KR101333610B1 - Phosphorescent material for Organic electroluminescent device - Google Patents

Abstract

Wherein each of X1, X2, X3, Y1, Y2, Y3, Z1, Z2 and Z3 is selected from carbon (C) or nitrogen (N), at least one of which is nitrogen, R2 and R3 are each independently selected from the group consisting of hydrogen (H), fluorine (F), chlorine (Cl), aliphatic compounds, aromatic compounds, alkylsilyl compounds, arylsilyl compounds, an aryloxy group, an alkyloxy group, an aryloxy group, an alkyl phosphoryl group, an alkyl sulfuryl group, an aryl sulfuryl group, an alkyl amino group, and an aryl amino group.
The

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphorescent material for an organic electroluminescent device,

The present invention relates to a phosphorescent material for an organic electroluminescent device, and more particularly to a phosphorescent material for an organic electroluminescent device having a high triplet energy.

An organic electroluminescent device is a device that injects electric charge into a light emitting material layer formed between an electron injecting electrode (cathode) and a hole injecting electrode (anode) to form an electron and a hole. Not only can the device be formed on a flexible transparent substrate such as a plastic but also has advantages in driving voltage and power consumption.

The organic electroluminescent device includes an anode, a hole injecting layer (HIL), a hole transporting layer (HTL), an emitting material layer (EML) An electron transporting layer (ETL), an electron injecting layer (EIL), and a cathode.

Here, a dopant is added to the light emitting material layer if necessary. For example, a red light emitting layer may be formed by depositing 4,4'-N, N'-dicarbazolbiphenyl (CBP) to a thickness of 30 nm to 60 nm, and bis (2-phenylquinoline) acetylacetonate iridium III) (Ir (phq) 2acac) is doped to about 5 to 10%.

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. Thus, a luminescent layer is formed together with the host material having higher thermal stability and higher triplet energy than the dopant.

In the light emitting process of an organic electroluminescent device including a phosphor, a hole injected from an anode and electrons injected from a cathode are encountered in a host material of the light emitting layer, and a single-excited exciton formed in the host is a single- Energy transition occurs, and the triplet exciton becomes 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.

At this time, for efficient energy transfer to the dopant, the triplet energy of the host material must be greater than the triplet energy of the dopant. However, referring to FIG. 1, since CBP, which is widely used as a host material, is less than the triplet energy of the well-known Firpic phosphorescent dopant since the triplet energy is 2.6 eV, an energy reverse transition phenomenon occurs from the host material to the dopant. Inefficient In particular, the reduction in efficiency occurs at a low temperature. Therefore, it is required to develop a novel phosphor having a triple energy of 2.6 eV or more and excellent thermal stability.

When the triplet energies of the hole transporting layer or the electron transporting layer adjacent to the front and rear of the light emitting material layer are smaller than the triplet energy of the dopant, the energy inversion occurs from the dopant or host to these layers, thereby significantly reducing the efficiency. Therefore, the triplet energy of the hole / electron transport layer material as well as the host material of the light emitting layer is a very important factor in the phosphorescent device.

The present invention provides a phosphorescent material having a triplet energy of 2.6 eV or more to prevent a problem of lowering the luminous efficiency of an organic electroluminescent device. In particular, the triplet energy of the host material is made higher than the triplet energy of the dopant to prevent the degradation of the luminous efficiency.

It is also possible to use a phosphorescent material having high triplet energy which can be used for a hole transporting layer or an electron transporting layer, thereby improving the efficiency of an organic electroluminescent device.

In order to solve the above problems, the present invention is represented by the following formula: wherein each of X1, X2, X3, Y1, Y2, Y3, Z1, Z2 and Z3 is selected from carbon (C) At least one of them is nitrogen and each of R1, R2 and R3 is selected from the group consisting of hydrogen (H), fluorine (F), chlorine (Cl), aliphatic compound, aromatic compound, alkylsilyl compound, an aryl silyl compound, an alkoxy compound, an aryloxy compound, an alkyl phosphoryl group, an alkyl sulfuryl group, an aryl sulfuryl group, an alkyl amino group, and an aryl amino group. do.

The

In addition, the present invention is represented by the following formula, each of X, Y, Z is selected from carbon (C) or nitrogen (N), at least one is nitrogen, each of R1, R2, R3, R4, R5 is hydrogen (H), fluorine (F), chlorine (Cl), aliphatic compound, aromatic compound, alkyl silyl compound, aryl silyl compound, alkoxy compound, aryloxy It provides a phosphorescent material for organic electroluminescent devices selected from (aryloxy) compounds, alkyl phosphoryl groups, alkyl sulfuryl groups, aryl sulfuryl groups, alkyl amino groups, aryl amino groups.

