KR20190021845A - Ortho-Donor-Appended triarylboron emitter and organic light emitting diode using the same - Google Patents

Abstract

The present invention relates to an ortho donor-appended triarylboron compound and an organic electroluminescent device using the same. A triarylboron compound according to the present invention has a structure that a donor unit is appended at a carbon position (ortho position) adjacent to one of boron-bonded aryl groups, thereby exhibiting thermally activated delayed fluorescence. The organic electroluminescent device containing the triarylboron compound can realize high color purity, high efficiency, and long lifespan characteristics.

Description

(Ortho-Donor-Appended Triarylboron Emitter and Organic Light Emitting Diode Using the Same)

The present invention relates to a triarylboron compound into which an ortho-ortho ring is introduced and an organic light-emitting device using the triarylboron compound.

Organic light emitting diodes (OLEDs) are organic light emitting diodes (OLEDs) that emit light by itself when a voltage is applied to a thin film made of an organic material, (1 / 3th of LCD), fast response speed (1000 times of LCD), low power consumption (1/2 of LCD), high definition and flexibility, so it can be used as a display for smart phones, Be in the spotlight.

The OLED is a self-light emitting 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 OLED can include a cathode and an anode, and an organic layer interposed between the cathode and the anode. The organic layer may include an electron injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer. When a voltage is applied between the cathode and the anode, holes injected from the anode migrate to the light emitting layer via the hole transporting layer, and electrons injected from the cathode migrate to the light emitting layer via the electron transporting layer. Carriers such as holes and electrons recombine in the light emitting layer region to generate an exciton, which is converted to a ground state and light is generated.

Generally, the excitation (exiton) generated when the OLED is driven has a singlet state of 25% and a triplet state of 75%, and in the case of a fluorescent material, a single state of 25 % Of the exciton is generated, and the internal quantum efficiency remains at a maximum of 25%. In order to improve these properties, it is known that trivalent energy-capable iridium or platinum complexes are used and possess excellent quantum efficiency characteristics. However, these materials are expensive, and their application is limited due to the instability of the blue light emitting material.

In order to solve this problem, recently, thermally activated delayed fluorescence (TADF) organic materials have been developed. It has been reported that the thermally activated delayed fluorescent organic material can transfer quantum efficiency of 100% theoretically by transferring the triplet state to the singlet state by heat corresponding to room temperature or device driving temperature.

The smaller the energy difference between the triplet state and the singlet state, the easier it is for Reverse Intersystem Crossing (RISC), which is a twisted structure of a donor unit and an acceptor unit of thermally- (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) by controlling the superposition of HOMO (Lowest Unoccupied Molecular Orbital).

Thus, most thermally active delayed fluorescent materials conventionally introduce a sterically hindered donut unit to induce a perpendicular structure between the donor unit and the acceptor unit and to limit free rotation of the donor unit.

However, most thermally active delayed fluorescent materials have a bonding structure in which donor units are introduced at the para position of the acceptor unit. The material of this structure is experimentally and theoretically seen as a twisted structure between the main unit and the receiving unit, but has a problem of free rotation in the solution state. Therefore, a substance in which a donor unit is introduced at the para position of the acceptor unit has a strong intracellular charge transfer (ICT) There is a problem in that it is weak or does not appear.

Korea Patent Publication No. 2017-0040010

It is an object of the present invention to provide a triarylboron compound having an excellent thermal activation delayed fluorescence effect and realizing high color purity, high efficiency and long life, and an organic light emitting device including the triarylboron compound.

In order to accomplish the above object, the present invention provides a triarylboron compound having a structure represented by the following general formula (1).

[Chemical Formula 1]

In Formula 1,

은 탄소수 6 내지 20의 아릴렌기를 나타내고, D와 B는

의 탄소 중에서 서로 인접하는 탄소에 각각 결합된 구조이며,

Represents an arylene group having 6 to 20 carbon atoms, and D and B represent

Lt; / RTI > is bonded to carbon adjacent to each other in the carbon of the formula

Ar ₁ and Ar ₂ each independently represent an aryl group having 6 to 20 carbon atoms or an arylamine group having 6 to 20 carbon atoms,

, Ar₁ 및 Ar₂의 수소들 중 하나 이상은 각각 독립적으로, 탄소수 1 내지 6의 알킬기로 치환 또는 비치환되며,remind

, One or more of the hydrogens of Ar ₁ and Ar ₂ are each independently substituted or unsubstituted with an alkyl group having 1 to 6 carbon atoms,

D is represented by the following formula (2) or (3)

(2)

(3)

In the above Formulas 2 to 3,

X represents a single _{bond, O, C (R 5)} (R 6) or N (R _7),

Each of R ₁ to R ₇ independently represents hydrogen, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an arylamine group having 6 to 20 carbon atoms.

Also, the present invention provides an organic light emitting device comprising the triarylboron compound, wherein, as one example of the organic light emitting device,

An anode, a cathode, and an organic layer between both electrodes,

And the organic layer includes the triarylboron compound.

The triarylboron compound according to the present invention has a structure in which a tridentate unit is introduced at an adjacent carbon position (ortho position) of one of the aryl groups bonded to boron, thereby exhibiting a thermally activated delayed fluorescence and containing the triarylboron compound The organic light emitting device can realize high color purity, high efficiency, and long life characteristics.

