WO1998037736A1

WO1998037736A1 - Organometallic complexes for use in electroluminescent devices

Info

Publication number: WO1998037736A1
Application number: PCT/KR1997/000134
Authority: WO
Inventors: Sewhan Son; Kong Keum Kim; Hyo-Seok Kim; Okhee Kim; Seokhee Yoon
Original assignee: Lg Chemical Ltd.
Priority date: 1997-02-22
Filing date: 1997-07-08
Publication date: 1998-08-27
Also published as: KR100259398B1; EP0897652A1; JP2000515926A; TW373211B; KR19980071472A

Abstract

The present invention provides an electron injecting material, being capable of driving with a lower drive voltage and having an improved efficiency in power conversion, for use in an organic electroluminescent device. In order to accomplish the technical features of the present invention, the organic electroluminescent device in accordance with the present invention comprises an anode, a cathode electrode, and an organic film layer formed between the anode and cathode electrodes, wherein the organic film layer is made of an organometallic complex represented by formula (1), wherein R1 to R8 represents hydrogen or C1 to C8 alkyl groups, independently.

Description

ORGANOMETALLIC COMPLEXES FOR USE IN ELECTROLUMINESCENT DEVICES

BACKGROUND OF INVENTION

Field of the Invention

The present invention relates to an electron injecting material for use in organic electroluminescence devices. More particularly, the present invention relates to an electron injecting material, being capable of driving with a lower drive voltage and having an improved efficiency in power conversion, for use in an organic electroluminescent device. In order to accomplish the technical features of the present invention, the organic electroluminescent device in accordance with the present invention comprises an anode electrode, a cathode electrode, and an organic film layer formed between the anode and cathode electrodes, wherein the organic film layer is made of a 2-(0-hydroxyphenyl)benzthiazole beryllium complex.

Description of the Related Art

Early attempts for fabricating an efficient organic electroluminescence device (hereinafter referred to as "EL device") comprising in the order of an anode, an electroluminescent layer and a cathode have not been successful due to the difficulty of injecting carriers from opposite electrodes into the electroluminescent layer containing organic dye molecules. To fabricate an efficient organic EL device, it is desirable that the organic dye molecules should have the capability of accepting carriers from the electrodes and the high mobility of the carriers inside the electroluminescent layer. In addition, it is also desirable that the recombination zone of the carriers should be located away from the electrodes to prevent occurrences of exciton quenching by the metallic electrodes.

In order to solve the problems in prior art, U.S. Patent No. 4,539,507 granted to Steven A. VanSlyke et al., issued on Sep. 3, 1985 teaches a device having two layers which comprises in the order of anode/hole transporting layer/electron transporting layer/cathode. In the organic EL device disclosed in the above-referenced patent, a triphenylamine-containing compound and an aluminum complex of 8-hydroxyquinoline are used as the hole transporting material and the electron transporting material respectively, wherein the latter also functions as an emitting layer of the device. Facile injection of carriers and high mobility of holes and electrons in the two-layer EL device makes the driving voltage to be lowered. Further, formation of the recombination zone near the interface of the transporting layer but away from the cathode caused by a lower mobility of holes, in the electron transporting layer, compared with that of electrons has reduced the probability of occurring the exciton quenching by the metallic cathode. As a result, the power conversion efficiency of the organic EL device has improved up to 1.5 lm/W and hundreds of cd/m in brightness thereof has been obtained at a voltage of less than 10 V.

U.S. Patent No. 4,539,507 also teaches an organic EL device having an improved durability and a higher efficiency than the two-layer device, being fabricated by interposing a hole injecting layer containing a metal phthalocyanine between an anode and a hole transporting layer. Enhancing the carrier injection is therefore considered one of the important factors for the improvement of EL devices.

