KR101546141B1 - Luminescent organic compound containing fluorene group, and organic light emitting diode including the same - Google Patents

Abstract

The present invention relates to an organic electroluminescent compound comprising a fluorene group having a structure represented by the following formula (1), wherein R ¹ is a carbazole or a carbazole derivative, R ² is a triazole or triazole derivative, R ³ or R ⁴ is any one selected from the group consisting of H, CN, optionally substituted C ₁ to C ₄ alkyl or aryl groups, and more particularly to an organic light emitting compound containing a fluorene group and having high efficiency, high-quality blue or green An organic light emitting compound containing a fluorene group which is excellent in thermal stability and emits light, and an organic light emitting diode including the organic light emitting compound.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting diode (OLED) and a light emitting diode (OLED)

The present invention relates to a luminescent organic compound containing a fluorene group and an organic light emitting diode including the luminescent organic compound. More particularly, the present invention relates to a carbazole or carbazole derivative having a hole transporting ability in a conjugated quinoline fluorene material, The present invention relates to an organic light emitting diode which can be used as a blue or green light emitting material by increasing the band gap energy by substituting a triazole or triazole derivative having an excellent luminous efficiency and color purity.

In recent years, organic light-emitting diodes (OLED) -based displays are a type of light emitting device based on fluorescent organic compounds. Unlike LCDs, they can emit light on their own to provide no backlight, thin film, and light weight. Color reproducibility is excellent, and it has recently attracted the most attention as a device for a next generation flat panel display.

The light emitting layer material used here is classified into a fluorescent light emitting material and a phosphorescent light emitting material and is again classified by color. Electrons injected from a hole transporting layer (HTL) and an electron transporting layer (ETL) The use of only a light emitting material which emits light has a problem that color purity and luminous efficiency are deteriorated in intermolecular interaction.

In order to solve this problem, a host / dopant system has been recently used. In order to minimize the interaction of a dopant, which is a luminescent material distributed in the host, and to increase the luminous efficiency through energy transfer, The electrons excite the host, and the energy emitted from the host is absorbed by the dopant and then emitted again to emit light.

At this time, it has been known that a distryl compound as a blue or green light emitting material shows good performance in the past. However, the blue or green light emitting material can not secure a sufficient lifetime due to problems such as color purity, efficiency, and long-term thermal stability. Therefore, materials used in practical commercial products are extremely limited. Further, Since the emission wavelength of green is shorter than that of the present wavelength, the necessity of research and development is urgent.

Korean Patent Publication No. 10-2007-0009318 Korean Patent Publication No. 10-2011-0131201

Disclosure of Invention Technical Problem [8] The present invention has been made to solve the above problems, and it is an object of the present invention to lower the energy level of the highest occupied molecular orbital (HOMO) (hereinafter referred to as HOMO) using a fluorene group having a conjugation- It is an object of the present invention to provide an organic light emitting compound containing a fluorene group that emits blue or green light by increasing the energy level of the lowest unoccupied molecular orbital (LUMO) .

Another object of the present invention is to provide an organic light emitting diode comprising a luminescent organic compound containing a fluorene group excellent in luminous efficiency and color purity.

According to one embodiment of the present invention, the above object is achieved by a luminescent organic compound comprising a fluorene group having a structure represented by the following formula (1).

[Chemical Formula 1]

Wherein R ¹ is a carbazole or a carbazole derivative, R ² is a triazole or triazole derivative, and R ³ or R ⁴ is H, CN, an optionally substituted C ₁ to C ₄ alkyl or aryl group May be any one selected from the group consisting of

Further, the R ¹ may be an organic light emitting compound containing a fluorene group, which is represented by the following formula (2).

(2)

In Formula 2, R ⁵ or R ⁶ may be any one selected from the group consisting of H, CN, optionally substituted C ₁ to C ₄ alkyl or aryl group.

Further, the R ² may be an organic light emitting compound containing a fluorene group, which is represented by the following formula (3).

(3)

In the above formula 3, R ⁷ Or R ⁸ can be any one selected from the group consisting of H, CN, optionally substituted C ₁ to C ₄ alkyl or aryl groups.

Further, it may be an organic light emitting diode including an anode, a cathode, and an organic light emitting compound containing a fluorene group according to any one of the compounds.

According to the organic luminescent compound containing the fluorene group of the present invention, the conjugation is cut off due to the shortening of the conjugation length unlike the prior art, so that the band gap energy is increased and thus blue or green luminescence with higher stability than the conventional one can be obtained .

