KR101807410B1 - OLED Containing Organic Metal Compound as Electron Transport Dopant - Google Patents

Abstract

Thereby providing an organic light emitting diode. The organic light emitting diode includes an anode, a hole conduction layer, a light emitting layer, an electron conduction layer, and a cathode sequentially stacked. The light emitting layer includes a light emitting host and a light emitting dopant. The electron transporting layer comprising an electron transporting layer having an electron transporting host and an electron transporting dopant, the electron transporting dopant having triplet energy higher than the triplet energy of the luminescent dopant.

Description

[0001] The present invention relates to an organic light emitting diode (OLED) containing an organic metal compound as an electron transporting dopant,

The present invention relates to organic electronic devices, and more particularly to organic light emitting diodes.

An organic light emitting diode (OLED) is a self-luminous type device having a wide viewing angle, excellent contrast, fast response time, excellent luminance, driving voltage and response speed characteristics, and multi-coloring.

A typical organic light emitting diode may include an anode and a cathode and an organic layer interposed between the anode and the cathode. The organic layer may include an electron injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, a cathode, and the like. When a voltage is applied between the anode and the cathode, holes injected from the anode move to the light emitting layer via the hole transporting layer, and electrons injected from the cathode move to the light emitting layer via the electron transporting layer. The carriers, such as holes and electrons, recombine in the light emitting layer region to produce an exiton, which is changed from the excited state to the ground state to produce light.

In such an organic light emitting diode, improvement in the charge mobility in the hole transporting layer and the electron transporting layer may lead to a reduction in the driving voltage of the organic light emitting diode. To this end, Korean Patent No. 0560778 discloses an organic light emitting diode doped with Liq (8-quinolinolato lithium) in an electron transport layer.

However, since Liq has a sufficiently high energy level of triplet excitons, it is difficult to bind the triplet excitons in the light emitting layer. Accordingly, Korean Patent No. 0560778 additionally forms a hole blocking layer, which is an exciton blocking layer, between the light emitting layer and the electron transporting layer have.

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic light emitting diode in which triplet excitons are efficiently trapped in a light emitting layer to improve efficiency.

According to one aspect of the present invention, there is provided an organic light emitting diode. The organic light emitting diode includes an anode, a hole conduction layer, a light emitting layer, an electron conduction layer, and a cathode sequentially stacked. The light emitting layer includes a light emitting host and a light emitting dopant. The electron transporting layer comprising an electron transporting layer having an electron transporting host and an electron transporting dopant, the electron transporting dopant having triplet energy higher than the triplet energy of the luminescent dopant.

The luminescent dopant may be a green phosphorescent dopant or a blue phosphorescent dopant. The electron transporting dopant may have a triplet energy of 2.4 to 3.3 eV. The electron transport host may have triplet energy higher than the triplet energy of the luminescent dopant. The electron transporting layer may be doped with the electron transporting dopant in the entire layer. Alternatively, the electron transporting layer may include a first electron transporting layer not doped with the electron transporting dopant and a second electron transporting layer doped with the electron transporting dopant. The electron transporting layer may contact the light emitting layer.

According to an aspect of the present invention, an organic light emitting diode is provided. The organic light emitting diode includes an anode, a hole conduction layer, a light emitting layer, an electron conduction layer, and a cathode sequentially stacked. The electron transporting layer includes an electron transporting layer, and the electron transporting layer includes an electron transporting dopant represented by the following formula (1).

[Chemical Formula 1]

Wherein M is a Group 1 or Group 2 metal, n is 1 or 2, X is O or S, A is a hexagonal ring aromatic, Y is C or N, and B ₁ , B ₂ , and B ₃ is independently of each other NR ₁ , O, or CR ₂ . R ₁ is hydrogen or a substituted or unsubstituted C1 to C30 alkyl group, irrespective of each other. R ₂ is independently selected from the group consisting of hydrogen, a halogen group, a cyano group, a substituted or unsubstituted C1 to C30 alkyl group, a substituted or unsubstituted C1 to C30 unsaturated alkyl group, a substituted or unsubstituted C6 or C60 aryl group , A substituted or unsubstituted C1 to C30 heteroaryl group, an amino group, a (substituted or unsubstituted C1 to C30 alkyl) amino group, a substituted or unsubstituted C6 or C60 aryl) amino group, a substituted or unsubstituted A substituted or unsubstituted C1 to C30 heteroaryl) amino group, (substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C6 or C60 aryl) amino group, and (substituted or unsubstituted C1 to C30 alkyl) Or an unsubstituted C1 to C30 heteroaryl) amino group. Two adjacent ones of R ₁ and R ₂ may optionally be fused to the B ring.

The M may be Li, Cs, Ca, or Mg. At least one of Y, B ₁ , B ₂ , and B ₃ may be N, NR ₁ , or O. One of B ₂ and B ₃ is NR ₁ or O, and the rest of B ₁ , B ₂ , and B ₃ may be the same or different CR _{2 s in} which R ₂ is the same or different.

The electron transporting dopant may be represented by the following formula (2).

