KR101807223B1 - organic light-emitting diodes - Google Patents

Abstract

The present invention provides an organic electroluminescent device employing a dopant compound having a specific structure, and the organic electroluminescent device of the present invention has a high luminous efficiency.

Description

Organic light-emitting diodes

[0001] The present invention relates to an organic electroluminescent device, and more particularly, to an organic electroluminescent device in which an organic material layer is interposed between an anode and a cathode, wherein the organic material includes a host material and a phenyl-pyridinyl derivative And an electroluminescent device.

Organic light-emitting diodes (OLEDs), one of the new flat panel displays, have been developed since 1982 when organic materials first discovered luminescent phenomena and started to develop. Flat panel TVs, flexible displays, and lighting applications.

In general, an OLED is formed on a glass substrate in the following order: an anode made of a transparent electrode, an organic thin film including a light emitting region, and a metal electrode. In this case, the organic thin film may include a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), or an electron injection layer (ETL) in addition to a light emitting layer (EIL), and may further include an electron blocking layer (EBL) or a hole blocking layer (HBL) on the light emitting property of the light emitting layer. When an electric field is applied to the OLED device having such a structure, holes are injected from the anode and electrons are injected from the cathode. The injected holes and electrons recombine in the light emitting layer through the hole transporting layer and the electron transporting layer, respectively, . The formed luminescent excitons emit light while transitioning to a ground state.

The emission of light from an OLED device can be broadly classified into fluorescence and phosphorescence. Fluorescence is a phenomenon in which organic molecules emit light when falling from a single excited state to a ground state, Phosphorescence is a phenomenon in which organic molecules emit light when they fall from a triplet excited state to a ground state.

Electrons and holes injected into the LUMO and HOMO of the organic light emitting layer constituting the organic light emitting device are recombined to form an exciton. The excited energy of the exciton is converted into light energy, and excitons are generated. Thereby realizing light of a color corresponding to the energy bandgap of the light emitting layer. In this process, a singlet exciton with a spin of zero and a triplet exciton with a spin of 1 are produced at a ratio of 1: 3. When the transition from the excited state to the ground state occurs, the transition process in which the electron spin quantum number is changed is the electron spin inhibition process, and after the electron spin flipping proceeds, the transition is made to the bottom state. , lifetime) becomes longer. That is, the emission duration of fluorescence emission is only several nanoseconds, but in the case of phosphorescence, the relatively long time is several microseconds. At this time, a luminescent dye (dopant) may be doped in the light emitting layer (host) to increase the efficiency and stability of the light emitting state.

Since the bottom state of an organic molecule is usually a singlet state, a single-term exciton can transition to a singlet ground state without changing the electron spin quantum number, so that it can emit fluorescence by efficiently transferring light to a ground state. However, Since the exciton has to change the spin quantum number, the exciton emits phosphorescent light efficiently and can not make the transition, and the excited energy of the triplet exciton can not be converted to light. Therefore, the maximum internal quantum efficiency of an organic light emitting device, in which a fluorescent dye is used as a light emitting layer or doped into a light emitting layer, is limited to 25%. However, if the spin-orbital coupling can be greatly increased, the mixing of singlet and triplet states is increased and the efficiency of intersystem crossing between singlet-triplet states is greatly increased, Anti-excitons can also undergo transition with phosphorescence in the ground state. If triplet excitons can be used to emit light together with singlet excitons, the internal quantum efficiency of the organic light emitting device can be improved to 100% theoretically.

Therefore, when the triplet is not consumed in other processes but emitted as light, a process for obtaining a highly efficient organic light emitting device can be obtained. In order to remarkably improve the luminous efficiency of the organic light emitting device, it is necessary to develop an efficient phosphor and to develop an organic light emitting device using the phosphor.

Particularly, since the spin-orbit coupling is proportional to the fourth power of the atomic number, a heavy atom complex such as platinum (Pt), iridium (Ir), europium (Eu), and terbium (Tb) has high phosphorescence efficiency. Among these, the platinum complex is a ligand-centered exciton (LC exciton) with the lowest triplet exciton centered on the ligand, and the triplet exciton with the lowest energy is mainly the charge between the central metal-ligand And a metalligand charge transfer (MLCT). Therefore, iridium (III) complexes are known as the most efficient compounds as phosphors for organic light emitting devices because they exhibit high phosphorescence efficiency and short triplet exciton lifetimes.

The development of many iridium (III) complexes has been progressed based on the excellent phosphorescent ability and luminescence efficiency improvement ability of the iridium (III) complex. The general structure of iridium (III) complexes is a complex of (C ^ N) ₃ Ir type consisting of three cyclometalating main ligands (C ^ N), two metal cyclic primary ligands and monovalent (C ^ N) ₂ Ir (LX) type complex containing a monoanionic bidentate ancillary ligand (LX).

The red phosphorescent material is a (C ^ N) ₂ Ir (LX) type complex structure including an auxiliary ligand, and acetylactone (acac) is the most widely used auxiliary ligand.

However, red phosphorescent materials with acetylacetone as an auxiliary ligand have excellent color purity and high luminous efficiency in red and violet regions and are highly likely to be commercialized. However, they have low thermal stability and high doping concentration and high current density Triplet-triplet annihilation or triplet-excition quenching phenomenon in the light-emitting layer, which can overcome this problem. need.

Applied Physics Letters, vol. 75, issue 1, 4-6, 1999

Accordingly, the present inventors have made efforts to solve the above-mentioned problems, and as a result, they have succeeded in inventing an organic electroluminescent device having a high thermal stability, excellent luminescence brightness, and high external quantum efficiency by employing a dopant compound having a specific structure.

An object of the present invention is to provide an organic electroluminescent device in which an organic material layer is inserted between an anode and a cathode, wherein the organic material layer contains a host compound and a dopant compound having a specific structure.

The present invention relates to an organic electroluminescent device, and more particularly to an organic electroluminescent device in which an organic material layer is inserted between a cathode and a cathode on a substrate, And a dopant compound represented by the following formula (1): < EMI ID = 1.0 >

[Chemical Formula 1]

[In the above formula (1)

R is (C1-C20) alkyl;

R ₁ to R ₈ are independently selected from the group consisting of hydrogen, (C 1 -C 20) alkyl, (C 1 -C 20) aryl or (C ₁ -C 20) alkylsilyl, where R ₁ to R ₈ are all hydrogen;

R ₉ is hydrogen, (C 1 -C 20) alkyl or (C 1 -C 20) aryl;

n is an integer from 1 to 3;

and o is an integer of 1 to 4.]