In addition, an organic light emitting diode having a fluorene group can be manufactured using an organic light emitting diode host material, and an organic light emitting diode having excellent luminous efficiency, color purity, and long-term thermal stability can be manufactured. It is possible to emit blue or green light having a short wavelength as short as possible.

FIG. 1 is a schematic diagram sequentially showing the synthesis mechanism of the compound of Formula 4,
2 is a graph showing the solution state of the compound of Formula 4, UV absorption of the film state, and photoluminescence (PL).

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings on an organic light emitting compound containing a fluorene group and an organic light emitting diode including the same according to the present invention. The present invention may be better understood by the following examples, which are for the purpose of illustrating the present invention and are not intended to limit the scope of protection defined by the appended claims.

The blue light emitting organic compound containing a fluorene group according to the present invention is a compound emitting blue or green light by receiving energy generated by the recombination of electrons and holes, and has a structure represented by the following formula (1).

[Chemical Formula 1]

Here, as a form in which two benzenes are substituted for a fluorene group, the conjugation structure of benzene is cut off and the conjugation length is reduced. As a result, the energy level of the HOMO of the compound is lowered and the energy level of the LUMO is increased, so that the band gap is increased to emit blue or green light.

In this case, R ¹ may be a substituent having a hole transporting ability, preferably a carbazole or a carbazole derivative, or more preferably a carbazole.

The carbazole or carbazole derivative has high thermal stability due to its physical properties, has excellent contact properties with the anode and flatness, and has transparency when a thin film is formed in a visible light region, so that the light emitting element of the organic light emitting diode When used, can exhibit high thermal stability and luminous efficiency.

The carbazole derivative may be substituted as long as it has the above properties, and is not limited to a specific carbazole derivative.

The R ² may be a substituent having an electron transporting ability, preferably a triazole or a triazole derivative, or more preferably a triazole.

The triazole or triazole derivative has a high electron mobility, an energy level capable of injecting electrons into the cathode, and an excellent electron transporting ability because the process of forming the anion radical with stable cathode reduction is reversible. In addition, the amorphous thin film can be formed and is a thermally stable material. When the organic light emitting diode is manufactured using the material, a high luminous efficiency can be secured.

The triazole derivative may be substituted as long as it has the above properties, and is not limited to a specific carbazole derivative.

According to the present invention, the carbazole derivative may be represented by the following formula (2).

(2)

Wherein R ⁵ or R ⁶ is H, CN, optionally substituted C ₁ to C ₁₂ Alkyl, can be an aryl group or a heteroaryl group, preferably H, CN, CH ₃ , And more preferably H. This is to minimize the volume as the substituent of the carbazole derivative.

Further, the triazole derivative according to the present invention may be represented by the following formula (3).

(3)

Here, R ⁷ Or R ⁸ is H, CN, optionally substituted C ₁ to C ₁₂ An alkyl group, an aryl group or a heteroaryl group, preferably H, CN, CH ₃ , and more preferably H. In the case of bulky substituents such as carbazole derivatives, it is preferable that the organic molecules of the compound of the present invention are substituted with bulky substituents since they are not easy to form a film.

Further, the organic electroluminescent compounds according to the invention R ¹ is substituted with the compound represented by Formula 1 on the fundamental structure And R ² , the organic compound having physical properties such as desired luminescence wavelength and charge transfer property can be obtained by appropriately selecting R ¹ and R ² , because the emission wavelength and charge / hole injection / transport properties are changed. Particularly, the organic luminescent compound is excellent in heat resistance to improve lifetime and productivity of a light emitting diode, and can emit blue or green light with high efficiency and high quality, and can also be used as a hole injecting and transporting material.

The present invention provides an organic light emitting diode comprising an organic compound disposed between a cathode, an anode and a cathode and an anode, wherein the organic component comprises an organic light emitting compound containing a fluorene group according to the present invention.

In the organic light emitting diode, the cathode may be a metal, preferably aluminum. The anode may also be a metal oxide, preferably ITO.

At this time, an electron injection layer may be further included between the cathode and the organic component, and an electron transport layer may further be included between the electron injection layer and the organic component.

Further, a hole injecting layer may be further included between the anode and the organic component, and a hole transporting layer may further be included between the hole injecting layer and the organic component.

Thus, electrons and holes are injected through the cathode and the anode when electrons are injected to the cathode and the anode. The injected electrons pass through the electron injecting layer and the electron transporting layer, and the holes recombine through the hole injecting layer and the hole transporting layer, To form an exciton and to convert the electron energy of this exciton into light energy.

