KR20140128552A - 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 is able to be represented by chemical formula 1. In chemical formula 1, R_1 to R_8 are one selected from a hydrogen, D, halogen of F, Cl and Br, CF_3, a cyano group, an alkyl group of C1-C18, an alkoxy group of C1-C18, a substituted or non-substituted aromatic group of C6 or more, a substituted or non-substituted heteroaromatic group of C5 or more, an amine group of C1-C18, an aromatic group substituted amine group of C6 or more, a heteroaromatic group substituted amine group of C5 or more, a silyl group substituted with an aromatic group of C6 or more or an alkyl group of C1-C18 and silyl group substituted with a heteroaromatic group of C5 or more, respectively. n is an integer of 1-3. X_1-L_1-X_2 is a bidentate ligand. X_1 and X_2 are a carbon atom, a nitrogen atom or an oxygen atom, respectively. And L_1 is an atom group forming a bidentate ligand.

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.

2. Description of the Related Art In recent years, the importance of a flat panel display (FPD) has been increasing with the development of multimedia. A plasma display panel (PDP), a field emission display (FED), an organic light emitting diode (OLED) display device, and the like A variety of displays such as a liquid crystal display (LCD)

The organic electroluminescent device can not only form a device on a flexible substrate such as a plastic but also can operate at a voltage as low as 10 V or less as compared with a plasma display panel or an inorganic electroluminescent display, There are advantages. In addition, organic electroluminescent devices can display three colors of red, green, and blue, which is a next generation display device that expresses rich colors, and has become a target of many people.

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. In such an organic electroluminescent device, excitons are formed by recombination of holes injected from the anode and electrons injected from the cathode, and stabilized in a ground state, thereby generating light. An exciton blocking layer having excellent stability may also be used to prevent the formed exciton from being quenched.

In the exciton, the ratio of singlet and triplet exists at 1: 3. In case of fluorescence, only singlet exciton is used. In case of phosphorescence, both singlet and triplet can be used to obtain better luminous efficiency. Since the phosphorescent material can have a very high quantum efficiency as compared with the fluorescent material, much research has been conducted to reduce the power consumption while increasing the efficiency of the organic electroluminescent device.

The color reproduction ratio means an area ratio of triangle composed of three RGB points to the area of a triangle formed by NTSC coordinates in the CIE chromaticity coordinate system, which means that the higher the value, the more vivid the color is reproduced. The color reproduction ratio is the part that is selected as the strength of OLED compared with LCD. In the case of a fluorescent light emitting material, an RGB material having an excellent color reproducibility is known, and a phosphorescent material and a phosphorescent green material having excellent color purity have also been reported.

However, in order to reduce power consumption, it is important to construct an RGB device with a phosphorescent material having a high luminous efficiency. In the case of a WRGB device using a color filter, the use of a blue phosphorescent material and an orange phosphorescent material is essential, and in the case of a blue phosphorescent material, the maximum emission wavelength of the material currently reported is 460 nm or more.

Therefore, development of a blue phosphorescent material having excellent color reproducibility and color purity has been demanded.

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

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,

R1 to R8 independently represent hydrogen, halogen, CF3, cyano group, C1 to C18 alkyl group, C1 to C18 alkoxy group, substituted or unsubstituted aromatic group of C6 or more, Or an unsubstituted heteroaromatic group, an amine group of C1 to C18, an amine group substituted with an aromatic group of C6 or more, an amine group substituted with a heteroaromatic group of C5 or more, a C1 to C18 alkyl group, or a silyl And a silyl group substituted with a heteroaromatic group having a carbon number of 5 or more, n is an integer of 1 to 3, X 1 -L 1 -X 2 is a 2-position ligand, X 1 and X 2 are each independently a carbon atom, A nitrogen atom or an oxygen atom, and L < 1 > is an atomic group forming a two-coordinate ligand.

According to the present invention, a new blue phosphorescent compound is prepared and formed as a dopant of the light emitting layer of the organic electroluminescent device, thereby improving the power efficiency, current efficiency and quantum efficiency of the organic electroluminescent device.

In particular, the novel blue phosphorescent compound can provide an organic electroluminescent device having high color purity and improved color reproducibility by using an iridium complex.

1 is a view illustrating an organic electroluminescent device according to an embodiment of the present invention; And
2 is a graph showing the UV-vis PL spectra of compound PD-1 prepared according to the synthesis example of the present invention.

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 according to the present invention may be formed of a blue phosphorescent compound represented by the following general formula (1).

 [Chemical Formula 1]

Wherein R ₁ to R ₈ are independently hydrogen, halogen, CF ₃ , cyano, C 1 to C 18 alkyl, C 1 to C 18 alkoxy, substituted or not more than C6, A substituted aromatic group, a substituted or unsubstituted heteroaromatic group of C5 or more, an amine group of C1 to C18, an amine group substituted with an aromatic group of C6 or more, an amine group substituted with a heteroaromatic group of C5 or more, an alkyl group of C1 to C18, A silyl group substituted with a C6 or higher aromatic group, or a silyl group substituted with a C5 or higher heteroaromatic group,

n is an integer from 1 to 3, X ₁ -L ₁ -X ₂ is a ligand of L 2, X _1, X ₂ are each independently a carbon atom, a nitrogen atom or an oxygen atom, L ₁ is a ligand of L 2 Lt; / RTI >

The blue phosphorescent compound represented by Formula 1 may be any one selected from the following materials.