Preferably, the formula (1) may be represented by the following formula (2).

(2)

[In the formula (2)

R ₁ to R ₈ independently of one another are hydrogen, (C 1 -C 20) aryl or (C ₁ -C 20) alkylsilyl, except when R ₁ to R ₈ are all hydrogen;

R ₉ is hydrogen, (C 1 -C 20) alkyl or (C 1 -C 20) aryl;

and o is an integer of 1 to 4.]

Preferably, R ₁ to R ₈ in Formula 2 according to an embodiment of the present invention are independently hydrogen, phenyl or tri (C ₁ -C 20) alkylsilyl groups, and when R ₁ to R ₈ are all hydrogen .

Preferably, the formula (1) of the present invention may be represented by the following formulas (3) to (5).

(3)

[Chemical Formula 4]

[Chemical Formula 5]

[In the above formulas 3 to 5,

R ₁ to R ₈ independently of one another are hydrogen, (C 1 -C 20) aryl or (C ₁ -C 20) alkylsilyl, except that R ₁ through R ₈ are all hydrogen,

R < ₁₁ > and R < ₁₂ > independently of one another are (C1-C20)

In formula (3), R ₁ to R ₈ are independently hydrogen, phenyl or tri (C ₁ -C 20) alkylsilyl groups, and when R ₁ to R ₈ are all hydrogen, they are excluded Lt; / RTI >

The dopant compounds represented by Formula 1 of the present invention can be selected from the following structural formulas.

The host compound according to an embodiment of the present invention may include 1,3,5-tricarbazolylbenzene, m-biscarbazolylphenyl, 4,4 ', 4 "-tri (N-carbazolyl) triphenylamine, (2-carbazolylphenyl) benzene, bis (4-carbazolylphenyl) silane, tris (4-carbamoylphenyl) (1-phenyl-1-H-benzimidazole) selected from 2,2 ', 2 "- (1,3,5-benzyltriyl) -tris Lt; / RTI >

The organic electroluminescent device of the present invention employs a specific dopant compound and has a high thermal stability compared to an organic electroluminescent device employing acetylacetonyl as a conventional assistant ligand and has excellent luminous efficiency.

Also, the organic electroluminescent device of the present invention has excellent luminous efficiency as a specific combination of host-dopant compounds of the present invention.

1 and 2 are geometrical molecular arrangements and laminated structures according to X-ray single crystals of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) as the dopant compounds of Examples 1 and 2 of the present invention.
3 is a thermogravimetric analysis curve of the dopant compounds (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) in Examples 1 and 2 of the present invention.
4 is an absorption spectrum of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) which are dopant compounds of Examples 1 and 2 of the present invention.
5 is an emission spectrum of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) which are the dopant compounds of Examples 1 and 2 of the present invention.
6 is a cyclic voltammetric curve of the dopant compounds (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) in Examples 1 and 2 of the present invention.
7 is a stacked structure of the organic electroluminescent devices of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) as the dopant compounds of Examples 1 and 2 of the present invention.
8 is an electroluminescence spectrum of an organic electroluminescent device of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) as the dopant compounds of Examples 1 and 2 of the present invention.
9 is a graph showing current density-voltage-luminescence intensities of organic electroluminescent devices of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) as the dopant compounds of Examples 1 and 2 of the present invention to be.
10 is a curve measuring the external quantum efficiency-luminescence brightness of organic electroluminescent devices of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) as the dopant compounds of Examples 1 and 2 of the present invention .

The present invention provides an organic electroluminescent device having characteristics of high light emission luminance and external quantum efficiency.

The organic electroluminescent device of the present invention is an organic electroluminescent device in which an organic material layer is interposed between a cathode and an anode, and the organic material layer includes a host compound and a dopant compound represented by the following formula (1).

[Chemical Formula 1]

[In the above formula (1)

R is (C1-C20) alkyl;

R ₁ to R ₈ are independently selected from the group consisting of hydrogen, (C 1 -C 20) alkyl, (C 1 -C 20) aryl or (C ₁ -C 20) alkylsilyl, and R ₁ to R ₈ are both hydrogen;

R ₉ is hydrogen, (C 1 -C 20) alkyl or (C 1 -C 20) aryl;

n is an integer from 1 to 3;

and o is an integer of 1 to 4.]

The organic electroluminescent device of the present invention can be used for the triplet-triplet annihilation or the triplet-luminescent exciton disappearance at a high doping concentration and a high current density by introducing the specific dopant compound represented by the formula (1) triplet-excition quenching phenomenon can be reduced, ultimately the luminous efficiency can be increased, and the thermal stability is also excellent.

)를 채용한 화합물을 도판트 화합물로 도입한 유기 전계 발광 소자와 대비하여 높은 열안정성, 발광휘도 및 외부양자효율을 가진다.More specifically, the organic electroluminescent device of the present invention employs a 4-methylquinoline-phenyl derivative as a main ligand and employs a phenyl-pyridine derivative as an auxiliary ligand to form an acetylacetonyl derivative (for example, acetylacetone,

) Has higher thermal stability, luminescence brightness, and external quantum efficiency as compared with an organic electroluminescent device doped with a dopant compound.

The dopant compound represented by the formula (1) of the present invention is a compound in which a 4-methylquinolinyl-phenyl derivative as a main ligand and a phenyl-pyridinyl derivative as an auxiliary ligand are intentionally selected as a combination of a high doping concentration and a high current density Triplet-triplet annihilation or triplet-excition quenching phenomenon is also reduced in the light emitting layer and the quantum efficiency of the light emitting layer, - Pyridinyl derivative introduction minimizes the interaction between the dopant compounds and reduces self-extinction of phosphorescence.

Preferably, the formula (1) may be represented by the following formula (2).

(2)

[In the formula (2)

R ₁ to R ₈ independently of one another are hydrogen, (C 1 -C 20) aryl or (C ₁ -C 20) alkylsilyl, except when R ₁ to R ₈ are all hydrogen;

R ₉ is hydrogen, (C 1 -C 20) alkyl or (C 1 -C 20) aryl;

and o is an integer of 1 to 4.]

(1), R ₁ to R ₈ independently represent hydrogen, phenyl or tri (C1-C20) alkylsilyl (C1-C20) alkylsilyl When R ₁ to R ₈ are both hydrogen, they may be excluded.

