KR20100025664A - Organic thin film materials for organic electroluminescent device, and organic electroluminescent device - Google Patents

Abstract

PURPOSE: An organic thin film material for an organic electroluminescent device is provided to obtain phosphorescent red light of high efficiency and excellent color purity, and to obtain an organic electroluminescent device showing high definition and high efficiency. CONSTITUTION: An organic thin film material for an organic electroluminescent device comprises a compound selected from the group consisting of naphthalenyl carbazole compounds as a phosphorescent host. The organic electroluminescent device comprises a positive electrode, a negative electrode, and a plurality of organic thin film layers positioned between the positive and negative electrodes. The organic layer material for an organic electroluminescent device is included in whole or a part of organic thin film layers.

Description

Organic thin film materials for organic electroluminescent device, and organic electroluminescent device comprising same

The present invention relates to an organic thin film material for an organic electroluminescent device including a phosphorescent host, and more particularly, to an organic thin film for an organic electroluminescent device, which can be usefully used for an organic electroluminescent device by exhibiting high efficiency phosphorescence emission with excellent color purity. A material and an organic electroluminescent device comprising the same.

Liquid crystal display (LCD), which is the most widely used at present, is a non-light-emitting display device, but the power consumption is low and light, but the device driving system is complicated and the characteristics such as response time and contrast are not satisfactory. Therefore, research on organic electroluminescent devices, which are recently attracting attention as a next-generation flat panel display, is being actively conducted.

The light emitting mechanism of the organic electroluminescent device is as follows. Holes injected from the anode into the valence band or highest occupied molecular orbital (HOMO) of the hole injection layer (HIL) proceed to the emitting layer through the hole transporting layer (HTL). At the same time, electrons move from the cathode to the light emitting layer through the electron injection layer and combine with holes to form excitons, which emit light as they fall to the ground. The organic electroluminescent device is an active light emitting display device using the above-mentioned phenomenon. The organic electroluminescent device has a structure that is light in weight, simple in components, and simple in manufacturing process, and secures a wide viewing angle in high quality. In addition, high color purity and video can be perfectly realized, and low power consumption and low voltage driving make it suitable for portable electronic devices.

The light emitting layer forming material of the organic electroluminescent device can be classified into a fluorescent material using excitons in a singlet state and a phosphorescent material using a triplet state according to the light emitting mechanism. The fluorescent or phosphorescent material is doped on its own or in a suitable host material to form a light emitting layer, and as a result of electron excitation, singlet excitons and triplet excitons are formed in the host. At this time, the statistical ratio of singlet excitons and triplet excitons is 1: 3.

Therefore, according to the inference of theoretical angular momentum statistics, when the phosphor is used as a light emitting layer forming material, both singlet and triplet excitons can be used, which has the advantage of reaching 100% of internal quantum efficiency. And a four-fold increase in power efficiency.

The introduction of expensive metals such as Ir, Pt, Rh, and Pd into organic molecules results in the mixing of triplet states through spin-orbital coupling caused by the heavy metal atom effect, which allows forbidden transitions and room temperature. Phosphorescence can also occur effectively at.

In accordance with the process of manufacturing such an organic electroluminescent device, a process technology such as a printing method using a solution in addition to the vacuum deposition method using small molecules has been studied. However, application from solutions such as printing is limited by the fact that the price of raw materials in the case of phosphorescent emitters using phosphorescence is quite expensive, thus providing thermal stability through well-known easy synthesis routes and It is essential to develop phosphorescent emitters that express properties capable of improving solubility.

A weak point of the phosphor having a complex structure of organometallic compounds known as the light emitting layer forming material of the organic electroluminescent device described so far is its low solubility. When the process using the solution state is applied to improve the solubility, the process application by the high resolution printing means, in particular, provides long-term benefits that are excellent in terms of scale capacity, structural capacity, coating efficiency and economy compared to the process by the current vacuum deposition method. It can bring, but due to the problem of low solubility of the complex of the organometallic compound synthesized from expensive raw materials, there are many difficulties in commercializing the above-described compounds in the organic electroluminescent device, there is also a limitation in the application to various displays.

