KR101532228B1 - Iridium electroluminescent compounds having bis trifluoromethyl substituents and organic electroluminescent device using the same - Google Patents

Abstract

According to an aspect of the present invention, there is provided an iridium luminescent compound having excellent luminescent efficiency and high solubility in a solvent, and an organic light emitting diode manufactured using the iridium luminescent compound together with a host for green luminescence.

Description

[0001] The present invention relates to an iridium phosphorescent light-emitting compound containing a bistrifluoromethyl substituent and an organic light-emitting device employing the same,

The present invention relates to an iridium phosphorescent light emitting compound containing a bis trifluoromethyl substituent and an organic light emitting device employing the same. More particularly, the present invention relates to an iridium phosphorescent emitting compound having a luminescence efficiency characteristic, Emitting device.

A long pursued goal in the art of phosphorescent light emitting materials as organic light emitting devices is to develop materials that emit more efficiently at various wavelengths. With respect to the phosphorescent light emitting material, research is continuously carried out to increase the amount of energy absorbed and emitted by the amount of a given luminescent material, which emits light in the visible light region. In particular, iridium (III) complexes are known to be the most efficient phosphorescent emitters because their lifetime in the excited state is not long, about 1 to 2 μs, and thus, the intermetallization or energy transfer occurs well (MA Baldo, et al., Appl. Lett., 75, pp. 4-6, 1999).

Color tuning of iridium (III) complexes can be done from blue to red by changing the organic ligand (S. Ramansky et al., J. Am. Chem. Soc. 123, pp. 4304-4312, 2001 ). Red electroluminescent phosphors were prepared by reacting an iridium (III) complex (S. Lamansky et al., J. Am. Chem. Soc. 123, pp. 4304-4312, 2001; S. Lamamnsky, et al. 2002, pp. 1570-1575, 1992) and Os (III) complex (X. Jiang et al., Appl. Phys. Lett., 80, pp. 713-715, 2002; , Appl. Phys. Lett., 81, pp. 3125-3127, 2002). It has also been reported that yellow and orange luminescence is also obtained from iridium (III) complexes (S. Lamansky et al., J. Am. Chem. Soc. 123, pp. 4304-4312, 2001. S. Lamamnsky, et al., J. Appl. Phys., 92, pp. 1570-1575, 1992).

Realization of green light emission with high efficiency due to such changes in ligand is a very important problem in the field of organic phosphorescent light emitting devices. facial- [Ir (ppy) 3] and its derivatives are representative compounds well known as green phosphorescent compounds. As a source patent for a green phosphorescent material, US Patent Publication No. 6830828B2 discloses a green phosphorescent phosphor (ppy = 2-phenylpyridine, 2-phenylpyridine) having a facial- [Ir (ppy) 3] structure, and US Patent No. 6939624B2 A green phosphorescent compound with Ir (ppy) 2 (acac) (acac = acetylacetone, acetylacetone) structure with ligand added was submitted by Thompson of Southern Califonia University and Professor of Forrest of Princeton University. The patented technology of the green phosphorescent device filed by them has the characteristics of luminescence and color coordinates (0.27, 0.63) and maximum luminous efficiency of 26 cd / A, 19 lm / W at 510 nm wavelength.

However, the above-mentioned luminescent compound has a problem that the (π-π) interaction is not inhibited and the solubility to the solvent is low and the luminous efficiency is relatively low.

U.S. Published Publications 6830828B2, 6939624B2

An aspect of the present invention provides a novel phosphorescent compound having improved luminescence properties and solubility and a green phosphorescent device employing the same.

According to an aspect of the present invention, there can be provided an iridium luminescent compound represented by the following general formula (1).

Formula 1

In Formula _1, R 1 is hydrogen (H), halogen (F, Cl, Br, I ), cyanide (CN), by oro methyl _{(CF 3), C 1 -C} 6 alkyl, C ₆ -C ₁₂ triple Aryl and C ₃ -C ₁₂ cycloalkyl, an amino group (NH ₂ ), a dialkylamino group (NR ₂ ), a monoalkylamino group (NHR), a hydroxy group (OH) and an alkoxy group (OR) Is an integer of 1 to 4;

According to an aspect of the present invention, there can be provided an iridium luminescent compound selected from the following compounds.

