KR20070102857A - Red luminescent organic compound and organic light-emitting diode including the same - Google Patents

Abstract

A red light emitting organic compound is provided to obtain an organic light emitting compound having excellent thermal stability and light emitting efficiency and useful for forming hole and electron injection/transport layers in an organic light emitting diode. A red light emitting organic compound is represented by the following formula 1, wherein R1-R5 are the same or different, and represent H, CN, a halogen atom, substituted or non-substituted C1-C20 alkyl or alkoxy group, substituted or non-substituted C4-C24 aryl group, heteroaryl group or fused multicyclic group; and Ar1-Ar6 are the same or different, and each represents H, a substituted or non-substituted C1-C20 alkyl group, substituted or non-substituted C4-C24 aryl group, heteroaryl group or fused multicyclic group.

Description

Red luminescent organic compound and organic light-emitting diode including the same}

1 is a cross-sectional view of an organic light emitting diode according to an embodiment of the present invention.

2 is a cross-sectional view of an organic light emitting diode according to another embodiment of the present invention.

The present invention relates to a red organic light emitting compound and an organic light-emitting diode (OLED) including the same, and more particularly, red, which is not only excellent in thermal stability, but also useful in forming a hole and an electron injection / transport layer. An organic light emitting compound and an organic light emitting diode comprising the same.

Organic light emitting diodes, also commonly referred to as EL (Electroluminescence device), are representative flat panels with Liquid Crystal Display (LCD), Plasma Display Panel (PDP), Field Emission Display (FED), etc. As one of the display devices, a backlight for emitting light is not required, and a device may be manufactured in a thin film and a bendable form, and pattern formation and mass production by a film fabrication technique may be easily performed. In addition, since EL is a spontaneous light emitting device, it has the advantage of excellent luminance and viewing angle characteristics, fast response speed, low driving voltage, and theoretically light emission of all colors in the visible region.

The organic light emitting diode forms an organic light emitting layer having a light emitting property between a transparent electrode such as ITO having a large work function and a metal electrode such as Mg having a small work function, and applies a voltage to the electrode to generate holes and When the electrons combine in the organic light emitting layer, the organic light emitting layer uses the property of generating light. In such an organic light emitting diode, in order to manufacture a full color organic light emitting diode, it is essential to synthesize an organic light emitting compound that emits light in red, green, and blue regions, respectively. As for the compounds emitting light in the red region, U.S. Pat. 5,908,581, 5,935,720 and the like. Representative of the disclosed red organic light emitting compound, 4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (4- (dicyanomethylene) -2, which emits light of 590 nm wavelength DCM-based 4-dicyanomethylene-6-cp-zulolidinostri-2-t-butyl-4H that emits light at wavelengths of 630 nm and -methyl-6- (p-dimethylaminostyryl) -4H-pyran; -Pyran (4-dicyanomethylene-6-cp-julolidinostyryl-2-tert-butyl-4H-pyran; DCJTB), but the DCM-based red light-emitting compound is mainly substituted with a substituent such as an alkyl group to nitrogen, thermal resistance such as heat resistance Insufficient stability, deteriorates the lifespan of the organic light emitting device, there is a disadvantage that the luminous efficiency is low.

Accordingly, an object of the present invention is to provide a red organic light emitting compound having excellent thermal stability and luminous efficiency and an organic light emitting diode including the same.

Another object of the present invention is to provide an organic light emitting compound useful for the formation of a hole and an electron injection / transport layer and an organic light emitting diode comprising the same.

In order to achieve the above object, the present invention provides a red organic light emitting compound represented by the following formula (1). The present invention also includes a first electrode having a high work function, a second electrode having a low work function, and the organic light emitting compound, and including at least one organic compound layer positioned between the first and second electrodes. It provides an organic light emitting diode. The organic compound layer may be a light emitting layer, a hole injection layer, a hole transport layer, an electron injection layer or an electron transport layer, and the organic light emitting compound may be used as a host or dopant material of the light emitting layer.

