KR20140067263A - Phosphorescent compound and organic light emitting diode device using the same - Google Patents

Abstract

The present invention provides a phosphorescent compound represented by the following chemical formula. In the chemical formula, each of X1, X2, Y1, Y2, Z1, and Z2 independently represent carbon or nitrogen and at least one of is nitrogen, and each of R1, R2, R3, and R4 is independently selected from aromatic compounds and heteroaromatic compounds comprising hydrogen, deuterium, and C1-C13, and silicone compounds, phosphoryl compounds, and their substituents.

Description

TECHNICAL FIELD The present invention relates to a phosphorescent compound and an organic light emitting diode (OLED)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphorescent compound used in an organic light emitting diode device, and more particularly, to a phosphorescent compound having high triplet energy and bipolar characteristics and high color purity and improved efficiency and an organic light emitting diode device using the same.

Recently, as the size of display devices has been increased, the demand for flat display devices with less space occupation is increasing. The technology of an organic light emitting diode device, also called an organic electroluminescent device (OELD) And several prototypes have already been announced.

When an electric charge is injected into a light emitting material layer formed between an electron injection electrode (cathode) and a hole injection electrode (anode), the organic light emitting diode device emits light while paired with electrons. The device can be formed on a flexible transparent substrate such as a plastic substrate and can be driven at a lower voltage (10 V or less) than a plasma display panel or an inorganic electroluminescence (EL) It also has a relatively low power consumption and excellent color purity. In addition, organic electroluminescence (EL) devices can display three colors of green, blue, and red, making them a next-generation rich color display device and attracting a lot of interest from many people. Here, the process of fabricating the organic light emitting diode device will be briefly described.

(1) First, a material such as indium tin oxide (ITO) is deposited on a transparent substrate to form an anode.

(2) A hole injecting layer (HIL) is formed on the anode. The hole injection layer mainly comprises 4,4'-bis [N- (4- {N, N-bis (3-methylphenyl) amino} phenyl] -N- phenylamino] biphenyl 10 nm to 60 nm thick.

(3) Next, a hole transport layer (HTL) is formed on the hole injection layer. This hole transporting layer is formed by depositing 4,4'-bis [N- (1-naphtyl) -N-phenylamino] -biphenyl (NPB)

(4) Next, an emitting material layer (EML) is formed on the hole transport layer. At this time, a dopant is added as needed. For example, tris ((3,5-difluoro-4-cyanophenyl) phosphine) represented by the following formula (1-4) is added to bis (N-carbazolyl) biphenyl (CBP) (III) bis [(4,6-difluorophenyl) -pyridinato-N, C2 '] picolinate (Firpic) represented by the following formula (1-5) .

(5) Next, an electron transport layer (ETL) and an electron injecting layer (EIL) are successively formed on the light emitting material layer.

(6) Next, a cathode is formed on the electron injection layer, and finally, a protective film is formed on the cathode.

Formula 1 -One

Formula 1 -2

Formula 1 -3

Formula 1 -4

In recent years, a phosphorescent material is used more frequently than a fluorescent material in a luminescent material layer. In the case of a fluorescent material, only about 25% of the single excitons formed in the emitter layer are used to make light, and 75% of the triplet is mostly lost to heat, while the phosphors convert both singlet and triplet to light It has a luminescent mechanism. Phosphorescent dopants generally contain heavy atoms such as Ir, Pt, and Eu in the center of organic matter, and have a high probability of electron transition from triplet to singlet.

However, since such a dopant is abruptly reduced in efficiency due to the concentration quenching phenomenon, the light emitting material layer can not be constituted by itself. Therefore, a light emitting layer is formed with a host having higher thermal stability and higher triplet energy than a dopant.

The hole injection from the anode and the electrons injected from the cathode are encountered in the host of the light emitting layer and the single-termed exciton formed in the host is a single or triple bond of the dopant. And the triplet exciton is energy transfer to the triplet of the dopant. Since the excitons transferred to a single term of the dopant are again transferred to the triplet of the dopant, all the excitons are terminated at the triplet level of the dopant. The excitons thus formed transition to the ground state and emit light.