According to an aspect of the present invention, there is provided an iridium luminescent compound represented by the following general formula (2).

(2)

In Formula 2,

R ₁ is hydrogen (H), halogen (F, Cl, Br, I ), cyanide (CN), oro methyl triple _{(CF 3), C 1 -C} 6 alkyl, C ₆ -C ₁₂ aryl and C ₃ - (OH) or alkoxy group (OR), m is an integer of from 1 to 4, and L is selected from the group consisting of C 1 -C ₁₂ cycloalkyl, amino group (NH ₂ ), dialkylamino group (NR ₂ ), monoalkylamino group ₁ is an organic auxiliary ligand.

According to an aspect of the present invention, the L ₁ may provide an iridium luminescent compound selected from the following structural formulas.

According to an aspect of the present invention, there is provided an organic light emitting device comprising an organic film provided between a pair of electrodes, wherein the organic film includes the iridium luminescent compound and a green luminescent host.

According to an aspect of the present invention, the green light emitting host may provide an organic light emitting device selected from the following structural formulas.

According to an aspect of the present invention, the green luminescent host may provide an organic luminescent device mixed with 60 to 99 wt% of the iridium luminescent compound.

INDUSTRIAL APPLICABILITY According to an aspect of the present invention, an iridium light-emitting compound and an organic light-emitting device employing the light-emitting material can provide a phosphorescent light-emitting device having improved light emission characteristics and solubility.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram of a method for preparing tris- (2- (2,4-bis- (trifluoromethyl) phenyl) -4-methylpyridine) methylpyridine) iridium).
FIG. 2 is a schematic diagram of a process for preparing tris- (2- (2,4-bis- (trifluoromethyl) phenyl) -4-methylpyridine) methylpyridine) iridium) light-emitting compound (TGA).
FIG. 3 is a graph showing the effect of the tris- (2- (2,4-bis- (trifluoromethyl) phenyl) -4-methylpyridine (tris- methylpyridine) iridium) in a solution state of a light emitting compound and optical emission at low temperature and room temperature.
FIG. 4 is a graph showing the relative dielectric constants of tris- (2- (2,4-bis- (trifluoromethyl) phenyl) -4-methylpyridine) methylpyridine) iridium) is a graph showing the electrochemical cycling method in a solution state of a light emitting compound.
FIG. 5 shows the structure of an OLED device fabricated in Examples 2 and 3 using an iridium light-emitting compound according to an aspect of the present invention.
FIG. 6 is a curve of IVL characteristics of the device manufactured in Examples 2 and 3 using an iridium light-emitting compound according to an aspect of the present invention.
7 is a graph showing current density-luminance characteristics of the device fabricated in Examples 2 and 3 using an iridium luminescent compound according to an aspect of the present invention.
8 is a graph showing current density-luminescence efficiency characteristics of the devices fabricated in Examples 2 and 3 using an iridium luminescent compound according to an aspect of the present invention.

The iridium luminescent compound according to one aspect of the present invention can be produced by introducing a trifluoromethyl substituent which is an electron-withdrawing substituent at the 2 ', 4' position of a 2-phenylpyridine ligand to form a pi- π) interaction can be suppressed to obtain a green phosphorescent compound having improved luminescence characteristics and can be used in a solution process which is not a vacuum deposition process because of its excellent solubility in an organic solvent unlike facial- [Ir (ppy) 3] .

An iridium luminescent compound according to an aspect of the present invention is represented by the following general formula (1).

Wherein R ₁ is selected from the group consisting of hydrogen, halogen (F, Cl, Br, I), cyan (CN), trifluoromethyl (CF ₃ ), C ₁ -C ₆ alkyl, C ₆ -C ₁₂ aryl and C ₃ -C ₁₂ cycloalkyl, amino (NH _2), dialkylamino (NR _2), monoalkylamino (NHR), alcohols (OH), may be selected from alkoxy (OR), m is an integer from 1 to 4 .