Preferably, the formula (1) of the present invention may be represented by the following formulas (3) to (5).

(3)

[Chemical Formula 4]

[Chemical Formula 5]

[In the above formulas 3 to 5,

R ₁ to R ₈ independently of one another are hydrogen, (C 1 -C 20) aryl or (C ₁ -C 20) alkylsilyl group, except that R ₁ to R ₈ are all hydrogen,

R < ₁₁ > and R < ₁₂ > independently of one another are (C1-C20)

In the present invention, R ₁ to R ₈ independently represent hydrogen, phenyl or tri (C ₁ -C 20) alkylsilyl group, and R ₁ to R ₈ may be excluded if they are all hydrogen.

Specifically, the dopant compound (iridium (III) complex compound) represented by Formula 1 of the present invention may be selected from the following structural formulas, but is not limited thereto.

The host compound according to an embodiment of the present invention may include 1,3,5-tricarbazolylbenzene, m-biscarbazolylphenyl, 4,4 ', 4 "-tri (N-carbazolyl) triphenylamine, (2-carbazolylphenyl) benzene, bis (4-carbazolylphenyl) silane, tris (4-carbamoylphenyl) (1-phenyl-1-H-benzimidazole) selected from 2,2 ', 2 "- (1,3,5-benzenetriyl) -tris And more preferred combinations with the dopant compounds of the present invention are bis (4-carbazolylphenyl) silane, tris (4-carbazolyl-9-phenyl) (1-phenyl-1-H-benzimidazole) (2,2 ', 2 ' 2 "- (1,3,5-benzinetriyl) -tris (1-phenyl-1-H-benzimidazole) (TPBi) or a mixture thereof.

The organic electroluminescent device of the present invention has a certain high efficiency characteristic as a combination of the specific dopant compound represented by the formula (1) and the host compound described above.

The substituents comprising " alkyl ", " alkoxy " and other " alkyl " moieties described in this invention encompass both linear and branched forms.

&Quot; Aryl " in the present invention means an organic radical derived from an aromatic hydrocarbon by one hydrogen elimination and is a single or fused ring containing 4 to 7, preferably 5 or 6 ring atoms, And includes a form in which a plurality of aryls are connected by a single bond. Specific examples thereof include phenyl, naphthyl, biphenyl, terphenyl, anthryl, indenyl, fluorenyl, phenanthryl, triphenylenyl, pyrenyl, perylenyl, But are not limited thereto.

&Quot; Alkylsilyl " as used in the present invention includes monoalkylsilyl, dialkylsilyl, and trialkylsilyl, respectively, unless otherwise specified.

The "(C 1 -C 20) alkyl group" described in the present invention is preferably (C 1 -C 10) alkyl, more preferably (C 1 -C 5) May preferably be (C6-C12) aryl.

The organic layer according to an embodiment of the present invention may include a light emitting layer and a charge generating layer at the same time.

The light emitting layer according to an embodiment of the present invention may be a single layer as a light emitting layer, or may be a plurality of layers in which two or more layers are stacked. In the case of using the dopant host in the constitution of the present invention in combination, it was confirmed that the luminous efficiency was remarkably improved.

It is needless to say that the organic electroluminescent device of the present invention can be manufactured within a range recognized by those skilled in the art.

Hereinafter, the luminescent characteristics of the dopant compound and the device according to the present invention will be described in order to facilitate a detailed understanding of the present invention. However, the scope of the present invention is not limited thereto.

[Reagents used in the present invention]

Iridium trichlorohydrate (IrCl ₃ ?? H ₂ O), silver trifluoromethanesulfonate, phenylboronic acid, 3,5-dimethylboronic acid (2,5- dimethylboronic aicd, 3-biphenylboronic acid, trimethylsilyl chloride, 2-bromopyridine, 2-ethoxyethanol, dicyclohexylcarbodiimide, Dichloromethane, 2-propanol, and ethanol were purchased from Junsei, Aldrich, Alpha Eisai and Sejin City, and used without purification.

[Preparation Example 1] Preparation of 2 - ([1,1'-biphenyl] -4-yl) pyridine (secondary cyclization ligand L1)

2- (4-bromophenyl) pyridine (3.0 g, 12.8 mmol) and phenylboronic acid (1.56 g, 12.8 mmol) were dissolved in anhydrous THF (100 mL) in a round flask equipped with a condenser. Here it was added dissolved in dry THF (20 mL) of the _{Pd (PPh 3) 4 (0.44} g, 0.38 mmol) catalyst. Then, a 2M aqueous K ₂ CO ₃ solution (120 mL) was added thereto, and then Aliquat 336 (0.5 g, 1.3 mmol) was added thereto, followed by stirring at 100 ^° C for 2 hours. After completion of the reaction, ethyl acetate / brine was added to extract the product, and then Compound L1 was obtained (2.53 g, 85.3%).

_{^{1 H-NMR (CDCl 3)}} : δ 8.70 (d, 1H), 8.25 (d, 2H), 7.98 (d, 1H), 7.90 (t, 1H), 7.78 (m, 4H), 7.49 (t, 2H ), 7.41 (d, 1 H), 7.33 (m, 1 H).

[Preparation Example 2] Preparation of 2- (4- (trimethylsilyl) phenyl) pyridine (secondary cyclization ligand L2)

2- (4-bromophenyl) pyridine (3.0 g, 12.8 mmol) was added to a round flask, and after vacuum treatment, anhydrous ether (120 mL) was added. To this was added n- BuLi (5.1 mL, 12.8 mmol, 2.5 M in hexane) slowly at -78 ^° C and stirred for 1 h. Chlorotrimethyl silane (1.4 g, 12.8 mmol) was slowly added thereto at -78 ^° C and then stirred at room temperature for 12 hours. After completion of the reaction, the reaction was terminated by slow addition of methanol, and extraction with ethyl acetate / brine was conducted to obtain compound L2 (2.24 g, 76.9%).

_{^{1 H-NMR (CDCl 3)}} : δ 7.75 (d, 1H), 7.99 (d, 2H), 7.73 (m, 2H), 7.65 (d, 2H), 7.22 (m, 1H), 0.30 (s, 9H , CH _3).