Phosphorescent host materials, which are low molecular organic compounds used in vacuum deposition processes, include CBP (4,4-N, N-dicarbazole-biphenyl) and mCP (1,3-N, N), which are bipolar materials with hole mobility and electron mobility. -dicarbazole-benzene) and its derivatives are well known. Recently, electron transporting Balq (bis (2-methyl-8-quinolinolato) (p-phenylphenolato) aluminium (III)) or similar Al complex materials are known to be useful as phosphorescent hosts. Further improvements are needed in terms of thermal safety and efficiency. As described above, in the case of configuring the display device using the organic electroluminescent device, it is one of the most important problems to enable the driving at low voltage and to prolong the life and reliability of the organic electroluminescent device.

Therefore, in order to overcome the limitations of application to various displays due to the problem of low solubility of phosphorescent emitters, it is highly efficient and has improved stability with high electrochemical properties compared to the materials used in conventional vacuum deposition. There is a need to develop new compounds having excellent processability by deposition and organic electroluminescent devices using the same.

Accordingly, an object of the present invention is to provide an organic thin film material for an organic electroluminescent device capable of high-efficiency phosphorescence when used in an organic electroluminescent device.

In another aspect, the present invention is to provide an organic electroluminescent device comprising the organic thin film material for the organic electroluminescent device.

The present invention for achieving the above object provides an organic thin film material for an organic electroluminescent device, comprising a compound selected from the group of naphthalenyl carbazole compounds represented by the following formula (1) to (34) as a phosphorescent host.

According to an aspect of the present invention, there is provided an organic electroluminescent device having an anode, a cathode, and a plurality of organic thin film layers positioned between the anode and the cathode. Provided is an organic electroluminescent device comprising an organic thin film material for an electroluminescent device.

As described above, the organic thin film material for an organic electroluminescent device comprising a compound selected from the group of naphthalenyl carbazole compounds represented by Chemical Formulas 1 to 34 of the present invention as a phosphorescent host is phosphorescent red having high color purity and high efficiency. It is possible to obtain luminescence, and thus an organic electroluminescent device which emits red phosphorescence with high efficiency and high quality when used as a material for an organic electroluminescent device which emits red phosphorescence can be obtained.

Hereinafter, the present invention will be described in more detail. The following detailed description illustrates the present invention by way of example, and the present invention is not limited thereto.

The present invention provides an organic thin film material for an organic electroluminescent device comprising as a phosphorescent host a compound selected from the naphthaletyl carbazole compound group represented by Chemical Formulas 1 to 34 as a compound exhibiting high efficiency characteristics when applied to an organic electroluminescent device. . The organic thin film material for an organic electroluminescent device can provide an organic electroluminescent device having high efficiency and high color purity when applied as a light emitting layer material through a method of vacuum depositing a suitable phosphorescent emitter (complex of a transition metal).

In particular, naphthalenyl carbazole compounds selected from Chemical Formulas 1 to 34 according to the present invention are EL _{max .} When used in the organic thin film material for phosphorescent host of the red light emitting material having a high luminescent efficiency. It is not necessarily limited to use as a phosphorescent host material for red light emission, but is suitable for a phosphorescent host that can be used as a blue and green light emitting material and can emit white light by multicolor light emission, and the organic electroluminescence of the present invention The device exhibits excellent characteristics in efficiency, color purity and driving voltage.

The compounds of Formulas 1 to 34 included in the organic thin film material for an organic electroluminescent device according to the present invention can be easily synthesized according to a known method.

Scheme 1 below represents a compound represented by Chemical Formula 1, and Scheme 2 represents a synthesis method of the compound represented by Chemical Formula 15. And the method of synthesizing the compound represented by the formula (4) and the compound represented by the formula (7) in the structural isomer relationship is shown in Scheme 3 and Scheme 4. Other compounds can be easily synthesized by those skilled in the art by synthesizing via the same synthetic route.

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Hereinafter, an organic thin film material and an organic electroluminescent device for an organic electroluminescent device according to the present invention will be described.

The present invention provides an organic thin film material for an organic electroluminescent device comprising a compound selected from the group of naphthalenylcarbazole compounds represented by Chemical Formulas 1 to 34 as a phosphorescent host. Any organic electroluminescent device material containing an organic thin film material for an organic electroluminescent device using the compound selected from the naphthalenylcarbazole compounds represented by Chemical Formulas 1 to 34 as a phosphorescent host is included in the present invention.

The organic thin film material for organic electroluminescent devices except for the compound selected from the naphthalenylcarbazole compound group of Chemical Formulas 1 to 34 according to the present invention is well known in the art, and thus, a detailed description thereof will be omitted. An example is given and demonstrated in the description about an electroluminescent element.

