KR100580815B1 - Electroluminescence iridium compound and display device adopting as light-emitting dopant - Google Patents

Abstract

The present invention relates to an electroluminescent iridium compound represented by the following formula (1) and a display device employing the same as a light emitting dopant, which is pure green in terms of the emission wavelength and also shows a very improved luminous efficiency. It is expected that the lifespan will be significantly improved, which will greatly contribute to improving the lifespan of the full color OLED panel.

IrL ¹ L ² L ³

Wherein L ¹ to L ³ are the same as or different from each other, and are represented by the following Chemical Formulas 2 to 4, except that at least two or more ligands are one ligand selected from Chemical Formulas 3 to 4, and the rest are ligands of Chemical Formula 2 to be.

Wherein one or two of R ₁ to R ₈ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms.

Wherein one or two of R ₁ to R ₇ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms.

Description

Electroluminescence iridium compound and display device adopting as light-emitting dopant             

1 is a cross-sectional view of an organic electroluminescent device,

2 is an EL spectrum of the iridium compound obtained in Example 1,

3 is a graph showing a change in current density according to the voltage of the iridium compound obtained in Example 1,

4 is an electroluminescence spectrum according to a driving voltage of an iridium compound obtained in Example 1,

5 is a graph showing the change in luminous efficiency according to the current density of the iridium compound obtained in Example 1,

6 is an EL spectrum of an iridium compound obtained in Example 2,

7 is a graph showing a change in current density according to the voltage of the iridium compound obtained in Example 2,

8 is an electroluminescence spectrum according to a driving voltage of an iridium compound obtained in Example 2,

9 is a graph showing the change in luminous efficiency according to the current density of the iridium compound obtained in Example 2,

10 is an EL spectrum of the iridium compound obtained in Example 3,

11 is a graph showing a change in current density with a voltage of an iridium compound obtained in Example 3,

12 is an electroluminescence spectrum according to a driving voltage of an iridium compound obtained in Example 3,

13 is a graph showing the change in luminous efficiency according to the current density of the iridium compound obtained in Example 3,

FIG. 14 is a graph showing device life characteristics of conventional light emitting materials Ir (ppy) ₃ and compounds 1 to 3 obtained from Examples 1 to 3. FIG.

* Detailed description of the main symbols in the drawings *

1-Glass for organic EL 2-ITO thin film for transparent electrode

3-hole transport layer 4-light emitting layer

5-hole blocking layer 6-electron transport layer

7-electron injection layer 8-cathode

The present invention relates to an electroluminescent iridium compound and a display element employing the same as a light emitting dopant, and more particularly to a novel iridium compound that can be used as a light emitting layer forming material of an electroluminescent element and a light emitting dopant A display element is related.

Among the display elements, an electroluminescence device (EL device) is a self-luminous display element and has advantages of wide viewing angle, excellent contrast, and fast response speed.

EL elements are classified into inorganic EL elements and organic EL elements according to materials for emitting layer formation and light emitting mechanisms. Among them, the organic EL device has a very advantageous advantage in terms of luminous efficiency, color purity, and driving voltage compared to the inorganic EL device has the advantage that it is easy to implement a full-color display.

Meanwhile, in 1987, Eastman Kodak Co., Ltd. developed for the first time an organic EL device using an aromatic complex of diamine and an aluminum complex as a light emitting layer forming material [Appl. Phys. Lett. 51, 913, 1987].

The most important factor that determines the luminous efficiency in the organic EL device is the light emitting material. Fluorescent materials are widely used as the light emitting materials to date, but the development of phosphorescent materials is one of the best ways to improve the luminous efficiency theoretically up to 4 times.

To date, iridium (III) complexes are widely known as phosphorescent materials. Among them, in the case of red and blue, many improvements are required in terms of luminous efficiency and lifetime.

Among the materials reported so far, a material called (acac) Ir (btp) ₂ of UDC represented by the following formula (5) or Firpic represented by the formula (6) is known as a high-performance red and blue phosphorescent material. However, in recent years, many phosphorescent materials have been studied in Japan and Europe and it is expected that more improved phosphorescent materials will be released.