[Preparation Example 3] Preparation of 2 - ([1,1'-biphenyl] -3-yl) pyridine (secondary cyclization ligand L3)

2-Bromopyridine (3.0 g, 19.0 mmol) and 3-biphenylboronic acid (3.8 g, 19.2 mmol) were dissolved in anhydrous THF (100 mL) to a round flask equipped with a condenser. Here it was added dissolved in dry THF (20 mL) of the _{Pd (PPh 3) 4 (0.66} g, 0.57 mmol) catalyst. Aliquat 336 (0.77 g, 1.9 mmol) was added after the addition of a 2M aqueous K ₂ CO ₃ solution (120 mL) and the mixture was stirred at 100 ^° C for 12 hours. After completion of the reaction, ethyl acetate / brine was added to extract the product, and then Compound L3 was obtained (3.18 g, 72.5%).

¹ H-NMR (CDCl ₃ ):? 8.71 (d, IH), 8.42 (s, IH), 8.13 (d, IH), 8.05 ), 7.60 (m, 3H), 7.42 (m, 2H).

[Preparation Example 4] Preparation of 2,5-diphenylpyridine (secondary cyclization ligand L4)

2,5-dibromopyridine (3.0 g, 12.6 mmol) and phenylboronic acid (3.0 g, 25.2 mmol) were dissolved in 100 mL of anhydrous THF in a round flask equipped with a condenser. Here it was added dissolved in dry THF (20 mL) of the _{Pd (PPh 3) 4 (0.88} g, 0.76 mmol) catalyst. To this was added K ₂ CO ₃ aqueous solution (120 mL) of ₂ M concentration, Aliquat 336 (0.51 g, 1.26 mmol) was added thereto, and the mixture was stirred at 100 ^° C for 12 hours. After completion of the reaction, ethyl acetate / brine was added to extract the product to obtain Compound L4 (2.28 g, 78.1%).

_{^{1 H-NMR (CDCl 3)}} : δ 8.78 (s, 1H), 8.29 (d, 2H), 8.03 (d, 1H), 7.69 (d, 1H), 7.61 (d, 2H), 7.51 (t, 2H ), 7.43 (m, 4H).

[Preparation Example 5] Preparation of 2 -phenyl-5- (trimethylsilyl) pyridine (Compound L5)

2,5-dibromopyridine (3.0 g, 12.6 mmol) is added to a round flask, and after vacuum treatment, anhydrous ether (150 mL) is added. At -78 ^° C, n- BuLi (5.1 mL, 12.6 mmol 2.5 M in hexane) was slowly added thereto and stirred for 1 hour. Chlorotrimethyl silane (1.4 g, 12.6 mmol) was slowly added thereto at -78 ^° C and stirred at room temperature for 12 hours. After completion of the reaction, methanol was added slowly, ethyl acetate / brine was added to extract the product, and then Compound L5-1 (2.2 g, 74.3%) was obtained.

_{^{1 H-NMR (CDCl 3)}} : δ 8.40 (s, 1H), 7.62 (d, 1H), 7.45 (d, 1H), 0.28 (s, 9H).

L5-1 (2.2 g, 9.6 mmol) and phenylboronic acid (1.8 g, 9.6 mmol) were dissolved in anhydrous THF (100 mL) previously prepared in a round flask equipped with a condenser. Here it was added dissolved in dry THF (20 mL) of the _{Pd (PPh 3) 4 (0.34} g, 0.29 mmol) catalyst. After adding 2M aqueous K ₂ CO ₃ solution (120 mL), Aliquat 336 (0.39 g, 0.96 mmol) was added and stirred at 100 ^° C for 12 hours. After completion of the reaction, ethyl acetate / brine was added to extract the product to obtain Compound L5 (1.49 g, 68.6%).

_{^{1 H-NMR (CDCl 3)}} : δ 8.78 (s, 1H), 8.32 (d, 2H), 7.93 (d, 1H), 7.69 (d, 1H), 7.55 (t, 2H), 7.47 (m, 1H ), 0.05 (s, 9H).

Production Example 6 Production of 2 - ([1,1'-biphenyl] -3-yl) -5- (trimethylsilyl) pyridine (secondary cyclization ligand L6)

2,5-dibromopyridine (3.0 g, 12.6 mmol) was added to a round flask, and after vacuum treatment, anhydrous ether (150 mL) was added. N- BuLi (5.1 mL, 12.6 mmol, 2.5 M in hexane) was slowly added under -78 ^° C and stirred for 1 hour. Chlorotrimethyl silane (1.4 g, 12.6 mmol) was slowly added thereto at -78 ^° C and stirred at room temperature for 12 hours. After completion of the reaction, the reaction was terminated by slow addition of methanol, and ethyl acetate / brine was added to extract the product, thereby obtaining 2.2 g (74.3%) of compound L6-1.

_{^{1 H-NMR (CDCl 3)}} : δ 8.40 (s, 1H), 7.62 (d, 1H), 7.45 (d, 1H), 0.28 (s, 9H).

L6-1 (2.2 g, 9.6 mmol) and 3-biphenylboronic acid (1.9 g, 9.6 mmol) were dissolved in anhydrous THF (100 mL) to a round flask equipped with a condenser. Here it was added dissolved in dry THF (20 mL) of the _{Pd (PPh 3) 4 (0.34} g, 0.29 mmol) catalyst. Then, 2M K ₂ CO ₃ aqueous solution (120 mL) was added thereto, and then Aliquat 336 (0.39 g, 0.96 mmol) was added thereto, followed by stirring at 100 ^° C. for 12 hours. After completion of the reaction, ethyl acetate / brine was added to extract the product to obtain Compound L6 (2.56 g, 88.6%).

¹ H-NMR (CDCl ₃ ):? 8.83 (s, IH), 8.31 (s, IH), 8.01 (d, IH), 7.88 ), 7.52 (m, 2H), 7.39 (d, 2H), 0.35 (s, 9H).

[Example 1] Synthesis of dopant compound 1 (MPQ) ₂ Preparation of Ir (Pppy)

Preparation of 4-methyl-2-phenylquinoline (Compound A-1)

2-chloro-4-methylquinoline (3.0 g, 16.8 mmol) and phenylboronic acid (2.0 g, 16.8 mmol) were dissolved in 100 mL of anhydrous THF in a round flask equipped with a condenser. The catalyst is _{Pd (PPh 3) 4 (0.58} g, 0.5 mmol) was added dissolved in dry THF (20 mL). To this was added K ₂ CO ₃ aqueous solution (120 mL) of ₂ M concentration, Aliquat 336 (0.69 g, 1.7 mmol) was added thereto, and the mixture was stirred at 100 ^° C for 12 hours. After completion of the reaction, ethyl acetate / brine was added to extract the product to obtain Compound A-1 (3.09 g, 83.5%).