Examples of the iridium luminescent compound of Formula 1 according to one aspect of the present invention may include the following compounds.

In addition, in the above formula (1), an organic ligand can be substituted for an auxiliary ligand instead of the three ligands. This may include a compound represented by the general formula (2).

In Formula 2, R ₁ is hydrogen (H), halogen (F, Cl, Br, I ), cyanide (CN), by oro methyl _{(CF 3), C 1 -C} 6 alkyl, C ₆ -C ₁₂ triple aryl, and C ₃ -C ₁₂ cycloalkyl, an amino group (NH _2), dialkylamino group (NR _2), mono-alkylamino group (NHR), and can be selected from a hydroxy group (OH) or alkoxy (oR), m is 1, And L < ₁ > is an organic auxiliary ligand. Examples of such L < ₁ > may include the following compounds.

The iridium luminescent compound of Formula 1 or Formula 2 according to one aspect of the present invention is excellent in luminescent efficiency as a green luminescent material when used together with a host for self or green luminescence and is useful as a coloring material for an organic luminescent device. The host for the green luminescence allows the green light to emit more efficiently with the iridium luminescent compound.

Examples of the green luminescent host may include the following compounds.

The mixed weight ratio of the iridium luminescent compound and the green luminescent host of the formula may be 1 (dopant): 99 (host) to 40:60. Here, when the content of the green luminescent host to the luminescent compound exceeds the above range and when the content of the green luminescent host is less than the above range, the luminescent efficiency tends to decrease.

Further, one aspect of the present invention can provide an organic light emitting device employing the above light emitting compound as a coloring material. That is, an organic light-emitting device comprising an organic film provided between a pair of electrodes, wherein the organic film includes one or a mixture of light-emitting compounds of an iridium compound.

Hereinafter, a method of manufacturing an organic light emitting diode according to an embodiment of the present invention will be described.

First, an anode electrode material is coated on the substrate. Here, a substrate used in a conventional organic light emitting device is used as a substrate, and an organic substrate or a plastic substrate having excellent transparency, surface smoothness, ease of handling, and water resistance can be used. As the material for the anode electrode, indium tin oxide (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), indium zinc oxide (IZO) and antimony tin oxide (ATO) .

A hole transport layer may be formed by vacuum evaporation or spin-coating a material for forming a hole transport layer on the anode. An iridium luminescent compound may be vacuum deposited on the hole transport layer to form a light emitting layer.

Examples of the hole transport layer material include N, N'-bis (3-methylphenyl) -N, N'-diphenyl- [1,1'-biphenyl] -4,4'- diamine (TPD), N NPN), 9,9-bis [4- (N, N-bis-biphenyl-4-yl- (Phenyl) -9H-fluorene (BPAPF), N, N'-bis (phenanthrene-9-yl) -N, N'- N'-N'-N'-tetra-naphthalene-benzidine (-TNB) can be used.

A metal for forming a cathode is vacuum-deposited on the light emitting layer to form a cathode, thereby completing the organic EL device. Here, the cathode forming metal is selected from the group consisting of Li, Mg, Al-Li, Ca-Al, LiF- Mg-In, Mg-Ag, Ba-Al, Au, Ag, and Cu may be used.

A hole barrier layer and an electron transport layer may be formed on the emission layer before forming the cathode. The hole blocking layer and the electron transporting layer may use a material for forming a hole blocking layer electron transporting layer.

The organic light emitting device according to an aspect of the present invention may further include an intermediate layer for improving characteristics between two layers selected from an anode, a hole transporting layer, a light emitting layer, an electron transporting layer, and a cathode. For example, a hole injection layer (HIL) may be further formed between the anode and the hole transport layer. When the hole injection layer is formed as described above, the hole transport layer (e.g., alpha -NPD) and the anode It is possible to improve adhesion and to help inject holes from the anode into the hole transport layer.

Examples of the hole injection layer forming material include CuPc, m-MTDATA, 1I-TNATA, 2T-NATA, NATA, NTNPB and MeO-TPD.