1 to 3 are cross-sectional views showing the structure of a thermally activated delayed fluorescence organic light emitting device according to the present invention, respectively.
4 to 6 show the ¹ H NMR measurement results of the compounds prepared in Examples 1 to 3 and Comparative Examples 1 and 2, respectively.
FIG. 7 shows X-ray crystal structures of the compounds prepared in Example 1, Example 3 and Comparative Example 2. FIG.
FIG. 8 shows the UV / Vis absorption spectrum and the photoluminescence (PL) spectrum of the compounds prepared in Examples 1 to 3 and Comparative Examples 1 and 2 in toluene.
Figure 9 shows the instantaneous PL disappearance curve of a compound according to the invention in a solvent.
Fig. 10 shows the instantaneous PL decay curve measured after doping a solution containing a compound according to the present invention in a host film.
Fig. 11 shows the instantaneous disappearance curve of PL according to the comparative example.
FIG. 12 shows the structure of the thermal activation delayed fluorescence organic light emitting device according to the present invention and the energy level of each element.
FIG. 13 is a graph showing the electroluminescence emission coloring spectrum, the current density-voltage-luminescence characteristics, and the external quantum efficiency-luminescence characteristics of the thermally activated delayed fluorescence organic light emitting device according to one embodiment.
FIG. 14 shows an EL spectrum of a thermal activation delayed fluorescent organic light emitting device according to an embodiment.
15 shows simulation results or experimental results on the maximum external quantum efficiency

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

In the present invention, the terms "comprising" or "having ", and the like, specify that the presence of a feature, a number, a step, an operation, an element, a component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

The term "HOMO" in the present invention means a molecular orbital energy possessed by a compound or a complex. As used herein, the term " HOMO " refers to a molecular orbital energy possessed by a compound or a complex. Lowest Unoccupied Molecular Orbital with the lowest energy level is called "LUMO".

Hereinafter, the present invention will be described in detail.

The OLED is a self-light emitting 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 OLED can include a cathode and an anode, and an organic layer interposed between the cathode and the anode. The organic layer may include an electron injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer. When a voltage is applied between the cathode and the anode, holes injected from the anode migrate to the light emitting layer via the hole transporting layer, and electrons injected from the cathode migrate to the light emitting layer via the electron transporting layer. Carriers such as holes and electrons recombine in the light emitting layer region to generate an exciton, which is converted to a ground state and light is generated.

Generally, the excitation (exiton) generated when the OLED is driven has a singlet state of 25% and a triplet state of 75%, and in the case of a fluorescent material, a single state of 25 % Of the exciton is generated, and the internal quantum efficiency remains at a maximum of 25%. In order to improve these properties, it is known that trivalent energy-capable iridium or platinum complexes are used and possess excellent quantum efficiency characteristics. However, these materials are expensive, and their application is limited due to the instability of the blue light emitting material.

In order to solve this problem, recently, thermally activated delayed fluorescence (TADF) organic materials have been developed. It has been reported that the thermally activated delayed fluorescent organic material can transfer quantum efficiency of 100% theoretically by transferring the triplet state to the singlet state by heat corresponding to room temperature or device driving temperature.

The smaller the energy difference between the triplet state and the singlet state, the easier it is for Reverse Intersystem Crossing (RISC), which is a twisted structure of a donor unit and an acceptor unit of thermally- (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) by controlling the superposition of HOMO (Lowest Unoccupied Molecular Orbital).

Thus, most thermally active delayed fluorescent materials conventionally introduce a sterically hindered donut unit to induce a perpendicular structure between the donor unit and the acceptor unit and to limit free rotation of the donor unit.

However, most thermally active delayed fluorescent materials have a bonding structure in which donor units are introduced at the para position of the acceptor unit. The material of this structure is experimentally and theoretically seen as a twisted structure between the main unit and the receiving unit, but has a problem of free rotation in the solution state. Therefore, a substance in which a donor unit is introduced at the para position of the acceptor unit has a strong intracellular charge transfer (ICT) There is a problem in that it is weak or does not appear.

Thus, the triarylboron compound of the present invention has a structure in which a tridentate unit is introduced at an adjacent carbon position (ortho position) of one of the aryl groups bonded to boron, thereby providing a triarylboron compound exhibiting thermally- The organic light emitting device including the triarylboron compound can realize high color purity, high efficiency, and long life.

Specifically, the triarylboron compound according to the present invention may be a triarylboron compound into which a donor group represented by the following general formula (1) is introduced.

The triarylboron compound according to the present invention can control the superposition of HOMO and LUMO through the effect of the steric hindrance through the above-mentioned structural features, and can realize the delayed fluorescence effect by reducing the difference between single-energy and triplet energy .

[Chemical Formula 1]

In Formula 1,

은 탄소수 6 내지 20의 아릴렌기를 나타내고, D와 B는

의 탄소 중에서 서로 인접하는 탄소에 각각 결합된 구조이며,

Represents an arylene group having 6 to 20 carbon atoms, and D and B represent

Lt; / RTI > is bonded to carbon adjacent to each other in the carbon of the formula

Ar ₁ and Ar ₂ each independently represent an aryl group having 6 to 20 carbon atoms or an arylamine group having 6 to 20 carbon atoms,

, Ar₁ 및 Ar₂의 수소들 중 하나 이상은 각각 독립적으로, 탄소수 1 내지 6의 알킬기로 치환 또는 비치환되며,remind

, One or more of the hydrogens of Ar ₁ and Ar ₂ are each independently substituted or unsubstituted with an alkyl group having 1 to 6 carbon atoms,

D is represented by the following formula (2) or (3)

(2)

(3)

In the above Formulas 2 to 3,

X represents a single _{bond, O, C (R 5)} (R 6) or N (R _7),

Each of R ₁ to R ₇ independently represents hydrogen, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an arylamine group having 6 to 20 carbon atoms.

In the present invention, the term "alkyl group" is defined as a functional group derived from a linear or branched saturated hydrocarbon.

Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 1,1-dimethylpropyl group, , 2-dimethylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group, 2-ethylpropyl group, n-hexyl group, Methylpropyl group, 1-methylbutyl group, 2-methylbutyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 2,2- Dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, 2-ethylbutyl group, 2-methylpentyl group and 3-methylpentyl group.

In the present invention, the "aryl group" is defined as a monovalent substituent derived from an aromatic hydrocarbon.

