KR20070016298A - Organin Host Materials And Organic Electroluminescent Device using this material - Google Patents

Abstract

The present invention relates to an organic host material and an organic electroluminescent device using the same, wherein the organic electroluminescent device includes an anode, a hole transport layer made of an organic compound, an emission layer made of an organic compound, an electron transport layer made of an organic compound, and a cathode stacked therein. Structure. The light emitting layer is composed of an organic host material of phosphorus organic guest material and an aluminum chelate complex including a naphthalene auxiliary ligand and a novel quinoline main ligand, and when applied to an organic electroluminescent device, the light emitting layer exhibits long life, high efficiency and high brightness characteristics, low voltage driving and An organic electroluminescent device having improved device stability can be provided.

Naphthalene, quinolene, aluminum, organic host, organic electroluminescent device

Description

Organic host materials and organic electroluminescent device using this material

1 and 2 are schematic cross-sectional views of an organic light emitting diode according to an embodiment of the present invention.

<Description of Signs of Major Parts of Drawings>

11, 21: transparent electrode (anode) 12, 22: hole injection layer

13, 23: hole transport layer 14, 24: light emitting layer

15, 25: electron transport layer 16, 26: electron injection layer

17, 27: metal electrode (cathode) 28, 38: hole blocking layer

3 is a graph showing voltage-luminance characteristics of the organic light emitting diode according to the embodiment of the present invention.

4 is a graph showing voltage-efficiency characteristics of an organic light emitting diode according to an embodiment of the present invention.

The present invention relates to an organic host material and an organic electroluminescent device using the same, wherein the organic electroluminescent device includes an anode, a hole transport layer made of an organic compound, an emission layer made of an organic compound, an electron transport layer made of an organic compound, and a cathode stacked therein. Structure. The light emitting layer is composed of an organic host material of phosphorus organic guest material and an aluminum chelate complex including a naphthalene auxiliary ligand and a novel quinoline main ligand, and when applied to an organic electroluminescent device, the light emitting layer exhibits long life, high efficiency and high brightness characteristics, low voltage driving and An organic electroluminescent device having improved device stability can be provided.

Recently, the flat panel display device plays a very important role as a device supporting a highly visual information society based on the Internet, which is rapidly growing.

In particular, an organic electroluminescent device (organic EL device) capable of low voltage driving with a self-emission type has an excellent viewing angle and contrast ratio compared to a liquid crystal display (LCD), which is a mainstream of flat panel display devices. It is light and thin because no backlight is required, and it is advantageous in terms of power consumption. In addition, the fast response speed and wide color reproduction range have attracted attention as a next generation display device.

In general, an organic EL device is formed on a glass substrate in order of an anode made of a transparent electrode, an organic thin film including a light emitting region, and a metal electrode. In this case, the organic thin film may include a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), or an electron injection layer (EML) in addition to the light emitting layer (EML). Electron Injection Layer (EIL), and may include an electron blocking layer (EBL) or a hole blocking layer (HBL) due to the light emission characteristics of the light emitting layer.

When an electric field is applied to the organic EL device having such a structure, holes are injected from the anode, electrons are injected from the cathode, and holes and electrons are recombined in the light emitting layer through the hole transport layer and the electron transport layer, respectively, thereby emitting excitons. ). The formed light exciton emits light as it transitions to ground states. At this time, the excitons are formed in the opposite direction of the spin direction, that is, the singlet state and the spin direction of the same direction, that is, 25%, and 75% of the triplet state, respectively.

Among the above-mentioned exciton states, the use of a singlet state for luminescence is called fluorescence, and the use of a triplet state generated at a rate of 75% for luminescence is called phosphescence. In some cases, the singlet excited excitons can be transferred to the triplet state by spin-orbit coupling (intersystem crossing), so that the phosphorescent material is theoretically used for organic electroluminescent devices. All 100% excitons can be used for light emission, making it possible to manufacture devices with high efficiency.