The blue phosphorescent compound may be used as a dopant of the light emitting layer 140. When a blue phosphorescent compound is used as a dopant, it can be doped in the light emitting layer 140 at a weight ratio of 0.1 to 50% and doped at a weight ratio of 1 to 20%.

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  : PD - To 1  Synthesis of blue phosphorescent compounds to be displayed

1) Synthesis of Compound A

Bromopyridine (1.35 g, 8.54 mmol), benzoimidazole (1 g, 8.54 mmol) and CuBr (II) (cupper bromide) (0.191 g, 0.85 mmol) in a 100 mL round bottom flask ), And tetrabutylammonium fluoride (11.7 g, 42.72 mmol) were placed, and the mixture was stirred at 145 占 폚 for 24 hours. When the reaction was completed, the volatiles were removed under reduced pressure, and the residue was subjected to column chromatography using ethylacetate and hexane to obtain Compound A (0.80 g, 4.10 mmol).

2) Synthesis of compound PD-1

Compound A (0.80 g, 4.10 mmol) and iridium (Ⅲ) acetylacetonate (0.40 g, 0.82 mmol) were added to a 25 mL round bottom flask and the reaction mixture was vacuum dried for 30 minutes, The reaction flask was filled with nitrogen gas (repeated three times). The reaction mixture was reacted at 250 DEG C for 48 hours, cooled to room temperature, and then washed with methylene chloride and methanol to obtain a white solid compound PD-1 (0.21 g, 0.27 mmol).

The UV-vis PL (Ultra violet-Photo Luminescence) spectra of the PD-1 (Examples) and Comparative Examples 1 and 2 prepared in the above-mentioned synthesis examples were measured and shown in FIG. 2, The maximum emission wavelengths are summarized in Table 1 below.

First, an example of fabricating an organic electroluminescent device using the blue phosphorescent compound of the above-described compound PD-1 as a blue dopant is as follows.

Example

A 1 wt% solution of 990 mg of PMMA and 10 mg of PD-1 in 100 ml of methylene chloride was prepared and then a thin film was prepared on a quartz substrate using a spin coater. At this time, the characteristics of the thin film were evaluated using a quantum efficiency meter (QE-1100, OTSUKA ELECTRONICS CO., LTD.). Thus, the organic electroluminescent device according to the example (compound PD-1) exhibited a quantum efficiency of 13.02% and a color coordinate property of (0.161, 0.133).

In addition, the material of Comparative Example 1 is represented by Chemical Formula 2 or Chemical Formula 3 shown below, and the material of Comparative Example 2 is represented by Chemical Formula 4 or Chemical Formula 5 shown below.

Comparative Example  One

(2)

(3)

Comparative Example  2

[Chemical Formula 4]

[Chemical Formula 5]

device Maximum emission wavelength (nm) Example 404 Comparative Example 1 459 to 492 Comparative Example 2 474 to 482

It was confirmed that the maximum emission wavelength was in the range of 459 to 492 and 474 to 482 nm in Examples 1 and 2, respectively.

Therefore, the blue phosphorescent compound of the present invention has an advantage that the color purity can be improved and the color reproduction ratio can be improved in the blue light emitting region.

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 (8)

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

In Formula 1,
R ₁ to R ₈ are independently hydrogen, halogen, CF ₃ , cyano group, C 1 to C 18 alkyl group, C 1 to C 18 alkoxy group, substituted or unsubstituted aromatic group having at least C6, An amine group substituted with an aromatic group of C6 or higher, an amine group substituted with a heteroaromatic group of C5 or higher, an alkyl group of C1 to C18, or an aromatic group of C6 or higher A substituted silyl group, and a silyl group substituted with a C5 or higher heteroaromatic group,
n is an integer from 1 to 3, X ₁ -L ₁ -X ₂ is a ligand of L 2, X _1, X ₂ are each independently a carbon atom, a nitrogen atom or an oxygen atom, L ₁ is a ligand of L 2 Lt; / RTI >
The method according to claim 1,
The blue phosphorescent compound may be,
A blue phosphorescent compound represented by the following formula:

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,
R ₁ to R ₈ are independently hydrogen, halogen, CF ₃ , cyano group, C 1 to C 18 alkyl group, C 1 to C 18 alkoxy group, substituted or unsubstituted aromatic group having at least C6, An amine group substituted with an aromatic group of C6 or higher, an amine group substituted with a heteroaromatic group of C5 or higher, an alkyl group of C1 to C18, or an aromatic group of C6 or higher A substituted silyl group, and a silyl group substituted with a C5 or higher heteroaromatic group,
n is an integer from 1 to 3, X ₁ -L ₁ -X ₂ is a ligand of L 2, X _1, X ₂ are each independently a carbon atom, a nitrogen atom or an oxygen atom, L ₁ is a ligand of L 2 Lt; / RTI >
The method according to claim 1,
The above-
Wherein the organic electroluminescent device is represented by the following formula.

The method of claim 3,
The light-
Wherein the organic electroluminescent element emits blue light.
The method of claim 3,
The above-
Wherein the light emitting layer is used as a dopant of the light emitting layer.
The method according to claim 6,
The dopant,
Wherein the light emitting layer is doped at a weight ratio of 0.1 to 50% with respect to the light emitting layer.
The method according to claim 6,
The dopant,
Wherein the light emitting layer is doped with 1 to 20% by weight of the light emitting layer.

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