More recently improvements in uniformity in light emission and its efficiency have also made in an organic EL device with an adhesive layer being located in contact with the cathode (see U.S. Patent No. 5,516,577, granted to Masahide Matsuura, et al., issued on May 14, 1996). In the Matsuura's device, the adhesive layer is composed of a metal complex of 8-hydroxyquinoline or a derivative thereof which is contaminated by adding a small amount of additional compounds to prevent it from crystallization. Therefore the morphologically stabilized adhesive layer provides the device with a uniform light emission and durability thereof. Moreover, the energy level of the lowest unoccupied molecular orbital (hereinafter referred to as "LUMO") of the metal complex of 8-hydroxyquinoline is located below that of another emissive molecules which are in contact with the adhesive layer in a device comprising in the order of anode/hole injecting layer/hole transporting layer/emitting layer/adhesive layer/cathode to ensure the facile electron injection from the cathode.

In general, injecting electrons with ease into the electron transporting layer from the cathode strongly influences the power conversion efficiency of the organic EL device. Therefore an intensive investigation has been performed in order to reduce the injection barrier of electrons by lowering the work function of the cathode to match the LUMO level of the electron transporting layer. It is well known that an alloy of Mg-Ag or Al÷Li is one of the most desirable cathode materials for this purpose. However, a metal having low work function shows poor environmental stability, which resultingly slows down further study for improvement of the cathode material.

A number of organometallic materials capable of transporting electrons have been disclosed to be useful for the fabrication of organic EL devices in prior arts (see U.S. Pat. No. 5,466,392; U.S. Pat. No. 5,150,006; U.S. Pat. No. 5,486,406; U.S. Pat. No. 5,529,853; U.S. Pat. No.4,539,507; European. Pat. Publication No. 0652273; Japanese Patent Application Laid-Open No. 113576/1996 and Japanese Patent Application Laid-Open No. 336586/1994). However, none of them have focused on a specific organometallic molecule with the capability of lowering the drive voltage of an organic EL device.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide an electron injecting material having a low drive voltage and an improved power conversion efficiency for organic electroluminescene (EL) devices.

According to the present invention, there is provided an electron injecting material of a structure represented by the following general formula (1):

wherein, Ri to Rs represent hydrogen or Ci to C₈ alkyl groups, independently.

A zinc derivative of compound (1), 2-(O-hydroxyphenyl)benzthiazole zinc complex, has been known as a blue light emitting electron transporting material (see European. Pat. Publication No. 0652273 and Japanese Patent Application Laid-Open No. 113576/1996). However, the present inventors discovered that the compounds represented by the above general formula (1) show excellent electron injection and transport properties which have not been found in the aforementioned patents.

BRIEF DESCRIPTION OF DRAWINGS

These and other advantages and features of the present invention can be better appreciated with reference to the following description which will be described in conjunction with the accompanying drawings in which:

FIGS. 1 to 3 are schematic diagrams of organic EL devices where the present invention can be used.

FIG. 4 is a graph showing a relationship of light intensity (arbitrary unit) vs. voltage respectively in Example 1, Comparative Example 1.1 and Comparative Example 1.2.

FIG. 5 is a graph showing a relationship of light intensity (arbitrary unit) vs. voltage respectively in Example 2 and Comparative Example 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Choosing cathode materials capable of forming a stable interface with an organic or organometallic electron transporting layer while maintaining a low work function and substantial environmental stability at the same time is not an easy task. Presently only a few alloys and a metal that are practically usable have been developed. Specific examples are: an indium metal (see U.S. Pat. No. 4,539,507); an alloy of Mg:Ag (see U.S. Pat. No. 4,885,211); Mg:Al (see U.S. Pat. No. 5,059,862); and an alloy of Al:Li (see U.S. Pat. No. 5,429,844) and Bi:Li (see U.S. Pat. No. 5,500,568). The use of stable cathode having a low work function is a critical factor to commercialize an efficient EL device. Since the LUMO level of the conventional electron injecting layer (a layer being located in contact with a cathode) does not match with the work function of the cathode material, a significant high energy barrier exists when injecting electrons from the cathode into the organic medium. For example, an energy barrier of about 0.6 eV exists when injecting electrons from a Mg:Ag alloy into 8-hydroxyqunoline aluminum salt (hereinafter referred to as Alq3) which is one of the most widely used electron injecting layers in an EL device. The present invention is based on a discovery that a complex represented by the above formula (1) can provide an EL device with both a high power efficiency and a low driving- voltage when it is interposed as a thin layer between a cathode electrode and the hole-transporting layer of a conventional EL device.