Specific examples of the aryl group include a phenyl group, a naphthyl group, an anthracenyl group, a naphthacenyl group, a pyrenyl group, a tolyl group, A biphenyl group, a terphenyl group, a chrycenyl group, a spirobifluorenyl group, a fluoranthenyl group, a fluorenyl group, a phenanthrene group, Examples thereof include a perylenyl group, an indenyl group, an azulenyl group, a heptalenyl group, a phenalenyl group, and a phenanthrenyl group .

The "arylene group" may mean a divalent substituent derived from the above-described aryl group.

In the present invention, the "arylamine group" may be an amine group to which the above-mentioned aryl group is bonded.

As an example, in the triarylboron compound represented by the above formula (1)

은 탄소수 6 내지 12의 아릴렌기를 나타내고,

Represents an arylene group having 6 to 12 carbon atoms,

Ar ₁ and Ar ₂ each independently represent an aryl group having 6 to 20 carbon atoms,

, Ar₁ 및 Ar₂의 수소들 중 하나 이상은 각각 독립적으로, 탄소수 1 내지 6의 알킬기로 치환 또는 비치환되며,remind

, One or more of the hydrogens of Ar ₁ and Ar ₂ are each independently substituted or unsubstituted with an alkyl group having 1 to 6 carbon atoms,

D is represented by the following formula (2) or (3)

(2)

(3)

In the above Formulas 2 to 3,

X represents a single _{bond, O, C (R 5)} (R 6) or N (R _7),

R ₁ to R ₇ each independently represent hydrogen, an alkyl group having 1 to 6 carbon atoms or an arylamine group having 6 to 12 carbon atoms.

As another example, the triarylboron compound represented by the formula (1) may be represented by the following formula (4).

[Chemical Formula 4]

In Formula 4,

는 탄소수 1 내지 6의 알킬기로 치환 또는 비치환된 탄소수 6 내지 12의 아릴렌기를 나타내고,

Represents an arylene group having 6 to 12 carbon atoms which is substituted or unsubstituted with an alkyl group having 1 to 6 carbon atoms,

D is represented by any one of the following formulas (5) to (11).

[Chemical Formula 5]

[Chemical Formula 6]

(7)

[Chemical Formula 8]

[Chemical Formula 9]

[Chemical formula 10]

(11)

As yet another example,

In the triarylboron compound represented by the general formula (4)

는 탄소수 1 내지 6의 알킬기로 치환 또는 비치환된 탄소수 6 내지 12의 아릴렌기를 나타내고,

Represents an arylene group having 6 to 12 carbon atoms which is substituted or unsubstituted with an alkyl group having 1 to 6 carbon atoms,

D can be represented by the following general formula (5), (7) or (10).

 [Chemical Formula 5]

(7)

[Chemical formula 10]

의 탄소 중에서 서로 인접(오르토 위치)하는 탄소에 각각 결합된 구조를 가짐으로써, 두 단위 간의 자유 회전을 방지하고, 열활성 지연형광을 나타낼 수 있다. 또한, 상기 트리아릴보론 화합물을 포함하는 유기 발광 소자는 고색순도, 고효율 및 장수명 특성을 구현할 수 있다.
The triarylboron compound according to the present invention is characterized in that D and B

(Ortho-positioned) to each other in the carbon atoms of the carbon atoms, thereby preventing free rotation between the two units and exhibiting thermally-activated delayed fluorescence. In addition, the organic light emitting device including the triarylboron compound can realize high color purity, high efficiency, and long life time characteristics.

The energy difference between singlet state and triplet state of the triarylboron compound may range from 0.001 to 0.3 eV. For example, the energy difference between singlet state and triplet state of the triarylboron compound may range from 0.005 to 0.3 eV, from 0.01 to 0.3 eV, or from 0.01 to 0.2 eV.

The triarylboron compound according to the present invention has a structure in which a tridentate unit is introduced at an adjacent carbon position (ortho position) of one of the aryl groups bonded to boron to change the energy difference between the singlet state and the triplet state in the range of 0.001 to 0.3 eV By reducing the energy difference between the singlet state and the triplet state to the above range, the triplet excited state can be easily transferred to the singlet excited state through the inverse phase transition by heat at room temperature or at the element operating temperature , Which may result in delayed fluorescence.

It is also known that the actual quantum efficiency of currently developed thermally activated retarded fluorescent organic materials is still very different from the theoretical quantum efficiency and still needs to be improved.

Accordingly, the present invention controls the energy difference between the singlet state and the triplet state in the range of 0.001 to 0.3 eV, so that the transition from the triplet state to the singlet state can be performed more efficiently, An active retardation fluorescent material and an organic light emitting device including the same can be provided.

를 이루는 편면(plane)(

면)과 이면각(dihedral angle)이 70 내지 90° 범위일 수 있다. The plane (D plane) constituting D in the triarylboron compound is represented by

The plane (

Plane and the dihedral angle may range from 70 to 90 degrees.

의 Ar₁면 또는 Ar₂면은 서로 평행하여, 상호간의 입체 장애(mutual steric hindrance)를 피할 수 있다. 이러한 구조를 유지하기 위해서는 D면은

면과 거의 직각 구조를 가져야 하며, 예를 들어, D면과

면의 이면각(dihedral angle)은 70 내지 90° 범위여야 한다. 예를 들어, D면은

면과 이면각(dihedral angle)이 75 내지 85°또는 75 내지 80°범위일 수 있다.
Specifically, in the above triarylboron compound,

The Ar ₁ side or the Ar ₂ side of the substrate is parallel to each other and mutual steric hindrance can be avoided. In order to maintain this structure,

It should have a nearly right-angled structure with the plane, for example,

The dihedral angle of the face should be in the range of 70 to 90 degrees. For example, the D side

The plane and dihedral angles may range from 75 to 85 degrees or from 75 to 80 degrees.