(2)

In Formula 2, M, X, A, B ₁ , B ₂ , B ₃ , Y and n are the same as M, X, A, B ₁ , B ₂ , B ₃ , . A ₁ , A ₂ , A ₃ , and A ₄ are independently of each other N or CR ₃ . R ₃ represents a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted C1 to C30 alkyl group, a substituted or unsubstituted C6 or C60 aryl group, a substituted or unsubstituted C1 to C30 heteroaryl (Substituted or unsubstituted C1 to C30 alkyl) silyl group, (substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C6 or C60 aryl) silyl group, (substituted or unsubstituted C1 to C30 alkyl) (Substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C1 to C30 heteroaryl) silyl group, (substituted or unsubstituted C6 or C60 aryl) silyl group, substituted or unsubstituted C1 to C30 (Substituted or unsubstituted C1 to C30 heteroaryl) amino group, (substituted or unsubstituted C6 or C60 aryl) amino group, (substituted or unsubstituted C1 to C30 heteroaryl) amino group, Substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C6 or C60 Aryl) amino group, and (substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C1 to C30 heteroaryl) amino group.

In the above formula (2), ring A may be benzene or pyridine.

The electron transporting dopant may be represented by the following general formula (3), (4), or (5).

(3)

[Chemical Formula 4]

[Chemical Formula 5]

According to embodiments of the present invention, the efficiency of the organic light emitting diode can be improved by doping an electron transporting dopant having triplet energy higher than the triplet energy of the luminescent dopant in the electron transporting layer.

1 is a cross-sectional view illustrating an organic light emitting diode according to an exemplary embodiment of the present invention.
FIG. 2 is a schematic diagram showing the triplet energy level of the organic light emitting diode shown in FIG. 1, and is limited to the light emitting layer and the electron injection layer.
3 is a cross-sectional view illustrating an organic light emitting diode according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Like reference numerals designate like elements throughout the specification.

Organometallic compound

The following Chemical Formula 1 represents an organometallic compound according to an embodiment of the present invention.

In Formula 1, M may be a Group 1 or Group 2 metal. Specifically, M may be Li, Cs, Ca, or Mg having relatively high ionization energy. In this case, the doping efficiency due to the organometallic compound according to Formula (1) can be improved. n may be 1 or 2. X can be O or S; A may be hexagonal ring aromatic.

Y is C or N, B ₁ , B ₂ , and B ₃ are independently of each other NR ₁ , O, or CR ₂ , and R ₁ is hydrogen or a substituted or unsubstituted C1 to C30 alkyl group , R ₂ is, regardless of each other hydrogen, halogen specifically F, a cyano group, a substituted or unsubstituted C1 to C30 alkyl group, a substituted or unsubstituted C1 to C30 unsaturated alkyl groups, substituted or unsubstituted in the ring of the ring C6 or C60 (Substituted or unsubstituted C1 to C30 alkyl) amino group, substituted or unsubstituted C6 or C60 aryl) amino group, substituted or unsubstituted C1 to C30 heteroaryl group, amino group, (Substituted or unsubstituted C1 to C30 heteroaryl) amino group, (substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C6 or C60 aryl) amino group, or a substituted or unsubstituted C1 to C30 alkyl ) (Substituted or unsubstituted C1 to C30 heteroaryl) amino group And two adjacent ones of R < ₁ > and R < ₂ > may be combined and fused to the B ring. In this case, the ring fused to the ring B may be pyridine, pyrimidine, triazole, or benzene.

Such an organometallic compound may be a compound for an organic light emitting diode. Specifically, the organic metal compound may be used as one of a hole injecting material, a hole transporting material, a light emitting host material, an electron injecting material, and an electron transporting material in an organic light emitting diode. More specifically, such an organometallic compound may be an electron injecting dopant in the electron injecting layer.

At least one of Y, B ₁ , B ₂ and B ₃ in formula (1) may be N, NR ₁ or O. In this case, due to the high electronegativity of N or O, the organometallic compound can have a high level of triplet energy. In addition, the triplet energy level of the organometallic compound may be higher than the triplet energy level of the luminescent dopant in the light emitting layer. Such an organometallic compound can be used as an electron injecting dopant in the electron injecting layer. In this case, the efficiency of the organic light emitting diode can be improved by restricting the triplet exciton into the emitting layer.

In one embodiment, Y is C, and at least one of B ₁ , B ₂ , and B ₃ can be NR ₁ or O, and the remainder R ₂ can be the same or different CR _{2 s} . More specifically, Y is C, one of B ₂ and B ₃ is NR ₁ or O, and the remaining of B ₁ , B ₂ , and B ₃ may be CR _{2 s in} which R ₂ is the same or different.

In another embodiment, Y is N, and B ₁ , B ₂ , and B ₃ may be CR _{2 wherein} R ₂ is the same or different.

In embodiments of the present invention, the C1 to C30 (unsaturated) alkyl group may be a C1 to C4 (unsaturated) alkyl group. The alkyl group may be a straight chain or branched chain alkyl group. Further, the hydrogen of the alkyl group may be substituted with a halogen group specifically F, and / or a cyano group.

In embodiments of the present invention, an aryl group of C6 or C60 may be a C6 aryl group. The hydrogen of the aryl group may be substituted with a halogen group specifically F, and / or a cyano group.