The organic electroluminescent device according to the present invention is an organic electroluminescent device having a plurality of organic thin film layers including an anode, a cathode, and a light emitting layer positioned between the anode and the cathode, wherein the organic thin film layer includes all or part of the plurality of organic thin film layers. An organic thin film material for organic electroluminescent elements is included.

The organic thin film layer may include at least one of a light emitting layer, an electron injection layer, and an electron transport layer. Preferably, the organic thin film layer is a light emitting layer.

A more specific example is described as follows.

1 is a cross-sectional view of an organic electroluminescent device according to an embodiment of the present invention. As shown in FIG. 1, the organic electroluminescent device includes an anode layer 110 formed on a transparent substrate 100, a hole injection layer 120, a hole transport layer 130, and an emission layer 140 on the anode layer 110. , The hole blocking layer 150, the electron transport layer 160, the electron injection layer 170, and the cathode layer 180 are vacuum deposited in the order. At least one or more of the hole injection layer 120, the hole transport layer 130, the hole blocking layer 150, the electron transport layer 160, and the electron injection layer 170 may be omitted as necessary.

The anode layer 110 of the present invention is an electrode for injecting holes into the hole injection layer 120. Therefore, the material for forming the anode layer 110 is not limited to that in which properties are imparted to the anode layer 110. Examples of the material for forming the anode layer 110 include metal oxides or metal nitrides such as ITO, IZO, tin oxide, zinc oxide, zinc aluminum oxide, and titanium nitride; Metals such as gold, platinum, silver, copper, aluminum, nickel, cobalt, lead, molybdenum, tungsten, tantalum and niobium; Alloys of these metals or alloys of copper iodides; Conductive polymers such as polyaniline, polythiopine, polypyrrole, polyphenylene vinylene, poly (3-methylthiopine), and polyphenylene sulfagard. The anode layer 110 may be formed of only one type of the above materials or may be formed of a mixture of a plurality of materials. In addition, a multilayer structure composed of a plurality of layers of the same composition or different compositions can be formed.

The material for forming the anode layer 110 preferably has a larger work function for easily injecting holes. Chromium has a work function of 4.5 eV, nickel has a work function of 5.15 eV, gold has a work function of 5.1 eV, palladium has a work function of 5.55 eV, ITO has a work function of 4.8 eV, Copper has a work function of 4.65 eV. The work function of the surface in contact with the hole injection layer 120 of the anode layer 110 is preferably 4 eV or more.

When the anode layer 110 is disposed on the light extraction end from the light emitting layer, the transmittance for the light to be extracted is preferably not less than 10%. When the light emitted from the light emitting layer is in the visible light region, ITO is preferable for forming the anode layer 110 because it has a high transmittance in the visible light region.

The hole injection layer 120 of the present invention forms a material such as PEDOT / PSS or copper phthalocyanine (CuPc), 4,4 ', 4 "-tris (3-Methylphenylphenylamino) tri phenylamine (m-MTDATA), about 5 to 60 nm. do.

The hole transport layer 130 of the present invention is 4,4'-bis [N- (1-napthyl) -N-phenyl-amino] -biphenyl (NPD) or N, N'-diphenyl-N, N'-bis ( Substances such as 3-methyl phenyl) -1,1'-biphenyl-4,4'-diamin (TPD) are used at about 20 to 60 nm.

The light emitting layer 140 of the present invention includes a compound selected from the group of naphthaletylcarbazole compounds of Formulas 1 to 34 according to the present invention as a phosphorescent host.

In the light emitting layer, a phosphorescent dopant may be used together with a compound selected from the compounds of Formulas 1 to 34 according to the present invention as a phosphorescent host to obtain red light, or a specific color having high luminance.

The dopant to be used is not limited, and known dopants may be selected and used according to needs.

As a phosphorescent dopant, it is a compound which can emit light from triplet excitons. It is not specifically limited as long as it emits from triplet excitons, It is preferable that it is a metal complex containing at least 1 metal selected from the group which consists of Ir, Ru, Pd, Pt, Os, and Re, Especially a porphyrin metal complex or ortho metallization Genus complexes are preferred. As a porphyrin metal complex, a porphyrin platinum complex is preferable.