In general, in the case of the green and red light emitting materials that can be put to practical use among the phosphor materials developed to date, a very large improvement compared to the fluorescent materials may be referred to as luminous efficiency or color purity. Ir (ppy) ₃ represented by the following general formula (7) which is the most basic green phosphorescent material is 10- (2-benzothiazolyl) -1,1,7,7-tetramethyl- In terms of luminous efficiency compared to 2,3,6,7-tetrahydro-1 H , 5 H , 11 H- [1] benzopyrano- [6,7,8- ij ] quinolizin-11-one aka C545T More than double the performance. In addition, various other green phosphorescent materials have been published.

In the case of the red phosphorescent material, the luminous efficiency is not superior to the fluorescent material, but in terms of color purity, it can be said that the luminous efficiency is exhibited to some extent while showing a pure reddish red color compared to the orange-based red fluorescence.

However, in the case of conventional phosphorescent materials, in particular, green phosphorescent materials, the lifespan is so short that the performance of the fluorescent material cannot be kept up. It is still possible to use Kodak material bis (2-methyl-8-quinolato)-( p -phenylphenolato) aluminum BAlq (Formula 10) instead of bathocuproine aka BCP (Formula 9). It is a characteristic that appears as a disadvantage.

Therefore, it cannot be simply described as a characteristic due to the hole blocking layer, and it is judged that the life of the light emitting material itself affects the life of the entire device.

Accordingly, an object of the present invention is to provide a green light emitting material having an excellent lifespan as compared to the green phosphorescent material known to date.                         

Another object of the present invention is to provide a display element employing such a green light emitting material.

The green light emitting material of the present invention for achieving the above object is characterized by that represented by the following formula (1).

Formula 1

IrL ¹ L ² L ³

Wherein L ¹ to L ³ are the same as or different from each other, and are represented by the following Chemical Formulas 2 to 4, except that at least two or more ligands are one ligand selected from Chemical Formulas 3 to 4, and the rest of the ligands of Chemical Formula 2 to be.

Formula 2

Formula 3

Wherein one or two of R ₁ to R ₈ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms.

Formula 4

Wherein one or two of R ₁ to R ₇ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms.

The present invention will be described in more detail as follows.

The iridium compound according to the present invention has the same structure as in Chemical Formula 1, and more specifically, may be a compound represented by the following Chemical Formulas 11 to 12.

Wherein one or two of R ₁ to R ₈ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms, and n is 0 or 1.

Wherein one or two of R ₁ to R ₇ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms, and n is 0 or 1.

Molecular structure design of the iridium compound represented by the formula (1), including the novel iridium (III) complex represented by the above formulas (11) to 12, the SF ₅ group to improve the life of the material to the part constituting the ligand of the iridium skeleton 1 By introducing two to two it is to increase the robustness of the material to improve the device life.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated more concretely based on an Example. However, the following examples are provided to aid the understanding of the present invention, and the scope of the present invention is not limited thereto.

Example 1 In Formula 11, n = 1, R2 = SF ₅ , R 1, R 3 to R 8 = H Synthesis of Compound

(1) synthesis of ligands

1.00 g (3.40 mmol, 1 eq), 10 mol% Pd / C 0.543 g (12.5 ml) of ethanol was added to the reaction vessel for 8 hours at room temperature at 60 psi pressure (4-nitrophenyl) sulfurpentafluoride). Hydrogenation for After completion of the reaction, Pd / C was removed through celite filtration and distilled to remove ethanol, thereby obtaining (4-aminophenyl) sulfurpentafluoride ((4-aminophenyl) sulfurpentafluoride) as an orange solid.

Hydrochloric acid and water were added to 1 g (4.56 mmol, 1 eq) of (4-aminophenyl) sulfurpentafluoride obtained in the above reaction and brought to 0 ° C. Dissolve 0.35 g (5.02 mmol, 1 eq) of NaNO _{2 in} 5 ml of distilled water and slowly add to the reaction mixture. Stir for 10 minutes, and then add 7.58 g (45.6 mmol, 10 eq) of potassium iodide in 31 ml of water and slowly add it. Reacted for a minute. After completion of the reaction, the mixture was extracted using methylene chloride and saturated aqueous sodium hydrogen carbonate. The organic layer was dried over anhydrous magnesium sulfate, concentrated and separated by silica gel column chromatography to obtain 0.90 g (60% yield) of (4-iodophenyl) sulfurpentafluoride.