FIGS. 1 to 3 show a respective schematic cross section of internal junction organic EL devices. These devices generally comprise a transparent support layer 1 onto which an anode electrode 2 having a high work function is coated. Specific examples of a conductive material for the anode electrode 2 may include Au, Indium Tin Oxide (ITO), Sn0₂, conducting polymers and ZnO₂.

A cathode electrode 7 is formed by way of a method of vapor deposition or sputtering of electrically conductive material with a low work function. The cathode electrode 7 may be made of a material selected from the group of aluminum, silver, magnesium, lithium, samarium, indium, tin, lead, yttrium, ruthenium and alloys of these (see U.S. Pat. No. 4,885,211; U.S. Pat. No. 4,539,507; U.S. Pat. No. 5,059,862; U.S. Pat. No. 5,429,844; and U.S. Pat. No. 5,500,568), but not limited thereto.

A hole transporting layer 3 is made of a material, which is capable of accepting holes from the anode electrode 2 and transporting them with high mobility, preferably a derivative of aryl amine or a mixture of at least two aryl amines with different molecular structure to suppress possible crystallization and to improve the performance of EL devices. Also the hole transporting layer 3 can be divided into multiple sub-layers each of which is made of different hole transporting material. An electron transporting layer 4 is made of a material, which is capable of accepting electrons from the cathode electrode 7 and transporting them. As shown in FIG. 1, the electron transporting layer 4 is located between the cathode electrode 7 and the hole transporting layer 3.

FIGS. 2 and 3 are a respective schematic cross section of organic EL devices having a hole injecting layer 5 sandwiched between an anode electrode 2 and a hole transporting layer 3 to enhance the injection of holes from the anode electrode 2 into the hole transporting layer 3 and to improve the lifetime of the organic EL devices as well. The hole injecting layer 5 is made of a material having ability of forming a stable interface with both the anode electrode 2 and the hole transporting layer 3. Also it is preferable that the hole injecting material has an energy level of the highest occupied molecular orbital (HOMO) in between the work function of the anode and the HOMO level of the hole transporting material (see U.S. Pat. No. 4,539,507 and U.S. Pat. No. 4,769,292).

In the organic EL devices schematically shown in FIGS. 1 and 2, the electron transporting layer 4, as described above, is made of a material capable of accepting electrons from the cathode electrode 7, upon application of an appropriate forward bias, and transporting them and is located between the cathode electrode 7 and the hole transporting layer 3. In the structure of these devices, the recombination of carriers generally takes place, but not necessarily, in the electron transporting layer 4, and it is preferable to select the electron transporting material among molecules having a high fluorescent quantum efficiency. To improve the power conversion efficiency further, highly fluorescent materials may be doped into the electron transporting layer 4 with a low concentration. When the electron transporting layer 4 is doped with a fluorescent dopant material, the emission of light takes place from the dopant as a result of energy transfer from the electron transporting material to the fluorescent dopant.

In this method, there are two important requirements such as the band gap of the dopant material and the location of it in the electron transporting layer 4 in the direction of thickness. If the band gap of the dopant material is larger than that of electron transporting material 4, effective energy transfer cannot be obtained. Therefore it is preferable to select a dopant material with a band gap similar to or lower than that of the electron transporting material.

Another requirement, i.e., the location of the doped region, should be fulfilled to maximize the power conversion efficiency of organic EL devices. If the LUMO level of the dopant is lower than that of the electron transporting layer 4, the dopant acts as a shallow trap of electrons. Since the shallow trap increases a space charge density, a higher voltage is required to drive the EL devices. Therefore it is preferable to locate the doped region in the direction of thickness where the exiton formation takes place.

