KR102152012B1 - Fluorescent compound and Organic light emitting diode device using the same - Google Patents

Abstract

The present invention is represented by the following formula, each of X and Y is independently selected from an aromatic ring compound, a heterocyclic compound, and an amine, and each of R1 and R2 is hydrogen or connected to each other to form an aliphatic-confused ring, It provides a fluorescent compound characterized in that it forms an aromatic fused ring (aromatic-confused ring) or a hetero-fused ring (hetero-confused ring).

Description

Fluorescent compound and organic light emitting diode device using the same

The present invention relates to a fluorescent compound used in an organic light emitting diode device, and in particular, a fluorescent compound having excellent hole transfer characteristics including a spiro-fluorene acridine core, and an organic light emitting diode device using the same. About.

Recently, as display devices become larger, the demand for flat display devices that occupy less space is increasing. As one of these flat display devices, the technology of organic light-emitting diode devices, also called organic electroluminescent devices (OELD), is rapidly increasing. Is developing into.

An organic light-emitting diode device is a device that emits light while electrons and holes form a pair and then disappear when charge is injected into a light emitting material layer formed between an electron injection electrode (cathode) and a hole injection electrode (anode). Not only can the device be formed on a flexible transparent substrate such as plastic, it can be driven at a lower voltage (less than 10V) compared to a plasma display panel or an inorganic electroluminescent (EL) display. In addition, it has the advantage of relatively low power consumption and excellent color purity. In addition, the organic light-emitting diode device can display three colors of green, blue, and red, and thus has been the subject of much interest of many people as a next-generation rich color display device. Here, a brief look at the process of manufacturing an organic light emitting diode device,

(1) First, an anode is formed by depositing a material such as indium tin oxide (ITO) on a transparent substrate.

(2) A hole injecting layer (HIL) is formed on the anode.

(3) Next, a hole transporting layer (HTL) is formed on the hole injection layer.

(4) Next, an emitting material layer (EML) is formed on the hole transport layer. At this time, a dopant is added as necessary.

(5) Next, an electron transporting layer (ETL) and an electron injecting layer (EIL) are formed on the light-emitting material layer. A hole blocking layer of 5 to 10 nm may be formed to confine excitons in the light emitting material layer.

(6) Next, a cathode is formed on the electron injection layer, and finally, a protective film is formed on the cathode.

As described above, in order to improve efficiency, the organic light emitting diode device has a structure in which a hole injection layer, a hole transport layer, a light emitting material layer, an electron transport layer, and an electron injection layer are stacked between an anode and a cathode. In addition, an electron blocking layer and a hole blocking layer may be additionally included in order to prevent the quenching of excitons, and such a complex structure increases cost and decreases productivity.

In addition, in the conventional organic light emitting diode device, it is difficult to efficiently inject holes due to a hole injection barrier, while electron injection and transfer rates are relatively high. Accordingly, the bonding region of holes and electrons is not located in the light emitting material layer, but is located between layers, that is, between the light emitting material layer and the hole transport layer, thereby reducing luminous efficiency.

In order to solve the above-described problem, it is necessary to simplify the structure of the organic light emitting diode device, and at the same time, the mobility of electrons and holes must be balanced so that the bonding region of electrons and holes exists in the light emitting material layer.

In particular, in the case of blue light emission, materials having an energy band gap wider than that of green and red are required, making it difficult to develop materials. However, since the blue light-emitting material has a large energy gap, there is an advantage that is commonly applicable to green and red light emission. Therefore, it is required to develop a material suitable for a simple device structure that is used for blue light emission.

An object of the present invention is to solve the problem of increasing cost and decreasing productivity due to a complex structure, and decreasing luminous efficiency due to reduction of hole mobility.

In order to solve the above problems, the present invention is represented by the following formula, each of X and Y is independently selected from an aromatic ring compound, a heterocyclic compound, and an amine, and each of R1 and R2 is hydrogen or is connected to each other to be aliphatic fusion. It provides a fluorescent compound characterized in that it forms an aliphatic-confused ring, an aromatic-confused ring, or a hetero-confused ring.

In the fluorescent compound of the present invention, each of X1 and X2 is independently carbazole, diphenylamine, α-carboline, β-carboline, and γ -It is characterized in that it is selected from carboline (γ-carboline), dibenzofuran (dibenzofuran), dibenzothiophene (dibenzothiophene), benzimidazole (benzimidazole).