In embodiments of the present invention, the heteroaryl group may be a 5- or 6-membered aromatic ring containing one or more O, N, or S atoms. For example, pyrrole, pyrazole, oxazole, isoxazole, thiazole, isothiazole, imidazole, oxadiazole, thiadiazole, pyridine, pyrazine, pyrimidine or pyridazine. The hydrogen of the heteroaryl group may be substituted with a halogen group specifically F, and / or a cyano group.

The organometallic compound according to one embodiment of the present invention can be represented by the following formula (2).

In the above formula (2) may be the same as M, X, B _1, B _2, B _3, Y and n is as defined in Formula 1 M, X, B _1, B _2, B _3, Y and n, respectively. A ₁ , A ₂ , A ₃ , and A ₄ may be independently N or the remaining R ₃ may be the same or different CR ₃ (s). R ₃ is hydrogen, halogen, specifically F, cyano, substituted or unsubstituted C1 to C30 alkyl, substituted or unsubstituted C6 or C60 aryl, substituted or unsubstituted C1 to C30 heteroaryl, (Substituted or unsubstituted C1 to C30 alkyl) silyl group, (substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C6 or C60 aryl) silyl group, (substituted or unsubstituted C1 to C30 alkyl) (Substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C1 to C30 heteroaryl) silyl group, (substituted or unsubstituted C6 or C60 aryl) silyl group, substituted or unsubstituted C1 to C30 heteroaryl (Substituted or unsubstituted C1 to C30 alkyl) amino group, (substituted or unsubstituted C6 or C60 aryl) amino group, (substituted or unsubstituted C1 to C30 heteroaryl) amino group, Unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C6 or C60 aryl) Group, or (substituted or unsubstituted alkyl of the unsubstituted C1-C30) (heteroaryl, substituted or unsubstituted C1 to C30) may be an amino group.

In formula (2), ring A may be benzene or pyridine.

The organometallic compound according to another embodiment of the present invention can be represented by any one of the following formulas 3 to 5.

In Formula 3, R ₂ may be the same as R _{2 in} Formula 1.

Organic light emitting diode

1 is a cross-sectional view illustrating an organic light emitting diode according to an exemplary embodiment of the present invention.

1, an organic light emitting diode includes an anode 10 and a cathode 70, a light emitting layer 40 disposed between the two electrodes, a hole conduction layer 20 disposed between the anode 10 and the light emitting layer 40, And an electron conduction layer 50 disposed between the light emitting layer 40 and the cathode 70. The hole conduction layer 20 may include a hole injection layer 23 for facilitating injection of holes and a hole transport layer 25 for transporting holes. In addition, the electron conduction layer 50 may include an electron injection layer 53 for facilitating the injection of electrons and an electron transport layer 55 for transporting electrons.

When a forward bias is applied to the organic light emitting diode, holes are injected from the anode 10 into the light emitting layer 40, and electrons from the cathode 70 are injected into the light emitting layer 40. Electrons and holes injected into the light emitting layer 40 are combined with each other to form an exciton, and light is emitted while the excitons transition to the ground state.

The light emitting layer 40 may be a phosphorescent light emitting layer, and may include a light emitting host and a light emitting dopant. In this case, the electrons and holes injected into the light emitting layer 40 are combined at the light emitting host to form excitons, and the excitons may be transferred to the light emitting dopant through the energy transfer process, and then emitted to the base state. Theoretically, 75% of the excitons transferred to the luminescent dopant are triplet excitons. Since such triplet excitons have a longer lifetime than singlet excitons, it is important to constrain the triplet excitons in the light emitting layer 40 to improve the luminous efficiency.

The luminescent dopant may be an organometallic compound comprising Ir, Pt, Os, Ti, Zr, Hf, Eu, Tb, Tm or combinations thereof. Specifically, the luminescent dopant is PtOEP (see the following chemical formula), Ir (piq) ₃ (See the following chemical formula) and Btp2Ir (acac) (see the following chemical formula); A green dopant such as Ir (ppy) ₃ (ppy = phenylpyridine) (see the following chemical formula), Ir (ppy) ₂ (acac) (see the following chemical formula) and Ir (mpyp) ₃ Or a blue dopant such as F ₂ Irpic (see the following chemical formula), (F ₂ ppy) ₂ Ir (tmd) (see the following chemical formula) and Ir (dfppz) ₃

On the other hand, the luminescent host can be selected from the group consisting of Alq3, CBP (4,4'-N, N'-dicarbazole-biphenyl), 9,10-di (naphthalene- N-phenylbenzimidazole-2-yl benzene), TBADN (3-tert-butyl-9,10-di (naphtho- 2-yl) anthracene), E3 (see the following formula), or BeBq2 (see the following formula).

The electron injection layer 53 and / or the electron transport layer 55 are layers having a LUMO level between the work function level of the cathode 70 and the LUMO level of the light emitting layer 40, and the cathode 70 to the light emitting layer 40 And the electron injection or transport efficiency of the electron transporting layer is increased.