FIG. 3 schematically illustrates an organic EL device fabricated by interposing a light emitting layer 6 between the electron transporting layer 4 and the hole transporting layer 3 based on an organic EL device as shown in FIG. 2 (see U.S. Pat. No. 4,539,507). In this device, according to the inventors of above U.S. patent, it is desirable that the thickness of the electron transporting layer 4 is smaller than that of the light emitting layer 6 to minimize the possibility of light emission from the electron transporting layer 4 which has a band gap (energy gap) smaller than that of the light emitting layer 6.

The present invention relates to an organic EL device having a low drive voltage and an improved power conversion efficiency. Electron injecting materials of the present invention are represented by the following formula (1):

wherein, Ri to Rs represent hydrogen or Cι to C₈ alkyl groups, independently. Specific examples of the electron injecting materials of the present invention are represented by the following formula (2) and (3):

(2)

The energy gap of compound (2) obtained from the wavelength of absorption ends of absoφtion spectrum ranging from UV light to visible light of a thin film corresponds to 2.82 eV. When radiometric photoluminescence spectra of the compound (2) excited at the wavelength of 400 run are converted into a CIE diagram, the emission color is found to be blue (CIE 0.138, 0.149). Therefore the compound (2) is an excellent candidate material for the electron transporting layer 4 and the light emitting layer 6 for emitting blue color. Also due to the large band gap energy corresponding to the blue-color emission, this material expands the possible choice of the dopant material having a band gap energy corresponding to a color range from blue to red compared with that from green to red when Alq3 is used as an electron transporting/host molecule which has a band gap energy corresponding to green color. For practical use, the compound (2) should meet other requirements such as thermal stability, electrochemical stability, electron accepting ability (low LUMO energy level) and so on. According to a DSC thermogram, compound (2) melts at the onset temperature of 325 °C which is high enough for practical use. The physical properties described above of the compound (2) are summarized in TABLE 1.

TABLE 1 absorption-edge-derived CIE (x, y) melting point(onset temperature) band gap (eV) CO

2.82 (0.138, 0.149) 325 Some embodiments of the present invention will be described hereinafter in detail in the following examples compared with the reference examples.

EXAMPLES

Synthesis of 2-(Q-hvdroxyphenyl)benzthiazole beryllium complex

Procedure A

To a solution of NaOH (176 mg) in a mixture of distilled water (20 ml) and ethyl alcohol (70 ml), 2-(0-hydroxyphenyl)benzthiazole (1 g) was added. The resulting solution was slowly added to a solution of beryllium chloride (170 mg) dissolved in 70 ml of distilled water. The resulting mixture was refluxed for 2 hours with stirring, and cooled down to room temperature. The precipitate was then collected by vacuum filtration, washed with diethyl ether and dried in a vacuum oven to yield 0.77 g of compound (2) (78% yield rate).

The yielded product was further purified by train sublimation. The results of analyzing the product are given as follows: m.p.: 325 °C (onset).

1H-NMR (DMSO-d6): δ 6.8-6.9 (2H), 7.0-7.1 (1H), 7.25 (t, 1H), 7.35 (t, 1H),

7.45 (t, 1H), 7.92 (d, 1H), 8.17 (d, 1H).

Elemental analysis: Calculated (C67.65, H .49, N:6.06, Be:1.95)

Experimental (C67.31, H:3.33, N:5.98, Be:1.90) Procedure B

To a solution of NaOH (35 mg) in a mixture of distilled water (2 ml) and ethyl alcohol (7 ml), 2-(0-hydroxyphenyl)benzthiazole (0.2 g) was added. The resulting solution was slowly added to a solution of beryllium sulfate tetrahydrate 0.08 g dissolved in 10ml of distilled water. To the resulting solution, aqueous sodium hydroxide (1 M) was added until the pH thereof became 10. The resulting mixture was stirred for 1 hour. The precipitate was then collected by vacuum filtration, washed with diethyl ether and dried in a vacuum oven to yield 0.14 g of compound (2) (70% yield rate). The yielded product was further purified by train sublimation.