The

The aliphatic compound is characterized by containing C1 to C20 aryl and C1 to C20 alkyl.

The aromatic group material is characterized by including phenyl, naphthyl, biphenyl, terphenyl, and phenanthrenyl.

In another aspect, the present invention comprises a first electrode; A second electrode facing the first electrode; A light emitting material layer disposed between the first and second electrodes, wherein the light emitting material layer is represented by the following formula: X1, X2, X3, Y1, Y2, Y3, Z1, Z2, (C) or nitrogen (N), at least one of which is nitrogen and each of R1, R2 and R3 is selected from the group consisting of hydrogen (H), fluorine (F), chlorine (Cl), aliphatic compounds, An alkyl silyl compound, an aryl silyl compound, an alkoxy compound, an aryloxy compound, an alkyl phosphoryl group, an alkyl sulfuryl group, an aryl sulfuryl group, an alkyl amino group, an aryl amino group And a dopant having triplet energy smaller than that of the host material. The present invention also provides an organic electroluminescent device comprising the same.

The

According to another aspect of the present invention, A second electrode facing the first electrode; And a light emitting material layer disposed between the first and second electrodes, wherein the light emitting material layer is represented by the following formula: wherein each of X, Y and Z is selected from carbon (C) or nitrogen (N) At least one is nitrogen and each of R 1, R 2, R 3, R 4 and R 5 is independently selected from the group consisting of hydrogen (H), fluorine (F), chlorine (Cl), aliphatic compounds, aromatic compounds, alkylsilyl A host material selected from the group consisting of an aryl silyl compound, an alkoxy compound, an aryloxy compound, an alkyl phosphoryl group, an alkyl sulfuryl group, an aryl sulfuryl group, an alkyl amino group, And a dopant having triplet energy smaller than that of the host material.

The

A hole injection layer positioned between the first electrode and the light emitting material layer; A hole transport layer disposed between the hole injection layer and the light emitting material layer; An electron injection layer disposed between the light emitting material layer and the second electrode; And an electron transport layer disposed between the electron injection layer and the light emitting material layer, wherein at least one of the hole transport layer and the electron transport layer is made of the host material.

Since the phosphorescent material of the present invention has a triplet energy of 2.8 eV or more, the efficiency of the organic electroluminescent device can be increased.

Since the phosphorescent material of the present invention is used in the light emitting material layer and has a larger triplet energy of the dopant, the problem of lowering the luminous efficiency can be prevented.

In addition, by using the phosphorescent material of the present invention having triplet energy of 2.8 eV or more for the hole transporting layer or the electron transporting layer, the luminous efficiency of the organic electroluminescent device can be improved.

1 is a PL spectrum of CBP which is a host material for a conventional organic electroluminescent device.
2A and 2B are each a UV spectrum and a PL spectrum of the phosphor for an organic light emitting display device according to the first embodiment of the present invention.
3A and 3B are each a UV spectrum and a PL spectrum of the phosphor for an organic light emitting display device according to the second embodiment of the present invention.
4 is a schematic cross-sectional view of an organic light emitting display device according to an embodiment of the present invention.

Hereinafter, a structure of a phosphor for an organic electroluminescence device according to the present invention, a synthesis example thereof, and an organic electroluminescence device using the same will be described.

- First Embodiment -

The phosphor according to the first embodiment of the present invention has a structure in which a carboline group or a carbazole group is substituted at 1,3,5 positions of benzene, and at least one of them is represented by Formula 1 below.

Formula 1

In Formula 1, each of X1, X2, X3, Y1, Y2, Y3, Z1, Z2 and Z3 is selected from carbon (C) or nitrogen (N), and at least one of them is nitrogen. For example, α-carbolin when X1 = N and Y1 = Z1 = C, β-carbolin when Y1 = N, X1 = Z1 = C, and γ-carbolin to be.

Each of R 1, R 2 and R 3 in the above formula (1) may be independently selected from the group consisting of hydrogen (H), fluorine (F), chlorine (Cl), aliphatic compound, aromatic compound, alkylsilyl compound, an alkoxy group, an aryloxy group, an alkyl phosphoryl group, an alkyl sulfuryl group, an aryl sulfuryl group, an alkyl amino group, and an aryl amino group.

For example, the aliphatic compound may be a C1 to C20 aryl or a C1 to C20 alkyl group, and the aromatic group material may include phenyl, naphthyl, biphenyl, , Terphenyl, and phenanthrenyl.

For example, the phosphor represented by Formula 1 may be any one of a plurality of materials of Formula 2 below.