In addition, the present invention, in one embodiment,

An anode, a cathode, and an organic layer between both electrodes,

Wherein the organic layer comprises the compound represented by Formula 1. < EMI ID = 1.0 >

The organic light emitting device according to the present invention may be a display that emits light by itself when a voltage is applied to a thin film made of an organic material to realize characters or images of various colors. Specifically, the organic light emitting diode may be a thermal activation delayed fluorescent organic light emitting diode (TADF-OLEDs).

In addition, the anode and the cathode may be transparent or opaque (reflective) electrodes as a material having excellent electrical conductivity. For example, in the case of a transparent electrode, the anode and the cathode may each comprise glass, indium tin oxide (ITO), tin oxide (SnO ₂ ), and the like. Layer structure of two or more layers. In the case of an opaque (reflective) electrode, the positive electrode and the negative electrode may include a metal such as nickel, magnesium, calcium, silver, aluminum, indium, or an alloy containing two or more of these metals. In addition, the opaque electrode may have a single-layer structure or a multi-layer structure of two or more layers.

Further, the organic layer may include a compound represented by the formula (1) according to the present invention as a dopant material, and may have a single layer or a multilayer structure of two or more layers. In addition, the organic layer may use a host material together with a dopant, and a low molecular weight or high molecular weight host may be used. Examples of the low molecular weight host include 9,9 '- (1,1'-biphenyl) -4,4'-diyl bis-9H-carbazole (CBP) and 9,9' (PNB-mCP), and poly- (N-vinylcarbazole) (hereinafter, referred to as " poly- PVCz): PBD (or OXD-7).

Generally, a multilayered device in which a light emitting layer and a charge transport layer are combined, exhibits excellent device characteristics, rather than a single-layered device composed of only a single light emitting layer. This is because an appropriate combination of a light emitting material and a charge transporting material, The barrier is reduced, and the charge transport layer confines the holes or electrons injected from the electrodes to the light emitting layer region, so that the number density of injected holes and electrons is balanced. Particularly, in the case of an organic light emitting device, since the emission duration of a compound is long, holes are confined in the light emitting layer to stay in the light emitting layer for a long time in order to increase the efficiency.

1 and 2, when the organic light emitting device 100 includes the anode 110, the first charge transport layer 120, the light emitting layer 130, the second charge transport layer 140, and the cathode 150 sequentially And the compound represented by Formula 1 may be included as a dopant in the light emitting layer 130. In order to improve device characteristics such as luminous efficiency and lifetime, the first charge transport layer 120 and the second charge transport layer The second charge transport layer 140 may include a hole injection layer 121 and / or a hole transport layer 122 and an electron transport layer 141 and / or an electron injection layer 142, respectively.

The hole injection layer 121 may be inserted into a conventional hole injection layer including, for example, PEDOT (poly (3,4) -ethylenedioxythiophene) or copper phthalocyanine (CuPc) The injection layer 142 can be inserted into a conventional electron injection layer containing, for example, LiF.

The hole transport layer 122 can be formed using conventional hole transport materials such as 1,1-bis [(di-4-tolylamino) phenyl] cyclohexane (TAPC), 4,4- N-diphenyl-N, N-bis (3-methylphenyl) -1,1-biphenyl-4,4-diamine ( TPD) and poly- (N-vinylcarbazole) (PVCz) may be used singly or in combination of two or more, and may have a multi-layer structure in which two or more layers are stacked as required.

The electron transporting layer (electron transporting light emitting layer) 141 may be a conventional electron transporting material such as (4,6-bis (3,5-di (pyridin-3- yl) phenyl) -2- methylpyrimidine B3PyMPM), tris (8-quinolinolato) aluminum (Alq3), 4,7-diphenyl-1,10-phenanthroline (Bphen) or rubrene, Layer structure in which two or more layers are stacked as required.

3, the organic light emitting device 100 includes an electron blocking layer 170 between the light emitting layer 130 and the first charge transporting layer, specifically, the hole transporting layer 122, and a light emitting layer 130 between the light emitting layer 130 and the first charge transporting layer, And a hole blocking layer 160 may be further provided between the first charge transporting layer and the second charge transporting layer, specifically, the electron transporting layer 141.

As the electron blocking layer 170, a material having a large LUMO value is generally used, and iridium (III) tris (1-phenylpyrazole-N, C2 ') (Ir (ppz) ₃ ) is suitable. Also, the hole blocking layer 160 has a lowest unoccupied molecular orbital (LUMO) value between 5.5 and 7.0, and has a hole transporting ability remarkably deteriorated, and a material having an excellent electron transporting ability, for example, 1,3,5-tris (BCP), 3- (4-biphenylyl) -4-phenyl-5- (4-t-butoxycarbonyl) -Butylphenyl) -1,2,4-triazole (TAZ), bis (8-hydroxy-2-methylquinolinato) -aluminum biphenoxide (BAlq) and the like.

The anode, the cathode, the light emitting layer, the transport layer, the injection layer, and the barrier layer may be formed by a conventional deposition method. At this time, the compound represented by Formula 1 is included as a dopant in the organic light emitting device and exhibits stable luminescence, and exhibits excellent external quantum efficiency and power efficiency. Therefore, .

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples.

However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the present invention is not limited to the following Examples and Experimental Examples.

Example  One: PXZ o B  Produce

[Formula 1a]

From 0 ℃ using a shrink flask (Schlenk Flask) in 100 mL n -BuLi (0.3 mL, 0.75 mmol) 10- (2-bromophenyl) -10 H -phenoxazine (0.21 g, 0.62 mmol) and in dry ether ( dry ether) (50 mL) was added dropwise. Then, the mixture was reacted by stirring at 0 ° C for 1 hour. To the mixture was slowly added a mixture of dimesitylboron fluoride (Mes ₂ BF) (0.17 g, 0.63 mmol) and dry ether (5 mL) Lt; / RTI > The reaction was then quenched by pouring an aqueous solution of NH ₄ Cl (20 mL) into the mixture, extracted three times with diethyl ether (30 mL), and then washed three times with water (30 mL). Then, the combined organic layer with MgSO ₄ was removed and concentrated under reduced pressure. The concentrated mixture was purified by silica gel column chromatography using n-hexane as an eluent to give pale yellow of 10- (2- (dimesitylboryl) phenyl) -10H-phenoxazine (PXZ o B) ) Powder (yield: 0.18 g, yield: 57%).