For effective energy transfer to the dopant, the triplet energy of the host must be greater than the triplet energy of the dopant. When the triplet energy of the host is smaller than the triplet energy of the dopant, the energy reversal from the dopant to the host occurs and the efficiency decreases. This triplet energy is also important in the hole transporting layer and the electron transporting layer adjacent to the light emitting layer including the host and the dopant.

That is, referring to FIG. 1, CBP, which is widely used as a conventional host material, has a triplet energy of 2.6 eV, so that efficiency is reduced because triplet energy is smaller than that of Firpic or FCNIr used as a blue phosphorescent dopant.

Thus, the development of a blue phosphorescent compound with triplet energy greater than that of the blue phosphorescent dopant, i.e., about 2.9 eV, is required.

The present invention seeks to provide a novel phosphorescent compound having a triplet energy of 2.9 eV or more.

Further, a phosphorescent compound having a high triplet energy is provided to improve the efficiency of the organic light emitting diode device.

In order to solve the above problems, the present invention provides a process for preparing a compound represented by the following formula: wherein each of X1, X2, Y1, Y2, Z1 and Z2 is independently carbon or nitrogen, , R2, R3, and R4 each independently represent a phosphorescent compound selected from the group consisting of hydrogen, deuterium, C1 to C13 aromatic compounds and heteroaromatic compounds, silicone compounds, phosphoryl compounds, and their substituents.

In the phosphorescent compound of the present invention, each of R 1, R 2, R 3 and R 4 is independently hydrogen, deuterium, phenyl, carbazole, dibenzothiophene, dibenzofuran, Is selected from the group consisting of tetraphenylsilane, pyridine, quinoline, isoquinoline, pyrimidine, diphenyl phosphine oxide and substituents therefor .

In the phosphorescent compound of the present invention, at least one of R1, R2, R3, and R4 is selected from deuterium, an aromatic compound, a heteroaromatic compound, a silicon compound, a phosphoryl compound, and a substituent thereof.

In another aspect, the present invention provides a liquid crystal display comprising: a first electrode; A second electrode facing the first electrode; A light emitting material layer disposed between the first and second electrodes; A hole transport layer disposed between the first electrode and the light emitting material layer; Wherein at least one of the light emitting material layer, the hole transporting layer, and the electron transporting layer is represented by the following chemical formula, X1, X2, Y1, Y2, Z1 and Z2 are independently carbon or nitrogen and at least one of them is nitrogen and each of R1, R2, R3 and R4 is independently selected from the group consisting of hydrogen, deuterium, C1 to C13 aromatic compounds and heteroaromatic compounds , A silicon compound, a phosphoryl compound, and a substituent thereof.

In the organic light emitting diode device of the present invention, each of R 1, R 2, R 3 and R 4 is independently hydrogen, deuterium, phenyl, carbazole, dibenzothiophene, dibenzofuran ), Tetraphenylsilane, pyridine, quinoline, isoquinoline, pyrimidine, diphenyl phosphine oxide, and substituents therefor. .

In the organic light emitting diode device of the present invention, at least one of R1, R2, R3, and R4 is selected from deuterium, an aromatic compound, a heteroaromatic compound, a silicone compound, a phosphoryl compound, and a substituent thereof.

The phosphorescent compound of the present invention has a triplet energy of 2.9 eV or more. Therefore, the energy reversal of the energy to the dopant can be prevented from lowering due to the development.

That is, by using a pyridine having excellent electron mobility characteristics as a core to lower the driving voltage and introducing carboline having bipolar characteristics and high triplet energy, high triplet energy is obtained.

Further, since the difference between the singlet energy and the triplet is small, the carrier injection is easy, and the luminous efficiency of the device is improved.

Further, since the phosphorescent compound of the present invention has triplet energy greater than that of the dopant, the luminous efficiency of the organic light emitting diode device can be improved by using the phosphorescent compound in the hole transporting layer or the electron transporting layer.