The electron transporting layer 55 may include an electron transporting host and an electron transporting dopant. Examples of the electron transport host include BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), aluminum (III) bis (2-methyl-8- quinolinato) -4-phenylphenolate, , TBPI (2,2 ', 2' - (1,3,5-phenylene) -tris (1-phenyl-1H-benzimidazole) - (4-tert-butylphenyl) -1,2,4-triazole), 3TPYMB (tris- [3- (3- pyridyl) mesityl] borane), TSPO1 (4- (triphenylsilyl) phenyldiphenylphosphine oxide) Phenyl) -dimethylsilane), TPPB (1,3,5-tris [3,5-bis (3-pyridinyl) phenyl ] benzene), TpPyPB (1,3,5-tri (p-pyrid-3-yl-phenyl) benzene), TmPyPB (1,3,5- Bis (4-pyridin-3-yl) phenyl] silane), 2- (4- (9- Di (naphthalen-2-yl) anthracene-2-yl) phenyl) -1-phenyl-1H- benzo [d] imidazole (phenanthren-9-yl) -2- (4- (pyridin-2-yl) phenyl) -1- Phenyl) pyrimidine (4,6-di (phenanthren-9-yl) -2- (4- (pyridin-2-yl) phenyl) pyrimidine).

The electron transporting dopant may be any one of the compounds represented by Chemical Formulas (1) to (5). Such an electron transporting dopant has a strong electron-donating property because it contains a metal of one group or two groups, particularly Li, Cs, Ca, or Mg, so that the electron mobility of the electron transporting layer 55 can be improved. Accordingly, the driving voltage of the organic light emitting diode can be reduced. Further, the electron transporting dopant in the electron transporting layer 55 may be doped to 5 to 30 wt%. As an example, in the electron transporting layer 55, the electron transporting dopant may be doped to 8 to 15 wt%. In one example, the electron transporting layer 55 may be doped with an electron transporting dopant.

FIG. 2 is a schematic diagram showing the triplet energy level of the organic light emitting diode shown in FIG. 1, and is limited to the light emitting layer and the electron injection layer.

Referring to FIGS. 1 and 2, the electron transport dopant in the electron injection layer 55, that is, the compound described in Chemical Formula 1, may have a high triplet energy level (T _55D ¹ ). Specifically, the compound described in Chemical Formula 1 may have a triplet energy level higher than the triplet energy level (T _40D ¹ ) of the luminescent dopant in the light emitting layer 40. In this case, the triplet exciton present in the luminescent dopant can be bound into the luminescent layer 40, and the luminescent efficiency can be improved. Further, the compound of formula ( ^I ) may have a higher triplet energy level (T _55D ¹ ) than the triplet energy level of the emitting host (T _40H ¹ ). In one example, the triplet energy level of the electron transport dopants when relative to the singlet ground state ^{_{(S 0) (T 55D 1}} ) may be at least 2.4eV. As an example, the triplet energy level (T _55D ¹ ) of the electron transporting dopant may be 2.4 eV to 3.3 ev, 2.4 eV to 3.0 ev, 2.7 eV to 3.3 ev, or 2.7 eV to 3.0 ev.

On the other hand, the triplet energy level (T _55H ¹ ) of the electron transport host may also be higher than the triplet energy level (T _40D ¹ ) of the luminescent dopant, and furthermore, the triplet energy level of the emitting host (T _40H ¹ ). In this case, formation of an exciton blocking layer for restricting excitons to the light emitting layer 40 can be omitted, and the structure of the organic light emitting diode can be simplified. When the exciton blocking layer is omitted, the electron transporting layer 55 may be formed to be in contact with the light emitting layer 40.

Referring again to FIG. 1, the electron injection layer 53 may be, for example, LiF, NaCl, CsF, Li2O, BaO, BaF2, or Liq (lithium quinolate).

The hole injection layer 23 and / or the hole transport layer 25 are layers having a HOMO level between the work function level of the anode 10 and the HOMO level of the light emitting layer 40, The hole injection or transport efficiency of the hole is enhanced.

The hole injecting layer 23 or the hole transporting layer 25 may include one or more materials conventionally used as the hole transporting material. The hole-transporting material may be, for example, mCP (N, N-dicarbazolyl-3,5-benzene); PEDOT: PSS (poly (3,4-ethylenedioxythiophene): polystyrenesulfonate); NPD (N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine); N, N'-diphenyl-N, N'-di (3-methylphenyl) -4,4'-diaminobiphenyl (TPD); N, N'-diphenyl-N, N'-dinaphthyl-4,4'-diaminobiphenyl; N, N, N'N'-tetra-p-tolyl-4,4'-diaminobiphenyl; N, N, N'N'-tetraphenyl-4,4'-diaminobiphenyl; Porphyrin compound derivatives such as copper (II) 1,10,15,20-tetraphenyl-21H, 23H-porphyrin and the like; TAPC (1,1-Bis [4- [N, N'-Di (p-tolyl) Amino] Phenyl] cyclohexane; Triarylamine derivatives such as N, N, N-tri (p-tolyl) amine and 4,4 ', 4'-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine; Carbazole derivatives such as N-phenylcarbazole and polyvinylcarbazole; Phthalocyanine derivatives such as nonmetal phthalocyanine and copper phthalocyanine; Starburst amine derivatives; Enamnstilbene derivatives; Derivatives of aromatic tertiary amines and styryl amine compounds; And polysilane.

