A HOLE TRANSPORT MATERIAL AND AN ORGANIC ELECTROLUMINESCENT DEVICE COMPRISING THE SAME

Abstract

The present invention relates to a hole transport material and an organic electroluminescent device comprising the same. By using the hole transport material according to the present invention, an organic electroluminescent device having significantly improved operational lifespan while maintaining low driving voltage and high current and power efficiencies can be produced.

Claims

1. A hole transport material comprising a compound represented by the following formula 1: ##STR00079## wherein X represents O, S, CR.sub.9R.sub.10, or NR.sub.11; L represents a single bond, or a substituted or unsubstituted (C6-C30)arylene; R.sub.1 to R.sub.11 each independently represent hydrogen, deuterium, a substituted or unsubstituted (C1-C30)alkyl, a substituted or unsubstituted (C6-C30)aryl, a substituted or unsubstituted 3- to 30-membered heteroaryl, a substituted or unsubstituted (C3-C30)cycloalkyl, a substituted or unsubstituted tri(C1-C30)alkylsilyl, a substituted or unsubstituted di(C1-C30)alkyl(C6-C30)arylsilyl, a substituted or unsubstituted (C1-C30)alkyldi(C6-C30)arylsilyl, a substituted or unsubstituted tri(C6-C30)arylsilyl, a substituted or unsubstituted mono- or di-(C1-C30)alkylamino, a substituted or unsubstituted mono- or di-(C6-C30)arylamino, or a substituted or unsubstituted (C1-C30)alkyl(C6-C30)arylamino; or are linked to each other to form a mono- or polycyclic, (C3-C30) alicyclic or aromatic ring, whose carbon atom(s) may be replaced with at least one hetero atom selected from nitrogen, oxygen, and sulfur; and the heteroaryl contains at least one hetero atom selected from B, N, O, S, Si, and P.

2. The hole transport material according to claim 1, wherein the substituents of the substituted (C1-C30)alkyl, the substituted (C3-C30)cycloalkyl, the substituted (C6-C30)aryl(ene), the substituted 3- to 30-membered heteroaryl, the substituted tri(C1-C30)alkylsilyl, the substituted di(C1-C30)alkyl(C6-C30)arylsilyl, the substituted (C1-C30)alkyldi(C6-C30)arylsilyl, the substituted tri(C6-C30)arylsilyl, the substituted mono- or di-(C1-C30)alkylamino, the substituted mono- or di-(C6-C30)arylamino, and the substituted (C1-C30)alkyl(C6-C30)arylamino in L, and R.sub.1 to R.sub.11 each independently are at least one selected from the group consisting of deuterium, a halogen, a cyano, a carboxyl, a nitro, a hydroxyl, a (C1-C30)alkyl, a halo(C1-C30)alkyl, a (C2-C30) alkenyl, a (C2-C30) alkynyl, a (C1-C30)alkoxy, a (C1-C30)alkylthio, a (C3-C30)cycloalkyl, a (C3-C30)cycloalkenyl, a 3- to 7-membered heterocycloalkyl, a (C6-C30)aryloxy, a (C6-C30)arylthio, a 3- to 30-membered heteroaryl unsubstituted or substituted with a (C6-C30)aryl, a (C6-C30)aryl unsubstituted or substituted with a 3- to 30-membered heteroaryl, a tri(C1-C30)alkylsilyl, a tri(C6-C30)arylsilyl, a di(C1-C30)alkyl(C6-C30)arylsilyl, a (C1-C30)alkyldi(C6-C30)arylsilyl, an amino, a mono- or di-(C1-C30)alkylamino, a mono- or di-(C6-C30)arylamino, a (C1-C30)alkyl(C6-C30)arylamino, a (C1-C30)alkylcarbonyl, a (C1-C30)alkoxycarbonyl, a (C6-C30)arylcarbonyl, a di(C6-C30)arylboronyl, a di(C1-C30)alkylboronyl, a (C1-C30)alkyl(C6-C30)arylboronyl, a (C6-C30)aryl(C1-C30)alkyl, and a (C1-C30)alkyl(C6-C30)aryl.