¹ H-NMR (CDCl ₃ ):? 8.18 (m, 3H), 7.97 (d, IH), 7.78 , CH _3).

Preparation of chlorine-crosslinked dimer (Compound A-2) containing iridium

To a round flask equipped with a condenser, 2-ethoxyethanol / water (3: 1, v / v) was added IrCl ₃ H ₂ O (0.67 g, 2.3 mmol) and Compound A- (100 mL). The mixture was refluxed at 135 ^° C for 24 hours. After completion of the reaction, the reaction mixture was cooled to room temperature and the resulting precipitate was filtered, washed with an ether solution and then dried in a vacuum oven. Through the dried solid compound, a chlorine-crosslinked dimer (A-2) containing iridium which is an intermediate of the final compound was obtained. The chlorine-crosslinked dimer containing iridium underwent the following reaction without further purification.

The iridium-based phosphorescent compound (MPQ) containing the secondary cyclization ligand L1 ₂ Ir (Pppy))

In a round flask, add Compound A-2 (0.5 g, 0.38 mmol) and silver trifluoromethanesulfonate (0.2 g, 0.76 mmol) and dissolve in dichloromethane / 2-propanol mixed solvent (120 mL). The mixture was stirred at room temperature for 24 hours. After completion of the reaction, the reaction product was concentrated under reduced pressure and filtered through a Celite powder. The filtrate was concentrated under reduced pressure to give a precipitate through hexane. The obtained precipitate was put into a round flask equipped with a condenser, together with the L1 secondary cyclization ligand (0.18 g, 0.76 mmol), and dissolved in an ethanol solvent (150 mL). The mixture was stirred at about < RTI ID = 0.0 > 80 C < / RTI > After completion of the reaction, dichloromethane / brine was added to extract the product, and then an iridium (III) complex (MPQ) ₂ Ir (Pppy) was obtained by column chromatography (0.29 g, 45.3%).

_{^{1 H-NMR (CDCl 3)}} : δ 8.21 (d, 1H), 8.07 (s, 1H), 8.03 (s, 1H), 7.88 (m, 2H), 7.81 (t, 2H), 7.72 (t, 2H ), 7.63 (d, IH), 7.52 (t, IH), 7.44 (m, 3H), 6.99 (m, 3H) , 2.82 (s, 3 H), 2.76 (s, 3 H).

MALDI-TOF (M ⁺¹ , C ₄₉ H ₃₆ IrN ₃ ): calcd for 859.25, found; 859.29. (Purity: 99.7% by HPLC)

[Example 2] Synthesis of dopant compound 2 (MPQ) ₂ Preparation of Ir (TMSppy)

Compound A-2 (0.5 g, 0.38 mmol) and silver trifluoromethanesulfonate (0.20 g, 0.76 mmol) were placed in a round flask and dissolved in a solvent (120 mL) mixed with dichloromethane / 2-propanol. The mixture was stirred at room temperature for 24 hours. After completion of the reaction, the reaction product was concentrated under reduced pressure and filtered through Celite powder. The filtered reaction was concentrated under reduced pressure to give a precipitate through hexane. The obtained precipitate was added to a round-bottom flask equipped with a condenser again with an L2 cyclic ligand (0.17 g, 0.76 mmol) and dissolved in an ethanol solvent (150 mL). The mixture was stirred at 80 < 0 > C for 24 hours. After completion of the reaction, dichloromethane / brine was added to extract the product, and then an iridium (III) complex (MPQ) ₂ Ir (TMSppy) was obtained by column chromatography (0.28 g, 43.9%).

_{^{1 H-NMR (CDCl 3)}} : δ 8.27 (d, 1H), 8.09 (s, 1H), 7.95 (s, 1H), 7.84 (m, 5H), 7.68 (d, 2H), 7.62 (d, 1H 2H), 6.84 (m, 2H), 6.74 (m, 2H), 7.48 (m, 2H) 2.74 (s, 3H), 0.04 (s, 9H).

MALDI-TOF (M ⁺¹ , C ₄₆ H ₄₀ IrN ₃ Si): calcd for 855.26, found; 855.73 (HPLC purity: 99.6%.)

[Example 3] Synthesis of dopant compound 3 (MPQ) ₂ Ir ( m Pppy)

Compound A-2 (0.5 g, 0.38 mmol) and silver trifluoromethanesulfonate (0.20 g, 0.76 mmol) were placed in a round flask and dissolved in a solvent (120 mL) mixed with dichloromethane / 2-propanol. The mixture was stirred at room temperature for 24 hours. After completion of the reaction, the reaction product was concentrated under reduced pressure and filtered through a Celite powder. The filtered reaction was concentrated under reduced pressure to give a precipitate through hexane. The resultant precipitate was placed in a round flask equipped with a condenser, together with an L3 secondary cyclization ligand (0.18 g, 0.76 mmol), and dissolved in an ethanol solvent (150 mL). The mixture was stirred at 80 < 0 > C for 24 hours. After completion of the reaction, dichloromethane / brine was added to extract the product, and then an iridium (III) complex (MPQ) ₂ Ir ( m Pppy) was obtained by column chromatography (0.26 g, 41.2%).

_{^{1 H-NMR (CDCl 3)}} : δ 8.56 (d, 1H), 8.39 (s, 1H), 8.30 (m, 2H), 8.16 (d, 2H), 7.97 (m, 4H), 7.81 (m, 2H ), 7.63 (t, IH), 7.59 (m, 4H), 7.51 (m, 6H), 7.41 (m, , 2.82 (s, 3 H), 2.76 (s, 3 H).

MALDI-TOF (M ⁺¹ , C ₄₉ H ₃₆ IrN ₃ ): calcd for 859.25, found; 859.14 (HPLC purity: 99.3%.)