There are various ligands for forming the ortho metallized metal complex of the phosphorescent dopant, but preferred ligands include 2-phenylpyridine derivative, 7,8-benzoquinoline derivative, 2- (2-thienyl) pyridine derivative, and 2- (1 -Naphthyl) pyridine derivative, 2-phenylquinoline derivative, etc. are mentioned. These derivatives may have a substituent as needed. As an auxiliary ligand, it may further have ligands other than the above ligands such as acetylacetonato and picric acid. Specific examples include bisthienylpyridine acetylacetonate Iridium, bis (benzothienylpyridine) acetylacetonate Iridium {bis (benzothienylpyridine) acetylacetonate Iridium}, bis (2-phenylbenzothiazole) acetylacetonate Iridium {Bis (2-phenylbenzothiazole) acetylacetonate Iridium}, bis (1-phenylisoquinoline) iridium acetylacetonate {bis (1-phenylisoquinoline) Iridium acetylacetonate}, tris (1-phenylisoquinoline) iridium {tris (1-phenylisoquinoline ) Iridium}, tris (phenylpyridine) Iridium}, tris (2-biphenylpyridine) Iridium}, tris (3-biphenylpyridine) Iridium {tris (3 -biphenylpyridine) Iridium}, tris (4-biphenylpyridine) Iridium}, etc. are mentioned.

The amount of the dopant included in the light emitting layer is not limited, but may be included in the range of 2 to 20 parts by weight relative to the total weight of the light emitting layer, and the total amount of the dopant may be in the range of 0.5 to 35 parts by weight.

By using the dopant together with a phosphorescent host, various phosphorescent colors such as red may be realized.

The hole blocking layer 150 may use 2 to 20 nm of BCP or BAlq, or may omit them in some cases.

The electron transport layer 160 may include an aryl substituted oxadiazole, an aryl-substituted triazole, an aryl-substituted phenanthroline, benzoxazole, or benzoxazole compound. For example, 1,3 -Bis (N, Nt-butyl-phenyl) -1,3,4-oxa diazole (OXD-7); 3-phenyl-4- (1'-naphthyl) -5-phenyl-1,2,4-triazole (TAZ); 2,9-dimethyl-4,7-diphenyl-phenanthroline (vasocuproin or BCP); Bis (2- (2-hydroxyphenyl) -benzoxazolate) zinc; Or bis (2- (2-hydroxyphenyl) -benz thiazolate) zinc; As the electron transporting material, (4-biphenyl) (4-t-butyl phenyl) oxydiazole (PDB) and tris (8-quinolinato) aluminum (III) (Alq3) may be used, preferably Tris ( 8-quinolinato) aluminum (III) (Alq3) is preferred.

In the electron injection layer 170 and the cathode layer 180 of the present invention, LiF may be used as the electron injection layer, and a metal having a low work function, such as Al, Ca, Mg: Ag, may be used as the cathode layer 180. Al is good. The above-described organic electroluminescent device according to the present invention may be applied to a display device, and the display device may be a display device using a backlight unit, and the organic electroluminescent device may be used as a light source and a single light source of a backlight unit. . In addition, the display device may be an organic electroluminescent display (OLED).

The following rescue example is only a specific example and is not intended to limit or limit the protection scope of the present invention.

Example  1: Fabrication and Evaluation of Organic Electroluminescent Device 1

A glass substrate with an ITO transparent electrode coated with an insulating film so as to be produced as a 2 mm × 2 mm unit device was subjected to ultrasonic cleaning in isopropyl alcohol for 5 minutes, followed by UV ozone cleaning for 30 minutes, and transferred to an organic chamber.

Inside the organic chamber, m-MTDATA, a hole injection layer, was deposited to a thickness of 50 nm, and NPD, a hole transport layer, was deposited to a thickness of 20 nm. Thereafter, a compound of Formula 1 and a phosphorescent dopant (12% by weight) according to the present invention, which is a phosphorescent host, are deposited on the hole transport layer by using a compound of Formula 35 to form a light emitting layer with a thickness of 40 nm to form Alq3, which is an electron transport layer. Deposited to a thickness of 20 nm.

After the deposition, transfer to the metal chamber, vacuum deposition of Alq3 (tris- (8-hydroxyquinoline) aluminium (III)) with a thickness of 20nm to the electron transport layer, and vacuum deposition of Al: Li layer on top of the 100nm thickness An organic electroluminescent device was manufactured by forming an aluminum / lithium electrode. The organic electroluminescent device manufactured according to the following evaluation method was confirmed the characteristics of the device, and the evaluation results are shown in Table 1.