The anode 10 may be a conductive metal oxide, a metal, a metal alloy, or a carbon material. The conductive metal oxide is indium tin oxide (indium tin oxide: ITO), fluorine tin oxide (fluorine tin oxide: FTO), antimony tin oxide (antimony tin oxide, ATO), fluorine-doped tin oxide (FTO), SnO _2, ZnO , Or a combination thereof. The metal or metal alloy suitable as the anode 10 may be Au and CuI. The carbon material may be graphite, graphene, or carbon nanotubes.

The cathode 70 is a conductive film having a lower work function than the anode 10 and is made of a metal such as aluminum, magnesium, calcium, sodium, potassium, indium, yttrium, lithium, May be formed using a combination of two or more of them.

The anode 10 and the cathode 70 may be formed using a sputtering method, a vapor deposition method, or an ion beam deposition method. The hole injecting layer 23, the hole transporting layer 25, the light emitting layer 40, the electron transporting layer 55 and the electron injecting layer 53 are formed by evaporation or coating methods such as spraying, Dipping, printing, doctor blading, or by electrophoresis.

The organic light emitting diode may be disposed on a substrate (not shown), which may be disposed under the anode 10 or above the cathode 70. In other words, the anode 10 may be formed on the substrate before the cathode 70, or the cathode 70 may be formed before the anode 10.

The substrate may be a light-transmissive substrate as a flat plate member, in which case the substrate may be glass; Ceramics material; And may be made of a polymer material such as polycarbonate (PC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polypropylene (PP) However, the present invention is not limited to this, and the substrate may be a metal substrate capable of light reflection.

3 is a cross-sectional view illustrating an organic light emitting diode according to another embodiment of the present invention. The organic light emitting diode according to the present embodiment is similar to the organic light emitting diode described with reference to FIG. 1, except as described below.

Referring to FIG. 3, the electron transporting layer 55 may be divided into a first electron transporting layer 55a not doped with an electron transporting dopant and a second electron transporting layer 55b doped with an electron transporting dopant. At this time, the first electron transporting layer 55a may be disposed adjacent to the light emitting layer 40 as compared with the second electron transporting layer 55b, and may have a thickness of about 1 to 10 nm.

Hereinafter, exemplary embodiments of the present invention will be described in order to facilitate understanding of the present invention. It should be understood, however, that the following examples are intended to aid in the understanding of the present invention and are not intended to limit the scope of the present invention.

[Experimental Examples; Examples]

Synthesis Example 1: Synthesis of Compound I

<Reaction Scheme 1>

1 g (6.21 mmol) of 2- (oxazol-2-yl) phenol, 0.16 g (6.83 mmol) of lithium hydroxide, ) Were placed in a reactor, and the mixture was stirred at room temperature under a nitrogen atmosphere for 12 hours. Then, it was washed with methylene chloride in a filtration filter and then dried. The dried Compound I (lithium 2- (oxazol-2-yl) phenolate) was further sublimed and purified to obtain 0.61 g (59% yield) of a white solid . Compound I showed a triplet energy of 2.59 eV.

^{1 H NMR (200 MHz, DMSO} ): δ 7.16 (s, 1H), 6.75 (d, J = 8.00 Hz, 1H), 6.34 (s, 1H), 6.22 (t, 1H), 5.74 (d, J = 8.4, IH), 5.56 (t, J = 7, IH)

GC-Mass (theory: 167.09 g / mol, measurement: 167 g / mol)

Synthesis Example 2: Synthesis of Compound II

<Reaction Scheme 1>

1.10 g (6.31 mmol) of 2- (1-methyl-imidazol-2-yl) phenol, 0.17 g (6.95 mmol) of lithium hydroxide, and 50 ml of methylene chloride was added to the reactor, and the mixture was stirred at a room temperature under a nitrogen atmosphere for 12 hours. Then, it was washed with methylene chloride in a filtration filter and then dried. The dried Compound II (lithium 2- (1-methyl-imidazol-2-yl) phenolate) was further sublimed and purified to obtain 0.32 g (28% Yield) as a white solid. Compound II showed a triplet energy of 2.76 eV.

^{1 H NMR (200MHz, DMSO)} : 6.12 (m, 2H), 5.93 (t, J = 7, 1H), 5.84 (s, 1H), 5.50 (d, J = 4, 1H), 5.24 (t, J = 7, IH), 2.64 (s, 3H)

GC-Mass (theory: 180.13 g / mol, measurement: 180 g / mol)

Synthesis Example 3: Synthesis of Compound (III)

<Reaction Scheme 3>

(5.58 mmol) of 2- (pyrazol-1-yl) pyridin-3-ol, 0.15 g (6.14 mmol) of lithium hydroxide, 50 ml of chloride were added to the reactor, and the mixture was stirred at room temperature under a nitrogen atmosphere for 12 hours. Then, the filter was washed with methylene chloride and then dried. (49% yield) of lithium 2- (pyrazol-1-yl) pyridin-3-olate (lithium 2- (pyrazol- As a white solid. Compound III showed a triplet energy of 2.75 eV.