Synthesis of 2-(Q-hvclroxy-5-methylphenyl)benzthiazoιe beryllium complex

To a solution of NaOH (27 mg) in a mixture of distilled water (10 ml) and ethyl alcohol (50 ml), 2-(0-hydroxy-5-methylphenyl)benzthiazole (0.18 g) was added. The resulting solution was slowly added to a solution of beryllium chloride (29 mg) dissolved in 5 ml of distilled water. The resulting mixture was refluxed for 2 hours with stirring, and cooled down to room temperature. The precipitate was then collected by vacuum filtration, washed with diethyl ether and dried in a vacuum oven to yield 185 mg of compound (3) (96% yield rate).

The yielded product was further purified by train sublimation. The results of analyzing the product are given as follows: m.p.: 349 °C (onset). i-NMR (DMSO-d6): δ 3.3 (s, 3H), 6.75 QH), 7.02 (1H), 7.2-7.4 (3H), 7.65 (1H), 8.15 (1H).

Reduction Potential of Compound (2)

The capability of compound (2) as an electron injecting material was measured using cyclic voltammeter by comparing its reduction potential with known electron transporting materials. The reference compounds used in this set of experiments is Alq3. A reduction potential of a zinc derivative of compound (2), 2-(0-hydroxyphenyl)benzthiazole zinc complex, was excluded from this set of experiments since it is insoluble in DMF as indicated in Japanese Patent Application Laid-Open No. 113576/1996 (A direct comparison of compound (2) with 2-(O-hydroxyphenyl)benzthiazole zinc complex as an electron injecting material will be made later).

The reduction potentials of compound (2) and reference compounds were determined by cyclic voltammetry relative to Ag/Ag+ reference electrode using DMF as a solvent. The results are summarized in TABLE 2.

TABLE 2

Compound (2) Alq3

Reduction potential (V) -1.63 -2.09

From this set of data, it was found that the compound (2) has a low reduction potential than that of Alq3.

EXAMPLE 1

To evaluate the performance of compound (2) as an electron injecting material, organic EL devices were fabricated with and without compound (2) as follows. Commercially available ITO coated glass was subjected to ultrasonic cleaning with methanol, acetone, isopropyl alcohol, acetone and methanol in success for 5 minutes in each solvent, and dried in a vacuum oven for 1 hour at 110^°C. The cleaned substrate was fixed on a substrate holder in a thermal vacuum deposition chamber. An organic EL device which comprises laminating layers in the order of ITO/TPD/Alq3/compound (2)/Mg:Ag (10:l)/Ag with a film thickness of 60 nm (TPD), 50 nm (Alq3), 20 nm (compound (2)), 100 nm (Mg:Ag) and 150 nm (Ag) respectively (TPD: N, N-diphenyl-N, N-bis(3-methylphenyl)-[l, l-biphenyl]-4, 4-diamine). During the process, the deposition rate was maintained in a range of 1~ 3 A/sec in a high vacuum of about 10^"6 torr with a substrate temperature set at room temperature. A shadow mask was used for the patterning of the cathode electrode to make 0.15 cm of active device area. The schematic cross section of this organic EL device is analogous to the device described in FIG. 1 except that the former has an additional layer made of compound (2) inbetween the electron transporting layer 4 and the cathode electrode 7.

The power conversion efficiency of this device was 2.1 lm/W at the brightness of 100 cd/m . 1 mA/cm of current density was injected at 7.1 V. The results are summarized in TABLE 3. Also, to make the improvement of the present invention obvious, comparative examples were produced.

Comparative Example 1.1

An organic EL device which comprises laminating layers in the order of ITO/TPD/Alq3/Mg:Ag(10:l)/Ag was obtained in the same manner as in EXAMPLE 1 except that the electron injecting material (2) was excluded. The schematic cross section of this organic EL device is described in FIG. 1.