0.99 g (3 mmol, 1 eq), 2-tributyl tin pyridine 1.66 g (4.5 mmol, 1.5 eq), 0.13 g (3 mmol) of (4-iodophenyl) sulfurpentafluoride obtained by the above reaction , 1eq), KOAc 0.88g (9mmol, 3eq), Pd (PPh ₃ ) 4 0.116g (0.1mmol, 10mol%) into seal tube, add 10ml of DMF, and place in 120 ℃ oil bath. The reaction was carried out for a time. After completion of the reaction, the mixture was extracted with saturated aqueous ammonium chloride solution and ethyl acetate. The organic layer was dried over anhydrous magnesium sulfate, concentrated, and separated by silica gel column chromatography to obtain 0.22 g (50% yield) of the ligand as an orange solid.

mp. 81-82 ° C .;

¹ H NMR (400 MHz, CDCl ₃ ): δ 8.73 (d, J = 4.8 Hz, 1H), 8.08 (d, J = 8.4 Hz, 2H), 7.85 (d, J = 8.8 Hz, 2H), 7.75- 7.82 (m, 2 H), 7.24-7.32 (m, 1 H)

(2) Synthesis of Ir Complex

0.06 g (0.2 mmol, 1 eq) of IrCl _{3 and} 0.113 g (0.4 mmol, 2 eq) of the ligand obtained from (1) were dissolved in 20 ml of a mixture of 2-ethoxyethanol and distilled water 3: 1 and refluxed under nitrogen gas for 24 hours. I was. The resulting solid was filtered, washed with distilled water, extracted with methylene chloride and recrystallized with a mixed solution of toluene and hexane 3: 1 to give 0.17 g (yield 55%) of yellow crystals as a di-dichlorodiiridium intermediate.

20 ml of 2-ethoxyethanol was obtained from 0.14 g (0.09 mmol, 1 eq) of the obtained μ-dichlorodiiridium intermediate, 0.05 g (0.5 mmol, 5 eq) of 2,4-pentadione, and 0.025 g (0.3 mmol, 3 eq) of sodium bicarbonate. Dissolved in. After refluxing for 4-6 hours, the resulting solid precipitate was filtered and extracted with methylene chloride. The product was separated by silica gel column chromatography, and then recrystallized from a mixed solution of methylene chloride and methanol 1: 3 to obtain 0.06 g (yield 40%) of Ir complex represented by the above formula (11).

mp. > 250 ° C .;

¹ H NMR (400 MHz, CD ₂ Cl ₂ ): δ 8.43 (d, J = 5.6 Hz, 2H), 7.89 (d, J = 7.6 Hz, 2H), 7.83 (t, J = 8.6 Hz, 2H), 7.58 (d, J = 8.8 Hz, 2H), 7.27 (t, J = 6.6 Hz, 2H), 7.19 (d, J = 11.2 Hz, 2H), 6.35 (d, J = 2.4 Hz, 2H), 5, 24 (s, 1H), 1.74 (s, 6H)

Example 2 In Formula 11, n = 1, R3 = SF ₅ , R 1, R 2, R 4 to R 8 = H Synthesis of Compound

Ir complex was synthesized in the same manner as in Example 1 except that (3-nitrophenyl) sulfurpentafluoride ((3-Nitrophenyl) sulfurpentafluoride) was used instead of (4-nitrophenyl) sulfurpentafluoride.

mp. > 240 ° C .;

¹ H NMR (400 MHz, CD ₂ Cl ₂ ): δ 8.45 (d, 2H), 7.97 (d, 2H), 7.85 (t, 2H), 7.60 (d, 2H), 7.27 (t, 2H), 7.11 (d, 2H), 6.39 (dd, 2H), 5,25 (s, 1H), 1.74 (s, 6H).

Example 3 In Formula 12, n = 1, R2 = SF ₅ , R 1, R 3 to R 7 = H Synthesis of Compound

Pyrazole 0.068 g (1 mmol, 1 eq), (4-iodophenyl) sulfurpentafluoride 495 mg (1.5 mmol, 1.5 eq), lithium chloride 42 mg (1.0 mmol, 1 eq), potassium carbonate 0.41 g (3.0 mmol, 3 eq) , 0.019 g (0.1 mmol, 10 mol%) of copper iodide was placed in a seal tube, and then 10 mL of DMF was added thereto, and reacted in a 120 ° C. oil bath for 24 hours. After completion of the reaction, the mixture was extracted using saturated aqueous ammonium chloride solution and ethyl acetate. The organic layer was dried over anhydrous magnesium sulfate, concentrated, and separated by silica gel column chromatography to obtain 0.17 g (yield 63%) of a pyrazole ligand in the form of a yellow oil.