[Example 4] Synthesis of dopant compound 4 ((MPQ) ₂ Ir (ppyP))

Preparation of Iridium-based phosphorescent compound _{((MPQ) 2 Ir (ppyP} )) , including secondary cyclization ligand L4

Compound A-2 (0.5 g, 0.38 mmol) and silver trifluoromethanesulfonate (0.20 g, 0.76 mmol) were placed in a round flask and dissolved in a solvent (120 mL) mixed with dichloromethane / 2-propanol. The mixture was stirred at room temperature for 24 hours. After completion of the reaction, the reaction product was concentrated under reduced pressure and filtered through a Celite powder. The filtered reaction was concentrated under reduced pressure to give a precipitate through hexane. The resulting precipitate was placed in a round flask equipped with a condenser, together with L4 secondary cyclization ligand (0.18 g, 0.76 mmol), and dissolved in an ethanol solvent (150 mL). The mixture was stirred at 80 < 0 > C for 24 hours. After completion of the reaction, dichloromethane / brine was added to extract the product, and then an iridium (III) complex (MPQ) ₂ Ir (ppyP) was obtained by column chromatography (0.29 g, 45.7%).

_{^{1 H-NMR (CDCl 3)}} : δ 8.34 (d, 1H), 8.25 (s, 1H), 8.13 (s, 1H), 7.95 (m, 2H), 7.68 (m, 2H), 7.62 (d, 1H 4H), 6.66 (m, 9H), 2.87 (s, 3H), 7.50 (d, , 2.71 (s, 3 H).

MALDI-TOF (M ⁺¹ , C ₄₉ H ₃₆ IrN ₃ ): calcd for 859.25, found; 859.21 (HPLC purity: 99.1%.)

[Example 5] Synthesis of dopant compound 5 ((MPQ) ₂ Ir (ppyTMS))

Compound A-2 (0.5 g, 0.38 mmol) and silver trifluoromethanesulfonate (0.20 g, 0.76 mmol) were placed in a round flask and dissolved in a solvent (120 mL) mixed with dichloromethane / 2-propanol. The mixture was stirred at room temperature for 24 hours. After completion of the reaction, the reaction product was concentrated under reduced pressure and filtered through a Celite powder. The filtrate was concentrated under reduced pressure to give a precipitate through hexane. The resulting precipitate was added to a round flask equipped with a condenser and an L5 secondary cyclization ligand (0.17 g, 0.76 mmol) and dissolved in an ethanol solvent (150 mL). The mixture was stirred at 80 < 0 > C for 24 hours. After completion of the reaction, dichloromethane / brine was added to extract the product, and an iridium (III) complex (MPQ) ₂ Ir (ppyTMS) was obtained through column chromatography (0.31 g, 48.3%).

_{^{1 H-NMR (CDCl 3)}} : δ 8.69 (s, 1H), 8.35 (d, 1H), 8.30 (d, 1H), 8.26 (d, 1H), 8.415 (m, 2H), 7.95 (m, 4H 2H), 7.33 (s, 3H), 7.18 (s, 1H), 7.68 (m, 2H) , 2.64 (s, 3H), 0.02 (s, 9H).

MALDI-TOF (M ⁺¹ , C ₄₆ H ₄₀ IrN ₃ Si): calcd for 855.26, found; 855.17 (HPLC purity: 99.4%.)

[Example 6] Synthesis of dopant compound 6 ((MPQ) ₂ Ir ( m PppyTMS))

Compound A-2 (0.5 g, 0.38 mmol) and silver trifluoromethanesulfonate (0.20 g, 0.76 mmol) were placed in a round flask and dissolved in a solvent (120 mL) mixed with dichloromethane / 2-propanol. The mixture was stirred at room temperature for 24 hours. After completion of the reaction, the reaction product was concentrated under reduced pressure and filtered through a Celite powder. The filtered reaction was concentrated under reduced pressure to give a precipitate through hexane. The resulting precipitate was added to a round-bottomed flask equipped with a L6 secondary cyclization ligand (0.23 g, 0.76 mmol) and dissolved in an ethanol solvent (150 mL). The mixture was stirred at 80 < 0 > C for 24 hours. After completion of the reaction, dichloromethane / brine was added to extract the product, and the iridium (III) complex (MPQ) ₂ Ir ( m PppyTMS) was obtained through column chromatography (0.32 g, 45.7%).

¹ H-NMR (CDCl ₃ ):? 8.78 (s, IH), 8.39 (s, IH), 8.36 (d, ), 7.79 (m, 4H), 7.59 (m, 4H), 7.53 (m, 4H), 7.76 (m, 6H) , 2.77 (s, 3H), 0.03 (s, 9H).

MALDI-TOF (M ⁺¹ , C ₅₂ H ₄₄ IrN ₃ Si): calcd for 931.29, found; 931.15 (HPLC purity: 99.7%.)

[Comparative Example 1] Synthesis of dopant compound 7 ((PQ) ₂ Ir (acac))

Preparation of 2-phenylquinoline (Compound B-1)

2-chloroquinoline (3.0 g, 18.3 mmol) and phenylboronic acid (2.2 g, 18.3 mmol) were dissolved in 100 mL of anhydrous THF in a round flask equipped with a condenser. Here it was added dissolved in dry THF (20 mL) of the _{Pd (PPh 3) 4 (0.64} g, 0.55 mmol) catalyst. After addition of a 2M aqueous K ₂ CO ₃ solution (120 mL), Aliquat 336 (0.73 g, 1.8 mmol) was added and stirred at 100 ^° C for 12 hours. After completion of the reaction, ethyl acetate / brine was added to extract the product to obtain Compound B-1 (3.12 g, 77.6%).

¹ H-NMR (CDCl ₃ ):? 8.30 (d, IH), 8.24 (d, 2H), 8.11 (d, IH), 7.82 (m, 3H), 7.59 (m, 4H).

Preparation of chlorine-crosslinked dimer (Compound B-2) containing iridium

_{IrCl 3 ?? H 2 O (0.74} g, 2.5 mmol) and Compound B-1 (1.0 g, 4.9 mmol) into a, 2-ethoxyethanol / water in a round flask equipped with a condenser is mounted (3: 1, v / v ) (100 mL). The mixture was refluxed at 135 ^° C for 24 hours. After completion of the reaction, the reaction mixture was cooled to room temperature and the resulting precipitate was filtered, washed with an ether solution and then dried in a vacuum oven. Through the dried solid compound, a chlorine-crosslinked dimer (B-2) containing iridium, which is an intermediate of the final compound, was obtained. The chlorine-crosslinked dimer containing iridium underwent the following reaction without further purification.