(2)

로 표시되는 본 발명의 제 1 실시예에 따른 유기전계발광소자용 인광 물질은 아래 제 1 합성예에 의해 얻어진다.In the formula (2)

The phosphorescent material for an organic electroluminescence device according to the first embodiment of the present invention is obtained by the following first synthesis example.

1st Synthetic example

1.Synthesis of N- (3,5-dibromopheny) -γ-carboline

N- (3,5-dibromopheny) -γ-carboline is synthesized by Scheme 1 below.

Scheme 1

Specifically, 1,3-dibromo-5-iodobenzen 5g (13.8mmole), γ-carboline 2.33g (13.8mmole), 50ml Dioxane, 0.2g CuI, 0.7ml trans-diaminocyclohexane, 6g K3PO4 It was refluxed for time. After completion of the reaction, the salt was removed by filtration, and 50 ml of water was added to the solution to obtain a precipitate. 3.0 g (yield 54%) of white powder was obtained by column chromatography using EA (ethylene acetate) as a developing solvent.

2. Phosphor Synthesis

The phosphor is synthesized by Scheme 2 below.

Scheme 2

Specifically, 2g (5mmole) of N- (3,5-dibromopheny) -γ-carboline, 1.87g (11mmole) of carbazole and 50ml of toluene, 0.1g of Pd2dba3, 0.23g of Xantphos, and 1.3g of Sodiumter-butoxide were added to a 100ml two-neck flask. It was refluxed for 12 hours. After completion of the reaction, the solvent was removed, washed with 50ml of water, and 0.95 g (yield 70%) of white powder was obtained by column chromatography using column chromatography using Acetone; Hexane = 1: 1.

Second embodiment

The phosphor according to the second embodiment of the present invention has a structure in which one carboline group and two diphenylamine groups are substituted at the 1,3,5 positions of benzene, and is represented by the following Chemical Formula 3.

(3)

In Formula 3, each of X, Y, and Z is selected from carbon (C) or nitrogen (N), at least one of which is nitrogen. For example,? -Carbolin when X = N and Y = Z = C,? -Carbolin when Y = N and X = Z = C, and? -Carbolin to be.

In addition, in Formula 3, R1, R2, R3, R4, and R5 each represent hydrogen (H), fluorine (F), chlorine (Cl), aliphatic compound, aromatic compound, alkyl silyl, and alkyl silyl. It is selected from a compound, an aryl silyl compound, an alkoxy compound, an aryloxy compound, an alkyl phosphoryl group, an alkyl sulfuryl group, an aryl sulfuryl group, an alkyl amino group, and an aryl amino group.

For example, the aliphatic compound may be a C1 to C20 aryl or a C1 to C20 alkyl group, and the aromatic group material may include phenyl, naphthyl, biphenyl, , Terphenyl, and phenanthrenyl.

For example, the phosphor represented by Formula 3 may be any one of a plurality of materials of Formula 4 below.

Formula 4

로 표시되는 본 발명의 제 2 실시예에 따른 유기전계발광소자용 인광 물질은 아래 제 2 합성예에 의해 얻어진다.In the formula (4)

The phosphorescent material for an organic electroluminescence device according to the second embodiment of the present invention is obtained by the following second synthesis example.

Second Synthetic example

1.Synthesis of N- (3,5-dibromopheny) -γ-carboline

N- (3,5-dibromopheny) -γ-carboline is synthesized by Scheme 3 below.

Scheme 3

Specifically, 1,3-dibromo-5-iodobenzen 5g (13.8mmole), γ-carboline 2.33g (13.8mmole), 50ml Dioxane, 0.2g CuI, 0.7ml trans-diaminocyclohexane, 6g K3PO4 It was refluxed for time. After completion of the reaction, the salt was removed by filtration, and 50 ml of water was added to the solution to obtain a precipitate. 3.0 g (yield 54%) of white powder was obtained by column chromatography using EA (ethylene acetate) as a developing solvent.

2. Synthesis of Phosphors

The phosphor is synthesized by Scheme 4 below.

Scheme 4

Specifically, 2g (5mmole) of N- (3,5-dibromopheny) -γ-carboline, 1.87g (11mmole) of diphenylamine and 50ml of toluene, 0.1g of Pd2dba3, 0.23g of Xantphos, and 1.3g of Sodiumter-butoxide were added to a 100ml two-neck flask. It was refluxed for 12 hours. After completion of the reaction, the solvent was removed, washed with 50 ml of water, and 1.1 g (yield 75%) of white powder was obtained by column chromatography using Acetone; Hexane = 1: 3 as a developing solvent.