3. The hole transport material according to claim 1, wherein X represents O, S, CR.sub.9R.sub.10, or NR.sub.11; L represents a single bond, or a substituted or unsubstituted (C6-C12)arylene; R.sub.1 to R.sub.8 each independently represent hydrogen, or a substituted or unsubstituted 5- to 15-membered heteroaryl; or are linked to each other to form a mono- or polycyclic, (C5-C15) alicyclic or aromatic ring; and R.sub.9 to R.sub.11 each independently represent hydrogen, a substituted or unsubstituted (C1-C6)alkyl, or a substituted or unsubstituted (C6-C15)aryl; or are linked to each other to form a mono- or polycyclic, (C5-C15) alicyclic or aromatic ring.

4. The hole transport material according to claim 1, wherein X represents O, S, CR.sub.9R.sub.10, or NR.sub.11; L represents a single bond, or an unsubstituted (C6-C12)arylene; R.sub.1 to R.sub.8 each independently represent hydrogen, or a 5- to 15-membered heteroaryl unsubstituted or substituted with a (C6-C12)aryl; or are linked to each other to form a monocyclic, (C5-C15) aromatic ring; and R.sub.9 to R.sub.11 each independently represent hydrogen, an unsubstituted (C1-C6)alkyl, or an unsubstituted (C6-C15)aryl; or are linked to each other to form a polycyclic, (C5-C15) aromatic ring.

5. The hole transport material according to claim 1, wherein the compound represented by formula 1 is selected from the group consisting of: ##STR00080## ##STR00081## ##STR00082## ##STR00083## ##STR00084## ##STR00085## ##STR00086## ##STR00087## ##STR00088## ##STR00089## ##STR00090## ##STR00091## ##STR00092## ##STR00093## ##STR00094## ##STR00095## ##STR00096## ##STR00097## ##STR00098## ##STR00099## ##STR00100## ##STR00101## ##STR00102## ##STR00103## ##STR00104## ##STR00105## ##STR00106## ##STR00107##

6. An organic electroluminescent device comprising the hole transport material according to claim 1.

Description

EXAMPLE 1: PREPARATION OF COMPOUND A-1

[0059] ##STR00064## ##STR00065##

[0060] Preparation of Compound 1-1

[0061] After introducing (9-phenyl-9H-carbazol-3-yl)boronic acid (30 g, 104.49 mmol), 1-bromo-4-iodobenzene (30 g, 104.49 mmol), tetrakis(triphenylphosphine)palladium (3.6 g, 3.13 mmol), sodium carbonate (28 g, 261.23 mmol), toluene 520 mL, ethanol 130 mL, and distilled water 130 mL in a reaction vessel, the mixture was stirred at 120° C. for 4 hours. After the reaction, the mixture was washed with distilled water, and an organic layer was extracted with ethyl acetate. The extracted organic layer was dried with magnesium sulfate, and the solvent was removed using a rotary evaporator. The remaining product was then purified with column chromatography to obtain compound 1-1 (27 g, yield: 65%).

[0062] Preparation of Compound 1-2

[0063] After introducing carbazole (20 g, 120 mmol), 2-bromonaphthalene (30 g, 143 mmol), copper(I) iodide (11.7 g, 59.81 mmol), ethylene diamine (8 mL, 120 mmol), potassium phosphate (64 g, 299 mmol), and toluene 600 mL in a reaction vessel, the mixture was stirred at 120° C. for 8 hours. After the reaction, the mixture was washed with distilled water, and an organic layer was extracted with ethyl acetate. The extracted organic layer was dried with magnesium sulfate, and the solvent was removed using a rotary evaporator. The remaining product was then purified with column chromatography to obtain compound 1-2 (13 g, yield: 37%).

[0064] Preparation of Compound 1-3

[0065] Compound 1-2 (13 g, 44 mmol) was dissolved in dimethylformamide in a reaction vessel. After dissolving N-bromosuccinamide in dimethylformamide, it was introduced to the mixture. After stirring the mixture for 4 hours, the mixture was washed with distilled water, and an organic layer was extracted with ethyl acetate. The extracted organic layer was dried with magnesium sulfate, and the solvent was removed using a rotary evaporator. The remaining product was then purified with column chromatography to obtain compound 1-3 (14 g, yield: 83%).

[0066] Preparation of Compound 1-4

[0067] After introducing compound 1-3 (14 g, 36 mmol), bis(pinacolato)diborane (11 g, 44 mmol), dichloro-di(triphenylphosphine)palladium (1.3 g, 2 mmol), potassium acetate (9 g, 91 mmol), and 1,4-dioxane 180 mL in a reaction vessel, the mixture was stirred at 140° C. for 2 hours. After the reaction, the mixture was washed with distilled water, and an organic layer was extracted with ethyl acetate. The extracted organic layer was dried with magnesium sulfate, and the solvent was removed using a rotary evaporator. The remaining product was then purified with column chromatography to obtain compound 1-4 (8 g, yield: 52%).