<Formula 35>

Example  2: Fabrication and Evaluation of Organic Electroluminescent Device 2

An organic electroluminescent device was manufactured in the same manner as in Example 1, except that the compound of Formula 22 was used instead of the compound of Formula 1, which is a phosphorescent host. The evaluation results are shown in Table 1.

Example  3: Fabrication and Evaluation of Organic Electroluminescent Device 3

An organic electroluminescent device was manufactured in the same manner as in Example 1, except that the compound of Formula 31 was used instead of the compound of Formula 1, which is a phosphorescent host. The evaluation results are shown in Table 1.

Comparative example  1: Fabrication and Evaluation of Organic Electroluminescent Device 4

An organic electroluminescent device was manufactured in the same manner as in Example 1, except that the phosphorescent host CBP represented by Formula 36 below was used instead of the compound of Formula 1, which is a phosphorescent host. The evaluation results are shown in Table 1.

<Formula 36>

Comparative example  2: Fabrication and Evaluation of Organic Electroluminescent Device 5

An organic electroluminescent device was manufactured in the same manner as in Example 1, except that the compound of Formula 37, which is a fluorescent host, was used instead of the compound of Formula 1, which is a phosphorescent host. The evaluation results are shown in Table 1.

<Formula 37>

Comparative example  3: Fabrication and Evaluation of Organic Electroluminescent Device 6

An organic electroluminescent device was manufactured in the same manner as in Example 1, except that the compound of Formula 22 was used instead of the compound of Formula 1, which is a phosphorescent host, and a fluorescent dopant (5% by weight) represented by Formula 38 was used instead of the phosphorescent dopant. Made. The evaluation results are shown in Table 1.

<Formula 38>

<Evaluation of Organic Electroluminescent Device>

1) Driving voltage

The change of current density according to the voltage change was measured for the manufactured organic electroluminescent device. The measurement measured the current value flowing through the unit device using a current-voltmeter (Kethely 237) while increasing the current density by 2.5 mA from 2.5 mA / cm 2 to 100 mA / cm 2.

2) color coordinates

The current density of the manufactured organic electroluminescent device was measured using a luminance meter (PR650) while increasing the current density by 2.5 mA from 2.5 mA / cm 2 to 100 mA / cm 2.

3) luminance

Power was supplied from a current-voltmeter (Kethley SMU 237) and measured using a luminance meter (PR650).

4) efficiency

Luminous efficiency was calculated using the brightness and current density measured above.

Current density (mA / ㎠) Luminous Efficiency (cd / A) Power Efficiency (lm / W) Color coordinates (x, y) Example 1 10 17.92 7.52 (0.654,0.343) Example 2 10 17.76 7.83 (0.657,0.342) Example 3 10 17.05 8.16 (0.654,0.345) Comparative Example 1 10 12.92 5.38 (0.648,0.347) Comparative Example 2 10 1.39 0.49 (0.149,0.091) Comparative Example 3 10 1.43 0.40 (0.147,0.095)

As can be seen from the results of Table 1, Examples 1 to 3 using a compound selected from the group of compounds of formulas 1 to 34 according to the present invention as a phosphorescent host of the phenylcarbazole structure represented by the general formula (36) Compared with Comparative Example 1 using a phosphorescent host material, excellent red light emission characteristics can be confirmed in electrical properties, efficiency, and color coordinates. In addition, in the case of Comparative Example 3 using the compound according to the present invention in the fluorescent conditions it could be confirmed that the energy transfer does not occur. Comparative Example 2 corresponds to a naphthalenylcarbazole-based compound having a structure similar to that of the compound of the present invention or a fluorescent host compound not used as a phosphorescent host for an organic electroluminescent device defined in the present invention. It did not happen.

1 is a schematic cross-sectional view of an organic electroluminescent device according to an embodiment of the present invention.

Claims (4)

An organic thin film material for an organic electroluminescent device, comprising a compound selected from the naphthalenylcarbazole compound groups represented by Chemical Formulas 1 to 34 as a phosphorescent host.

An organic electroluminescent device having an anode, a cathode, and a plurality of organic thin film layers positioned between the anode and the cathode, wherein all or part of the plurality of organic thin film layers include the organic thin film material for organic electroluminescent devices of claim 1. An organic electroluminescent device, characterized in that. The method according to claim 2, And the organic thin film layer comprises at least one of a hole injection layer, a hole transport layer, a light emitting layer, an electron injection layer, and an electron transport layer. The method according to claim 2, The organic light emitting device, characterized in that the organic thin film layer is a light emitting layer.

Images