KR101145686B1 - Blue phosphorescent host material and organicelectroluminescent device using same - Google Patents

Abstract

The present invention relates to a novel blue phosphorescent host material and an organic electroluminescent device including the same, and more particularly, the blue phosphorescent host material according to the present invention is represented by the following Chemical Formula 1.

[Formula 1]

[In Formula 1, R ₁ , R ₂ , R ₃ , R ₄ , Ar ₁ , Ar ₂ , a and b are as defined in the detailed description of the invention, respectively.]

The blue phosphorescent host material according to the present invention may be included in the organic electroluminescent device to greatly improve the lifespan and efficiency, and to improve the low voltage driving and the stability of the device. Can be. In addition, the blue phosphorescent host material may be used in an illumination material by improving roll off characteristics at high voltage by imparting electron transfer characteristics compared to conventionally known materials.

Blue, phosphorescent, host, light emitting device

Description

Blue phosphorescent host material and organic electroluminescent device using same

The present invention relates to a novel blue phosphorescent host material and an organic electroluminescent device including the same, and more particularly, the blue phosphorescent host material according to the present invention is represented by the following Chemical Formula 1.

[Formula 1]

The flat panel display plays a very important role in supporting a highly visual information society, centered on the internet, which is rapidly growing in recent years. In particular, organic electroluminescent devices (organic EL devices) capable of low voltage driving with self-luminous type have superior viewing angles and contrast ratios compared to liquid crystal displays (LCDs), which are mainstream flat panel displays, and require no backlight. Light weight and thinness are possible, and it has an advantage in terms of power consumption. In addition, the fast response speed and wide color reproduction range have attracted attention as a next generation display device.

In general, an organic EL device is formed on a glass substrate in order of 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 (electron injection) in addition to the emitting layer (EML). layer, EIL), and may further include an electron blocking layer (EBL) or a hole blocking layer (HBL) due to light emission characteristics of the light emitting layer.

When an electric field is applied to the organic EL device having such a structure, holes are injected from the anode and electrons are injected from the cathode, and the injected holes and electrons are recombined in the emission layer through the hole transport layer and the electron transport layer, respectively, and emit excitons. To form. The light emitting excitation emits light as it transitions to ground states, in which a light emitting layer (guest) is doped into the light emitting layer (host) to increase the efficiency and stability of the light emitting state.

Recently, it has been known that not only fluorescent light emitting materials but also phosphorescent light emitting materials can be used as light emitting materials of organic EL devices. Such phosphorescent light emission is carried out through intersystem crossing after electrons transfer from the ground state to the excited state. The singlet excitons are non-luminescent to triplet excitons, and then the triplet excitons are light-transmitted as they transition to the ground state. At this time, the transition to the triplet excitons does not directly transition to the ground state (spin forbidden), since the process of transition to the ground state after the flipping of the electron spin proceeds (lifetime) than fluorescence (lifetime) It has a longer characteristic. That is, the emission duration of fluorescence emission is only several nanoseconds, but the phosphorescence emission corresponds to several micro seconds, which is a relatively long time.

In the case of an electrophosphorescent device, the selection of a phosphorescent host material directly affects the luminous efficiency. Since luminescence of the phosphor occurs from the triplet, the triplet energy transfer from the host material to the guest material can occur more effectively as the triplet energy of the host is greater than the triplet energy of the guest. In addition, since triplet energy is generally about 1 eV lower than singlet energy, a material having a larger gap between highest occupied molecular orbital (HOMO) and lower unoccupied molecular orbital (LUMO) than a fluorescent material is preferable as a host material. In other words, if the triplet of the host is lower than the triplet energy of the guest phosphor, the endothermic energy transfer is used, and thus the external luminous efficiency is lowered. If the triplet of the host is higher than the triplet energy of the guest, the exothermic energy transfer is used. Will be displayed.

Accordingly, an object of the present invention is to provide a blue phosphorescent light emitting host material having high luminous efficiency and an organic electroluminescent device including the same.