The power conversion efficiency of this device was 1.2 lm/W at the brightness of 100 cd/m . 1 mA/cm² of current density was injected at 9.1 V. The results are summarized in TABLE 3.

Comparative Example 1.2

An organic EL device which comprises laminating layers in the order of ITO/TPD/Alq3/2-(0-hydroxyphenyl)benzthiazole zinc complex/Mg:Ag(10:l)/Ag was obtained in the same manner as in EXAMPLE 1 except that the electron injecting material (2) was replaced with the zinc complex of material (2) with the same thickness as the compound (1). The schematic cross section of this organic EL device is analogous to a device described in FIG. 1 except that the former has an additional layer made of 2-(O-hydroxyphenyl)benzthiazole zinc complex inbetween the electron transporting layer 4 and the cathode electrode 7.

The power conversion efficiency of this device was 1.6 lm/W at the brightness of 100 cd/m². 1 mA/cm² of current density was injected at 8.4 V. The results are summarized in TABLE 3.

TABLE 3

Voltage at 1 mA/cm'* ^: (V) Power conversion efficiency at 100 cd/m² (lm/W)

EXAMPLE 1 7.1 2.1

Comparative Example 1.1 9.1 1.21

Comparative Example 1.2 8.4 1.6

From this set of experiments, it was found that both compound (2) and its zinc derivative lower the driving voltage of a conventional organic EL device when they are used as electron injecting materials. However, as shown in TABLE 3, compound (2) clearly outperforms its zinc analogue. The superior performance of compound (2) to its zinc analogue is also illustrated in FIGURE 4 which depicts a graph of plotted light intensities (arbitrary unit) at various voltages from devices used for EXAMPLE 1, Comparative Example 1.1 and Comparative Example 1.2. At the same voltage, the device in EXAMPLE 1 gives off the highest light intensity.

EXAMPLE 2

An organic EL device which comprises laminating layers in the order of ITO/TPD/Alq3/compound (2)/Ag was obtained in the same manner as in EXAMPLE 1 with a film thickness of 60 nm (TPD), 20 nm (Alq3), 50 nm (compound (2)), and 200 nm (Ag) respectively. In this device, Alq3 was used as an emitting material and compound (2) as an electron injecting/transporting material. Also low work function magnesium silver (Mg:Ag) alloy was replaced with the high work function silver (Ag) electrode. The schematic cross section of this organic EL device is analogous to a device depicted in FIG. 3 except that the former does not have a hole injecting layer 5 but has an additional layer made of compound (2) inbetween the electron transporting layer 4 and the cathode electrode 7. The results are summarized in TABLE 4. Also, -to make the improvement of the present invention obvious, a comparative example was produced.

Comparative Example 2

An organic EL device which comprises laminating layers in the order of ITO/TPD/Alq3/2-(0-hydroxyphenyl)benzthiazole zinc complex/Ag was obtained in the same manner as in EXAMPLE 1 with a film thickness of 60 nm (TPD), 20 nm (Alq3), 50 nm (2-(0-hydroxyphenyl)benzthiazole zinc complex), and 200 nm (Ag) respectively. In this device, Alq3 was used as light emitting material and the 2-(0-hydroxyphenyl)benzthiazole zinc complex as an electron injecting/transporting material. Also a low work function magnesium silver alloy was replaced with a high work function silver electrode. The schematic cross sections of this organic EL devices is an analogue of a device depicted in FIG. 3 except that the former does not have a hole injecting layer 5 but has an additional layer made of 2-(O-hydroxyphenyl)benzthiazole zinc complex in between the electron transporting layer 4 and the cathode electrode 7. The results are summarized in TABLE 4.