The fluorescent compound of the present invention is characterized in that it is any one of a number of substances represented by the following formula.

In another aspect, the present invention comprises a first electrode; A second electrode facing the first electrode; An organic light-emitting diode device comprising a light-emitting material layer disposed between the first and second electrodes, and the light-emitting material layer includes the above-described fluorescent compound.

In another aspect, the present invention comprises a first electrode; A second electrode facing the first electrode; A light emitting material layer positioned between the first and second electrodes; A hole injection layer positioned between the first electrode and the light-emitting material layer; And a hole transport layer positioned between the hole injection layer and the light-emitting material layer, and at least one of the light-emitting material layer, the hole injection layer, and the hole transport layer comprises the above-described fluorescent compound. It provides an organic light emitting diode device.

The fluorescent compound of the present invention includes a spiro-fluorene acridine core having strong hole characteristics, thereby minimizing an energy barrier between an electrode and a light emitting material layer, thereby improving luminous efficiency.

Further, since the fluorescent compound of the present invention can be used as a light emitting layer, a hole injection layer, and a hole transport layer, the structure of an organic light emitting diode device can be simplified. Therefore, it has the effect of reducing the cost and improving the productivity of the organic light emitting diode device.

1A to 1D are UV and PL spectra of a fluorescent compound according to an embodiment of the present invention.
2 is a graph showing current characteristics in a hole only device.
3 is a schematic cross-sectional view of an organic light emitting diode device according to an embodiment of the present invention.

Hereinafter, the structure of the fluorescent compound according to the present invention, examples of its synthesis, and an organic light emitting diode device using the same will be described.

The fluorescent compound of the present invention is represented by the following formula (1). That is, it has a spiro-fluorene acridine core, and the balance between electrons and holes in an organic light emitting diode device can be improved by the strong hole characteristics of the spiro-fluorene acridine core.

Formula 1

In Formula 1, each of X and Y may be independently selected from an aromatic-ring compound, a hetero-ring compound, and an amine. X and Y may be the same or different.

For example, each of X and Y is carbazole, diphenylamine, α-carboline, β-carboline, and γ-carboline (γ- carboline), dibenzofuran, dibenzothiophene, benzimidazole, and substituents thereof.

That is, each of X and Y may be selected from a plurality of materials represented by Formula 2 below.

Formula 2

In addition, each of R1 and R2 in Formula 1 may be hydrogen or be connected to each other to form an aliphatic-confused ring, an aromatic-confused ring, or a hetero-confused ring. have.

The fluorescent compound of the present invention may be one of a number of substances represented by Formula 3 below.

Formula 3

In the following, synthesis examples and properties of the compounds will be described by taking compounds represented by the following Formulas 4-1 to 4-4 among the fluorescent compounds according to the present invention as an example.

Formula 4 -One

Formula 4 -2

Formula 4 -3

Formula 4 -4

1. Synthesis of Formula 4-1 compound (compound 1)

(1) Synthesis of 9-(2-bromophenyl)-9H-carbazole

Scheme 1

In a 500 mL two-neck flask, carbazole (7.39 g, 0.0442 mol), 1-bromo-2-iodobenzene (25 g, 0.0883 mol), CuI (0.421 g, 2.22 mmol), K2CO3 (12.12 g, 0.0883 mol) mol) was dissolved in xylene and stirred under reflux at 120°C. After cooling to room temperature, extraction was performed with CH ₂ Cl ₂ , water was dried over MgSO ₄ , and the solvent was removed. Columns were performed with hexane solvent to obtain 3.63 g (25.5%) of a white solid.

(2) Synthesis of 2,7-dibromospiro[fluorene-9,8'-indolo[3,2,1-de]acridine]

Scheme 2

In a 250 mL two-necked flask, 9-(2-bromophenyl)-9H-carbazole (1.65g, 5.12 mmol) was dissolved in 50 mL of THF. After cooling to -78°C, n-BuLi (2.5 M in hexane, 2.15 mL, 5.38 mmol) was slowly added dropwise. After 2 hours, 2,7-dibromo-9H-fluoren-9-one (1.73 g, 5.12 mmol) was added. After 3 hours, the reaction was terminated with an aqueous NH ₄ Cl solution, followed by extraction with diethyl ether. After drying water with MgSO ₄ , the solvent was removed. After precipitation with ethanol, the solid was filtered. After dissolving the obtained solid in acetic acid (50 mL), a catalytic amount of HCl is added. After stirring at reflux for 6 hours, it was cooled to room temperature, and the resulting solid was filtered, washed with ethanol and dried to obtain 2.11 g (73%) of a white solid.