Mono-crystals of pale yellow color suitable for X-ray diffraction measurement were obtained by vapor diffusion of n-hexane with a CH ₂ Cl ₂ solution of PXZoB.

_{^{1 H NMR (CDCl 3):}} δ 7.71 (t, J = 7.4 Hz, 2H), 7.49 (td, J = 8.0, 1.1 Hz, 1H), 7.40 (d, J = 7.6 Hz, 1H), 6.76-6.34 (m, 10H, phenoxazine- H and Mes- H), 5.98 (s, 2H), 2.44-1.47 (m, 18 H, Mes-C H 3).

HR EI-MS: m / z calcd for C ₃₆ H ₃₄ BNO, 507.2733; found, 507.2731.

Example  2: DPA o B  Produce

[Chemical Formula 1b]

N - (2-bromophenyl) - N -phenylbenzenamine (0.30 g, 0.93 mmol), n-BuLi (0.4 mL, 1.0 mmol), and _{Mes 2 BF (0.26 g, 0.97} mmol) in Example 1 using PXZoB by the method similar to the method for producing 2- (Dimesitylboryl), such as formula 1b - N, N -diphenylbenzenamine (DPA o B) Bright yellow (bright yellow) powder of a color (yield: 0.59 g, yield: 74%) .

_{^{1 H NMR (CDCl 3):}} δ 7.48 (dd, J = 7.8, 2.1 Hz, 1H), 7.40 (td, J = 6.8, 1.5 Hz, 1H), 7.26 (m, 1H), 7.10 (t, J = 7.8 Hz, 6H), 6.92 ( t, J = 7.2 Hz, 2H), 6.67 (m, diphenylamine- H and Mes- H, 7H), 2.23 (s, 6H, Mes-C H 3), 1.77 (s, _{12H, Mes-C H 3)} .

Example  3: Cz o B  Produce

[Chemical Formula 1c]

9- (2-bromophenyl) -9 using H -carbazole (0.30 g, 0.93 mmol ), n-BuLi (0.4 mL, 1.0 mmol), and _{Mes 2 BF (0.26 g, 0.97} mmol) of Example 1 PXZoB method similar manner as 9- (2- (Dimesitylboryl) phenyl) -9 H -carbazole (Cz o B) powder (the number of white (white) the yield of the color, such as of the general formula 1c: 0.23 g, yield: 50%).

Colorless single crystals suitable for X-ray diffraction measurements were obtained by vapor diffusion of n-hexane with a solution of Cz o B in CH ₂ Cl ₂ .

_{^{1 H NMR (CDCl 3):}} δ 7.87 (d, J = 7.4 Hz, 2H), 7.81-7.73 (m, 2H), 7.60 (dd, J = 7.6, 1.2 Hz, 2H), 7.32-7.27 (m, 2H), 7.18 (t, J = 7.5 Hz, 4H), 6.36 (s, 4H, Mes- H), 2.64-1.55 (m, 18 H, Mes-C H 3).

HR EI-MS: m / z calcd for C ₃₆ H ₃₄ BN, 491.2784; found, 491.2791

Comparative Example  One: DPA p B  Produce

(A)

N - (4- (dimesitylboryl) phenyl) -N- phenylbenzenamine (DPA p B) of formula (a) was prepared by a known method.

Comparative Example  2: Cz p B  Produce

[Formula b]

A conventional known method to prepare a 9- (4- (dimesitylboryl) phenyl) -9 H -carbazole (Cz p B) of the formula b.

Experimental Example  1: Structural analysis of compounds

(One) ^One H NMR measurement

The results of ¹ H NMR measurement in CDCl ₃ of the compounds prepared in Examples 1 to 3 and Comparative Examples 1 and 2 are shown in FIGS. 4 to 6. (* Means residual CDCl ₃ , and + means H ₂ O.)

Specifically, Example 1 was a indicate the ¹ H NMR measurement spectrum of PXZ o B in Figure 4 prepared in Example 2, the DPA o B and Comparative ¹ H NMR measurement seupekteueul of DPA p B prepared in Example 1 produced in 5, and ¹ H NMR measurement spectra of Cz o B prepared in Example 3 and Cz p B prepared in Comparative Example 2 are shown in FIG.

As in the examples, when proton is connected to one of the adjacent carbon positions (ortho position) of the aryl groups bonded to the boron of triarylboron, very broad proton resonances for BMes ₂ are seen at room temperature, , Which may mean that the movement of Mes groups is restricted due to steric hindrance in solution.

On the other hand, as a comparative example, a tree when the dog main attached at the para position of the aryl boronic has confirmed that the methyl and C _Ar -H proton Resonance the M _es group appears sharp.

(2) Confirmation of X-ray crystal structure

X-ray crystal structures of the compounds prepared in Example 1 (PXZ o B), Example 3 (Cz o B) and Comparative Example 2 (Cz p B) , And the hydrogen atom is omitted for clarity of the structure.

Referring to FIG. 7, in the case of the compounds according to the embodiments, a three-dimensionally complex structure can be clearly confirmed between the faces constituting each ring. Also, it can be seen that the faces of the phenoxazine (PXZ) and the carbazole (Cz) ring are almost parallel to one Mes, respectively.

In the compound of Example 1, the plane and the back angle of the PXZ plane and the phenylene ring connected to the PXZ plane were 79.0 °, and the compound of Example 3 had the Cz plane and the phenyl connected to the Cz plane It can be seen that the plane of the lens ring and the back angle are almost orthogonal at 76.6 °.