^{1 H NMR (200MHz, DMSO)} : 6.85 (s, 1H), 6.36 (m, 2H), 5.82 (s, 1H), 5.34 (s, 2H)

GC-Mass (theory: 167.09 g / mol, measurement: 167 g / mol)

Production Example 1: Preparation of green phosphorescent organic light emitting diode

(ITO / PEDOT: PSS / TAPC / mCP / CBP: Ir (ppy) ₃ / BmPyPb: Compound I / LiF / Al)

The anode ITO substrate was cleaned with ultrasonic waves for 30 minutes using pure water and isopropyl alcohol. The cleaned ITO substrate was surface-treated with ultraviolet light of short wavelength and then a hole injection layer of 60 nm was formed by spin coating PEDOT: PSS (poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate), CH8000, Baytron) . Subsequently, 20 nm of TAPC (1,1-Bis [4- [N, N'-Di (p-tolyl) Amino] Phenyl] Cyclohexane, which is a hole injection or transporting material, and mCP (N, N-dicarbazolyl- 5-benzene) was deposited at a rate of 0.1 nm / s under a pressure of 1 x 10 ^-6 torr to form a hole transport layer. Thereafter, a green phosphorescent host CBP-at a rate of (4,4'-N, N'- dicarboxylic carbazole biphenyl) and 0.015 nm / s to the Ir (ppy) ₃ green phosphorescent dopant at a pressure of 1x10 ^-6 torr Followed by co-deposition to form a 25 nm light emitting layer doped with 5 wt% of a dopant. (1,3-bis (3,5-dipyrid-3-yl-phenyl) benzene) as an electron transport host and Compound I synthesized in Synthesis Example 1 as an electron transporting dopant were mixed at a pressure of 1 × 10 ^-6 torr nm / s to form a 35 nm electron transporting layer doped with 10 wt% of electron transporting dopant. Thereafter, LiF as an electron injecting material was vapor-deposited at a pressure of ¹ x 10 ^-6 torr at a rate of 0.01 nm / s to form an electron injecting layer of 1 nm. Thereafter, Al was deposited at a rate of 0.5 nm / sec under a pressure of ¹ x 10 ^-6 torr to form a 200 nm cathode, thereby forming a green phosphorescent organic light emitting diode. After the device was formed, the device was sealed using a CaO wetting agent and a glass cover glass.

The organic light emitting diode according to the present example showed a quantum efficiency of 20% at a voltage of 5 V and a driving voltage of 6.7 V based on a current density of 10 mA / cm 2.

Production Example 2: Preparation of blue phosphorescent organic light emitting diode

(ITO / PEDOT: PSS / TAPC / mCP / mCP: F2Irpic / BmPyPb: Compound II / LiF / Al)

The anode ITO substrate was cleaned with ultrasonic waves for 30 minutes using pure water and isopropyl alcohol. The cleaned ITO substrate was surface-treated with ultraviolet light of short wavelength and then a hole injection layer of 60 nm was formed by spin coating PEDOT: PSS (poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate), CH8000, Baytron) . Subsequently, 20 nm of TAPC (1,1-Bis [4- [N, N'-Di (p-tolyl) Amino] Phenyl] Cyclohexane, which is a hole injection or transporting material, and mCP (N, N-dicarbazolyl- 5-benzene) were sequentially deposited at a rate of 0.1 nm / s under a pressure of 1 x 10 ^-6 torr to form a hole transporting layer. Subsequently, mCP as a blue phosphorescent host and F ₂ Irpic (Bis (4,6-difluorophenylpyridinato-N, C2) picolinatoiridium) as a blue phosphorescent dopant were co-deposited at a rate of 0.015 nm / s under a pressure of ¹ × 10 ^-6 torr, To form a 25 nm-light-emitting layer doped with 5 wt%. To as the electron transporting host BmPyPB (1,3-bis (3,5- dipyrid-3-yl-phenyl) benzene) with a compound Ⅱ synthesized in Synthesis Example 2 as the electron transporting dopant under a pressure of 1x10 ^-6 torr 0.1 nm / s to form an electron transport layer having a thickness of 35 nm doped with 10 wt% of an electron transporting dopant. Thereafter, LiF as an electron injecting material was vapor-deposited at a pressure of ¹ x 10 ^-6 torr at a rate of 0.01 nm / s to form an electron injecting layer of 1 nm. Thereafter, Al was vapor-deposited at a rate of 0.5 nm / sec under a pressure of ¹ x 10 ^-6 torr to form a 200 nm cathode, thereby forming a blue phosphorescent organic light-emitting diode. After the device was formed, the device was sealed using a CaO wetting agent and a glass cover glass.

The organic light emitting diode according to the present example exhibited a quantum efficiency of 19% at a voltage of 5 V and a driving voltage of 8.2 V based on a current density of 10 mA / cm 2.

Production Example 3: Preparation of blue phosphorescent organic light emitting diode

(ITO / PEDOT: PSS / TAPC / mCP / mCP: F2Irpic / BmPyPb: Compound III / LiF / Al)

A blue phosphorescent organic light emitting diode was produced in the same manner as in Production Example 2, except that an electron transporting layer of 35 nm doped with 10 wt% of an electron transporting dopant was formed using the compound III synthesized in Synthesis Example 2 as an electron transporting dopant And then sealed.