Recently, research has been actively conducted to apply not only fluorescent light emitting materials but also phosphorescent light emitting materials to light emitting layers of organic EL devices (DF O'Brien and MA Baldo et al. "Improved energy transfer in electrophosphorescent devices" Applied Physics Letter Vol 74 No. 3, pp 442-444, Jan. 18, 1999; MA Baldo et al. "Very high-efficiency green organic light-emitting devices based on electrophosphorescence" Applied Physics letters Vol. 75 No. 1, pp 4- 6, Jul. 5, 1999).

However, in such phosphorescence emission, since the triplet excitons cannot directly transition to the ground state (spin forbidden), the process of transition to the ground state after the flipping of the electron spin proceeds, so that the phosphorescence is longer than the fluorescence Has a characteristic of long life.

That is, the emission duration corresponds to several nanoseconds in the case of fluorescent emission, and the phosphorescence emission corresponds to several micro seconds in a relatively long time. The long duration of light emission causes various problems when phosphorescence is applied to an organic light emitting device, and a representative problem is triplet-triplet annihilation. In order to minimize the triplet-triplet quenching phenomenon, the recombination area, that is, the light emitting area should be maximized, and the light emitting time of the light emitting body should be minimized. The density can be increased.

Therefore, the organic light emitting host uses a material having a relatively large light emitting area, that is, a material having a large hole-diffusion phenomenon, and thus, the use of a host material that can minimize the triplet-triplet elimination phenomenon by increasing the emission area Typical and representative substance is CBP (4,4-N, N'-dicarbazolebiphenyl). However, since these materials have a large hole flow phenomenon, in order to maximize efficiency, a hole blocking layer is additionally inserted into the device structure, thereby shortening the life of the device.

In the case of an electrophosphorescent device, in order to obtain high luminous efficiency, the selection of an organic host material has a direct effect.

Since the phosphor emits from the triplet, the triplet energy of the host must be greater than the triplet energy of the phosphor in order for the triplet energy transfer from the host to the guest phosphor to occur effectively.

In general, triplet energy is about 1 eV lower than singlet energy, so the host occupied molecular orbital (HOMO) -lowest unoccupied molecular orbital (LUMO) has a larger host material than the fluorescent material. It is preferably used as a substance. When the triplet of the host is lower than the triplet energy of the phosphorescent dye, endothermic energy transfer should be used. In this case, the external luminous efficiency is relatively low while the triplet of the host is higher than the triplet energy of the phosphor. The exothermic energy transfer results in high quantum efficiency.

In order to realize such a high-efficiency, full-color organic EL device, it is required to introduce a new electron injection (transport) and hole injection (transport) layer or to develop a new material having excellent luminous efficiency.

Accordingly, the inventors of the present invention have made an effort to solve the above problems, and as a result, the organic compound layer formed by using an aluminum chelate complex containing a naphthalene ligand and a novel quinoline ligand as a host material and doped with a red phosphor is organic. When applied as a light emitting layer of an EL device, the host material has an appropriate hole flow phenomenon and a hole blocking ability, thereby minimizing triplet-triplet elimination phenomenon, and manufacturing a highly efficient phosphorescent EL device without additionally introducing a hole blocking layer. It has been found that the present invention has been completed.

Therefore, the present invention, when applied to the light emitting layer of the organic EL device, an organic host material that exhibits characteristics such as long life, high efficiency, high brightness, and can provide an organic electroluminescent device with improved low-voltage driving and stability and an organic electroluminescent device using the same The purpose is to provide.

The present invention features an organic host material which is an aluminum chelate complex comprising a naphthalene ligand and a novel quinoline ligand represented by the following formula (1).

<Formula 1>

In Formula 1, R ₁ to R ₂ is a hydrogen atom, a halogen atom, a substituted or unsubstituted C _1-18 alkyl group, a substituted or unsubstituted C _1-18 alkoxy group, an aromatic heterocyclic group and a substituted or unsubstituted It is selected from the aryl group of C _6-18 ring.

The present invention also includes an organic EL device comprising the aluminum chelate complex as an organic host material.

Hereinafter, the present invention will be described in detail.

The present invention uses the aluminum chelate complex containing a naphthalene ligand as an organic host material and forms a light emitting layer doped with a red phosphor, and then applies it to an organic electroluminescent device, thereby exhibiting long life, high efficiency and high brightness, and low voltage driving. And it is proposed to provide an organic EL device with improved stability of the device.

