high triplet energy and excellent thermal stability and is formed as a host of the luminescent layer of the organic electroluminescent device, thereby facilitating the energy transfer in the luminescent layer, There is an advantage that life can be improved.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the following claims rather than the detailed description. Also, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

100: organic electroluminescent device 110: anode
120: Hole injection layer 130: Hole transport layer
140: light emitting layer 150: electron transporting layer
160: electron injection layer 170: cathode

Claims (9)

A blue phosphorescent compound represented by the following formula (1):
[Chemical Formula 1]

In Formula 1,
X is at least one selected from the group consisting of a carbazole group, an alpha-carboline group, a beta-carboline group, a gamma-carboline group, a fluorene group, (Silicon) group, a phenyl group, a pyridine group, and a substituent thereof.
The method according to claim 1,
The substituent of X,
A halogen atom, a C1 to C6 aryl group, a C1 to C6 alkyl group, and a C1 to C12 heteroaryl group.
The method according to claim 1,
The substituent of X,
Wherein the phosphorescent compound is any one selected from the substances shown below.

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The method according to claim 1,
The material of the above formula (1)
Wherein the phosphorescent compound is any one selected from the substances shown below.

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A first electrode;
A second electrode facing the first electrode;
A light emitting layer positioned between the first and second electrodes;
A hole transport layer disposed between the first electrode and the light emitting layer;
And an electron transport layer disposed between the second electrode and the light emitting layer,
Wherein at least one of the light emitting layer, the hole transporting layer, and the electron transporting layer comprises a phosphorescent compound represented by the following Formula 1:
[Chemical Formula 1]

In Formula 1,
X is at least one selected from the group consisting of a carbazole group, an alpha-carboline group, a beta-carboline group, a gamma-carboline group, a fluorene group, (Silicon) group, a phenyl group, a pyridine group, and a substituent thereof.
6. The method of claim 5,
The light-
Wherein the organic electroluminescent element emits blue light.
6. The method of claim 5,
The substituent of X,
Wherein the organic group is any one selected from the group consisting of C1 to C6 aryl groups, C1 to C6 alkyl groups and C1 to C12 heteroaryl groups.
6. The method of claim 5,
The substituent of X,
Wherein the organic electroluminescent device is one selected from the following materials.

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The method according to claim 6,
The material of the above formula (1)
Wherein the organic electroluminescent device is any one selected from the following materials.

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