[0068] Preparation of Compound A-1

[0069] After introducing compound 1-1 (7 g, 17 mmol), compound 1-4 (8 g, 19 mmol), tetrakis(triphenylphosphine)palladium (0.6 g, 0.5 mmol), sodium carbonate (4.5 g, 43 mmol), toluene 100 mL, ethanol 25 mL, and distilled water 25 mL in a reaction vessel, the mixture was stirred at 120° C. for 4 hours. After the reaction, the mixture was washed with distilled water, and an organic layer was extracted with ethyl acetate. The extracted organic layer was dried with magnesium sulfate, and the solvent was removed using a rotary evaporator. The remaining product was then purified with column chromatography to obtain compound A-1 (4 g, yield: 87%).

TABLE-US-00001 MW UV PL M.P A-1 610.74 354 nm 397 nm 198° C.

EXAMPLE 2: PREPARATION OF COMPOUND A-4

[0070] ##STR00066##

[0071] Preparation of Compound A-4

[0072] After dissolving compound 2-1 (9-phenyl-9H, 9′H-3,3′-bicarbazole) (15 g, 36.70 mmol), compound 2-2 (2-bromonaphthalene) (7.6 g, 36.70 mmol), Pd.sub.2(dba).sub.3 (1.0 g, 1.10 mmol), P(t-Bu).sub.3 (3.7 mL, 2.20 mmol), and NaOtBu (5.3 g, 55.10 mmol) in toluene 200 mL in a flask, the mixture was stirred under reflux at 120° C. for 4 hours. After the reaction, the mixture was separated with column chromatography, and methanol was added thereto. The produced solid was filtered under reduced pressure. The produced solid was recrystallized with toluene to obtain compound A-4 (13.5 g, yield: 69%).

TABLE-US-00002 MW UV PL M.P A-4 534.65 368 nm 407 nm 186.5° C.

EXAMPLE 3: PREPARATION OF COMPOUND A-7

[0073] ##STR00067## ##STR00068##

[0074] Preparation of Compound 3-1

[0075] After dissolving 9H-carbazole (20 g, 119.60 mmol), 2-bromonaphthalene (37 g, 179.46 mmol), CuI (11 g, 59.8 mmol), ethylene diamine (8 mL, 119.6 mmol), and K.sub.3PO.sub.4 (50 g, 239.2 mmol) in toluene 598 mL in a flask, the mixture was stirred under reflux at 120° C. for 5 hours. After the reaction, an organic layer was extracted with ethyl acetate, the residual moisture was removed using magnesium sulfate, and dried. The remaining product was then separated with column chromatography to obtain compound 3-1 (24.4 g, yield: 70%).

[0076] Preparation of Compound 3-2

[0077] After dissolving compound 3-1 (9-(naphthalene-2-yl)-carbazole) (24 g, 93.2 mmol) and N-bromosuccinimide (14 g, 79 mmol) in tetrahydrofuran (THF) 832 mL, the mixture was stirred at room temperature for 20 hours. After the reaction, an organic layer was extracted with ethyl acetate, the residual moisture was removed using magnesium sulfate, and dried. The remaining product was then separated with column chromatography to obtain compound 3-2 (26.4 g, yield: 84%).

[0078] Preparation of Compound 3-3

[0079] After dissolving compound 3-2 (3-bromo-9-(naphthalen-2-yl)-carbazole (16 g, 43 mmol) in THF 400 mL, the mixture was cooled to −78° C. 2.5 M n-butyl lithium (21 mL, 51.6 mmol) was then added to the mixture, and stirred for 1 hour. Triisopropyl borate (15 mL, 66 mmol) was then added to the mixture, and reacted for 8 hours. After the reaction, the produced white solid was filtered to obtain compound 3-3 (8.7 g, yield: 50%).