1 is a PL spectrum of CBP which is a host material for a conventional organic light emitting diode device.
FIGS. 2A, 2B, and 2C are UV spectra and PL spectra of a phosphorescent compound for an organic light emitting diode device according to an embodiment of the present invention.
3 is a schematic cross-sectional view of an organic light emitting diode device according to an embodiment of the present invention.

Hereinafter, the structure of the phosphor according to the present invention, the synthesis example thereof, and the organic light emitting diode device using the same will be described.

The phosphorescent compound of the present invention is represented by the following general formula (2). That is, carboline is introduced into at least one of positions 2 and 5 of the pyridine core to have high triplet energy and bipolar characteristics.

(2)

In Formula 2, each of X1, X2, Y1, Y2, Z1 and Z2 may independently be carbon or nitrogen, and at least one of them may be nitrogen. That is, at least one of the substituents introduced on both sides of the pyridine is carbolin.

For example, when X1 and X2 are nitrogen, and Y1, Y2, Z1 and Z2 are carbon,? 1-carboline group, Z1 and Z2 are nitrogen, and X1, X2, Y1 and Y2 are carbon, It is Bolin. On the other hand, when X, Y, and Z are both carbon, they are carbazole.

Each of R 1, R 2, R 3 and R 4 in Formula 2 may be independently selected from hydrogen, deuterium, an aromatic compound composed of C 1 to C 13, a heteroaromatic compound, a silicon compound, a phosphoryl compound, and a substituent thereof.

For example, each of R1, R2, R3 and R4 is independently selected from the group consisting of hydrogen, deuterium, phenyl, carbazole, dibenzothiophene, dibenzofuran, tetraphenylsilane ), Pyridine, quinoline, isoquinoline, pyrimidine, diphenyl phosphine oxide, and substituents therefor.

 At least one of R 1, R 2, R 3 and R 4 is selected from deuterium, an aromatic compound, a heteroaromatic compound, a silicon compound, a phosphoryl compound, and a substituent thereof.

For example, each of R 1, R 2, R 3 and R 4 in Formula 2 may independently be any of a plurality of materials represented by Formula 3 below.

(3)

For example, the material of Formula 2 may be any of a number of materials represented by Formula 4 below.

The phosphorescent compound represented by the formula (2) has higher triplet energy than the dopant as described below to prevent a decrease in luminous efficiency. In addition, since the difference between the singlet energy and the triplet energy is small, the carrier injection is easy and the light efficiency characteristic of the device is improved.

Hereinafter, synthesis examples of phosphorescent compounds represented by A-1, A-2 and A-3 of the following general formula (5) in the phosphorescent compound according to the present invention will be described.

1. First Synthesis Example (A-1)

(1) Synthesis of 6-bromo-9- (6-bromopyridin-3-yl) -9H-pyrido [2,3-b]

Scheme 1

2-bromo-5-iodopyridine (20.3 mmol) and CuI (6 mmol) were added to a 250 mL two-neck flask. ), K3PO4 (40.6 mmol) and trans-1,2-diaminocyclohexane (6 mmol) were dissolved in 100 mL of 1,4-dioxane, and the mixture was refluxed and stirred for 24 hours. After completion of the reaction, 1,4-dioxane was distilled off under reduced pressure. After extraction with dichloromethane and water, distillation under reduced pressure, silica gel column was followed by distillation of the solvent under reduced pressure. 6-bromo-9- (6-bromopyridin-3-yl) -9H-pyrido [2,3-b] indole was obtained as a white powder by recrystallization and filtration using dichloromethane and petroleum ether. g.