The organic light emitting device may be manufactured in the order as described above, that is, in the order of anode / hole transporting layer / light emitting layer / hole blocking layer / electron transporting layer / cathode, / Hole transport layer / anode.

The following is an actual synthesis example of the iridium luminescent compound according to one aspect of the present invention.

Synthesis Example 1 Preparation of ligand

Synthesis of 2- (2,4-bis (trifluoromethyl) phenyl) -4-methylpyridine (2- (2,4-bis

Scheme 1

As shown in Scheme 1, 1-bromo-2,4-bis (trifluoromethyl) benzene was added to a reaction vessel containing 80 mL of tetrahydrofuran (THF) butyllithium (n-BuLi) (20.4 mmol) was added dropwise over 30 minutes at -78 ° C, and the mixture was stirred for 1 hour. Trimethylborate (B (OMe) ₃ ) (20.4 mmol) were added dropwise, and the mixture was stirred at -78 ° C for 30 minutes and then at room temperature for 1 hour. Then, the reaction is terminated by adding 5% aqueous solution of sodium hydroxide (NaOH) (60 mL), and after 10 minutes, 6 normal aqueous hydrochloric acid (HCl) solution is added dropwise to acidify. After extraction with diethyl ether, the organic solvent is evaporated by rotary vacuum distillation. The resultant was precipitated with hexane and filtered to obtain a white solid in a yield of 70.1% (2.7 g). The results are as follows. ¹ HNMR (DMSO-d ₆ , 300 MHz)? (Ppm) = 7.98 (d, 2H), 7.77 (d, 1H). MS (EI): m / z (%) 258

The reaction vessel was charged with 2,4-bis- (trifluoromethyl) phenylboronic acid (9.00 g, 34.8 mmol), 2-bromo-4-methylpyridine (2 -bromo-4-methylpyridine) into a (7.2g, 41.8mmol), tetrakis (triphenylphosphine) palladium (tetrakis (triphenylphosphine) palladium, Pd (PPh 3) 4) (5mol%, 1.7mmol) in tetrahydrofuran (THF). After adding an aqueous 5% potassium carbonate (K ₂ CO ₃ ) solution (100 mL), the mixture is refluxed in a nitrogen atmosphere for 24 hours. Water is added at room temperature, and the mixture is extracted with diethyl ether. The organic layer is dried using anhydrous sodium sulfate (Na ₂ SO ₄ ) and the organic solvent is removed by rotary vacuum distillation. The resultant was purified by silica gel column chromatography to obtain a light green solid in a yield of 53.5% (5.7 g). The results are shown below. _{^{1 HNMR (DMSO-d 6,}} 300MHz) δ (ppm) = 8.52 (d, 1H), 8.14 (d, 2H), 7.78 (d, 1H), 7.39 (s, 1H), 7.31 (d, 1H), 2.38 (s, 3 H). MS (EI): m / z (%) 305

Synthesis Example 2: Preparation of an iridium luminescent compound

Tris- (2- (2,4-bis- (trifluoromethyl) phenyl) -4-methylpyridine) tris- ) Synthesis of

Scheme 2

As shown in Scheme 2, iridium (III) chloride trihydrate (1.29 g, 3.66 mmol), 2- (2,4-bis- (trifluoromethyl) phenyl) 4-methylpyridine (2.00 g, 7.32 mmol) was added to the flask and 2-ethoxyethanol: water = 3: 1 60 mL Lt; / RTI > Heat at 140 < 0 > C for 24 hours under a nitrogen atmosphere. After completion of the reaction, the reaction mixture was extracted with dichloromethane, dried over anhydrous magnesium sulfate (MgSO ₄ ), and the organic solvent was removed using a rotary vacuum distillation apparatus. The resultant was precipitated with hexane and filtered to obtain a yellow solid in a yield of 85.1% (2.60 g). The results are as follows. ¹ H NMR (CDCl ₃ , 300 MHz)? (Ppm) = 9.00 (d, 4H), 8.25 (s, 4H), 7.44 (s, 4H), 6.81 (d, 4H), 2.72 (s, 12H).