[0080] Preparation of Compound A-7

[0081] After dissolving compound 3-2 (3-bromo-9-(naphthalen-2-yl)-carbazole (8 g, 21.5 mmol), compound 3-3 ((9-(naphthalen-2-yl)-9H-carbazol-3-yl)boronic acid) (8.7 g, 25.8 mmol), and tetrakis(triphenylphosphine)palladium(O) (Pd(PPh.sub.3).sub.4) (993 mg, 0.86 mmol) in a mixed solvent of 2M K.sub.2CO.sub.3 27 mL, toluene 108 mL, and ethanol 27 mL, the mixture was stirred under reflux at 120° C. for 2 hours. After the reaction, an organic layer was extracted with ethyl acetate, the residual moisture was removed using magnesium sulfate, and dried. The remaining product was then separated with column chromatography to obtain compound A-7 (1.5 g, yield: 12%).

TABLE-US-00003 MW UV PL M.P A-7 584.71 306 nm 407 nm 301° C.

EXAMPLE 4: PREPARATION OF COMPOUND A-15

[0082] ##STR00069##

[0083] Preparation of Compound 4-1

[0084] After dissolving 9-[1,1′-phenyl]-3-yl-3-bromo-9H-carbazole (12 g, 31.8 mmol), 3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole (9.3 g, 31.8 mmol), and tetrakis(triphenylphosphine)palladium(O) (Pd(PPh.sub.3).sub.4) (1.1 g, 0.95 mmol) in a mixed solvent of 2M K.sub.2CO.sub.3 40 mL, toluene 160 mL, and ethanol 40 mL, the mixture was stirred under reflux for 4 hours. After the reaction, an organic layer was extracted with ethyl acetate, the residual moisture was removed using magnesium sulfate, and dried. The remaining product was then separated with column chromatography to obtain compound 4-1 (9.5 g, yield: 63%).

[0085] Preparation of Compound A-15

[0086] After introducing compound 4-1 (7 g, 14.4 mmol), 2-bromonaphthalene (3.3 g, 15.8 mmol), tris(dibenzylideneacetone)dipalladium (0.6 g, 0.72 mmol), tri-tert-butylphosphine (0.7 mL (50%), 1.44 mmol), sodium tert-butoxide (3.4 g, 36.1 mmol), and toluene 80 mL in a flask, the mixture was stirred under reflux for 2.5 hours. After cooling the mixture to room temperature, distilled water was added thereto. The mixture was extracted with methylene chloride, and dried with magnesium sulfate. The remaining product was then filtered under reduced pressure, and separated with column chromatography to obtain compound A-15 (6.7 g, yield: 76%).

TABLE-US-00004 MW UV PL M.P A-15 610.74 352 nm 406 nm 192° C.

DEVICE EXAMPLES 1 TO 4: PRODUCTION OF AN OLED DEVICE ACCORDING TO THE PRESENT INVENTION

[0087] An OLED device of the present invention was produced as follows: A transparent electrode indium tin oxide (ITO) thin film (10 Ω/sq) on a glass substrate for an organic light-emitting diode (OLED) device (Geomatec, Japan) was subjected to an ultrasonic washing with acetone and isopropan alcohol, sequentially, and then was stored in isopropan alcohol. The ITO substrate was then mounted on a substrate holder of a vacuum vapor depositing apparatus. Compound HI-1 was introduced into a cell of said vacuum vapor depositing apparatus, and then the pressure in the chamber of said apparatus was controlled to 10.sup.−6 torr. Thereafter, an electric current was applied to the cell to evaporate the above introduced material, thereby forming a first hole injection layer having a thickness of 60 nm on the ITO substrate. Compound HI-2 was then introduced into another cell of said vacuum vapor depositing apparatus, and was evaporated by applying an electric current to the cell, thereby forming a second hole injection layer having a thickness of 5 nm on the first hole injection layer. Compound HT-1 was then introduced into another cell of said vacuum vapor depositing apparatus, and was evaporated by applying an electric current to the cell, thereby forming a first hole transport layer having a thickness of 20 nm on the second hole injection layer. Next, the compound of formula 1 of the present invention was introduced into another cell of said vacuum vapor depositing apparatus, and was evaporated by applying an electric current to the cell, thereby forming a second hole transport layer having a thickness of 5 nm on the first hole transport layer. Thereafter, compound H-15 was introduced into one cell of the vacuum vapor depositing apparatus, as a host, and compound D-38 was introduced into another cell as a dopant. The two materials were evaporated at different rates and were deposited in a doping amount of 2 wt % based on the total amount of the dopant and host to form a light-emitting layer having a thickness of 20 nm on the second hole transport layer. 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo[d]imidazole was introduced into one cell and lithium quinolate was introduced into another cell. The two materials were evaporated at the same rate and were deposited in a doping amount of 50 wt % each to form an electron transport layer having a thickness of 35 nm on the light-emitting layer. After depositing lithium quinolate as an electron injection layer having a thickness of 2 nm on the electron transport layer, an Al cathode having a thickness of 80 nm was then deposited by another vacuum vapor deposition apparatus on the electron injection layer. Thus, an OLED device was produced. All the materials used for producing the OLED device were purified by vacuum sublimation at 10.sup.−6 torr prior to use.