The present invention relates to a novel blue phosphorescent host material and an organic electroluminescent device including the same, and more particularly, the blue phosphorescent host material according to the present invention is represented by the following Chemical Formula 1.

[Formula 1]

[In Formula 1,

R ₁ and R ₂ independently of one another are (C ₁ -C 20) alkyl or (C 6 -C 20) aryl, which aryl may be further substituted with (C 3 -C 20) heteroaryl;

Ar ₁ and Ar ₂ are independently of each other (C6-C20) arylene;

R ₃ and R ₄ independently of one another are (C3-C20) heteroaryl or (C3-C20) heteroaryl substituted (C6-C20) aryl;

a and b are each independently an integer of 1 or 2;

Provided that when R ₁ = R ₂ = (C ₁ -C 20) alkyl or (C 6 -C 20) aryl, Ar ₁ = Ar ₂ = phenylene, a = b = 1 and R ₃ = R ₄ = pyridinyl Excluded.]

In the compound of Formula 1 of the present invention, Ar ₁ and Ar ₂ in Formula 1 are preferably phenylene, biphenylene, naphthalene, anthracenylene or fluorenylene.

The compound of formula 1 of the present invention is selected from the following formulas (2) to (4).

[Formula 2]

(3)

[Formula 4]

[Wherein,

R ₁ and R ₂ independently of one another are methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, phenyl, biphenyl, naphthyl, an Tril or pyridinylphenyl;

R ₁₁ to R ₁₆ are independently of each other pyridinyl.]

The compound of formula 1 of the present invention may be specifically exemplified as the following compound, but the following compound does not limit the present invention.

The blue phosphorescent host material according to the present invention can be prepared as shown in Scheme 1 below.

Scheme 1

[In Reaction Scheme 1, R ₁ , R ₂ , R ₃ , R ₄ , Ar ₁ , Ar ₂ , a and b are the same as defined in the formula (1).]

By using the blue phosphorescent host material of Chemical Formula 1 according to the present invention, it is possible to fabricate an organic electroluminescent device having excellent electrical stability and luminous efficiency, and capable of implementing high luminance and high color purity. In addition, the blue phosphorescent host material can significantly reduce roll off at a high voltage and be used in an illumination material or the like.

The present invention provides an organic electroluminescent device, and the organic electroluminescent device according to the present invention comprises an organic electroluminescent device comprising a light emitting layer between an anode, a cathode and a positive electrode, wherein the compound of Formula 1 is a blue phosphorescent host An organic electroluminescent device included in a light emitting layer as a material.

[Formula 1]

[In Formula 1,

R ₁ and R ₂ independently of one another are (C ₁ -C 20) alkyl or (C 6 -C 20) aryl, which aryl may be further substituted with (C 3 -C 20) heteroaryl;

Ar ₁ and Ar ₂ are independently of each other (C6-C20) arylene;

R ₃ and R ₄ independently of one another are (C3-C20) heteroaryl or (C3-C20) heteroaryl substituted (C6-C20) aryl;

a and b are integers of 1 or 2.]

The blue phosphorescent host material included in the light emitting layer of the organic electroluminescent device of the present invention is selected from the following compounds.

The blue phosphorescent host material according to the present invention can improve the electrical stability and luminous efficiency in an organic electroluminescent device, and can manufacture an organic electroluminescent device of blue light emission capable of high luminance and high color purity. In addition, the blue phosphorescent host material can significantly reduce roll off at a high voltage and be used in an illumination material or the like.

Hereinafter, a blue phosphorescent host material according to the present invention, a method for preparing the same, and a light emitting property of the device will be described with reference to a representative compound of the present invention for a detailed understanding of the present invention, which is merely to illustrate the embodiments. It does not limit the scope of the present invention.

Preparation Example 1 Preparation of Compound 1

Preparation of Compound A

2-bromopyridine (30 g, 189.87 mmol) was added to an ether solution (260 mL) under nitrogen stream, and it cooled to -78 degreeC, and n-butyllithium hexane solution (2.5M, 91.14 mL) was dripped at this. . After dropping, the temperature was maintained while stirring for one hour. And tributyltin chloride (61.81g, 189.87mmol) was added continuously, maintaining -78 degreeC, it was made to adjust slowly to room temperature and stirred for 12 hours. Water was added to the reaction solution to complete the reaction, followed by extraction with ether. The extractant was distilled off and purified by vacuum fractional distillation to obtain Compound A (clear liquid, 51.2 g, 73%).