(2) 9- (6- (9H-carbazol-9-yl) pyridin-3-yl)

(9H-carbazol-9-yl) -9H-pyrido [2,3-b] indole (A-1)

Scheme 2

1 g (2.48 mmol) of 6-bromo-9- (6-bromopyridin-3-yl) -9H-pyrido [2,3-b] indole with carbazole (5.46 mmol), K3PO4 (1.4 mmol) of trans-1,2-cyclohexanediamine (1.4 mmol), and 50 ml of 1,4-dioxane, and the mixture was refluxed under a nitrogen atmosphere for 24 hours. After completion of the reaction, 1,4-dioxane was distilled off under reduced pressure. Dichloromethane and water were used for extraction, and then vacuum distillation. The silica gel column was distilled off under reduced pressure. 9H-carbazol-9-yl) pyridin-3-yl) -6- (9H-carbazol-9-yl) -9H-pyrido [2,3-b] indole.

2. Second Synthesis Example (A-2)

(1) Synthesis of 6- (9H-carbazol-9-yl) -9H-pyrido [2,3-b]

Scheme 3

(5 g, 20.3 mmol), carbazole (20.3 mmol), CuI (6 mmol), K3PO4 (40.6 mmol), trans-1, 2-diaminocyclohexane (6 mmol) was added, dissolved in 100 mL of 1,4-dioxane, refluxed and stirred for 24 hours. After completion of the reaction, 1,4-dioxane was distilled off under reduced pressure. After extraction with dichloromethane and water, distillation under reduced pressure, silica gel column was followed by distillation of the solvent under reduced pressure. Then, recrystallization was performed using dichloromethane and petroleum ether, and filtration was conducted to obtain 5.5 g of 6- (9H-carbazol-9-yl) -9H-pyrido [2,3-b] indole.

(2) 9- (6- (9H-carbazol-9-yl) -9H-pyrido [2,3- b] indol-9- yl) pyridin-

(9H-carbazol-9-yl) -9H-pyrido [2,3-b] indole (A-2)

Scheme 4

(6 mmol), 2,5-diiodopyridine (3 mmol), K3PO4 (9 mmol) and CuI (1.8 mmol) were added to a 100 ml two-necked flask. ), and trans-1,2-cyclohexanediamine (1.8 mmol) of 1,4-dioxane were placed, and the mixture was refluxed under a nitrogen atmosphere for 24 hours. After completion of the reaction, 1,4-dioxane was distilled off under reduced pressure. Dichloromethane and water were used for extraction, and then vacuum distillation. The silica gel column was distilled off under reduced pressure. 9-yl) -9H-pyrido [2,3-b] indol-9-yl) pyridin-3-yl] -methanone as a white powder was obtained by recrystallization using dichloromethane and petroleum ether. 3-yl) -6- (9H-carbazol-9-yl) -9H-pyrido [2,3-b] indole.

3. Third synthetic example (A-3)

(1) Synthesis of 9- (6-bromopyridin-3-yl) -6- (9H-carbazol-9-yl) -9H-pyrido [2,3-b]

Scheme 5

(5 g, 15 mmol), 2-bromo-5-iodopyridine (15 mmol) and CuI (5 mmol) were added to a 250 mL two- 4.5 mmol), K3PO4 (30 mmol), and trans-1,2-diaminocyclohexane (4.5 mmol) were added to the solution, and the solution was dissolved in 100 mL of 1,4-dioxane. The mixture was refluxed for 24 hours and stirred. After completion of the reaction, 1,4-dioxane was distilled off under reduced pressure. After extraction with dichloromethane and water, distillation under reduced pressure, silica gel column was followed by distillation of the solvent under reduced pressure. 9-yl) -9H-pyrido [2,3-b] indole was obtained in a yield of 6.5% g.

(2) 9- (6- (3- (9H-carbazol-9-yl) -9H-carbazol-9- yl) pyridin-

    (9H-carbazol-9-yl) -9H-pyrido [2,3-b] indole (A-3)

Scheme 6

1.5 g (3 mmol) of 9- (6-bromopyridin-3-yl) -6- (9H-carbazol-9-yl) -9H- (3 mmol), CuI (0.9 mmol), K3PO4 (6.1 mmol) and trans-1,2-cyclohexanediamine (0.9 mmol) 1,4-dioxane were placed, Lt; / RTI > After completion of the reaction, 1,4-dioxane was distilled off under reduced pressure. Dichloromethane and water were used for extraction, and then vacuum distillation. The silica gel column was distilled off under reduced pressure. 9-yl) -9H-carbazol-9-yl) pyridin-3-yl) -6- ( 9H-carbazol-9-yl) -9H-pyrido [2,3-b] indole.