The reaction vessel was charged with (bis- (2- (2,4- bis (trifluoromethyl) phenyl) -4-methylpyridine)) iridium (tri) chloride dimer (trifluoromethyl) phenyl) -4-methylpyridine)) iridium (III) chloride dimer) (2.60 g, 1.55 mmol) and 2- (2,4-bis- (trifluoromethyl) phenyl) -4-methylpyridine 1.70 g, 6.20 mmol) and silver trifluoromethanesulfonate (0.84 g, 3.26 mmol), and dissolve in 3 mL of chloroform. The reaction is carried out in a nitrogen atmosphere in a solid state for 24 hours. After completion of the reaction, the reaction mixture was extracted with dichloromethane, dried over anhydrous magnesium sulfate (MgSO ₄ ), and the organic solvent was removed using a rotary vacuum distillation apparatus. The resultant product was purified by silica gel column chromatography to obtain a yellow solid in a yield of 35.5% (1.20 g). The results are shown below. ¹ H NMR (CDCl ₃ , 300 MHz)? (Ppm) = 8.15 (s, 3H), 7.55 (d, 3H), 7.68 s, 9H).

The resultant tris- (2- (2,4-bis- (trifluoromethyl) phenyl) -4-methylpyridine) tris- (2- (2,4-bis trifluoromethyl) phenyl) -4-methylpyridine) iridium). FIG. 1 is a hydrogen nuclear magnetic resonance spectroscopic data of the resultant product, and FIG. 2 is a graph showing a thermogravimetric analysis (TGA) . 3 is a graph showing optical absorption of the resultant in a solution state and optical emission at a low temperature and a normal temperature. 4 is a graph showing an electrochemical circulation transfer method in a solution state of the resultant product.

≪ Example 1 > Comparison of solubility of the prepared iridium luminescent compound

Tris- (2- (2,4-bis- (trifluoromethyl) phenyl) -4-methylpyridine) tris- ) And the existing compound [facial- [Ir (ppy) 3] were compared in terms of solubility in dichloromethane solvent. The results are shown in Table 1 below.

Iridium-emitting compound Solubility facial- [Ir (ppy) 3] 55 ml / 0.1 g Tris- (2- (2,4-bis- (trifluoromethyl) phenyl) -4-methylpyridine) iridium 8 ml / 0.1 g

As can be seen from Table 1, tris- (2- (2,4-bis- (trifluoromethyl) phenyl) -4-methylpyridine) iridium (tris- , 4-bis (trifluoromethyl) phenyl) -4-methylpyridine) iridium) required about 1/7 dichloromethane solvent as compared with the conventional iridium luminescent compound. These experimental results indicate that the solubility in solvents is significantly improved.

≪ Example 2 > Preparation of organic light emitting device

The organic light emitting device according to one aspect of the present invention was fabricated with a single green light emitting structure to evaluate a green phosphorescent dopant. Each layer of the device is as follows. First, ITO (Indium Tin Oxide) was deposited on a substrate having a thickness of 150 nm as a hole injection layer by using a 10 nm thick dipotrazino ([2,3-f: 2 ', 3'-h] quinoxaline-2 , 3,6,7,10,11-hexacarbonitrile) was used as a hole transporting layer and TACP (Di- [4- (N, N-ditolyl-amino) -phenyl] cyclohexane TCTA (4,4 ', 4 "-tris (carbazol-9-yl) triphenylamine) having a thickness of 7 nm was used as a barrier layer. As a light emitting layer on top, a compound of the present invention was doped into a host material to form a thin film (4,4 ', 4 "-tris (carbazol-9-yl) triphenylamine) and DPTPD (bis -3-yl) phenyl) dimethylsilane) was mixed at a ratio of 2: 1, and a phosphorescent green dopant was doped with 10% of the host weight by using the iridium luminescent compound synthesized in the present invention. First, a DPTPD (bis (4- (4,5-diphenyl-4H-1,2,4-triazol- 3-yl) phenyl) dimethylsilane, and TmPyPB (1,3,5-tri (m-pyrid-3-yl-phenyl) benzene) having a thickness of 40 nm were used to form an electron transport layer. (8-Hydroxyquinolinolato-lithium) is used as the etchant, and aluminum is used as the etchant to complete the deposition, and then the encapsulation process is carried out. The absorbent absorbent (Getter) was attached and sealed with a double-sided tape to manufacture a device.