Further, an organic luminescent compound containing the fluorene group of the present invention may be used as a luminescent host in an apparatus commonly used in the organic light emitting diode.

Hereinafter, the present invention will be described in more detail with reference to specific examples. The following examples are provided to illustrate the present invention, and the present invention is not limited by the following examples.

The intermediates A to G were sequentially prepared according to the production mechanism of the organic light emitting compound containing the fluorene group shown in FIG. 1 to prepare the following Formula 4, which is one embodiment of the present invention.

[Chemical Formula 4]

[Example 1] Synthesis of Compound of Formula 4

end. Synthesis of intermediate A (Fig. 1-A)

(0.046 mol) of benzoyl hydrazine, 4.6 g (0.046 mol) of triethylamine and 230 mL (0.2 M) of chloroform were added to a 500 mL round-bottomed flask, and 1 g Lt; / RTI > After the reaction was completed, the resulting precipitate was filtered, washed with water and ethanol, and 1.3 g (77%) of intermediate A was obtained.

I. Synthesis of intermediate B (Figure 1-B)

11.3 g (0.035 mol) of Intermediate A was added to a 500 mL round-bottomed flask, and 16.2 g (0.078 mol) of phosphorus pentachloride and 177 mL (0.2 M) of toluene were added and the mixture was stirred at 120 ° C for 3 hours. After the reaction was completed, the reaction mixture was cooled to room temperature and concentrated under reduced pressure to remove the solvent. The resulting precipitate was washed with water and filtered to give 10.9 g (86%) of intermediate B.

All. Synthesis of intermediate C (Fig. 1-C)

(0.034 mol) of Intermediate B was added to a 500 mL two-necked round bottom flask, and 3.2 g (0.034 mol) of aniline and 170 mL (0.2 M) of N, N-dimethylaniline were added and the mixture was stirred at 135 ° C for 12 hours. After cooling to room temperature, 2N hydrochloric acid was added and the mixture was stirred for 0.5 hours. The resulting precipitate was filtered and washed with hexane to obtain 9 g (78%) of intermediate C.

la. Synthesis of intermediate D (Fig. 1-D)

9 g (0.024 mol) of Intermediate C was added to a 250 mL two-neck round bottom flask and 6.4 g (0.025 mol) of bis (pitacolato) diboron, 4.7 g (0.048 mol) of potassium acetate and 120 mL ) Were added and stirred. 1.4 g (0.001 mol) of tetrakis (triphenylphosphine) palladium (0) was added to the mixed solution, and the mixture was heated and stirred at 80 ° C. for 12 hours. After the reaction was completed, the reaction mixture was cooled to room temperature and the solvent was removed using a distillation apparatus. The reaction solution was rinsed with water and extracted with dichloromethane. The organic layer was dried over magnesium sulfate and concentrated under reduced pressure to remove the solvent. The resulting material was separated by column chromatography using a mixed solvent of hexane and ethyl acetate to obtain 5.4 g (53%) of intermediate D.

hemp. Synthesis of intermediate E (Fig. 1-E)

(0.035 mol) of calcium carbonate, 1.1 g (0.017 mol) of kappa and 7.0 g (0.042 mol) of carbazole were placed in a 250 mL two-necked round bottom flask, (0.002 mol) of 18-crown-6 and 177 mL (0.2 M) of dimethylformamide were placed and the mixture was heated and stirred at 160 DEG C for 18 hours. After the reaction was completed, the reaction mixture was cooled to room temperature and the solvent was removed using a distillation apparatus. The reaction solution was washed with water and extracted with ethyl acetate. The organic layer was dried over magnesium sulfate and concentrated under reduced pressure to remove the solvent. The resulting product was subjected to column separation using a mixed solvent of hexane and ethyl acetate to obtain 8.9 g (78%) of intermediate E.

bar. Synthesis of Intermediate F (Figure 1 F)

Under a nitrogen atmosphere, 9.8 g (0.030 mol) of the intermediate E compound and 152 mL (0.2 M) of tetrahydrofuran were added to a 500 mL 2-necked round bottom flask and the temperature was lowered to -78 ° C. To this was slowly added n-butyllithium dilution solution (1.6M, 38.02 mL), and the mixture was stirred for 1 hour while maintaining the temperature at -78 ° C. 17.2 g (0.091 mol) of triisopropylborate was slowly added to the above mixture, the temperature of the mixture was slowly raised to room temperature, and the mixture was stirred for 12 hours. When the reaction was completed, 1N hydrochloric acid was added, and after 10 minutes, the reaction mixture was washed with water and extracted with ethyl acetate. The organic layer was dried over magnesium sulfate and concentrated under reduced pressure to remove the solvent. The resulting material was separated by column chromatography using a mixed solvent of hexane and ethyl acetate to obtain 5.9 g (67%) of intermediate F.