[Formula 1]

Wherein, R ₁ to R ₈ may be the same as or different from each other, H, CN, halogen, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms or an alkoxy group, a substituted or unsubstituted aryl group having 4 to 24 carbon atoms, Heteroaryl group or fused ring, Ar ₁ to Ar ₆ may be the same or different from each other, H, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, substituted or unsubstituted 4 to 24 carbon atoms It is an aryl group, heteroaryl group, or condensed polycyclic group.

Hereinafter, with reference to the accompanying drawings will be described in more detail the present invention.

The red organic light emitting compound according to the present invention receives energy generated by recombination of electron-holes and emits red light, or has charge injection / transport characteristics such as electrons and holes, and has a structure represented by the following Chemical Formula 1.

Wherein R ₁ to R ₈ may be the same as or different from each other, H, CN, halogen, substituted or unsubstituted C1-20, preferably C1-6 alkyl or alkoxy, substituted or unsubstituted An aryl group or heteroaryl group having 4 to 24 carbon atoms, preferably 6 to 20 carbon atoms, a substituted or unsubstituted condensed polycyclic group having 4 to 24 carbon atoms, Ar ₁ to Ar ₆ may be the same or different from each other, H, Substituted or unsubstituted C1-C20, preferably C1-C6 alkyl group, Substituted or unsubstituted C4-C24, Preferably C6-C20 aryl group or heteroaryl group, Substituted or unsubstituted It is a C4-C24 condensed polycyclic group.

In addition, R ₁ to R ₈ and Ar ₁ to Ar ₆ may be connected to each other to form a ring, for example, adjacent R ₂ and Ar ₃ , R ₃ and Ar ₄ , R ₆ and Ar ₅ or R ₇ and Ar ₆ may be connected to each other to form a heterocyclic group, and examples of the condensed polycyclic group may include naphthyl group and anthracene group. In addition, when at least one or two or more of Ar ₁ to Ar ₆ is an aryl group, particularly when Ar ₁ and Ar ₂ is an aryl group having 6 to 24 carbon atoms, the light emitting compound is preferable because the luminous efficiency and thermal stability is improved. Substituents which may be substituted with R ₁ to R ₈ and Ar ₁ to Ar ₆ include an alkyl group having 1 to 24 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryloxy group having 6 to 30 carbon atoms, and having 1 to 20 carbon atoms. Alkylthioxy group, C6-C30 arylthioxy group, C7-C30 arylalkyl group, C5-C30 monocyclic group, C10-C30 condensed polycyclic group, C5-C30 heterocyclic group, C4 And alkenyl groups of 40 to 40 may be exemplified.

Specific examples of the red light emitting compound represented by Formula 1 may include the following compounds.

(1),

(2),

(3),

(One),

(2),

(3),

(4),

(5),

(6)

(4),

(5),

(6)

In the red organic light emitting compound according to the present invention, since the emission wavelength and the electron / hole injection / transport characteristic change according to the type of the substituent substituted by the compound represented by the formula (1), the desired emission wavelength is selected by appropriately selecting the substituent. And an organic compound layer having physical properties such as charge transfer characteristics. The red light emitting compound according to the present invention has excellent heat resistance and not only improves the lifetime and productivity of the organic light emitting device, but also emits high efficiency and high quality red light. The red organic light emitting compound according to the present invention may be prepared by various conventional organic synthesis methods.

1 is a cross-sectional view of an organic light emitting diode according to an exemplary embodiment of the present invention. As shown in FIG. 1, the organic light emitting diode includes a first electrode 12 having a high work function on the substrate 10. The light emitting layer 14 including the organic light emitting compound according to the present invention is formed on the first electrode 12 and formed as a hole injection electrode (anode). In addition, the light emitting layer 14 may include a conventional host, a conventional light emitting compound, a fluorescent dye, and / or a dopant together with the organic light emitting compound according to the present invention. When the luminescent compound of the present invention is used as a dopant with a conventional host material such as 9,10-di (2-naphthyl) anthracene (9,10-di (2-naphthyl) anthracene; ADN), The content of tart is preferably 1 to 20% by weight, more preferably 5 to 10% by weight, based on the entire host / dopant. A second electrode 16 having a low work function is formed on the emission layer 14 so as to face the first electrode 12 as an electron injection electrode (cathode). When voltage is applied to the first and second electrodes 12 and 16 of the organic light emitting diode, holes and electrons generated in the first and second electrodes 12 and 16 are injected into the light emitting layer 14, and the light emitting layer In the molecular structure of (14), electrons and holes combine to emit red light, and the emitted light passes through the first electrode 12 and the substrate 10 made of a transparent material to display an image. The substrate 10 of the organic light emitting diode is electrically insulative, and in particular, when fabricating a device emitting light toward the first electrode 12, the substrate 10 is made of a transparent material, preferably made of glass or transparent plastic film. The first electrode 12 may be made of indium tin oxide (ITO), polyaniline, silver (Ag), or the like, and the second electrode 16 may be formed of a metal such as Al, Mg, Ca, or LiAl, It may be made of a metal alloy such as Mg-Ag.