¹ H-NMR (300 MHz, CDCl ₃ ) δ: 8.75 (d, 1H), 7.49 (t, 1H), 7.42 (d, 1H), 7.14 (t, 1H), 1.55 (m, 3H), 1.13 (m , 6H), 0.92 (m, 3H); MS (FAB) (calcd for C ₁₇ H ₃₁ NSn, 369.15; found, 370.2) m / e: 370.2, 369.2, 368.2, 367.2, 366.2.

Preparation of Compound B

Under nitrogen stream, 1,3-dibromobenzene (5 g, 21.20 mmol) was added to an ether solution (60 mL), cooled to -78 ° C, and n-butyllithium hexane solution (1.6 M, 14.57 mL) was added thereto. It was dripped. After dropping, the temperature was maintained while stirring for one hour. Subsequently, dichlorodiphenylsilane (2.15 g, 8.478 mmol) was added thereto while maintaining the temperature at -78 ° C, and the mixture was slowly heated to reflux for 12 hours. Water was added to the reaction solution to complete the reaction, followed by extraction with ether, followed by distillation of the extraction solvent, followed by hexane addition to form a white solid. After washing with hexane to remove impurities, Compound B (white solid, 3.16 g, 30%) was obtained. .

¹ H-NMR (300 MHz, CDCl ₃ ) δ: 7.62-7.63 (m, 4H), 7.53 (t, 2H), 7.36-7.46 (m, 12H)

Preparation of Compound 1

Under nitrogen stream, Compound A (1.63 g, 4.45 mmol) and Compound B (1.00 g, 2.02 mmol) were added to toluene solution (16 mL), followed by nitrogen bubbling for 30 minutes. And after heating to 50 ℃ palladium (0) catalyst (0.14g, 3mol%) was added and refluxed at 95 ℃ for two days. 2N hydrochloric acid was added to the reaction solution, stirred for about an hour, extracted with chloroform, and treated with sodium carbonate. After distilling off the extractant, the mixture was purified by column chromatography to obtain Compound 1 (0.73 g, 73%).

¹ H-NMR (300 MHz, CDCl ₃ ) δ: 8.67 (d, 1H), 8.20 (s, 1H), 8.13 (s, 1H), 7.70-7.41 (m, 7H), 7.26 (d, 1H); ¹³ C-NMR (300 MHz, CDCl ₃ ) δ: 157.5, 149.5, 138.7, 137.1, 136.8, 136.4, 134.7, 134.5, 133.9, 129.7, 128.6, 128.4, 127.9, 122.1, 120.8; MS (EI +) (calcd for C ₃₄ H ₂₆ N ₂ Si, 490.7; found, 490.0) m / e: 489.0, 413.0, 412.0, 334.0, 336.0.

Preparation Example 2 Preparation of Compound 2

Preparation of Compound C

Under nitrogen stream, 1,3,5-tribromobenzene (10 g, 31.77 mmol) was added to an ether solution (260 mL), cooled to -78 ° C, and n-butyllithium hexane solution (1.6 M, 19.85 mL) was added thereto. ) Was dropped. After dropping, the temperature was maintained while stirring for one hour. Subsequently, dichlorodiphenylsilane (4.02 g, 15.88 mmol) was added thereto while maintaining the temperature at -78 ° C, and the mixture was slowly heated to reflux for 12 hours. Water was added to the reaction solution to complete the reaction, followed by extraction with ether. The extractant was distilled off and purified by silica gel column chromatography to obtain Compound C (white solid, 6.84 g, 33%).

¹ H-NMR (300 MHz, CDCl ₃ ) δ: 7.71 (s, 2H), 7.45-7.36 (m, 14H); ¹³ C-NMR (300 MHz, CDCl ₃ ) δ: 138.6, 137.1, 136.2, 135.7, 130.7, 128.5, 123.6.