four. Synthesis of intermediate G (Figure 1 G)

5 g (0.009 mol) of 9,9-bis (4-bromophenyl) fluorene was added to a 250 mL two-necked round bottom flask and 0.3 g (0.004 mol) (0.0004 mol) of 18-crown-6 and 90 mL (0.1 M) of dimethylformamide were placed and the mixture was heated and stirred at 160 DEG C for 18 hours. After the reaction was completed, the reaction mixture was cooled to room temperature and the solvent was removed using a distillation apparatus. The reaction solution was washed with water and extracted with ethyl acetate. The organic layer was dried over magnesium sulfate and concentrated under reduced pressure to remove the solvent. The resulting material was separated by column chromatography using a mixed solvent of hexane and ethyl acetate to obtain 2 g (37%) of Intermediate G.

character. [Chemical Formula 4] Synthesis of Compound

(0.003 mol) of Intermediate G, 1.3 g (0.003 mol) of Intermediate D, 65 mL (0.05 M) of tetrahydrofuran, 0.6 g (0.004 mol) of calcium carbonate and 30 mL of water were placed and stirred in a 250 mL two- 0.2 g (0.0001 mol) of tetrakis (triphenylphosphine) palladium (0) was added and the mixture was heated and stirred at 80 ° C. for 24 hours. After the reaction was completed, the mixture was cooled to room temperature, The organic layer was washed twice with water. The separated organic layer was dried with magnesium sulfate and concentrated under reduced pressure to remove the solvent. The resulting material was separated by column separation using a mixed solvent of hexane and ethyl acetate to obtain 2.1 g (82%) of the compound of the formula (4).

[Chemical Formula 4] ^One H- NMR  spectrum

2H), 7.45-7.32 (m, 3H), 7.93-7.91 (d, 1H), 7.85-7.83 (M, 2H), 7.09 (d, 1H), 6.92 (m, 2H), 7.29-7.26 , ≪ / RTI > 1H), 6.85-6.82 (t, 2H)

The nuclear magnetic resonance spectrum (NMR) of the compound of formula (4) is measured against a solution in Diterrorfluoroform (CDCl ₃ ), and the peak position is in ppm from the deuterochloroform to the author intima. The peak shape is denoted by the following abbreviations; s: singlet, d: doublet, t: triplet, g: quartet, m: polyline.

FIG. 2 is a graph showing the solution state of a compound represented by Chemical Formula 4, ultraviolet absorption of a film state, and photoluminescence (PL), and has a fluorene structure among compounds represented by Chemical Formula 4 Because the conjugation is cut off, the rotation of the chain can move freely. Therefore, it can be seen that the maximum value of the optical luminescence in the solution state and the film state is very blue-shifted compared with the general structure at 367 nm and 377 nm. In addition, red-shift phenomenon is small in the film state as compared with the solution state.

In addition, the energy level of the HOMO state of the compound of Formula 4 is 2.98, the energy level of the LUMO state is 6.44 eV, and the energy level of the general LUMO state of the host material of the carbazole derivative is about 5.5 eV And triazole derivatives, the energy level of LUMO is increased by about 120% compared with the conventional one, and thus it is advantageous to have a LUMO which is large enough to use a blue phosphorescence fund.

Hereinafter, an organic light emitting diode including the compound of Formula 4 prepared according to [Example 1] is prepared, which is for illustrating the present invention, and the present invention is not limited by the following examples.

[ Example  2] Preparation of Green Organic Light Emitting Diode Including Compound

An organic light emitting diode was fabricated using Ir (ppy) ₃ as a green phosphorescent dopant as a host material, and the structure of the organic light emitting diode was ITO / PH4083 / NPB (30 nm) / compound + Ir (ppy) ₃ 7% (30 nm) / BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolin) (10 nm) / Alq ₃ (30 nm) / LiF (1 nm) / Al. Further, PEDOT / PSS was spin-coated with a hole injecting material, NPB was vacuum-deposited thereon as a hole transporting layer, and Ir (ppy) ₃ and Ir (ppy) ₃ were simultaneously evaporated to form a light emitting layer. BCP and Alq ₃ were used as the hole blocking layer and the electron transport layer, and LiF and Al were used as the cathode.