(3) Synthesis of 2,7-di(9H-carbazol-9-yl)spiro[fluorene-9,8'-indolo[3,2,1-de]acridine]

Scheme 3

In a 250 mL two-necked flask, 2,7-dibromospiro[fluorene-9,8'-indolo[3,2,1-de]acridine] (1 g, 1.78 mmol), cabazole (0.65 g, 3.91 mmol), Pd ₂ ( dba) ₃ (0.098g, 0.107 mmol), sodium tert-butoxide (0.512 g, 5.33 mmol), and tri-tert-butylphosphine (0.022g, 0.107 mmol) were dissolved in toluene and stirred under reflux. After cooling to room temperature, extraction was performed with CH ₂ Cl ₂ , water was dried with MgSO _4, and the solvent was removed. Hexane: After column with CH ₂ Cl ₂ , precipitated with petroleum ether, the resulting solid was filtered to obtain 1.1 g (84%) of a white solid (compound 1).

2. Synthesis of Formula 4-2 compound (compound 2)

(1) Synthesis of N ² ,N ² ,N ⁷ ,N ⁷ -tetraphenylspiro[fluorene-9,8'-indolo[3,2,1-de]acridine]-2,7-diamine

Scheme 4

In a 250 mL two-necked flask, 2,7-dibromospiro[fluorene-9,8'-indolo[3,2,1-de]acridine] (1.07 g, 1.90 mmol), diphenylamine (0.68 g, 3.99 mmol), Pd ₂ ( dba) ₃ (0.104 g, 0.11 mmol), sodium tert-butoxide (0.55 g, 5.70 mmol), and tri-tert-butylphosphine (0.023 g, 0.11 mmol) were dissolved in toluene and stirred under reflux. After cooling to room temperature, extraction was performed with CH ₂ Cl ₂ , water was dried with MgSO _4, and the solvent was removed. Hexane: After column with CH ₂ Cl ₂ , precipitated with petroleum ether, the resulting solid was filtered to obtain 1.0 g (71%) of a white solid (compound 2).

3. Synthesis of Formula 4-3 compound (compound 3)

(1) Synthesis of 2,7-diiodospiro[fluorene-9,8'-indolo[3,2,1-de]acridine]

Scheme 5

In a 250 mL two-necked flask, 9-(2-bromophenyl)-9H-carbazole (1.98 g, 6.15 mmol) was dissolved in 50 mL of THF. After cooling to -78°C, n-BuLi (2.5 M in hexane, 2.58 mL, 6.45 mmol) was slowly added dropwise. After 2 hours, 2,7-diiodo-9H-fluoren-9-one (2.65 g, 6.15 mmol) was added. After 3 hours, the reaction was terminated with an aqueous NH ₄ Cl solution, followed by extraction with diethyl ether. After drying water with MgSO ₄ , the solvent was removed. After precipitation with ethanol, the solid was filtered. The obtained solid was dissolved in acetic acid (50 mL), and a catalytic amount of HCl was added. After refluxing and stirring for 6 hours, the mixture was cooled to room temperature, and the resulting solid was filtered, washed with ethanol and dried to obtain 1.0 g (25%) of a white solid.

(2) Synthesis of 2,7-di(9H-pyrido[2,3-b]indol-9-yl)spiro[fluorene-9,8'-indolo[3,2,1-de]acridine]

Scheme 6

In a 250 mL two-necked flask, 2,7-diiodospiro[fluorene-9,8'-indolo[3,2,1-de]acridine] (1.0 g, 1.52 mmol), α-carboline (0.54 g, 3.19 mmol), CuI (0.174 g, 0.913 mmol), K ₃ PO ₄ (0.646 g, 3.04 mmol), and trans-1,2-dicyclohexane-diamine (0.105 g, 0.913 mmol) were added and dissolved in 50 mL of 1,4-dioxane. Stir at reflux for 24 hours. After completion of the reaction, the solvent was distilled under reduced pressure and column was performed using CH ₂ Cl ₂ :hexane. Then, by precipitation with petroleum ether, 0.85 g (75.9%) of a white solid (compound 3) was obtained.