The organic host material of the present invention is an aluminum chelate complex represented by Formula 1, wherein R ₁ to R ₂ are hydrogen atoms, halogen atoms, substituted or unsubstituted C _1-18 alkyl groups, substituted or unsubstituted C _{1 ~ 18} alkoxy group, aromatic heterocyclic group and substituted or unsubstituted C _6-18 aryl group and the like can be used. Preferably, R ₁ and R ₂ is a hydrogen atom, phenyl, 4-alkyl In the case of a compound selected from the group consisting of phenyl, 1-naphthyl, 2-naphthyl, anthracenyl, and the like, more preferably, it is selected from the compounds represented by the following formulas 1a to 1d.

<Formula 1a>

<Formula 1b>

<Formula 1c>

<Formula 1d>

Compounds 1a to 1d are composed of two 8-hydroxyquinolidine derivative main ligands and one 1-hydroxylnaphthalene derivative as an auxiliary ligand. It was prepared by introducing into.

In addition, the present invention provides an organic EL device comprising the organic host material, the organic host material may be included in the light emitting layer.

That is, the anode, the cathode, and the two electrodes have a single organic layer (light emitting layer) including the aluminum chelate complex as a light emitting material or a multilayer structure with a charge transport layer, the anode, the organic thin film and the cathode are laminated in this order The organic EL device of the structure can be manufactured.

In general, a stacked device in which a light emitting layer and a charge transport layer are combined is superior to a single layer device having only a light emitting layer. This is because an appropriate combination of the light emitting material and the charge transport material reduces the energy barrier when charge is injected from the electrode, and the charge transport layer binds the holes or electrons injected from the electrode to the light emitting layer region to balance the number of holes and electrons injected. This is because it helps to achieve.

A schematic cross-sectional view of an organic EL device according to an embodiment of the present invention is shown in Figs.

The organic EL device shown in FIG. 1 includes transparent electrodes (anodes) 11 and 21, hole injection layers 12 and 22, hole transport layers 13 and 23, light emitting layers 14 and 24, and electron transport layers 15 and 25. ), The electron injection layers 16 and 26 and the metal electrodes (cathodes) 17 and 27 are sequentially stacked.

The organic EL device illustrated in FIG. 2 includes transparent electrodes (anodes) 11 and 21, hole injection layers 12 and 22, hole transport layers 13 and 23, light emitting layers 14 and 24, and hole blocking layers 28. The electron transport layers 15 and 25, the electron injection layers 16 and 26, and the metal electrodes (cathodes) 17 and 27 are sequentially stacked.

The transparent electrodes (anodes) 11 and 21 and the metal electrodes (cathodes) 17 and 27 are conventional electrode materials, for example, the transparent electrodes are made of indium tin oxide (ITO) or SnO ₂ , and the metal electrodes The metal may be made of a metal such as Li, Mg, Ca, Ag, Al, In, or an alloy thereof, and the metal electrode may have a single layer or a multilayer structure of two or more layers.

The light emitting layers 14 and 24 may be composed of a single layer or a multilayer of two or more layers including the compound of Formula 1 of the present invention, preferably the compounds of Formulas 1a to 1d, as organic host materials, and other organic host materials. Specifically, for example, CBP, which is a representative organic host material represented by the following Chemical Formula 2, may be configured by stacking a single layer or a multilayer of two or more layers.

<Formula 2>

The compound of formula 1 of the present invention, preferably the compounds of formulas 1a to 1d, may be used alone in the light emitting layer, and in particular may be used in combination with a red phosphorescent dopant. As a compound proposed by the applicant, for example, it may be used in combination with a red phosphorescent dopant well known in the art represented by the following general formula (3).

<Formula 3>

The hole transport layers 13 and 23 are conventional hole transport materials, for example 4,4-bis [N- (1-naphthyl) -N-phenyl-amine] biphenyl (α-NPD), N, N-diphenyl-N, N-bis (3-methylphenyl) -1,1-biphenyl-4,4-diamine (TPD) and poly- (N-vinylcarbazole) of formula 5 (PVCz) These may be constituted alone or in combination of two or more thereof, or may be two or more layers in which other layers are laminated.