[ Example  3] Preparation of blue organic light emitting diode containing compound

The organic light emitting diode was fabricated using ITO / PH4083 / NPB (30 nm) / compound and FIrpic 7% by weight as a host material, using FIrpic, a blue phosphorescent dopant, as a dopant. (30 nm) / BCP (10 nm) / Alq ₃ (30 nm) / LiF (1 nm) / Al. Further, PEDOT / PSS was spin-coated with a hole injecting material, NPB was vacuum-deposited thereon as a hole transporting layer, and Ir (ppy) ₃ and Ir (ppy) ₃ were simultaneously evaporated to form a light emitting layer. BCP and Alq ₃ were used as the hole blocking layer and the electron transport layer, and LiF and Al were used as the cathode.

[ Comparative Example  One] CBP (4,4'-N, N- dicarbazolebiphenyl ) To manufacture a green organic light emitting diode

The organic light emitting diode was fabricated using ITO / PH4083 / NPB (30 nm) / CBP + Ir (ppy) ₃ as the host material and Ir (ppy) ₃ as the green phosphorescent dopant. 7% (30 nm) / BCP (10 nm) / Alq ₃ (30 nm) / LiF (1 nm) / Al. Further, PEDOT / PSS was spin-coated with a hole injecting material, NPB was vacuum-deposited thereon as a hole transporting layer, and Ir (ppy) ₃ and Ir (ppy) ₃ were simultaneously evaporated to form a light emitting layer. BCP and Alq ₃ were used as the hole blocking layer and the electron transport layer, and LiF and Al were used as the cathode.

[ Comparative Example  2] CBP Was used as a host to manufacture a blue phosphorescent organic light emitting diode

The organic light emitting diode was fabricated using ITO / PH4083 / NPB (30 nm) / CBP + FIrpic 7% (30 nm) / ITO / CBP as a host material and FIrpic as a blue phosphorescent dopant as a dopant. CBP (10 nm) / Alq ₃ (30 nm) / LiF (1 nm) / Al. Further, PEDOT / PSS was spin-coated with a hole injecting material, NPB was vacuum-deposited thereon as a hole transporting layer, and Ir (ppy) ₃ and Ir (ppy) ₃ were simultaneously evaporated to form a light emitting layer. CBP and Alq ₃ were used as the hole blocking layer and electron transporting layer, and LiF and Al were used as the cathode.

Table 1 shows the luminescent efficiencies and color coordinates of the examples and comparative examples.

Luminous efficiency Color coordinates Example 2 31 cd / A (0.32, 0.62) Example 3 32 cd / A (0.17, 0.35) Comparative Example 1 7.6 cd / A (0.29, 0.61) Comparative Example 2 6.1 cd / a (0.18, 0.36)

(0.17, 0.35) in the same manner as in Example 2 having a green color coordinate (0.32, 0.62) when a compound represented by Formula 4 containing a fluorene group was used as a host material according to an embodiment of the present invention 3 also shows that the blue LED device having a luminous efficiency of 32 cd / A and a luminous efficiency lower than that of the conventional green LED device has a higher luminous efficiency than that of green.

In addition, the organic light emitting diode of the present invention has a luminous efficiency which is approximately 1.5 to 3 times higher than that of a blue organic light emitting diode device, which conventionally has an emission efficiency of 10 cd / A to 20 cd / A.

On the other hand, comparing the luminous efficiencies of Comparative Example 1 having a green color coordinate system and Comparative Example 2 having a blue color coordinate system, Comparative Example 1 of green has a luminous efficiency of about 1.2 times higher than Comparative Example 2 of blue, There still exists a problem of low luminous efficiency of the diode element.

Further, when comparing Examples 2 and 3 and Comparative Examples 1 and 2 which are different from the host material, the organic light emitting diode devices of Examples 2 and 3 including the compound of Formula 4, which is one embodiment of the present invention, It is seen that the luminous efficiency is about 4 to 5 times better than that of the organic light-emitting diode devices of Comparative Examples 1 and 2 which are used as materials.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention.

Claims (4)

An organic light-emitting compound comprising a fluorene group having a structure represented by the following formula (1).
[Chemical Formula 1]

Wherein R ⁵ , R ⁶ , R ⁷ and R ⁸ are H in the above formula (1).
delete delete cathode;
anode; And
An organic light-emitting diode comprising an organic light-emitting compound comprising a fluorene group according to claim 1.

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