The UV spectrum and the room temperature (RT) and low temperature (LT) PL (photoluminescence) spectra of the phosphorescent compounds A-1, A-2 and A-3 are shown in FIGS. 2A, 2B and 2C. The characteristics of the conventional phosphorescent compound CBP and the phosphorescent compounds A-1, A-2 and A-3 of the present invention are shown in Table 1.

HOMO (eV) LUMO (eV) Band gap energy (eV) ΔE _ST E _T (eV) CBP -6.0 -2.5 3.5 0.9 2.6 A-1 -5.7 -2.2 3.5 0.54 2.96 A-2 -5.8 -2.35 3.45 0.52 2.93 A-3 -5.71 -2.21 3.5 0.54 2.94

As shown in Table 1, the phosphorescent compound of the present invention has a higher triplet energy (E _T ) than the conventional phosphorescent compound CBP. Further, since the difference (DELTA _EST ) between the triplet energy and the singlet energy is small, the entry barrier of the carrier is lowered and the voltage characteristic is improved.

Hereinafter, the phosphorescent compound according to the present invention and the performance of the organic light emitting diode device using the phosphorescent compound according to the present invention will be described in comparison with Experimental Example 1, Experimental Example 2 and Comparative Example in which an organic light emitting diode device is manufactured using the phosphorescent compound of the present invention do.

Experimental Example 1

The ITO layer was patterned to have a light emitting area of 3 mm x 3 mm on the substrate and then cleaned. The pressure in the vacuum chamber of about 1 * 10 HAT-CN ^-6 torr in the state on the ITO layer (hexaazatriphenylene-hexacarbonitirile, 50Å), NPB (550Å), TAPC (di- (4- (N, N'-ditolyl -amino) -phenyl) cyclohexane, 100A), host A-1 + dopant FCNIr (15%) (300A), TmPyPB (1,3,5- 400 Å), LiF (5 Å), and Al (1000 Å).

Experimental Example 2

The device was formed with the same composition except for the experiment 1 and the host, and the A-3 compound was used as a host.

Comparative Example

The device was formed with the same constitution except that in Experimental Example 1 and the host, and mCP represented by the following Formula 5 was used as a host.

Formula 5

The experimental results of the above-described Experimental Examples 1 and 2 and Comparative Examples are shown in Table 1 below.

V J (mA / cm ² ) Quantum efficiency (%) Cd / A Lm / W CIE (x) CIE (y) Comparative Example 6.05 10 7.7 13.5 7.13 0.156 0.285 Experimental Example 1 4.9 10 13.5 21 13.5 0.157 0.250 Experimental Example 2 4.82 10 11 18.7 12.2 0.158 0.253

As can be seen from Table 2, the organic light emitting diode device using the phosphorescent compound of the present invention has characteristics superior to the organic light emitting diode device using mCP, which is a conventional phosphorescent compound, in terms of luminous efficiency, driving voltage, and color.

An embodiment of an organic light-emitting diode device including the phosphorescent compound is shown in FIG.

As shown, the organic light emitting diode device includes first and second substrates (not shown) facing each other, and an organic light emitting diode (E) formed between the first and second substrates (not shown) .

The organic light emitting diode E includes a first electrode 110 serving as an anode, a second electrode 130 serving as a cathode, and an organic emission layer 120 formed between the first and second electrodes 110 and 130. [ ).

The first electrode 110 is made of a relatively high work function material such as indium-tin-oxide (ITO), and the second electrode 130 is made of a material having a relatively low work function value, For example, aluminum (Al) or an aluminum alloy (AlNd). In addition, the organic light emitting layer 120 has red, green, and blue organic light emission patterns.