4. Synthesis of Formula 4-4 compound (compound 4)

(1) Synthesis of 2-bromo-N,N-diphenylaniline

Scheme 7

In a 250 mL two-necked flask, diphenylamine (12.5 g, 73.6 mmol), 1-bromo-2-iodobenzene (25 g, 88.4 mmol), CuI (0.701 g, 3.68 mmol), K ₂ CO ₃ (20.4 g, 147 mmol) Dissolved in xylene and stirred under reflux at 120°C. After cooling to room temperature, extraction was performed with CH ₂ Cl ₂ , water was dried over MgSO ₄ , and the solvent was removed. Columns were performed with a hexane solvent to obtain 8.95 g (37.3%) of a white solid.

(2) Synthesis of 2',7'-dibromo-10-phenyl-10H-spiro[acridine-9,9'-fluorene]

Scheme 8

In a 250 mL two-necked flask, 2-bromo-N,N-diphenylaniline (4.8 g, 14.8 mmol) was dissolved in 100 mL of THF. After cooling to -78°C, n-BuLi (2.5 M in hexane, 6.22 mL, 15.5 mmol) was slowly added dropwise. After 2 hours, 2,7-dibromo-9H-fluoren-9-one (5.0 g, 14.8 mmol) was added. After 3 hours, the reaction was terminated with an aqueous NH ₄ Cl solution, followed by extraction with diethyl ether. After drying water with MgSO ₄ , the solvent was removed. After precipitation with ethanol, the solid was filtered. After dissolving the obtained solid in acetic acid (50 mL), a catalytic amount of HCl is added. After stirring at reflux for 6 hours, it was cooled to room temperature, and the resulting solid was filtered, washed with ethanol, and dried to obtain 7.6 g (91%) of a white solid.

(3) Synthesis of 2',7'-di(9H-carbazol-9-yl)-10-phenyl-10H-spiro[acridine-9,9'-fluorene]

Scheme 9

In a 250 mL two-necked flask, 2',7'-dibromo-10-phenyl-10H-spiro[acridine-9,9'-fluorene] (1.5 g, 2.65 mmol), cabazole (0.93 g, 5.57 mmol), Pd2 (dba )3 (0.15 g, 0.159 mmol), sodium tert-butoxide (0.77 g, 769 mmol), and tri-tert-butylphosphine (0.03 g, 0.159 mmol) were dissolved in toluene and stirred under reflux. After cooling to room temperature, extraction was performed with CH ₂ Cl ₂ , water was dried with MgSO _4, and the solvent was removed. CH ₂ Cl ₂ : After column using hexane (=2:1), precipitated with petroleum ether, the resulting solid was filtered to obtain 1.2 g (61.2%) of a white solid (compound 4).

The UV spectrum and room temperature (RT) and low temperature (LT) PL (photoluminescence) spectrum of the fluorescent compounds (compound 1, compound 2, compound 3, compound 4) obtained by the above synthesis example are shown in FIGS. 1A to 1D, respectively. The properties of the compounds are listed in Table 1.

Hereinafter, the hole mobility characteristics of the fluorescent compound according to the present invention will be compared and described through Experimental Examples and Comparative Examples in which a hole only device is manufactured using the fluorescent compound of the present invention.

Experimental Example 1

In a state where the pressure of the vacuum chamber is about 1*10-6torr, the compound 1 of Formula 4-1 is doped with 10wt% of HATCN (hexaazatriphenylene-hexacarbonitirile) on the indium-tin-oxide (ITO) layer, and is about 5nm thick, compound 1 was deposited to a thickness of about 25 nm and NPB of 10 nm, and an Al layer was deposited on the NPB layer. (ITO/(compound 1+HATCN)/compound 1/NPB/Al)

Experimental Example 2

In a state where the pressure in the vacuum chamber is about 1*10-6torr, the indium-tin-oxide (ITO) layer is doped with 20wt% HATCN in the compound 3 of Chemical Formula 4-3 to a thickness of about 5 nm, and compound 3 is about 25 nm thick. , NPB was deposited to a thickness of 10 nm, and an Al layer was deposited on the NPB layer. (ITO/(compound 3+HATCN)/compound 3/NPB/Al)

The current density according to the voltage was measured in the device of the experimental example described above, and is shown in FIG.

delete

delete

As shown in FIG. 2, when the fluorescent material of the present invention is used, a high current density is shown. That is, it can be seen that the hole movement characteristics are improved. Therefore, it can be used as a hole injection layer and a hole transport layer in an organic light emitting diode device.

In addition, as can be seen from FIGS. 1A to 1D, the fluorescent material of the present invention can generate blue wavelength light, and thus may be used for a light emitting material layer in an organic light emitting diode device.