The organic light emitting diode according to the present example showed a driving voltage of 8.2 V based on a current density of 10 mA / cm 2.

Production Example 4: Preparation of blue phosphorescent organic light emitting diode

(ITO / PEDOT: PSS / TAPC / mCP / mCP: F2Irpic / BmPyPb / BmPyPb: Compound II / LiF / Al)

In forming the electron transport layer, BmPyPB (1,3-bis (3,5-dipyrid-3-yl-phenyl) benzene), an electron transport host, was deposited at a pressure of 1 × 10 ^-6 torr at a rate of 0.1 nm / s ⅱ the compound synthesized in synthesis example 2 as an electron transporting host, and an electron transporting BmPyPB dopant after forming the electron transporting 5㎚ first electron transport layer of the dopant is not doped, on the first electron transport layer of 1x10 ^-6 torr Phosphorescent organic light emitting diode was produced in the same manner as in Production Example 2 except that a 30 nm second electron transport layer doped with 10 wt% of an electron transporting dopant was co-deposited under a pressure of 0.1 nm / s to form a blue phosphorescent organic light emitting diode And then sealed.

The organic light emitting diode according to the present example showed a driving voltage of 8.3 V based on a current density of 10 mA / cm 2.

Comparative Example 1: Preparation of green phosphorescent organic light emitting diode

(ITO / PEDOT: PSS / TAPC / mCP / CBP: Ir (ppy) ₃ / BmPyPb: Liq / LiF / Al)

A green phosphorescent organic light emitting diode was prepared and sealed in the same manner as in Production Example 1, except that Liq (lithium quinolate) was used as an electron transporting dopant in the electron transporting layer.

The organic light emitting diode according to the present example exhibited a quantum efficiency of 15% at a voltage of 5V.

Comparative Example 2: Preparation of green phosphorescent organic light emitting diode

(ITO / PEDOT: PSS / TAPC / mCP / CBP: Ir (ppy) ₃ / BmPyPb / LiF / Al)

A green phosphorescent organic light emitting diode was prepared and sealed in the same manner as in Production Example 1, except that an electron transporting dopant was not used in the electron transporting layer.

The organic light emitting diode according to the present example showed a driving voltage of 7.3 V based on a current density of 10 mA / cm 2.

Comparative Example 3: Preparation of blue phosphorescent organic light emitting diode

(ITO / PEDOT: PSS / TAPC / mCP / mCP: F2Irpic / BmPyPb: Liq / LiF / Al)

A blue phosphorescent organic light emitting diode was prepared and sealed in the same manner as in Production Example 2, except that Liq (lithium quinolate) was used as an electron transporting dopant in the electron transporting layer.

The organic light emitting diode according to the present example exhibited a quantum efficiency of 13% at a voltage of 5V.

Comparative Example 4: Preparation of blue phosphorescent organic light emitting diode

(ITO / PEDOT: PSS / TAPC / mCP / mCP: F2Irpic / BmPyPb / LiF / Al)

A blue phosphorescent organic light emitting diode was prepared and sealed in the same manner as in Production Example 2, except that the electron transporting dopant in the electron transporting layer was not used.

The organic light emitting diode according to the present example showed a driving voltage of 8.6 V based on a current density of 10 mA / cm 2.

The light- Electron transport layer Driving voltage
(Current density of @ 10 mA / cm 2) Quantum efficiency
(@ 5V) Production Example 1
CBP: Ir (ppy) ₃ BmPyPb: Compound I 6.7V 20% Comparative Example 1 BmPyPb: Liq 6.7V 15% Comparative Example 2 BmPyPb 7.3V 19% Production Example 2
mCP: F2Irpic
BmPyPb: Compound II 8.2V 19% Production Example 4 BmPyPb / BmPyPb: Compound II 8.3V 19% Comparative Example 3 BmPyPb: Liq 8.2V 13% Comparative Example 4 BmPyPb 8.6V 19%

It can be seen from the above results that the quantum efficiency of the organic light emitting diode according to Production Example 1 is improved as compared with the case of using Liq as the electron transporting dopant (Comparative Example 1). This is because in Example 1, when the triplet energy of the green phosphorescent dopant in the light emitting layer is 2.4 eV, Compound I having a triplet energy of 2.59 eV is used as an electron transporting dopant in the electron transport layer, Can be understood as a result. Further, it can be seen that the driving voltage of the organic light emitting diode according to Production Example 1 is reduced as compared with the case where the electron transporting dopant is not used (Comparative Example 2).

Similarly, it can be seen that the quantum efficiency of the organic light emitting diode according to Production Example 2 and Production Example 4 is improved as compared with the case where Liq is used as the electron transporting dopant (Comparative Example 3). This is because, in Production Example 2 and Production Example 4, when the triplet energy of the blue phosphorescent dopant in the light emitting layer is 2.7 eV, the compound II having the triplet energy of 2.76 eV is used as the electron transportation dopant in the electron transport layer, Can be understood as a result of being bound into the light emitting layer. In addition, it can be seen that the driving voltage of the organic light emitting diode according to Production Example 2 and Production Example 4 is reduced as compared with the case where the electron transporting dopant is not used (Comparative Example 4).

