KR20190105837A - A host material for blue phosphorescence and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a blue phosphorescent host compound, which has higher triplet energy compared to mCP (1,3-Bis (N-carbazolyl) benzene), which is commercially available as a blue host material, and has excellent thermal stability. Therefore, high efficiency and driving effects compared to mCP can be expected, and when applied to a light emitting layer of an organic light emitting element, a high efficiency display driving effect can be obtained.

Description

A blue phosphorescent host compound and a method for manufacturing the same

The present invention relates to a blue phosphorescent host compound and a method for preparing the same, and more particularly, to a blue phosphorescent host compound including selenium in a molecule and having a high triplet energy and excellent thermal stability.

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 the 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 general, PhOLED's host material should have a higher triplet energy level (ET) than phosphorescent emitters for efficient energy transfer from host to guest and confinement of triplet excitation of the guest material.

Although studies on carbazole derivative based low molecular host materials have been well established (V. Cleave, G. Yahioglu, P. LeBarny, RH Friend and N. Tessler, Adv. Mater., 1999, 11, 285-288); K. Brunner, A. van Dijken, H. Borner, JJAM Bastiaansen, NMM Kiggen and BMW Langeveld, J. Am. Chem. Soc., 2004, 126, 6035-6042.), Polymer host materials are also prepared for their high solutions. It is considered to be of interest because of its potential, which can be useful for volume production of OLEDs using printing techniques in applications in electrical signals, luminescence, and displays.

In view of this, much research is underway in the development of conjugated polymer hosts for phosphors. In particular, red PhOLED devices with high device efficiencies similar to vacuum deposited devices have been demonstrated by several groups (H. Zhen, C. Luo, W. Yang, W. Song, B. Du, J. Jiang, C.). Jiang, Y. Zhang and Y. Cao, Macromolecules, 2006, 39, 1693-1700 .; F.-I. Wu, P.-I. Shih, Y.-H. Tseng, G.-Y. Chen, C .-H. Chien, C.-F. Shu, Y.-L. Tung, Y. Chi and AK-Y. Jen, J. Phys. Chem. B, 2005, 109, 14000-14005.

However, there have been few reports of successful polymer host materials as blue emitters, and in order to manufacture efficient blue phosphorescent organic light emitting diodes (PhOLEDs), new host materials are required.

Republic of Korea Patent Publication No. 10-2011-0046839 (May 06, 2011)

The present invention has been made in accordance with the above requirements, and specifically relates to a blue phosphorescent host compound having high triplet energy and excellent thermal stability including selenium in a molecule thereof and a method for preparing the same.

The present invention relates to a blue phosphorescent host compound and a preparation method thereof.

One aspect of the present invention relates to a blue phosphorescent host compound having a structure of Formula 1, Formula 2 or Formula 3.

[Formula 1]

[Formula 2]

[Formula 3]

Another aspect of the present invention,

a) reacting carbazole with halogen-substituted benzene to produce a first reactant;

b) preparing a second reactant by reacting halogen and potassium halide with the first reactant; And

c) preparing a compound of the following Chemical Formula 1 by reacting the selenocyanate potassium salt with the second reactant;

It relates to a method for producing a blue phosphorescent host compound comprising a.

[Formula 1]

In addition, the manufacturing method is after the step c),

d) reacting the compound of Chemical Formula 1 with m-chloroperbenzoic acid to prepare a compound of Chemical Formulas 2 and 3;

[Formula 2]

[Formula 3]

It may further include.

In addition, the halogen may be iodine, and the potassium halide may be potassium iodide.

In addition, the m-chloroperbenzoic acid may be added in an amount of 0.1 to 5 mmol relative to 1 mmol of the compound of Formula 1, and d) may be performed at -5 to 5 ° C.

Another aspect of the present invention relates to a blue phosphorescent organic light emitting device comprising the blue phosphorescent host compound in a light emitting layer.

The blue phosphorescent host compound according to the present invention has high triplet energy and superior thermal stability as compared to mCP (1,3-Bis (N-carbazolyl) benzene), which is commercially available as a conventional blue host material. Therefore, high efficiency and driving effect can be expected compared to mCP, and when applied to the light emitting layer of the organic light emitting device, a high efficiency display driving effect can be obtained.

Figure 1 shows the degree of decomposition according to the temperature of the compound prepared in Example 1.
Figure 2 shows the degree of decomposition according to the temperature of the compound prepared in Example 3.
3 shows the emission spectrum of the compound prepared in Example 1. FIG.
Figure 4 shows the emission spectrum of the compound prepared through Example 3.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated and described in the detailed description. However, this is not intended to limit the present invention to the specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, detailed descriptions of related well-known technologies will be omitted when it is determined that the present invention may obscure the gist of the present invention.

Terms including ordinal numbers such as first and second may be used to describe various components, but the components are not limited by the terms. These terms are only used to distinguish one component from another.