로 표시된 본 발명의 인광물질에 대하여 UV 흡수 스펙트럼과 상온/저온(77K)에서의 PL(photoluminescence) 스펙트럼을 측정하여 도 2a 및 도 2b에 나타내었다. 또한, 상기 화학식4에서

로 표시된 본 발명의 인광물질에 대하여 UV 흡수 스펙트럼과 상온/저온(77K)에서의 PL(photoluminescence) 스펙트럼을 측정하여 도 3a 및 도 3b에 나타내었다.In the formula (2)

For the phosphor of the present invention, the UV absorption spectrum and the PL (photoluminescence) spectrum at room temperature / low temperature (77K) were measured and shown in FIGS. 2A and 2B. In addition, in Formula 4

For the phosphor of the present invention, the UV absorption spectrum and the PL (photoluminescence) spectrum at room temperature / low temperature (77K) were measured and shown in FIGS. 3A and 3B.

As shown in FIGS. 2A, 2B, 3A, and 3B, the phosphor of the present invention has a triplet energy of at least 2.8 eV and a singlet energy of at least 3.3 eV. Therefore, it has higher triplet energy than CBP used as a host material of the conventional light emitting material layer, and is larger than 2.7 eV, which is the triplet energy of the commonly used dopant, so that the energy transfer from the host material to the dopant is prevented can do. Therefore, the light emitting efficiency is improved.

In addition, since the phosphorescent material of the present invention has triplet energy higher than that of the dopant, the phosphorescent material of the present invention can be used as a hole transporting layer or an electron transporting layer, and it is possible to prevent the occurrence of energy reversal from a dopant to a hole transporting layer or an electron transporting layer.

An embodiment of an organic light emitting display device including the phosphor is illustrated in FIG. 4.

As shown, the organic electroluminescent 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 includes red, green, and blue organic light emitting 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.

Here, at least one of the light emitting material layer 123, the hole transport layer 122 and the electron transport layer 124 comprises the phosphor material of the present invention represented by any one of the formula (1) and (2).

For example, when the light emitting material layer 123 includes the phosphorescent material of the present invention as a host material, about 1 to 10 wt% dopant is added. At this time, since the phosphorescent material has a triplet energy of 2.8 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. Therefore, the luminous efficiency can be increased. For example, the dopant may be FIrpic (iridum-bis (4,6-difluorophenylpyridinato-N, C2) -picolinate).

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 a triplet energy of 2.8 eV or more, which is larger than the dopant of the light emitting material layer 123, Is prevented. Therefore, the organic electroluminescent device has an advantage that the energy efficiency of the organic electroluminescent device can be prevented from lowering.

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 (7)

delete Represented by the following formula, each of X, Y, Z is selected from carbon (C) or nitrogen (N), at least one of which is nitrogen, and each of R1, R2, R3, R4, R5 is hydrogen (H), fluorine (F), chlorine (Cl), aliphatic compound, aromatic compound, alkyl silyl compound, aryl silyl compound, alkoxy compound, aryloxy compound, For organic electroluminescent devices selected from alkyl phosphoryl group, alkyl sulfuryl group, aryl sulfuryl group, alkyl amino group, aryl amino group phosphor.
The

The method of claim 2,
Wherein the aliphatic compound comprises a C1 to C20 alkyl.
The method of claim 2,
Wherein the aromatic group material includes phenyl, naphthyl, biphenyl, terphenyl, and phenanthrenyl. 2. The phosphorescent material according to claim 1, wherein the aromatic group material is selected from the group consisting of phenyl, naphthyl, biphenyl, terphenyl and phenanthrenyl.
delete A first electrode;
A second electrode facing the first electrode;
A light emitting material layer positioned between the first and second electrodes,
The light emitting material layer is represented by the following formula, each of X, Y, Z is selected from carbon (C) or nitrogen (N), at least one is nitrogen, each of R1, R2, R3, R4, R5 is hydrogen (H), fluorine (F), chlorine (Cl), aliphatic compound, aromatic compound, alkyl silyl compound, aryl silyl compound, alkoxy compound, aryloxy (aryloxy) compound, an alkyl phosphoryl group, an alkyl sulfuryl group, an aryl sulfuryl group, an alkyl amino group, an alkyl amino group, an aryl amino group selected from An organic light emitting display device comprising: a host material and a dopant having a triplet energy smaller than that of the host material.
The

The method according to claim 6,
A hole injection layer positioned between the first electrode and the light emitting material layer;
A hole transport layer disposed between the hole injection layer and the light emitting material layer;
An electron injection layer disposed between the light emitting material layer and the second electrode;
And an electron transport layer disposed between the electron injection layer and the light emitting material layer,
Wherein at least one of the hole transporting layer and the electron transporting layer is made of the host material.

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