The structure of Comparative Example 2 (Cz p B) similar to the structure of Example 3 (CzoB) is as follows. The plane of the phenylene ring connected to the Cz plane and the Cz plane is 68.3 deg. I could confirm. This may mean a substantial conjugation between the free rotation of the Cz portion and the main axis and the receiver, taking into account the ¹ H NMR measurement of the Cz p B.

Experimental Example  2: Compound Optical physical  Character analysis

The UV / Vis absorption spectrum and the light emission (PL) spectrum of the compounds prepared in Examples 1 to 3 and Comparative Examples 1 and 2 in toluene were measured and reported in the following Table 1 and FIG.

λ _abs [nm] ^a) ? _PL [nm] ^a) 陸 _PL [%]
(N ₂ / air) ^b) τ _p ( Φ _PF ) [ns (%)] ^c) τ _d ( Φ _DF ) [μs (%)] ^c) HOMO / LUMO [eV] ^d) E _S / E _T [eV] ^e) △ E _ST [eV] ^f) Example 1
(PXZ o B) 320, 445 585 23/6 62 (8) 2.92 (15) -5.07 / -2.35 2.44 /
2.44 <0.01 Example 2
(DPA o B) 302, 415 498 73/38 27 (42) 14.4 (31) -5.33 / -2.41 2.76 /
2.56 0.20 Example 3
(Cz o B) 324, 380 463 79/19 38 (24) 71.6 (55) -5.55 / -2.32 2.95 /
2.80 0.15 Comparative Example 1
(DPA p B) 309, 380 437 91/80 4.0 (91) n / o ^{g )} - ^h) 3.12 /
2.71 0.41 Comparative Example 2
(Cz p B) 291, 360 401 75/65 3.7 (75) n / o - 3.33 /
2.94 0.39

a) Measure the absorption peak wavelength (λ _abs ) and photoluminescence (PL) wavelength after mixing each compound at a concentration of 5.0 × 10 ^-5 M in 298K temperature and oxygen-blocked toluene.

b) Absolute photoluminescence quantum yields (PLQYs) were measured at 298K temperature and in an oxygen-free nitrogen (N ₂ ) and air atmosphere.

c) the PL lifetime of the instant (prompt, τ _p ) and delayed (τ _d ) decay components in an oxygen-blocked toluene solution at a temperature of 298 K; The PL lifetime fraction of the moment ( Φ _PF ) and delay ( Φ _DF ) measured in the transient decay curves is given in [%] parentheses.

d) Measure electrochemical oxidation (HOMO) and reduction (LUMO).

e) singlet energy (E _S ) and triplet energy (E _T ) measured from the onset wavelengths of the fluorescence and phosphorescence spectra obtained at 77K.

f) E _ST = E _S - E _T

g) Not observed.

h) Not measured.

Referring to Table 1 and FIG. 8, PXZ o B, DPA o B, and Cz o B show broad and low energy absorption peaks at 445, 415, and 380 nm, respectively, and show the form of intramolecular charge transfer. This is because the acceptor portions of the three compounds are the same and the absorption wavelength is closely related to the HOMO level of the donor.

The PXZ o B, when measured by the cyclic voltammetry of DPA and Cz o B o B seen by measuring the LUMO and HOMO level, the LUMO level of the three compounds can be confirmed that a part different. Also, the HOMO level showed a significant difference in the order of energy, PXZ o B, DPA o B and Cz o B. 8, the PL spectra of the three compounds show broad emission bands in the orange region and the blue region, and the absorption peak differences depending on the energy of the three compounds can be confirmed.

In Table 1, the absolute photoluminescence quantum yields (PLQYs) are 2 to 4 times higher when the compounds according to the Examples are mixed with oxygen-blocked toluene than when they are mixed with toluene in an air atmosphere. From this, it can be seen that in the solution containing oxygen, the triplet excited state (T ₁ ) is quenched by triplet oxygen. This also means that it is easy to reverse-transition (RISC) from triplet excited state (T ₁ ) to singlet excited state (S ₁ ) in an oxygen-blocked solution.

The transient PL decay was measured to confirm upconversion from triplet excitation state (T ₁ ) to singlet excitation state (S ₁ ), which is shown in FIG.

Referring to the PL decay curves of FIG. 9, the compounds according to an embodiment include two decay components. The two extinction components are a nanosecond-range prompt component (τ _p ) and a microsecond-range delayed component (τ _d ).

It was also confirmed that as the temperature was increased from 150K to 300K, the emission intensity of the retardation component was increased, and it was confirmed that the delayed emission could be converted into thermally activated delayed fluorescence (TADF).

As described above, the emission spectrum is similar when the compound according to the embodiment is mixed with oxygen-containing toluene and air-oxygen-containing toluene, respectively, using nitrogen. It can be seen from this that delayed emission appears from singlet excited state (S ₁ ) through inter-system transition, and PXZ o B (6 wt%), DPA o B (30 wt%) and Cz o B (TADF) similar to that shown in FIG. 10, which is a result of measurement of the instantaneous PL decay curve after doping a host film with a dopant (wt.%) in a host film.

On the other hand, as a comparative example, a tree, when the case of the aryl DPA p B dog main attached to the para position of boron and Cz p B, the reference to Table 1 and to Figure 11, the oxygen barrier to nitrogen (in N ₂₎ toluene And toluene with air due to air, showed single-exponential PL decay and short life in nanosecond units, respectively. Thus, it can be seen that when DPA and Cz are connected to the para position of triarylboron, delayed fluorescence does not appear despite fluorescence intensity and intramolecular charge transfer (ICT).

As a result, it has been found through this experiment that photochemical properties are different due to structural differences in the case where one of the aryl groups bonded to the boron is bonded to one adjacent carbon position (ortho position) and the other is bonded to the para position Could know.

(DPA o B) and Comparative Examples 1 (DPA p B) to 3 (Cz o B) and Comparative Example 2 (DPA o B) (Cz p B) NMR spectrum and crystal structure.