As described above, doping of an electron transporting dopant having a higher level of triplet energy than the triplet energy of the luminescent dopant in the luminescent layer into the electron transporting layer improves the quantum efficiency as well as the driving voltage of the organic light emitting diode.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, This is possible.

Claims (13)

An organic light emitting diode comprising an anode, a hole conduction layer, a light emitting layer, an electron conduction layer, and a cathode sequentially stacked,
The light emitting layer is a phosphorescent light emitting layer including a light emitting host and a light emitting dopant,
Wherein the electron conduction layer comprises an electron transporting layer having an electron transporting host and an electron transporting dopant,
Wherein the electron transporting dopant is an organometallic compound and has triplet energy higher than the triplet energy of the luminescent dopant,
Wherein the electron transporting host has triplet energy higher than triplet energy of the luminescent dopant. The method according to claim 1,
Wherein the luminescent dopant is a green phosphorescent dopant or a blue phosphorescent dopant. 3. The method according to claim 1 or 2,
Wherein the electron transporting dopant has a triplet energy of 2.4 to 3.3 eV. The method according to claim 1,
Wherein the electron transporting layer is doped with the electron transporting dopant in the entire layer. The method according to claim 1,
Wherein the electron transporting layer comprises a first electron transporting layer not doped with the electron transporting dopant and a second electron transporting layer doped with the electron transporting dopant. The method according to claim 1,
Wherein the electron transport layer is in contact with the light emitting layer. The method according to claim 1,
Wherein the electron transporting dopant is an organic light emitting diode represented by the following Formula 1:
[Chemical Formula 1]

In Formula 1,
M is a Group 1 or Group 2 metal,
n is 1 or 2,
X is O or S,
A is a hexagonal ring aromatic,
Y is C or N,
B ₁ , B ₂ , and B ₃ are independently of each other NR ₁ , O, or CR ₂ ,
R &lt; _{1 &gt;} is hydrogen or a substituted or unsubstituted C1 to C30 alkyl group,
R ₂ is independently selected from the group consisting of hydrogen, a halogen group, a cyano group, a substituted or unsubstituted C1 to C30 alkyl group, a substituted or unsubstituted C1 to C30 unsaturated alkyl group, a substituted or unsubstituted C6 or C60 aryl group , A substituted or unsubstituted C1 to C30 heteroaryl group, an amino group, a (substituted or unsubstituted C1 to C30 alkyl) amino group, a substituted or unsubstituted C6 or C60 aryl) amino group, a substituted or unsubstituted A substituted or unsubstituted C1 to C30 heteroaryl) amino group, (substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C6 or C60 aryl) amino group, and (substituted or unsubstituted C1 to C30 alkyl) Or an unsubstituted C1 to C30 heteroaryl) amino group,
Two adjacent ones of R ₁ and R ₂ are optionally fused to the B ring. 8. The method of claim 7,
Wherein M is Li, Cs, Ca, or Mg. 8. The method of claim 7,
Wherein at least one of Y, B ₁ , B ₂ , and B ₃ is N, NR ₁ , or O. 10. The method of claim 9,
Wherein Y is C, one of the B ₂ and the B ₃ is NR ₁ or O, and wherein B _1, wherein B _2, and the B ₃ of the rest of R ₂ is the same or different wherein CR _2, which are the OLED diode. 8. The method of claim 7,
Wherein the electron transporting dopant is an organic light emitting diode represented by the following Formula 2:
(2)

In Formula 2, M, X, A, B 1, B 2, B 3, Y and n is as defined in Formula 1 M, X, A, B 1, B 2, B 3, Y and n and the same and each ,
A ₁ , A ₂ , A ₃ , and A ₄ are independently of each other N or CR ₃ ,
R ₃ represents a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted C1 to C30 alkyl group, a substituted or unsubstituted C6 or C60 aryl group, a substituted or unsubstituted C1 to C30 heteroaryl (Substituted or unsubstituted C1 to C30 alkyl) silyl group, (substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C6 or C60 aryl) silyl group, (substituted or unsubstituted C1 to C30 alkyl) (Substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C1 to C30 heteroaryl) silyl group, (substituted or unsubstituted C6 or C60 aryl) silyl group, substituted or unsubstituted C1 to C30 (Substituted or unsubstituted C1 to C30 heteroaryl) amino group, (substituted or unsubstituted C6 or C60 aryl) amino group, (substituted or unsubstituted C1 to C30 heteroaryl) amino group, Substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C6 or C60 Aryl) amino group, and (substituted or unsubstituted C1 to C30 alkyl) (substituted or unsubstituted C1 to C30 heteroaryl) amino group. 12. The method of claim 11,
Wherein Ring A in Formula 2 is benzene or pyridine. 8. The method of claim 7,
Wherein the electron transporting dopant is represented by the following general formula (3), (4), or (5).
(3)

[Chemical Formula 4]

[Chemical Formula 5]

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