Preparation of Compound 2

Under nitrogen stream, Compound C (1.5 g, 2.30 mmol) and Compound A (5.08 g, 13.8 mmol) were added to toluene solution (20 mL), followed by nitrogen bubbling for 30 minutes. After heating to 50 ° C., a palladium (0) catalyst (0.16 g, 6 mol%) was added thereto, and the mixture was refluxed at 95 ° C. for two days. 2N hydrochloric acid was added to the reaction solution, stirred for about an hour, extracted with chloroform, and treated with sodium carbonate. After distilling off the extractant, the mixture was purified by column chromatography to obtain Compound 2 (1.1 g, 74.2%).

¹ H-NMR (300 MHz, CDCl ₃ ) δ: 8.81 (s, 1H), 8.68 (d, 2H), 8.34 (s, 2H), 7.43-7.77 (m, 9H), 7.21 (t, 2H); MS (EI +) (calcd for C ₄₄ H ₃₂ N ₂ Si, 644.24; found, 565) m / e: 643, 554, 488, 411.

Preparation Example 3 Preparation of Compound 3

Preparation of Compound D

3-bromopyridine (30 g, 189.87 mmol) was added to an ether solution (260 mL) under nitrogen stream, and it cooled to -78 degreeC, and n-butyllithium hexane solution (2.5M, 91.14 mL) was dripped at this. . After dropping, the temperature was maintained while stirring for one hour. And tributyltin chloride (61.81g, 189.87mmol) was added continuously, maintaining -78 degreeC, it was slowly adjusted to room temperature and stirred for 12 hours. Water was added to the reaction solution to complete the reaction, followed by extraction with ether. The extractant was distilled off and purified by vacuum fractional distillation to obtain compound D (yellow liquid, 48.6 g, 69.5%).

¹ H-NMR (300 MHz, CDCl ₃ ) δ: 8.83 (s, 1H), 8.51 (d, 1H), 8.10 (d, 1H), 7.38 (t, 1H), 1.78 (t, 3H), 1.32-1.28 (m, 6H), 0.93 (d, 3H)

Preparation of Compound 3

Under nitrogen stream, Compound B (1 g, 2.02 mmol) and Compound D (1.71 g, 4.65 mmol) were added to toluene solution (20 mL), followed by nitrogen bubbling for 30 minutes. After heating to 50 ° C., a palladium (0) catalyst (0.12 g, 5 mol%) was added thereto, and the mixture was refluxed at 95 ° C. for two days. 2N hydrochloric acid was added to the reaction solution, stirred for about an hour, extracted with chloroform, and treated with sodium carbonate. After distilling off the extractant, the mixture was purified by column chromatography, obtaining a compound 3 (0.4 g, 40%).

¹ H-NMR (300 MHz, CDCl ₃ ) δ: 8.80 (s, 1H), 8.58 (s, 1H), 7.81 (d, 2H), 7.66-7.60 (m, 9H), 7.52-7.39 (m, 13H)

Example 1 Fabrication of Organic Electroluminescent Device Using Blue Phosphorescent Host Material of the Present Invention

First, the transparent electrode ITO thin film (15 Ω / □) obtained from the glass for OLED was subjected to ultrasonic cleaning using trichloroethylene, acetone, ethanol, and distilled water in sequence, and then stored in isopropanol and used. 4,4 ', 4 "-tris (N, N- (2-naphthyl) -phenylamino) triphenylamine (2-TNATA) was deposited on the ITO thin film to form a hole injection layer of 30 nm. 1,1'-bis [(di-4-tolylamino) phenyl] cyclohexane (TAPC) was deposited thereon to form a hole transport layer of 60 nm, followed by iridium (III) bis [4,6-di -Fluorophenyl-pyridinate N, C2] Picolinate (Firpic) N, N'-dicarbazolyl-3,5-benzene (mCP) doped with 8% by weight was deposited on the hole transport layer. A first light emitting layer was formed at 20 nm, and 15 wt% of iridium (III) bis [4,6-di-fluorophenyl-pyridinato N, C2] Picolinate (Firpic) was doped on the first light emitting layer. Compound 1 (GSH-1) of the present invention was deposited to form a second light emitting layer having a thickness of 10 nm, followed by bis (2-methyl-8-quinolinate) ( p− ) as a hole blocking layer on the second light emitting layer. Phenylphenolrato) aluminum (III) (BAlq) was deposited to a thickness of 40 nm, As an electron injection layer, a compound lithium quinolate (Liq) having the following structure was deposited to a thickness of 1 nm, and Al was deposited on the electron injection layer to form a cathode of 100 nm, thereby manufacturing an organic electroluminescent device according to the present invention.