<Formula 4>

<Formula 5>

The hole blocking layers 18 and 28 may have a LUMO value of 5.5 to 7.0, and may be composed of a material having excellent electron transport ability with a marked drop in hole transport capacity. Bathocuproine, BCP), 3- (4-biphenylyl) -4-phenyl-5- (4-t-butylphenyl) -1,2,4-triazole (TAZ) of formula 7, and Bis (8-hydroxy-2-methylquinolinato) -aluminum biphenoxide (BAlq) is suitable.

<Formula 6>

<Formula 7>

<Formula 8>

The electron transporting layers (electron transporting emissive layers) 15 and 25 are conventional electron transporting materials, for example, tris (8-quinolinolato) aluminum (Alq3), rubrene, etc. alone or in combination of two or more. It may be configured, and may be two or more layers in which other layers are laminated.

In addition, in order to improve device characteristics such as efficiency and lifespan, a conventional copper phthalocyanine (CuPc) is included between the anodes 11 and 21 and the hole transport layers 13 and 23 as necessary. Hole injection layers 12 and 22 may be inserted, and conventional electron injection layers 16 and 26 including, for example, LiF may be inserted between cathodes 17 and 27 and electron transport layers 15 and 25. can do.

The positive electrode, the negative electrode, and various organic thin films may be formed by conventional deposition methods well known in the art.

The organic EL device using the aluminum chelate complex containing the naphthalene ligand of the present invention as an organic host material can be expected to greatly improve the lifespan and efficiency, low voltage driving and stability of the device.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

Preparation Example: Preparation of Organic Host Compound

Reference is made to the organic host compounds of Formulas 1a to 1d [1) Guang Wang, Fushun Liang, Zhiyuan Xie, Guangping Su, Lixiang Wang, Xiabin Jing, Fosong Wang, Synthetic Metal. 131 (2002) 1-5; (2) Y. Qiu, Y. Shao, D.Q. Zhang, X.Y. Hong, Jpn. J. Appl. Phys. 39 (2002) 1151, according to the known method described in Scheme 1 below.

<Scheme 1>

Under a nitrogen atmosphere, 3 g of triethylaluminum was added to a 50 mL toluene solution to dissolve the reaction vessel. 2.5 g of 1-hydroxynaphthalene was dissolved in 50 mL of toluene, slowly added to a reaction vessel, stirred for 1 hour, and 5.5 g of 5,7-diphenyl-8-hydroxyquinalidine was dissolved in 40 mL of toluene. Slowly added, stirred for 3 hours and then filtered.

The filtered solid was recrystallized in methylene chloride to obtain the final compound (Formula 1a).

Compounds of Formulas 1b to 1d according to the present invention were also prepared according to the method of Scheme 1 above.

Example 1:

Fabrication of Organic Electroluminescent Device Using Compound of Formula 1a as Host Material

A 150 nm ITO (Indium Tin Oxide) -coated glass substrate (Asahi Glass Co., Ltd., sheet resistance 8 Ω / cm 2) was ultrasonically washed with water-based detergent, ultrapure water, isopropyl alcohol, and methanol sequentially. The transparent electrodes 11 and 21 were produced.

Copper phthalocyanine (CuPc) was deposited on the transparent electrodes 11 and 21 to form the hole injection layers 12 and 22 at 20 nm, and thereafter, 4,4-bis [N− was formed on the hole injection layers 12 and 22. (1-naphthyl) -N-phenyl-amine] biphenyl (α-NPD) was deposited to form 20 nm hole transport layers 13 and 23.

Subsequently, the prepared organic host material of Formula 1a and the phosphorescent dopant material of Formula 3 were deposited on the hole transport layers 13 and 23 at a speed of 1 nm / sec using a weight ratio of 10: 1 to emit light layer 14 of 30 nm. , 24). After the vacuum deposition was completed, tris (8-quinolinolato) aluminum (Alq3) was deposited thereon to form electron transport layers 15 and 25 at 40 nm, and LiF was deposited to form an electron injection layer at 16 nm. , 26).