0.11 g (0.4 mmol, 2 eq) of the obtained pyrazole ligand and 0.06 g (0.2 mmol, 1 eq) of IrCl ₃ were dissolved in 20 mL of a mixed solution of 2-ethoxyethanol and distilled water 3: 1 and refluxed under nitrogen gas for 24 hours. The resulting solid was filtered, washed with distilled water, extracted with methylene chloride and recrystallized with a mixed solution of toluene and hexane 3: 1 to give 0.17 g (yield 55%) of yellow crystals as a di-dichlorodiiridium intermediate.

The obtained μ-dichloro diiridium intermediate, 0.05 g (0.5 mmol, 5 eq) of 2,4-pentadione, and 0.025 g (0.3 mmol, 3 eq) of sodium hydrogen carbonate were dissolved in 20 ml of 2-ethoxyethanol. After refluxing for 4-6 hours, the resulting solid precipitate was filtered and extracted with methylene chloride. The product was separated by silica gel column chromatography, and then recrystallized with a mixed solution of methylene chloride and methanol 1: 3 to obtain 0.04 g (yield 35%) of the Ir complex represented by Chemical Formula 12.

¹ H NMR (400 MHz, CD ₂ Cl ₂ ): δ 8.41 (d, 2H), 7.88 (d, 2H), 7.80 (t, 2H), 7.27 (d, 2H), 7.18-6.72 (m, 4H) , 5,24 (s, 1H), 1.72 (s, 6H)

Example 4: Evaluation of OLED Device Characteristics

An OLED device was fabricated using the organic light emitting compound obtained in Examples 1 to 3 as a light emitting dopant.

As shown in Fig. 1, a transparent electrode ITO thin film 2 (15? / Cm) obtained from an OLED glass 1 (manufactured by Samsung-Corning) was used sequentially using trichloroethylene, acetone, ethanol, and distilled water. After ultrasonic cleaning, it was stored in isopropanol and used. Next, an ITO substrate is installed in the substrate folder of the vacuum deposition equipment, and N, N' -bis (α-naphthyl) -N, N' -diphenyl-4,4 of the following formula (13) is placed in a cell in the vacuum deposition equipment. '-Diamine ( N, N' -bis (α-naphthyl) -N, N'-diphenyl-4,4'-diamine, NPB) was added and evacuated until the vacuum in the chamber reached 10 ^-6 torr. After that, a current was applied to the cell to evaporate the NPB to deposit a 40 nm thick hole transport layer 3 on the ITO substrate.

In addition, 4,4'- N, N' -dicarbazole-biphenyl (4,4'- N, N'- dicarbazole-biphenyl, CBP) of Chemical Formula 14 was added to another cell in the vacuum deposition apparatus. In another cell, each of the organic light emitting compounds prepared in Examples 1 to 3 was added thereto, and the light emitting layer 4 having a thickness of 20 nm was deposited on the hole transport layer by evaporating and doping the two materials at different rates. The doping concentration at this time was 4 to 10 mol% based on CBP.

Subsequently, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrosine (BCP) or BAlq was deposited to a thickness of 10 nm as the hole blocking layer 5 on the light emitting layer in the same manner as in NPB. Subsequently, aluminum quinolate (Alq) was deposited as an electron transfer layer 6 to a thickness of 40 nm. Next, after depositing lithium quinolate (Liq) with a thickness of 1nm as the electron injection layer (7), Al cathode (8) is deposited to a thickness of 150nm using another vacuum deposition equipment to the organic electroluminescent device Prepared.

For each organic electroluminescent device (OLED) manufactured as described above, the current density change according to the voltage, the luminance change according to the voltage change, and the luminous efficiency according to the current density change were measured.

The specific measuring method is as follows.

1) Measurement of current density change according to voltage change

The change in current density according to the voltage change was measured for the manufactured organic electroluminescent device. The result was obtained by dividing the measured current value by area by using a current-voltmeter (Kethley SMU 236) while increasing the voltage by 0.5V in the range of 0V to 15V.

2) Measurement of luminance change according to voltage change

The resulting organic electroluminescent device was measured using a luminance meter (Minolta CS-100) while increasing the voltage from 0V to 15V in 0.5V steps to obtain a result.