An iridium phosphorescent compound ((PQ)) containing an acetylacetone auxiliary ligand ₂ Ir (acac))

(0.5 g, 0.39 mmol), Na ₂ CO ₃ (0.17 g, 1.56 mmol) and acetylacetone (0.23 g, 2.34 mmol) were added to a round flask and dissolved in 2-ethoxyethanol (120 mL). The reaction was refluxed at 135 < 0 > C for 24 hours. After completion of the reaction, dichloromethane / brine was added to the reaction mixture to extract the product, and the iridium (III) complex (PQ) ₂ Ir (acac) was obtained by column chromatography (0.19 g, 35.3%).

^{1 H-NMR (DMSO-d} 6): δ 8.52 (d, 2H), 8.38 (m, 4H), 8.01 (m, 4H), 7.56 (m, 4H), 6.89 (t, 2H), 6.54 (t , 2H), 6.29 (d, 2H), 4.70 (s, IH), 1.46 (s, 6H).

MALDI-TOF (M ⁺¹ , C ₃₅ H ₂₇ IrN ₂ O ₂ ): calcd for 700.17, found; 700.03 (HPLC purity: 99.8%.)

[Geometric arrangement structure of X-ray crystallography of iridium (III) complexes]

(MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy), which are iridium (III) complexes containing the phenyl-pyridinyl-based secondary cyclized ligands prepared in Examples 1 and 2, The remarkable characteristics of the dopant compound of the present invention in comparison with (PQ) ₂ Ir (acac), which is a complex containing acetylacetone, is described below.

Figures 1 and 2 show the geometrical molecular arrangement and geometry of a single crystal X-ray crystallography of the iridium (III) complexes (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) synthesized in Examples 1 and 2, Fig. As shown in Figures 1 and 2, the iridium (III) complexes (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy), which are dopant compounds of the present invention (including secondary cyclization ligands) (PQ) ₂ Ir (acac), which is the dopant compound of Comparative Example 1, which contains the N, N-trans, has an arrangement of facial. In addition, these stacked structure of metal of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) dopant compounds of the invention metal or ligands - (PQ) of the Comparative Example 1, the distance between the ligand ₂ Ir (acac) is deposited relatively farther than that of Ir (acac). Therefore, it can be seen that the dopant compound of the present invention is distant from the stacked molecules, minimizing bimolecular interaction and improving the phenomenon such as self-extinction of phosphorescence.

[Thermal stability of iridium (III) complexes]

FIG. 3 is a thermogravimetric analysis curve of the dopant compounds (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) synthesized in Examples 1 and 2. The 5% weight loss of the inventive dopant compounds (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) including the secondary cyclization ligands L1 and L2 appeared at about 415 ° C and 410 ° C. It was confirmed that the 5% weight reduction temperature (5% weight reduction is 367 ° C) of (PQ) ₂ Ir (acac) of Comparative Example 1 including the acetylacetone auxiliary ligand was significantly higher than that of the It can be seen that the dopant compound of the present invention including a fluorine ligand has a high thermal stability.

[UV-visible absorption spectrum of iridium (III) complexes]

FIG. 4 is a graph showing the results of measurement of a UV-3600 spectrometer (Shimadzu) in a state in which (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) of the present invention synthesized in Examples 1 and 2 were dissolved in toluene ≪ / RTI > is the UV-visble absorption spectrum as measured by < RTI ID = In order to examine the properties of the methyl group of the 4-methyl-2-phenylquinoline and the introduced secondary cyclized ligand of the dopant compounds (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) 1 (PQ) ₂ Ir (acac).

As shown in FIG. 4, (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) containing secondary cyclization ligands L1 and L2 according to the present invention exhibited spin-allowed π- , And a spin-allowed metal to ligand charge transfer band (MLCT) at 350-600 nm. Particularly, the absorption spectrum of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) is relatively stronger than that of (PQ) ₂ Ir (acac) which is a dopant compound of Comparative Example 1 containing an acetylacetone auxiliary ligand The MLCT absorption peak indicates that a single anti-triplet energy transfer due to strong spin-orbit coupling in the iridium (Ⅲ) metal and the secondary cyclization ligand is active.

[Photoluminescence spectrum of iridium (III) complexes]

FIG. 5 is a graph showing the results of measurement of the fluorescence spectra of the dopant compounds (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) of the present invention synthesized in Examples 1 and 2 dissolved in toluene in an RF 5301 PC fluorometer (Shimadzu) Lt; / RTI > (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy), which are the dopant compounds of the present invention including the secondary cyclized ligand, exhibited emission wavelengths of the compound at 597 nm and 598 nm, respectively. It can be confirmed that the red light migrates relative to the emission wavelength of (PQ) ₂ Ir (acac) (592 nm), which is a dopant compound of Comparative Example 1 containing an acetylacetone auxiliary ligand.

[Cyclo voltammetry curves of iridium (III) complexes]

6 is a cyclic voltammetric curve measured by a CH Instrument of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) which are the dopant compounds of the present invention synthesized in Examples 1 and 2. The HOMO / LUMO energy levels of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) including the secondary cyclization ligands L1 and L2 were measured to be -5.16 / -3.02 eV and -5.13 / -3.01 eV, respectively . (HOMO / LUMO = -5.21 / -3.12 eV) compared to the HOMO and LUMO energy levels of (PQ) ₂ Ir (acac), the dopant compound of Comparative Example 1 containing an acetylacetone ancillary ligand I can confirm that it is wearing. This elevation of the HOMO energy level is due to the fact that while the acetylacetone ancillary ligands have no electron distribution contribution of the HOMO and LUMO energy levels in the iridium (III) complex, the secondary cyclization ligands L1 and L2 of the present invention selectively have an HOMO energy level Electronic distribution contribution.

[Fabrication of organic electroluminescent device of iridium (III) complex compound]

The dopant compounds (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) synthesized in Examples 1 and 2 were used as the light emitting layer dopant of the organic electroluminescent device. 7 shows a laminated structure of the organic electroluminescent device fabricated in FIG.