Specifically, due to the structural difference between the two compounds, the difference between singlet energy and triplet energy ( ΔE _ST ) may be different. In Table 1, ΔE _ST was 0.2 and 0.15 eV for the compounds of Example 2 (DPA o B) and Example 3 (Cz o B), respectively, and ΔE _ST values of the respective compounds were Is sufficiently small to implement efficient thermally activated delayed fluorescence (TADF).

However, for the compounds of Comparative Example 1 (DPA p B) and Comparative Example 2 (Cz p B), the D E _ST was 0.41 and 0.39 eV, respectively. As a result, it can be seen that it is not easy to transfer back-to-back transition from singlet state to triplet state.

Experimental Example  3: Evaluation of performance of organic light emitting device including compound

(TADF-OLEDs) containing a compound according to the present invention in a light emitting layer were fabricated in two types of structures as shown in FIG. 12 (a). Specifically, the mCP: B3PyMPM: emitter in the type 1 (Type-I) is N - dicarbazolyl-3,5-benzene (mCP, E _T = 2.90 eV) and bis-4,6- -3-pyridylphenyl) -2-methylpyrimidine ( B3PyMPM, E T = 2.68 eV) is 1: the molar ratio excimer formation nose host system (exciplex-forming co-host system consisting of 1) (mCP: B3PyMPM, ( E T = 2.97 eV) doped with PXZ o B ( E _T = 2.44 eV) to DPA o B ( E _T = 2.56 eV).

In addition, in type 2 DPEPO (Type-Ⅱ): emitter is single host bis (2- (diphenylphosphino) phenyl) ether oxide (DPEPO, E T = 3.30 eV) in the system (single host system) consisting of Cz o B (E _T = 2.80 eV).

The energy level diagram (eV) for the two types of organic light emitting devices is shown in FIG. 12 (b).

Table 2 shows the results of the performance evaluation of the thermally-activated delayed-fluorescence organic light-emitting device of the present invention, wherein the content of the emitter according to the present invention in the light-emitting layer was varied as shown in Table 2 below. The optical physical properties of the thermal activation delayed fluorescence organic light emitting device are shown in Table 3 below.

Device ITO thickness (nm) Emitter (wt%) CIE (x, y) ^c) V _on (V) ^d) CE (cdA ^-1 ) ^e) EQE (%) ^f) D1 ^{a )} 150 PXZ o B  (6) (0.460, 0.505) 2.9 45.7 16.3 D1-2 ^a) 150 PXZ o B (20) (0.497, 0.490) 3.0 36.1 13.9 D1-3 ^a) 150 PXZ o B (30) (0.517, 0.476) 2.9 29.9 12.2 D2-1 ^a) 150 DPA o B (10) (0.160, 0.434) 3.0 35.9 14.6 D2-2 ^a) 150 DPA o B (20) (0.170, 0.482) 2.9 48.2 18.7 D2 ^{a )} 150 DPA o B  (30) (0.172, 0.488) 2.9 55.6 21.4 D2-4 ^a) 150 DPA o B (40) (0.178, 0.491) 2.9 43.9 16.9 D3-1 ^b) 150 Cz o B (10) (0.142, 0.139) 4.3 26.3 21.7 D3 ^{b )} 150 Cz o B  (20) (0.139, 0.150) 3.9 28.5 22.6 D3-3 ^b) 150 Cz o B (30) (0.139, 0.154) 3.8 27.6 21.4 D4-1 ^a) 70 DPAoB (10) (0.175, 0.502) 3.0 45.2 18.7 D4-2 ^a) 70 DPAoB (20) (0.182, 0.531) 3.0 54.9 21.0 D4 ^{a )} 70 DPAoB  (30) (0.187, 0.546) 2.9 64.6 24.2 D5-1 ^b) 70 Cz o B (10) (0.141, 0.182) 4.3 29.2 21.2 D5 ^{b )} 70 Cz o B  (20) (0.139, 0.198) 3.9 33.8 24.1 D5-3 ^b) 70 Cz o B (30) (0.138, 0.205) 3.8 32.9 24.0

a) Manufactured in a type 1 structure.

b) Manufactured in type 2 structure.

c) Color coordinates at maximum luminance (CIE 1931)

d) the applied voltage at a luminance of 1 cd m ^-2 .

e) Maximum current efficiency

f) Maximum external quantum efficiency.

Doped host movie Device performance Emitter [wt%] ^a) λ _PL [nm] 陸 _PL [%] τ _p (Φ _PF ) [ns (%)] ^b) τ _d ( Φ _DF ) [μs (%)] ^b) △ E _ST [eV] ^c) Device ITO thickness [nm] CIE (x, y) ^f) V _on [V] ^g) CE [cd? ^-1 ] ^h) EQE [%] ⁱ⁾ PXZ o B (6) 557 49 108 (11) 5.39 (38) 0.035 D1 ^{d )} 150 (0.460, 0.505) 2.9 45.7 16.3 DPA o B (30) 502 80 26 (45) 66.3 (35) 0.158 D2 ^{d )} 150 (0.172, 0.488) 2.9 55.6 21.4 Cz o B (20) 466 84 41 (23) 56.3 (61) 0.124 D3 ^{e )} 150 (0.139, 0.150) 3.9 28.5 22.6 DPA o B (30) - - - - - D4 ^{d )} 70 (0.187, 0.546) 2.9 64.6 24.2 Cz o B (20) - - - - - D5 ^{e )} 70 (0.139, 0.198) 3.9 33.8 24.1

a) mCP: B3PyMPM: PXZ o B, mCP: B3PyMPM: DPA o B or DPEPO: Cz o B.

b) the PL lifetime of the instant (prompt, τ _p ) and delayed (τ _d ) decay components in an oxygen-blocked toluene solution at a temperature of 298 K; The PL lifetime fraction of the moment (Φ _PF ) and delay (Φ _DF ) measured in the transient decay curves is given in [%] parentheses.

c) Calculation by known methods.

d) Manufactured in type 1 structure.

e) Manufactured in a Type 2 structure.

f) Color coordinates at maximum luminance (CIE 1931)

g) the applied voltage at a luminance of 1 cd m ^-2 .

h) Maximum current efficiency

i) Maximum external quantum efficiency

The electroluminescence (EL) emission color system (x, y) of D1 to D3 is shown in FIG. 13 (a) and the EL spectrum is shown in FIG. As a result, similar to the PL spectrum, the orange (CIE 1931 ( x , y ) = 0.460, 0.505) color is emitted when the emission color is D1 due to the difference in the HOMO level of the donor group, (CIE 1931 ( x , y ) = 0.172, 0.488) for greenish-blue (CIE 1931 ( x , y ) = 0.460, 0.505) for D3.