The organic electroluminescent device manufactured was [ITO / 2-TNATA (30 nm) / TAPC (60 nm) / mCP: 8% FIrpic (20 nm) / GSH-1 (or UGH2): 15% FIrpic (10 nm) / BAlq (40 nm) / LiF (1 nm) / Al (100 nm)] has a structure in which they are sequentially stacked from below.

Example 2 Fabrication of Organic Electroluminescent Device Using Blue Phosphorescent Host Material of the Present Invention

A device was manufactured in the same manner as in Example 1, except that BAlq, which was a hole blocking layer, was deposited to a thickness of 50 nm. The organic electroluminescent device manufactured was [ITO / 2-TNATA (30 nm) / TAPC (60 nm) / mCP: 8% FIrpic (20 nm) / GSH-1 (or UGH2): 15% FIrpic (10 nm) / BAlq (50 nm) / LiF (1 nm) / Al (100 nm)] have a structure in which they are sequentially stacked from below.

Example 3 Fabrication of Organic Electroluminescent Device Using Blue Phosphorescent Host Material of the Present Invention

A device was manufactured in the same manner as in Example 1, except that BAlq, which was a hole blocking layer, was deposited to a thickness of 60 nm. The organic electroluminescent device manufactured was [ITO / 2-TNATA (30 nm) / TAPC (60 nm) / mCP: 8% FIrpic (20 nm) / GSH-1 (or UGH2): 15% FIrpic (10 nm) / BAlq (60 nm) / LiF (1 nm) / Al (100 nm)] are laminated in order from the bottom.

Comparative Example 1

A device was manufactured in the same manner as in Example 1, except that Comparative Compound (UGH2) having the following structure instead of Compound 1 was used in the second light emitting layer. The organic electroluminescent device manufactured was [ITO / 2-TNATA (30 nm) / TAPC (60 nm) / mCP: 8% FIrpic (20 nm) / UGH2: 15% FIrpic (10 nm) / BAlq (40 nm) / LiF (1 nm) / Al (100 nm)] is laminated in order from the bottom.

Comparative Example 2

A device was manufactured in the same manner as in Example 2, except that Comparative Compound (UGH2) having the following structure instead of Compound 1 was used in the second light emitting layer. (ITO / 2-TNATA (30 nm) / TAPC (60 nm) / mCP: 8% FIrpic (20 nm) / UGH2: 15% FIrpic (10 nm) / BAlq (50 nm) / LiF (1 nm) / Al (100 nm)] is stacked in order from the bottom.

Comparative Example 3

A device was manufactured in the same manner as in Example 3, except that Comparative Compound (UGH2) having the following structure was used instead of Compound 1 in the second emission layer. The organic electroluminescent device manufactured was [ITO / 2-TNATA (30 nm) / TAPC (60 nm) / mCP: 8% FIrpic (20 nm) / UGH2: 15% FIrpic (10 nm) / BAlq (60 nm) / LiF (1 nm) / Al (100 nm)] is laminated in order from the bottom.

IVL characteristics [FIGS. 9 and 10], luminance efficiency-current density characteristics [FIGS. 11 and 12], and quantum efficiency- of the devices fabricated in Examples 1 to 3 and the devices fabricated in Comparative Examples 1 to 3 Current density characteristics [Fig. 13 and Fig. 14] were measured, and EL intensities of the elements were measured [Fig. 15 and Fig. 16]. Table 1 below describes the maximum external quantum efciency (EQE), power efficiency (PE) and luminance (efficiency) (LE) according to varying the thickness of the BAq hole blocking layer.