FIG. 2 is a cross-sectional view of an organic light emitting diode according to another embodiment of the present invention. In the organic light emitting diode illustrated in FIG. 2, holes and electrons generated in the first and second electrodes 12 and 16 are respectively emitted. The hole injection and transport layers 21 and 22 and the electron injection and transport layers 25 and 26 are further formed so as to be easily injected into 14, which is different from the organic light emitting diode shown in FIG. The hole injection and transport layers 21 and 22 have a function of facilitating injection of holes generated from the hole injection electrode 12 and a function of stably transporting holes, and the hole injection layer 21 is not limited. Porphyrinic compounds such as phthalocyanine copper, m-MTDATA (4,4 ', 4 "-tris (3-methylphenylphenylamino) triphenyl amine), etc. disclosed in US Pat. No. 4,356,429, The hole transport layer 22 is NPB (N, N'-diphenyl-N, N'-bis (1-naphthyl) -1,1'-biphenyl) -4,4'-diamine), triphenyldiamine Derivatives, styrylamine derivatives, α-NPD (N, N'-diphenyl-N, N'-bis (α-naphthyl)-[1,1'-biphenyl] 4,4'-diamine) It can be formed using a conventional amine derivative having an aromatic condensed ring The electron injection and transport layer (25, 26) is a function to facilitate the injection of electrons generated from the electron injection electrode 16 and electrons As a function of stably transporting, conventional electron injection and transport compounds such as, but not limited to, quinoline derivatives, in particular, tris (8-quinolinorate) aluminum (aluminaquinone, Alq3), LiF, can be used as the electron transport layer 26. These layers 21, 22, 25, and 26 function to augment, confine, and combine holes and electrons injected into the light emitting layer 14, and to improve luminous efficiency. 14), the thicknesses of the hole injection and transport layers 21 and 22 and the electron injection and transport layers 25 and 26 are not particularly limited and vary depending on the formation method, but usually have a thickness of about 5 to 500 nm.

The organic light emitting compound according to the present invention may be used as a host or dopant material of the light emitting layer 14, and according to the potential difference with other layers, the hole injection and transport layers 21 and 22 and / or the electron injection and transport layer ( 25, 26), it may also function to inject / transport electrons and holes. The organic layers may be formed by a vacuum deposition method, a spin coating method, or the like, which is commonly used for fabricating an organic electroluminescent device, and may be preferably formed by a vacuum deposition method. The organic light emitting compound of the present invention can be applied not only to the organic light emitting diode having the structure shown in FIG. 1 or 2 but also to organic electroluminescent devices and various semiconductor devices having various structures that exhibit light emission by hole-electron coupling. Such structures of various organic light emitting diodes are disclosed in, for example, US Pat. Nos. 4,539,507, 5,151,629, 6,214,481, 6,387,544, and the like.