To fabricate an organic electroluminescent device, a transparent electrode substrate coated with ITO (Indium Tin Oxide) was washed with distilled water and 2-propanol, and then subjected to ozone treatment. PEDOT: PSS was spin-coated on the ozone-treated transparent electrode substrate and heat-treated at 150 ° C for about 30 minutes. As the hole transport layer, 1,1-bis [(di-4-tolyamino) phenyl] cyclohexane (TAPC) and 1,3-bis ( N- carbazolyl) benzene (mCP) were deposited on a transparent electrode substrate coated with PEDOT: PSS Vacuum deposition was performed. In order to form the light emitting layer, tris (4-carbazoyl-9-ylphenyl) amine (TCTA) and 2,2 ', 2 "- (1,3,5-benzinetriyl) (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (Pppy) prepared in Examples 1 and 2 of the present invention and Comparative Example 1 were used as the dopant materials, Each of the prepared (PQ) ₂ Ir (acac) was vacuum deposited at a doping concentration of about 5, 10, and 15%, and the hole blocking layer and electron transport layer were formed using 4- (triphenylsilyl) phenyldiphenylphosphine oxide (TSPO1) fluoride (LiF) was sequentially deposited to a thickness of 1 nm and an Al electrode was formed to a thickness of 200 nm to form an organic electroluminescent device. The vacuum degree for vacuum deposition was maintained at 2.0 x 10 ^-6 Torr or less Thin film thickness and formation rate were controlled by using a crystal sensor.

[Characteristics of organic electroluminescent device including iridium (III) complex prepared]

(MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) which are the dopant compounds (iridium (III) complexes) of the present invention synthesized in Examples 1 and 2 were used as dopants of the light emitting layer of an organic electroluminescent device Electrooptical properties were investigated. The current density and luminance with increasing voltage of the fabricated organic electroluminescent device were measured using a Keithley 2400 source (Keithley Instruments Inc, Keithley 2400 source meter 2400) and a CS 1000 spectroradiometer (Konica Minolta, CS 1000). The electroluminescent properties of the iridium (III) complexes (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) containing L1 or L2 as secondary cyclization ligands are shown in Table 1.

Dopant x% ? _max (nm) CIE
(x, y) V _t
(V) L _max
(cd / m ² ) EQE
(%) LE
(cd / A) PE
(lm / W) (MPQ) ₂ Ir
(Pppy) 5 597 (0.57, 0.43) 4.0 9,712 18.0 34.4 25.7 10 597 (0.59, 0.41) 4.0 14,470 18.7 32.5 19.3 15 597 (0.59, 0.41) 4.0 14,690 21.4 35.5 20.5 (MPQ) ₂ Ir
(TMSppy) 5 597 (0.57, 0.42) 3.5 7,863 17.1 32.3 28.6 10 597 (0.58, 0.42) 3.5 10,570 17.1 30.7 26.7 15 597 (0.59, 0.41) 3.5 12,220 18.4 31.8 29.9 (PQ) ₂ Ir
(acac) 5 592 (0.59, 0.41) 4.5 5,235 11.1 20.4 11.1 10 592 (0.60, 0.40) 4.5 6,730 6.28 10.9 5.26 15 592 (0.60, 0.40) 4.5 5,464 4.27 7.02 3.25

8 is an electroluminescence spectrum of a phosphorescent organic electroluminescent device using (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) as respective dopants. (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) exhibited the maximum luminescence of 597 nm. It was confirmed that the electroluminescence spectrum of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) was induced to emit red light of about 5 nm in comparison with (PQ) ₂ Ir (acac) of Comparative Example 1 containing acetylacetone .

9 is a graph showing the current density-voltage-luminescence intensities of phosphorescent organic electroluminescent devices using (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) and the dopant of the present invention. (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) were driven at voltages of 4.0 V and 3.5 V, respectively, and the amount of carrier injected As a result, it was found that the current density and emission luminance increase exponentially. These electroluminescent characteristics have relatively low driving voltage as compared with (PQ) ₂ Ir (acac) containing acetylacetone, and the luminescence brightness is greatly improved.

10 is an external quantum efficiency-light emission luminance curve of an organic electroluminescent device of (MPQ) ₂ Ir (Pppy) and (MPQ) ₂ Ir (TMSppy) of the present invention and (PQ) ₂ Ir (acac) of Comparative Example 1 . As _{illustrated, (MPQ) 2 Ir (Pppy} ) and _{(MPQ) 2 (PQ) 2} Ir (acac) is 5% of the comparative example 1 a maximum external quantum efficiency (EQE) of Ir (TMSppy) is including acetylacetone The external quantum efficiency (EQE) increases with increasing doping concentration, and the maximum external quantum efficiency is 21.4% and 18.4%, respectively, when the doping concentration is increased to 15% Respectively. These results show that phosphorescence self-quenching and triplet-triplet annihilation phenomena in the organic electroluminescent device, which is a cause of the reduction in efficiency in (PQ) ₂ Ir (acac) of Comparative Example 1, It can be confirmed that it is greatly improved.

Claims (7)

1. An organic electroluminescent device comprising an anode and a cathode, wherein an organic material layer is interposed between the anode and the cathode, wherein the organic material layer comprises a host compound and a dopant compound represented by the following formula (2).
(2)

[In the formula (2)
R 1 to R 8 independently of one another are hydrogen, (C 6 -C 20) aryl or (C 1 -C 20) alkylsilyl, except when R 1 to R 8 are all hydrogen;
R9 is hydrogen, (C1-C20) alkyl or (C6-C20) aryl;
and o is an integer of 1 to 4.] delete The method according to claim 1,
In the formula (2)
R ₁ to R ₈ are each independently hydrogen, phenyl or tri (C ₁ -C 20) alkylsilyl groups, except when R ₁ to R ₈ are all hydrogen. The method according to claim 1,
Wherein the formula (2) is represented by the following formulas (3) to (5).
(3)

[Chemical Formula 4]

[Chemical Formula 5]

[In the above formulas 3 to 5,
R ₁ to R ₈ independently of one another are hydrogen, (C 6 -C 20) aryl or (C ₁ -C 20) alkylsilyl, except that R ₁ to R ₈ are all hydrogen,
R < ₁₁ > and R < ₁₂ > independently of one another are (C1-C20) 5. The method of claim 4,
In Formula 3, R ₁ to R ₈ are independently hydrogen, phenyl or tri (C 1 -C 20) alkylsilyl groups. The method according to claim 1,
Wherein the dopant compound is selected from the following structural formulas.

The method according to claim 1,
Wherein the host compound is selected from the group consisting of 1,3,5-tricarbazolylbenzene, m-biscarbazolylphenyl, 4,4 ', 4 "-tri (N-carbazolyl) triphenylamine, (4-carbazolylphenyl) benzene, 1,3,5-tris (2-carbazolyl-5-methoxyphenyl) benzene, bis Amine and one or two selected from 2,2 ', 2 "- (1,3,5-benzenetriyl) -tris (1-phenyl-1-H-benzimidazole).

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