3) Measurement of luminous efficiency according to the change of current density

Luminous efficiency was calculated using the luminance and current density measured from 1) and 2) above.

4) Device Life Measurement

For the manufactured organic electroluminescent device, the time when the current density was 50% relative to the initial luminance while driving DC while fixing the current density at 50 mA / cm 2 was measured.

EL characteristics

In the case of the material of the present invention, it could be confirmed that the properties of the green (phosphorus) material (ir (ppy) ₃ ) is improved by 50% or more. In particular, in the case of life, it can be seen from the result of FIG.

Table 1 compares the performance of each material.

compound PL peak (nm) EL peak (nm) Luminous Efficiency (@ 1,000cd / ㎡) CIE color coordinates (@ 1,000cd / ㎡) Element life (hr) Ir (ppy) ₃ 512 514 16.1 (0.299, 0.607) 185 Example 1 527 518 17.8 (0.319, 0.552) 1100 Example 2 527 518 15.2 (0.318, 0.546) 1800 Example 3 526 512 16.2 (0.310, 0.575) 375

Evaluation results :

2 shows the EL spectrum of the compound (Compound 1) obtained from Example 1, FIG. 3 shows the current density-voltage characteristics, FIG. 4 shows the luminance-voltage characteristics, and FIG. 5 shows the luminous efficiency-current. The graph which measured the density characteristic is shown.

6 shows the EL spectrum of the compound (compound 2) obtained in Example 2, current density-voltage characteristics in FIG. 7, luminance-voltage characteristics in FIG. 8, and luminous efficiency-current density characteristics in FIG.

FIG. 10 shows the EL spectrum of the compound (Compound 3) obtained in Example 3, current density-voltage characteristics in FIG. 11, luminance-voltage characteristics in FIG. 12, and luminous efficiency-current density characteristics in FIG.

In Fig. 14, device life characteristics of the conventional Ir (ppy) ₃ and the compounds (compounds 1 to 3) obtained from Examples 1 to 3 are shown.

From these results, it can be seen that the compounds obtained in Examples 1 to 3 are pure green in terms of emission wavelength, and the emission efficiency is also very improved. In particular, it can be seen that the device life is significantly improved.

As described above, the iridium compound obtained according to the present invention has a pure green color in terms of the emission wavelength and also shows a very improved luminous efficiency. It is expected to make a big contribution.

Claims (5)

An electroluminescent iridium compound represented by the following formula (1). Formula 1 IrL ¹ L ² L ³ Wherein L ¹ to L ³ are the same as or different from each other, and are represented by the following Chemical Formulas 2 to 4, except that at least two or more ligands are one ligand selected from Chemical Formulas 3 to 4, and the rest of the ligands of Chemical Formula 2 to be. Formula 2

Formula 3

Wherein one or two of R ₁ to R ₈ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms. Formula 4

Wherein one or two of R ₁ to R ₇ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms. The electroluminescent iridium compound according to claim 1, wherein the electroluminescent iridium compound is selected from Chemical Formulas 11 to 12. Formula 11

Wherein one or two of R ₁ to R ₈ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms, and n is 0 or 1. Formula 12

Wherein one or two of R ₁ to R ₇ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms, and n is 0 or 1. A display device comprising the compound represented by the following formula (1) as a light emitting material. Formula 1 IrL ¹ L ² L ³ Wherein L ¹ to L ³ are the same as or different from each other, and are represented by the following Chemical Formulas 2 to 4, except that at least two or more ligands are one ligand selected from Chemical Formulas 3 to 4, and the rest of the ligands of Chemical Formula 2 to be. Formula 2

Formula 3

Wherein one or two of R ₁ to R ₈ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms. Formula 4

Wherein one or two of R ₁ to R ₇ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms. The display device of claim 3, further comprising a compound selected from Chemical Formulas 11 and 12 as a light emitting material. Formula 11

Wherein one or two of R ₁ to R ₈ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms, and n is 0 or 1. Formula 12

Wherein one or two of R ₁ to R ₇ are SF ₅ groups and the remaining substituents are alkyl groups, cycloalkyl groups, haloalkyl groups or halogen groups having 2 to 20 carbon atoms, and n is 0 or 1. The display device according to claim 3 or 4, wherein the display device is an organic electroluminescent device.

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