Table 1 Comparison of the maximum efficiency according to the thickness of BAlq of the existing host material and the synthesized host material

Table 1 is a comparison of the maximum efficiency characteristics while varying the thickness of the hole blocking material by configuring the device as in the conventional materials, Examples 1 to 3 and Comparative Examples 1 to 3 are shown to be similar, Figure 11 and Comparing FIG. 12, it can be seen that the blue phosphorescent host material of the present invention has better characteristics at high current density (roll-off reduction effect).

Figure 1-UV absorbance and PL intensity spectrum of compound 1

Figure 2-Current-voltage characteristics of Compound 1

Figure 3-TGA of Compound 1 (5% weight loss 314 ° C.)

Figure 4-DSC of Compound 1

5-UV absorbance and PL intensity spectrum of Compound 2

Figure 6-Current-voltage characteristics of Compound 2

Figure 7-TGA of Compound 2 (5% weight loss 393 ° C)

Figure 8-DSC of Compound 2

9-Graph showing the I-V-L characteristics of the devices of Examples 1 to 3

10-Graph showing I-V-L characteristics of devices of Comparative Examples 1 to 3

11-Graph showing luminance efficiency-current density characteristics of devices of Examples 1 to 3

12-Graph showing luminance efficiency-current density characteristics of devices of Comparative Examples 1 to 3

13-Graph showing the quantum efficiency-current density characteristics of the devices of Examples 1 to 3

14-Graph showing quantum efficiency-current density characteristics of devices of Comparative Examples 1 to 3

Figure 15-EL spectra of the devices of Examples 1-3

Figure 16-EL spectra of the devices of Comparative Examples 1 to 3

Claims (6)

A compound represented by the following formula (1). [Formula 1]

[In Formula 1, R ₁ and R ₂ independently of one another are (C ₁ -C 20) alkyl or (C 6 -C 20) aryl, which aryl may be further substituted with (C 3 -C 20) heteroaryl; Ar ₁ and Ar ₂ are independently of each other (C6-C20) arylene; R ₃ and R ₄ independently of one another are (C3-C20) heteroaryl or (C3-C20) heteroaryl substituted (C6-C20) aryl; a and b are integers of 1 or 2; Provided that R ₁ = R ₂ = (C ₁ -C 20) alkyl or (C 6 -C 20) aryl, Ar ₁ and Ar ₂ are independently of each other phenylene or naphthalene, a = b = 1 and R ₃ = R ₄ = Except for pyridinyl.] The method of claim 1, Ar ₁ and Ar ₂ are each independently phenylene, biphenylene, naphthalene, anthracenylene or fluorenylene. 3. The method of claim 2, A compound selected from the formulas (2) to (4). [Formula 2]

(3)

[Formula 4]

[Wherein R ₁ and R ₂ independently of one another are methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, phenyl, biphenyl, Naphthyl, anthryl or pyridinylphenyl; R ₁₁ to R ₁₆ are independently of each other pyridinyl.] The method of claim 3, A compound selected from the following compounds.

An organic electroluminescent device comprising a light emitting layer between an anode, a cathode, and a positive electrode, wherein the compound of Formula 1 is included in the light emitting layer as a host material for blue phosphorescence emission. [Formula 1]

[In Formula 1, R ₁ and R ₂ independently of one another are (C ₁ -C 20) alkyl or (C 6 -C 20) aryl, which aryl may be further substituted with (C 3 -C 20) heteroaryl; Ar ₁ and Ar ₂ are independently of each other (C6-C20) arylene; R ₃ and R ₄ independently of one another are (C3-C20) heteroaryl or (C3-C20) heteroaryl substituted (C6-C20) aryl; a and b are integers of 1 or 2.] The method of claim 5, The blue phosphorescent host material is an organic electroluminescent device, characterized in that selected from the following compounds.

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