The organic light emitting layer 120 may include a hole injection layer (HTL) 121, a hole transporting layer (HIL) 121, and a hole transporting layer (HIL) 121 sequentially from the first electrode 110 in order to maximize luminous efficiency. An emission layer 122, an emitting material layer (EML) 123, an electron transporting layer 124, and an electron injection layer 125.

At least one of the light emitting material layer 123, the hole transporting layer 122, and the electron transporting layer 124 includes the phosphorescent material according to the present invention.

For example, when the light emitting material layer 123 includes the phosphorescent material of the present invention as a host material, a dopant is added in an amount of about 1 to 30 wt% to emit blue light. At this time, since the phosphorescent material has a triplet energy of 2.9 eV or more, which is larger than that of the dopant, the occurrence of the energy reversal phenomenon from the host material to the dopant is prevented. Further, since the difference (DELTA _EST ) between the triplet energy and the singlet energy is small, the entry barrier of the carrier is lowered and the voltage characteristic is improved.

When the hole transport layer 122 or the electron transport layer 124 is made of the phosphorescent material of the present invention, the phosphorescent material has triplet energy greater than the dopant of the light emitting material layer 123, 122 or the electron transporting layer 124 is prevented from occurring. Therefore, the organic light emitting diode device has an advantage that the energy efficiency of the organic light emitting diode device can be prevented from being lowered.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It can be understood that

110: first electrode 120: organic light emitting layer
121: Hole injection layer 122: Hole transport layer
123: luminescent material layer 124: electron transport layer
125: electron injection layer 130: second electrode

Claims (6)

A phosphorescent compound represented by the following formula:

Wherein each of X1, X2, Y1, Y2, Z1 and Z2 is independently carbon or nitrogen and at least one of them is nitrogen and each of R1, R2, R3 and R4 is independently hydrogen, deuterium, C13, heteroaromatic compounds, silicone compounds, phosphoryl compounds, and substituents thereof).
The method according to claim 1,
Each of R1, R2, R3 and R4 is independently selected from the group consisting of hydrogen, deuterium, phenyl, carbazole, dibenzothiophene, dibenzofuran, tetraphenylsilane, wherein the phosphorescent compound is selected from the group consisting of pyridine, quinoline, isoquinoline, pyrimidine, diphenyl phosphine oxide, and their substituents.
The method according to claim 1,
Wherein at least one of R1, R2, R3, and R4 is selected from deuterium, an aromatic compound, a heteroaromatic compound, a silicone compound, a phosphoryl compound, and a substituent thereof.
A first electrode;
A second electrode facing the first electrode;
A light emitting material layer disposed between the first and second electrodes;
A hole transport layer disposed between the first electrode and the light emitting material layer;
And an electron transport layer disposed between the second electrode and the light emitting material layer,
Wherein at least one of the light emitting material layer, the hole transporting layer, and the electron transporting layer comprises a phosphorescent compound represented by the following formula.

Wherein each of X1, X2, Y1, Y2, Z1 and Z2 is independently carbon or nitrogen and at least one of them is nitrogen and each of R1, R2, R3 and R4 is independently hydrogen, deuterium, C13, heteroaromatic compounds, silicone compounds, phosphoryl compounds, and substituents thereof).
5. The method of claim 4,
Each of R1, R2, R3 and R4 is independently selected from the group consisting of hydrogen, deuterium, phenyl, carbazole, dibenzothiophene, dibenzofuran, tetraphenylsilane, wherein the organic light emitting diode is selected from the group consisting of pyridine, quinoline, isoquinoline, pyrimidine, diphenyl phosphine oxide, and substituents thereof.
5. The method of claim 4,
Wherein at least one of R 1, R 2, R 3 and R 4 is selected from deuterium, an aromatic compound, a heteroaromatic compound, a silicon compound, a phosphoryl compound, and a substitution product thereof.

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