An organic EL device was fabricated by depositing Al on the electron injection layers 16 and 26 to form a cathode of 150 nm.

The organic EL device manufactured was [ITO transparent electrode (150 nm) / CuPc hole injection layer (20 nm) / α-NPD hole transport layer (40 nm) / light emitting layer (30 nm) / Alq3 consisting of a compound of Formula 1a and Formula 3 Electron transport layer (40 nm) / LiF electron injection layer (1 nm) / Al electrode (150 nm)] has a structure in which they are sequentially stacked from below, and a structural cross-sectional view thereof is shown in FIG.

Example 2:

Fabrication of Organic Electroluminescent Device Using Compound of Formula 1b as Host Material

Using the compound of Formula 1b as an organic host, an organic EL device was manufactured in the following structure.

A 150 nm ITO (Indium Tin Oxide) -coated glass substrate (Asahi Glass Co., Ltd., sheet resistance 8 Ω / cm 2) was ultrasonically washed with water-based detergent, ultrapure water, isopropyl alcohol, and methanol sequentially. The transparent electrodes 11 and 21 were produced.

Copper phthalocyanine (CuPc) was deposited on the transparent electrodes 11 and 21 to form the hole injection layers 12 and 22 at 20 nm, and thereafter, 4,4-bis [N− was formed on the hole injection layers 12 and 22. (1-naphthyl) -N-phenyl-amine] biphenyl (α-NPD) was deposited to form 20 nm hole transport layers 13 and 23.

Subsequently, the organic host material of Chemical Formula 1b and the phosphorescent dopant material of Chemical Formula 3 are deposited on the hole transport layers 13 and 23 at a speed of 1 nm / sec using a weight ratio of 10: 1 to emit light layer 14 of 30 nm. , 24). After the vacuum deposition was completed, tris (8-quinolinolato) aluminum (Alq3) was deposited thereon to form electron transport layers 15 and 25 at 40 nm, and LiF was deposited to form an electron injection layer at 16 nm. , 26).

An organic EL device was fabricated by depositing Al on the electron injection layers 16 and 26 to form a cathode of 150 nm.

The organic EL device manufactured was [ITO transparent electrode (150 nm) / CuPc hole injection layer (20 nm) / α-NPD hole transport layer (40 nm) / light emitting layer (30 nm) / Alq3 consisting of a compound of Formula 1b and Formula 3 Electron transport layer (40 nm) / LiF electron injection layer (1 nm) / Al electrode (150 nm)] has a structure in which they are sequentially stacked from below, and a structural cross-sectional view thereof is shown in FIG.

Example 3:

Fabrication of organic electroluminescent device using compound of formula 1c as host material

Using the compound of Formula 1c as an organic host, an organic EL device was manufactured in the following structure.

A 150 nm ITO (Indium Tin Oxide) -coated glass substrate (Asahi Glass Co., Ltd., sheet resistance 8 Ω / cm 2) was ultrasonically washed with water-based detergent, ultrapure water, isopropyl alcohol, and methanol sequentially. The transparent electrodes 11 and 21 were produced.

Copper phthalocyanine (CuPc) was deposited on the transparent electrodes 11 and 21 to form the hole injection layers 12 and 22 at 20 nm, and thereafter, 4,4-bis [N− was formed on the hole injection layers 12 and 22. (1-naphthyl) -N-phenyl-amine] biphenyl (α-NPD) was deposited to form 20 nm hole transport layers (13,23).

Subsequently, the organic host material of Chemical Formula 1c and the phosphorescent dopant material of Chemical Formula 3 were deposited on the hole transport layers 13 and 23 at a speed of 1 nm / sec using a weight ratio of 10: 1 to emit light layer 14 of 30 nm. , 24). After the vacuum deposition was completed, tris (8-quinolinolato) aluminum (Alq3) was deposited thereon to form electron transport layers 15 and 25 at 40 nm, and LiF was deposited to form an electron injection layer at 16 nm. , 26).

An organic EL device was fabricated by depositing Al on the electron injection layers 16 and 26 to form a cathode of 150 nm.