TABLE 4

Voltage at 500 cd/m^ (V) Power conversion efficiency at 500 cd/m² (lm W)

EXAMPLE 2 11.8 1.0

Comparative

Example 2 14.1 0.3

From this set of experiments, it was confirmed that the performance of compound (2) is superior to its zinc analogue as an electron injecting material as shown in TABLE 4. Also FIG. 5 which depicts a graph of plotted light intensities (arbitrary unit) at various voltages from devices used for EXAMPLE 2 and Comparative Example 2 clearly illustrates the performance of compound (2) superior to its zinc analogue. At the same voltage, the device in EXAMPLE 2 gives off much higher light intensity compared with that in Comparative Example 2.

EXAMPLE 3

An organic EL device which comprises laminating layers in the order of ITO/TPD/compound (2): coumarine 540(100:l)/Mg:Ag/Ag was obtained in the same manner as in EXAMPLE 1 with a film thickness of 60 nm (TPD), 50 nm (compound (2): coumarine 540), 100 nm (Mg:Ag) and 150 nm (Ag) respectively. In this device, coumarine 540 was used as a dopant molecule and compound (2) as a host molecule with the role of electron injecting and transporting at the same time. The chemical structure of coumarine 540 is illustrated below and the schematic cross section of this organic EL device is illustrated in FIG. 1.

Coumarine 540

The results are summarized in TABLE 5. Also, to make the improvement of the present invention obvious, a comparative example was produced.

Comparative Example 3

An organic EL device which comprises laminating layers in the order of ITO/TPD/Alq3:coumarine 540(100:l)/Mg:Ag/Ag was obtained in the same manner as in EXAMPLE 3 with a film thickness of 60 nm (TPD), 50 nm (compound (2): coumarine 540), 100 nm (Mg:Ag) and 150 nm (Ag) respectively. In this device, coumarine 540 was used as a dopant molecule and Alq3 as a host molecule with the role of electron injecting and transporting at the same time. The schematic cross section of this organic EL device is illustrated in FIG. 1. The results are summarized in TABLE 5. TABLE 5

Voltage at 1 mA/cm² (V) Power conversion efficiency Voltage at 100 cd/m (V) at 100 cd/m² (lm/W)

EXAMPLE 3 4.7 4.1 5.2

Comparative

Example 3 7.2 2.6 7.8

Claims

What is claimed is;

1. An organic electroluminescence device comprising an anode electrode, a cathode electrode, and an organic film layer formed between the anode and cathode electrodes, wherein the organic film layer is made of an organometallic complex represented by the following general formula (1):

wherein, Ri to R₈ represent hydrogen or Ci to C₈ alkyl groups, independently.

2. The organic electroluminescence device of claim 1, wherein

to Rs represent hydrogen.

3. The organic electroluminescence device of claim 1, wherein Ri, R2, R4 to R₈ represent hydrogen and R3 represents methyl.

4. The organic electroluminescence device of claims 1 to 3, wherein said organic film layer comprises in the order of a hole transporting layer and an electron transporting layer, and the electron transporting layer is made of the organometallic complex (1).

5. The organic electroluminescence device of claims 1 to 3, wherein the organic film layer comprises in the order of a hole injecting layer, a hole transporting layer and an electron transporting layer, and the electron transporting layer is made of the organometallic complex (1).

6. The organic electroluminescence device of claims 1 to 3, wherein the organic layer comprises in the order of a hole transporting layer, a light emitting layer, and an electron transporting layer, and the electron transporting layer is made of the organometallic complex (1).

7. The organic electroluminescence device of claims 1 to 3, wherein the organic layer comprises in the order of a hole injecting layer, a hole transporting layer, a light emitting layer, and an electron transporting layer, and the electron transporting layer is made of the organometallic complex (1).

8. In one of the organic electroluminescent device according to claims 1 to 3, the electron transporting layer is doped with a fluorescent molecule.

9. In one of the organic electroluminescent device according to claims 1 to 3, the anode electrode is an indium-tin-oxide (ITO) electrode.

10. A 2-(O-hydroxyphenyl)benzthiazole beryllium complex represented by the following formula (2):

(2)