[0088] The driving voltage at 1,000 nit of luminance, luminous efficiency, CIE color coordinate, and the time period for the luminance to decrease from 100% to 90% at 2,000 nit and constant current of the organic electroluminescent devices are shown in Table 1 below.

COMPARATIVE EXAMPLES 1 TO 4: PRODUCTION OF AN OLED DEVICE USING A CONVENTIONAL COMPOUND

[0089] An OLED device was produced in the same manner as in Device Example 1, except for using conventional compounds for a hole transport material instead of the compound of formula 1 of the present invention in the second hole transport layer.

[0090] The evaluation results of the device of Device Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Tables 1 and 2 below.

TABLE-US-00005 TABLE 1 Second Hole Color Color Transport Voltage Efficiency Coordinate Coordinate Lifespan Layer (V) (cd/A) (x) (y) (T90hr) Comparative B-1 4.1 4.6 0.139 0.092 50 Example 1 Comparative B-2 4.1 4.2 0.14 0.093 23 Example 2 Comparative B-4 4.2 6 0.139 0.098 50 Example 3 Device A-4 4.3 6 0.14 0.094 71.6 Example 1 Device A-7 4.4 6.1 0.14 0.094 77 Example 2 Device A-15 4.4 6.4 0.14 0.094 64.4 Example 3

TABLE-US-00006 TABLE 2 Second Hole Color Color Transport Voltage Efficiency Coordinate Coordinate Lifespan Layer (V) (cd/A) (x) (y) (T90hr) Comparative B-3 4.3 6.2 0.139 0.098 35 Example 4 Device A-1 4.2 6.6 0.139 0.101 41 Example 4

TABLE-US-00007 TABLE 3 The compounds used in the Device Examples and the Comparative Examples Hole Injection Layer/ Hole Transport Layer [00070]   HI-1 [00071]   HI-2 [00072]   HT-1 Light- Emitting Layer [00073]   H-15 [00074]   D-38 Comparative Compounds [00075]   B-1 [00076]   B-2 [00077]   B-3 [00078]   B-4

[0091] As seen from Tables 1 and 2 above, it is confirmed that the lifespan characteristic of Device Examples 1 to 4 is superior to that of the Comparative Examples due to higher anion stability of the second hole transport layer. That is, the problem of the decrease in lifespan followed by the increase of efficiency is overcome.

[0092] [Triplet]

[0093] The triplet energy was calculated by, first, conducting structure optimization in the ground state by applying 6-31G* basis set to B3LYP, which is one of the Density Functional Theory (DFT) methods, and then, TD-DFT calculation using the same basis set and the same theory in the optimized structure. In all the calculations, the program, Gaussian 03, was used.

[0094] [Determination of Structure]

[0095] The optimization of structure in the ground state was conducted by applying 6-31G* basis set to B3LYP, which is one of the DFT methods.

[0096] [Anion Stability]

[0097] The anion stability was calculated by conducting structure optimization in the ground state by applying 6-31G* basis set to B3LYP, which is one of the DFT methods, and then, reoptimization in an electron state of −1 by randomly adding one electron to the calculated ground state structure, and determining the energy difference between the ground state and the electron state of −1.

[0098] Herein, it is preferable that the anion stability is at least a positive number (0 Kcal/mol or higher).

[0099] In similar molecular structures, a compound having a higher anion stability value is stable for electrons.

[0100] The anion stability values of the compounds used in the second hole transport layer of the Device Examples and the Comparative Examples found are shown in Table 4 below.

TABLE-US-00008 TABLE 4 Second hole Anion stability transport layer value B-1 0.416 B-3 −2.04 B-4 −7.56 A-1 3.83 A-4 0.548 A-7 7.18  A-15 5.42