The organic EL device manufactured was [ITO transparent electrode (150 nm) / CuPc hole injection layer (20 nm) / α-NPD hole transport layer (40 nm) / light emitting layer (30 nm) / Alq3 consisting of the compound of Formula 1c and Formula 3 Electron transport layer (40 nm) / LiF electron injection layer (1 nm) / Al electrode (150 nm)] has a structure in which they are sequentially stacked from below, and a structural cross-sectional view thereof is shown in FIG.

Example 4:

Fabrication of organic electroluminescent device using compound of Formula 1d as host material

Using the compound of Formula 1d as an organic host, an organic EL device was manufactured in the following structure.

A 150 nm ITO (Indium Tin Oxide) -coated glass substrate (Asahi Glass Co., Ltd., sheet resistance 8 Ω / cm 2) was ultrasonically washed with water-based detergent, ultrapure water, isopropyl alcohol, and methanol sequentially. The transparent electrodes 11 and 21 were produced.

Copper phthalocyanine (CuPc) was deposited on the transparent electrodes 11 and 21 to form the hole injection layers 12 and 22 at 20 nm, and thereafter, 4,4-bis [N− was formed on the hole injection layers 12 and 22. (1-naphthyl) -N-phenyl-amine] biphenyl (α-NPD) was deposited to form 20 nm hole transport layers 13 and 23.

Subsequently, the organic host material of Chemical Formula 1d and the phosphorescent dopant material of Chemical Formula 3 were deposited on the hole transport layers 13 and 23 at a speed of 1 nm / sec using a weight ratio of 10: 1 to emit light layer 14 of 30 nm. , 24). After the vacuum deposition was completed, tris (8-quinolinolato) aluminum (Alq3) was deposited thereon to form electron transport layers 15 and 25 at 40 nm, and LiF was deposited to form an electron injection layer at 16 nm. , 26).

An organic EL device was fabricated by depositing Al on the electron injection layers 16 and 26 to form a cathode of 150 nm.

The organic EL device manufactured was [ITO transparent electrode (150 nm) / CuPc hole injection layer (20 nm) / α-NPD hole transport layer (40 nm) / light emitting layer (30 nm) / Alq3 consisting of the compound of Formula 1d and Formula 3 Electron transport layer (40 nm) / LiF electron injection layer (1 nm) / Al electrode (150 nm)] has a structure in which they are sequentially stacked from below, and a structural cross-sectional view thereof is shown in FIG.

TABLE 1

Host-Dopant @ 10,000 cd / m ² Voltage (V) Efficiency (cd / A) Color coordinates Example 1 13.0 7.6 0.67, 0.32 Example 2 12.7 7.3 0.67, 0.32 Example 3 14.0 6.1 0.67, 0.32 Example 4 12.5 6.9 0.67, 0.32

As described above, the host material using the aluminum chelate complex containing the naphthalene ligand and the novel quinoline ligand of the present invention greatly improves low voltage driving and efficiency of the device, and fabricates an organic EL device having greatly improved device stability and lifetime. This is possible.

Claims (6)

An organic host material comprising an aluminum chelate complex comprising a naphthalene ligand represented by Formula 1; <Formula 1>

In Formula 1, R ₁ and R ₂ are a hydrogen atom, a halogen atom, a substituted or unsubstituted C _1-18 alkyl group, a substituted or unsubstituted C _1-18 alkoxy group, aromatic heterocyclic group and substituted or unsubstituted It is selected from the aryl group of C _6-18 ring. The organic host of claim 1, wherein in Formula 1, R ₁ and R ₂ are compounds selected from a hydrogen atom, phenyl, 4-alkylated phenyl, 1-naphthyl, 2-naphthyl, and anthracenyl. matter. The organic host material of claim 1, wherein the aluminum chelate complex is a compound selected from Formulas 1a to 1d. <Formula 1a>

<Formula 1b>

<Formula 1c>

<Formula 1d>

An organic electroluminescent device comprising an organic host material selected from claims 1 to 3. The organic electroluminescent device according to claim 4, wherein the organic host material is included in a light emitting layer. The organic electroluminescent device according to claim 5, wherein the organic host material is included in a light emitting layer doped with a red phosphor.

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