DPTD (7 nm) / TmPyPB (30 nm): 10% ITO / HAT-CN (10 nm) / TAPC (40 nm) / TCTA (7 nm) / TCTA + DPTPD / Liq (3 nm) / Al (100 nm)] are laminated in order from bottom to top.

≪ Example 3 > Preparation of organic light emitting device

Another device fabricated in the present invention is as follows. Each layer of the device is as follows. First, HAT-CN having a thickness of 5 nm was used as a hole injecting layer, a 40 nm thick TAPC was used as a hole transporting layer, and a 10 nm thick CPMPC (9- ( 9-yl) phenyl) (methyl) silyl) phenyl) -9H-carbazole. As a light emitting layer on the top, a compound of the present invention was doped into a host material to form a thin film. As a phosphorescent host, CPMPC and DPTPD were mixed at a ratio of 2: 1, and a phosphorescent green dopant was doped in the present invention by doping it with an iridium compound to a host weight of 10%. Two materials were used for the electron transport layer. First, an electron transport layer was formed using DPTPD having a thickness of 7 nm and TmPyPB having a thickness of 40 nm. 3 nm thick Liq was used for the electron injection layer and 100 nm thick aluminum was used for the cathode. The next step is the sealing process. A moisture absorbent for absorbing moisture and oxygen was attached to the Gap Glass, and the device was sealed by sealing with double-sided tape.

DPPD (7 nm) / TmPyPB (30 nm) / TPTPD (10 nm) / TAPP (40 nm) / CPMPC (7 nm) / CPMPC + Liq (3 nm) / Al (100 nm)] are laminated in order from bottom to top.

FIG. 5 schematically shows structures of the respective organic light emitting devices fabricated in Examples 2 and 3.

6 is a graph showing the IVL characteristic curves of the organic light emitting devices, and FIG. 7 is a graph showing the IVL characteristic curves of the OLEDs according to Examples 2 and 3. FIG. FIG. 8 is a graph showing current density-light emission efficiency characteristics of an organic light emitting device.

The results of the green organic light emitting devices of Examples 2 and 3 are summarized in Table 2 below in comparison with devices using facial- [Ir (ppy) 3]. As shown in Table 2, the organic light emitting device using the novel phosphorescent compound synthesized as described above has a high efficiency of 56.2 cd / A and 56.4 lm / w at maximum, and the color coordinates are also (0.34, 0.61) Green region.

Host Maximum luminous efficiency
(cd / A) Maximum Power Efficiency
(lm / W) Color coordinates Example 2 53.9 56.4 (0.34, 0.61) Example 3 56.2 37.8 (0.36, 0.60) facial- [Ir (ppy) 3] 26 19 (0.27, 0.63)

Claims (7)

An iridium light-emitting compound represented by the following formula
Formula 1

In Formula 1,
R ₁ is independently selected from F, Cl, Br, I, trifluoromethyl (CF ₃ ), amino group (NH ₂ ), or hydroxy group (OH)
m is an integer of 1 to 4; The method according to claim 1,
An iridium-emitting compound selected from the following compounds.

An iridium-emitting compound represented by the following formula (2):
(2)

In Formula 2,
R ₁ is independently selected from F, Cl, Br, I, trifluoromethyl (CF ₃ ), amino group (NH ₂ ) or hydroxy group (OH)
m is an integer of 1 to 4,
L ₁ is an organic auxiliary ligand. The method of claim 3,
Wherein L < ₁ > is selected from the following compounds.

And an organic film provided between the pair of electrodes,
Wherein the organic film comprises any one of the iridium luminescent compounds of claims 1 to 4 and a green luminescent host. 6. The method of claim 5,
Wherein the green luminescent host is selected from the following structural formulas.

6. The method of claim 5,
And the green luminescent host is mixed with 60 to 99 wt% of the iridium luminescent compound.

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