In other words, since the fluorescent material of the present invention can be used as a hole injection layer, a hole transport layer, and a light emitting material layer in an organic light emitting diode device, the structure of the device can be greatly simplified.

Manufacturing cost increases and productivity decreases due to the conventional multi-layer structure for improving luminous efficiency, but since the hole injection layer, the hole transport layer, and the light-emitting material layer can be formed of one material, manufacturing according to the deposition process It can prevent the problem of cost increase and productivity decrease in each process.

Further, since the fluorescent material of the present invention has a wide energy band gap, it can be used for a hole injection layer and a hole transport layer in green and red pixel regions. Therefore, in forming the laminated structure of the organic light emitting diode device, it has the effect of simplifying the process.

3 shows an example of an organic light emitting diode device comprising the fluorescent compound of the present invention.

As shown, the organic light emitting diode device includes first and second substrates (not shown) facing each other, and a light emitting diode E formed between the first and second substrates (not shown).

The light emitting diode E includes a first electrode 110 serving as an anode, a second electrode 130 serving as a cathode, and an organic light emitting layer 120 formed between the first and second electrodes 110 and 130 Consists of

The first electrode 110 is made of a material having a relatively high work function value, for example, indium-tin-oxide (ITO), and the second electrode 130 is a material having a relatively low work function value, for example For example, it is made of aluminum (Al) or aluminum alloy (AlNd). In addition, the organic emission layer 120 includes red, green, and blue organic emission patterns.

The organic light emitting layer 120 has a multilayer structure, that is, a hole injection layer (HTL) 121 and a hole transporting layer (HIL) sequentially from the first electrode 110 to maximize luminous efficiency. ) 122, a emitting material layer (EML) 123, an electron transporting layer 124, and an electron injection layer 125.

Here, at least one of the hole injection layer 121, the hole transport layer 122, and the light emitting material layer 123 includes the fluorescent compound of the present invention represented by Formula 1 above.

For example, when the light-emitting material layer 123 includes the fluorescent compound of the present invention as a host material, about 1 to 30 wt% of a dopant is added, and blue light is emitted.

In addition, when the hole injection layer 121 is made of the fluorescent compound of the present invention, a doping process for improving hole injection characteristics may be performed.

When all of the hole injection layer 121, the hole transport layer 122, and the light emitting material layer 123 are made of the fluorescent compound of the present invention, the hole injection layer 121 and the hole transport layer ( 122), since the light emitting material layer 123 can be formed, a manufacturing process is simplified and productivity is improved.

In addition, since the fluorescent material of the present invention has excellent hole characteristics, holes and electrons are combined in the light emitting material layer 123. Accordingly, the luminous efficiency of the organic light emitting diode device is improved.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention within the scope not departing from the spirit and scope of the present invention described in the following claims. You will understand that you can do it.

110: first electrode 120: organic light emitting layer
121: hole injection layer 122: hole transport layer
123: light-emitting material layer 124: electron transport layer
125: electron injection layer 130: second electrode
E: light-emitting diode

Claims (6)

Represented by the following formula, each of X and Y is independently selected from carbazole, diphenylamine, carboline, dibenzofuran, dibenzothiophene, benzimidazole, and are different from each other, and each of R1 and R2 is hydrogen. Fluorescent compound.

delete The method of claim 1,
A fluorescent compound, characterized in that it is any one of a number of substances represented by the following formula.

A first electrode;
A second electrode facing the first electrode;
Including a light emitting material layer positioned between the first and second electrodes,
The organic light-emitting diode device, characterized in that the light-emitting material layer includes any one of the fluorescent compounds of claim 1 or 3.
The method of claim 4,
A hole injection layer and a hole transport layer positioned between the first electrode and the light-emitting material layer, and at least one of the hole injection layer and the hole transport layer contains the fluorescent compound of claim 1 or is composed of the fluorescent compound of claim 1. An organic light-emitting diode device characterized by this.
A first electrode;
A second electrode facing the first electrode;
A light emitting material layer positioned between the first and second electrodes;
A hole injection layer positioned between the first electrode and the light-emitting material layer;
A hole transport layer positioned between the hole injection layer and the light emitting material layer,
At least one of the light-emitting material layer, the hole injection layer, and the hole transport layer contains the fluorescent compound of any one of claims 1 and 3, or is a fluorescent compound of any one of claims 1 and 3. An organic light emitting diode device characterized by being made.

Images