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

Example 1 Synthesis of 2- [3,4-bis- (4-diphenylamino-phenyl) -2,5-diphenyl-cyclopenta-2,4-dienylidine] -malononitrile

As shown in Scheme 1 below, 2- [3,4-bis- (4-bromo-phenyl) -2,5-diphenyl-cyclopenta-2,4-dienyridine] -malononitrile (C ₃₂ H ₁₈ Br ₂ N ₂ ) and diphenylamine (C ₁₂ H ₁₁ N) to react 2- [3,4-bis- (4-diphenylamino-phenyl) -2,5-diphenyl- Cyclopenta-2,4-dienilidine] -malononitrile (2- [3,4-Bis- (4-diphenylamino-phenyl) -2,5-diphenyl-cyclopenta-2,4-dienylidene] -malononitrile) Was synthesized. First, in a glove box filled with an inert gas, 2- [3,4-bis- (4-bromo-phenyl) -2,5-diphenyl-cyclopenta-2,4-dienyridine ] -In a reactor containing 5.9 g (10 mmol) of malononitrile and 3.7 g (22 mmol) of diphenylamine, 91.5 mg (0.1 mmol) of palladium dibenzylideneacetone (Pd (dba)), tri-t- 40.4 mg (0.2 mmol) of butyl) phosphine (P (t-Bu) ₃ ) and 2.40 g (25 mmol) of sodium-t-butoxide (NaO-t-Bu) were added thereto, and 60 ml of xylene was added dropwise. The reaction was refluxed in an inert atmosphere for about 3 hours, then cooled, and 150 ml of methanol was added to form a precipitate. The precipitate was filtered, washed with methanol and water and dried to give 5.2 g (yield 67%) of the title compound.

Example 2 Fabrication of Organic Light Emitting Diode

The glass substrate coated with indium tin oxide (ITO) was ultrasonically cleaned, washed again with deionized water, then degreased with toluene gas and dried. Next, m-MTDATA was deposited on the ITO electrode to form a hole injection layer by vacuum deposition at a thickness of 500 kV, and α-NPD was vacuum deposited on the hole injection layer to form a hole transport layer on the ITO electrode. The red organic light emitting compound synthesized in Example 1 was deposited on the hole transport layer to a thickness of 300 kV, and then, alumina quinone (Alq3) was deposited to a thickness of 200 kW as the electron transport layer. An electron injection layer was formed by vacuum depositing LiF to a thickness of 10 Å on the electron transport layer, and aluminum was then deposited to a thickness of 1200 에 on the upper portion of the electron injection layer to form a cathode, thereby manufacturing an organic light emitting diode. The manufactured organic light emitting diodes emit high quality red light and exhibit excellent luminous efficiency.

As described above, the red organic light emitting compound according to the present invention is not only excellent in heat resistance and luminous efficiency, but also has an advantage of showing high quality and red light emission of various wavelengths according to substituents. The red organic light emitting compound according to the present invention is useful for the production of full color organic light emitting diodes, and may include field effect transistors, photodiodes, photovoltaic cells, solar cells, and organic lasers. It can be widely applied to various organic semiconductor devices such as an organic laser, a laser diode.

Claims (6)

Red organic light emitting compound represented by the formula (1). [Formula 1]

Wherein, R ₁ to R ₈ may be the same as or different from each other, H, CN, halogen, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms or an alkoxy group, a substituted or unsubstituted aryl group having 4 to 24 carbon atoms, A heteroaryl group or a condensed polycyclic group, Ar ₁ to Ar ₆ may be the same as or different from each other, H, a substituted or unsubstituted C 1 -C 20 alkyl group, a substituted or unsubstituted C 4 -C 24 aryl group, hetero It is an aryl group or a condensed polycyclic group. The red organic light emitting compound of claim 1, wherein Ar ₁ and Ar ₂ are aryl groups having 4 to 24 carbon atoms. The method of claim 1, wherein at least one selected from the group consisting of adjacent R ₂ and Ar ₃ , R ₃ and Ar ₄ , R ₆ and Ar _5, and R ₇ and Ar ₆ are connected to each other to form a heterocyclic group. A red organic light emitting compound. A first electrode having a high work function; A second electrode having a low work function; And An organic light emitting diode comprising the organic compound of Formula 1 and comprising at least one organic compound layer positioned between the first and second electrodes. The organic light emitting diode of claim 4, wherein the organic compound layer is a light emitting layer, and the organic compound is a host or dopant material of the light emitting layer. The organic light emitting diode of claim 4, wherein the organic compound layer is a layer selected from the group consisting of a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer.

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