When a component is said to be 'connected' or 'connected' to another component, it may be directly connected to or connected to that other component, but other components may be present in between. It should be understood that. On the other hand, when a component is said to be 'directly connected' or 'directly connected' to another component, it should be understood that no other component exists in the middle.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, the term 'comprises' or 'having' is intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

The blue phosphorescent host compound according to the present invention may have a structure of Formula 1, Formula 2, or Formula 3,

[Formula 1]

[Formula 2]

[Formula 3]

More specifically, as in Scheme 1 below

a) reacting carbazole with halogen-substituted benzene to produce a first reactant;

b) preparing a second reactant by reacting halogen and potassium halide with the first reactant; And

c) preparing a compound of the following Chemical Formula 1 by reacting the selenocyanate potassium salt with the second reactant;

Or after step c),

d) reacting the compound of Chemical Formula 1 with m-chloroperbenzoic acid to prepare a compound of Chemical Formulas 2 and 3;

It may be prepared through a manufacturing method further comprising.

Scheme 1

In the present invention, the halogen is iodine, and the potassium halide may be potassium iodate. In addition, the m-chloroperbenzoic acid may be added in an amount of 0.1 to 5 mmol relative to 1 mmol of the compound of Formula 1, and d) may be performed at -5 to 5 ° C.

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 Synthesis of First Reactant (9-Phenyl-9H-carbazole)

Carbazole (5 g, 29.9 mmol) and iodinebenzene (6.71 g, 32.89 mmol, 1.1 eq), copper (5.81 g, 91.5 mmol) and K ₂ CO ₃ (12.65 g, 91. 5 mmol) was added dropwise to the flask. Next, 25 ml of N, N-dimethylformamide anhydride (anhydrous dimethylformamide) was added thereto under a nitrogen atmosphere, followed by stirring under reflux. After the reaction was completed, the reactant was cooled, MC / water was added to separate the organic layer, and the separated organic layer was dried with MgSO ₄ , and then concentrated by rotary evaporator. The product was then purified by recrystallization with ethanol (yield 97%).

Preparation Example 2 Synthesis of Second Reactant (3-Iodo-9-phenyl-9H-carbazole)

0.5 g (2.06 mmol) of the first reactant (9-Phenyl-9H-carbazole) synthesized in Preparation Example 1 was dissolved in 8 ml of acetic acid, and 8 ml of methanol was added thereto. 0.21 g (0.82 mmol, 0.4 eq) of iodine and 0.13 g (0.62 mmol, 0.3 eq) of potassium iodide were added thereto, and the mixture was stirred while maintaining a temperature of 30 ° C. under a nitrogen atmosphere. When the reaction was completed, the reaction was extracted by adding water and Na ₂ SO ₃ to the reaction, and the water was removed with anhydrous MgSO ₄ and concentrated by rotary evaporator. The product was then purified by recrystallization with ethanol (yield 63%).

Example 1 DPhCzSe Synthesis of Chemical Formula 1

In a microwave reaction vessel, 2 g (5.42 mmol, 1 eq) of 2nd reactant (3-Iodo-9-phenyl-9H-carbazole) synthesized in Preparation Example 2 and 0.937 g (6.50 mmol, 1.2 eq) of potassium selenocyanate were prepared. Put, and dissolved in 5 ml of anhydrous dimethylformamide. Next, 5.0 mol% of nano copper oxide (cupper (II) oxide) and 0.606 g (10.8 mmol, 2 eq) of potassium hydroxide were added and reacted for 1 hour through a microwave reaction at 180 ° C. After the reaction was completed, the reaction mixture was cooled, and then the organic layer was separated by adding an EA / water 1: 1 mixture. The separated organic layer was washed with brine, dried with Na ₂ SO ₄ , concentrated with a rotary evaporator, and the product was purified by column chromatography (yield: 71%). Thermogravimetric analysis of the prepared compounds was measured and shown in FIG. 1.

Thermogravimetric analysis of the compound prepared as shown in FIG. 1 confirmed that T _d , a temperature at which 5% of the weight was reduced, was 408.8 ° C.

Example 2 DPhCzSeO1 Synthesis of Chemical Formula 2

2 g (3.55 mmol) of DPhCzSeO1 synthesized in Example 1 was dissolved in 70 mL of anhydrous dichloromethane, and 0.61 g of m-CPBA (0.355 mmol, 1 eq) was slowly added at 0 ° C. After the addition, the reaction was stirred at room temperature, and when the reaction was completed, NaHCO ₃ and MC were added to separate the organic layer. The separated organic layer was washed with water, dried with anhydrous MgSO ₄ , concentrated with a rotary evaporator, and the product was purified by column chromatography (yield: 81%).

Example 3 DPhCzSeO2 Synthesis of Chemical Formula 3

2.5 g (4.44 mmol) of DPhCzSe synthesized in Example 1 was dissolved in 80 mL of anhydrous dichloromethane, and 2.3 g (13.3 mmol, 3 eq) of m-CPBA was slowly added at 0 ° C. Next, after the reaction was stirred at room temperature, the reaction was completed, NaHCO ₃ and MC were added to separate the organic layer. The separated organic layer was washed with water, dried with anhydrous MgSO ₄ , concentrated with a rotary evaporator, and the product was purified by column chromatography (yield: 90%).

Thermogravimetric analysis of the compound prepared as shown in FIG. 2 confirmed that T _d , a temperature at which 5% of the weight was reduced, was 331 ° C.

Experimental Example 1

UV-vis, photoluminescence spectra (PL spectroscopies), cyclic voltammograms (VC) and HOMO-LUMO energy levels were measured using the compounds represented by Formulas 1 to 3 prepared in Examples 1 to 3, and the results Are shown in Table 1, FIG. 3 and FIG.

λ _abs λ _em HOMO
(eV) LUMO
(eV) T _d (℃) T _g (℃) E _g (eV) S ₁ (eV) T ₁ (eV) Example 1 246,
273 347, 361 5.14 0.87 408 78 3.29 3.57 3.14 Example 2 246, 287 353, 364 5.00 1.15 - - - 3.41 - Example 3 247, 283 350, 364 5.72 1.25 331 - - 3.40 2.85

The compounds prepared in Examples 1 and 3 as shown in Table 1 showed a high decomposition temperature of 408 ℃, 331 ℃, respectively. In addition, the glass transition temperature of the formula (1) was 78 ℃. However, Examples 2 and 3 are stable amorphous materials, and the decomposition temperature (Example 2) and the glass transition temperature (Examples 2 and 3), respectively, were not measured. Among them, the compound of Example 1 had a glass transition temperature of 78 ° C., which was higher than that of 1,3-Bis (N-carbazolyl) benzene (mCP), which is used as a conventional host material (55 ° C.). In addition, the compound having the improved glass transition temperature and decomposition temperature can be used as a host material to enable the formation of high quality amorphous thin film, it can be seen that it can improve the stability and life of the device.

FIG. 3 shows the emission spectrum of the compound prepared in Example 1, wherein the prepared compound UV-vis spectrum was in the ultraviolet region and the PL spectrum was in the near ultraviolet region. It can also be seen that the energy gap (E _g ) of the compound is estimated to be 3.29 eV.

In addition, the HOMO / LUMO energy levels of Example 1 measured through cyclic voltammetry were found to be 5.14 and 0.87 eV, respectively, and the triplet energy result according to the low temperature (77K) emission measured to evaluate energy transfer efficiency was 3.57, 3.14 eV. This is higher than the general host materials CBP (2.56eV) and Flrpic (2.65eV), it can be seen that the compound according to the present invention is a material suitable for use as a host material of the blue phosphorescent organic light emitting device.

In addition, Figure 4 shows the emission spectrum of the compound prepared in Example 3, the compound UV-vis spectrum prepared in the far ultraviolet and ultraviolet region, PL spectrum was found in the near ultraviolet region. However, the energy gap of the compound was not measured.

In addition, the HOMO / LUMO energy levels of Example 3 measured through cyclic voltammograms were respectively 5.72 and 1.25 eV, and the triplet energy result of the low temperature (77K) emission measured to evaluate energy transfer efficiency was 3.40, 2.85 eV. This is higher than CBP (2.56eV) and Flrpic (2.65eV) as in Example 1, it can be seen that the compound according to the invention is a material suitable for use as a host material of the blue phosphorescent organic light emitting device.

The blue phosphorescent host compound according to the present invention has a high triplet energy as in the above embodiment, and is confirmed to have excellent thermal stability. Therefore, a high efficiency and driving effect is expected compared to the mCP used as a host of the conventional organic light emitting device, and when applied as a host of the blue phosphorescent organic light emitting device can exhibit a high efficiency display driving effect.

Claims (6)

Blue phosphorescent host compound having a structure of Formula 1, Formula 2 or Formula 3.
[Formula 1]

[Formula 2]

[Formula 3]

a) reacting carbazole with halogen-substituted benzene to produce a first reactant;
b) preparing a second reactant by reacting halogen and potassium halide with the first reactant; And
c) preparing a compound of the following Chemical Formula 1 by reacting the selenocyanate potassium salt with the second reactant;
Method for producing a blue phosphorescent host compound comprising a.
[Formula 1]

The method of claim 2,
After step c),
d) reacting the compound of Chemical Formula 1 with m-chloroperbenzoic acid to prepare a compound of Chemical Formula 2 and Chemical Formula 3;
Method for producing a blue phosphorescent host compound, characterized in that it further comprises.
[Formula 2]

[Formula 3]

The method of claim 3,
The m-chloroperbenzo phosphoric acid is a method for producing a blue phosphorescent host compound, characterized in that 0.1 to 5 mmol is added relative to 1 mmol of the compound of Formula 1.
The method of claim 4, wherein
Step d) is a method for producing a blue phosphorescent host compound, characterized in that carried out at -5 to 5 ℃.
A blue phosphorescent organic light emitting device comprising the blue phosphorescent host compound according to claim 1 in a light emitting layer.

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