Referring to FIG. 13B, in the current density-voltage-light-emitting ( J - V - L ) characteristics, D1 and D2 produced by the type 1 structure have a higher current density and lower current density than the D3 of the type 2 structure. And exhibit turn-on voltages. From this it can be seen that the compounds according to the invention can achieve an excellent charge balance.

_Referring to FIG. 13 (c), in the external quantum efficiency-luminescence (eta _EQE - L ) characteristic, D1 to D3 according to the present invention all exhibit high external quantum efficiency at optimum emission intensity. Specifically, the external quantum efficiencies of D1 (PXZ o B, 6 wt%) and D2 (DPA o B, 30 wt%) were 16.3% and 21.4%, respectively, and D3 (Cz o B, 20 wt% , The external quantum efficiency is 22.6%, which is the highest value compared with the external quantum efficiency of the fluorescence delayed fluorescence device reported to date. Thus, Cz o B compound heat activated delayed fluorescent element excellent performance As can be seen in Table 3, 0.124 eV small △ E _ST value and high PLQY (Φ _PF with the largest Φ _DF of 0.61, with the containing = 0.84).

Generally, the external quantum efficiency of the thermal activation delayed fluorescence organic light emitting device can be expressed by the following equation (1).

[Equation 1]

In Equation 1, η _int is the internal EL quantum efficiency (internal EL quantum efficiency), η _out is the light outcoupling efficiency (light outcoupling efficiency), γ is the charge balancing element (charge balance factor), η _s Η _T represents the triplet exciton formation ratio, and Φ _{I SC} represents the intersystem crossing efficiency.

Generally, 侶_out is used in the range of 20 to 30%, and when the value of γ is assumed to be 1, the calculated η _int of D3 (Cz o B) is about 0.84. Thus, the high eta _int of D3 coincides with the high external quantum efficiency (eta _EQE ).

In order to understand the above experimental results and to increase the outcoupling efficiency, the horizontal transition dipole ratio (Θ) of the device including the light emitting layer including Cz 0 B (20 wt%) and the ITO layer thickness was performed with all the optical analysis of the functions of the external quantum efficiency. the results are shown in Figure 15. Figure 15 (a), the horizontal transition dipoles of the device the light-emitting layer is formed containing a Cz o B (20 wt%) The horizontal transit dipole ratio (Θ) is 0.74 for the maximum external quantum efficiency, and the maximum external quantum efficiency as a function of the ratio (Θ) and ITO layer thickness is shown by a contour line diagram. It was confirmed that the thickness of the ITO layer was 70 nm and 150 nm.

As a result, the maximum external quantum efficiency was found to be 24.6% when the thickness of the ITO layer was 70 nm when the horizontal transition dipole ratio (?) Was 0.74, and the thickness of the ITO layer was 150 nm The maximum external quantum efficiency was confirmed to be 21.9%. The match to be, having a 70 nm thickness of the ITO layer when the actual manufacturing D5 (Cz o B), shows a very high external quantum efficiency of 24.1%. 15 (b) shows the simulation results of the maximum external quantum efficiency of FIG. 15 (a), and actual experimental results are shown when the thickness of the ITO layer is 70 and 150 nm. .

The improvement in efficiency of the device similar to the above was also confirmed in D4 (DPA o B) having an ITO layer with a thickness of 70 nm.

Claims (14)

A triarylboron compound into which a triplet represented by the following formula (1) is introduced:
[Chemical Formula 1]

In Formula 1,

Represents an arylene group having 6 to 20 carbon atoms, and D and B represent

Lt; / RTI &gt; is bonded to carbon adjacent to each other in the carbon of the formula
Ar ₁ and Ar ₂ each independently represent an aryl group having 6 to 20 carbon atoms or an arylamine group having 6 to 20 carbon atoms,
remind

, One or more of the hydrogens of Ar ₁ and Ar ₂ are each independently substituted or unsubstituted with an alkyl group having 1 to 6 carbon atoms,
D is represented by the following formula (2) or (3)
(2)

(3)

In the above Formulas 2 to 3,
X represents a single _{bond, O, C (R 5)} (R 6) or N (R _7),
Each of R ₁ to R ₇ independently represents hydrogen, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an arylamine group having 6 to 20 carbon atoms.
The compound according to claim 1, wherein in formula (1)

Represents an arylene group having 6 to 12 carbon atoms,
Ar ₁ and Ar ₂ each independently represent an aryl group having 6 to 20 carbon atoms,
remind

, One or more of the hydrogens of Ar ₁ and Ar ₂ are each independently substituted or unsubstituted with an alkyl group having 1 to 6 carbon atoms,
D is represented by the following formula (2) or (3)
(2)

(3)

In the above Formulas 2 to 3,
X represents a single _{bond, O, C (R 5)} (R 6) or N (R _7),
R ₁ to R ₇ each independently represent hydrogen, an alkyl group having 1 to 6 carbon atoms or an arylamine group having 6 to 12 carbon atoms.
The method according to claim 1,
The triarylboron compound represented by the formula (1) is represented by the following formula (4)
[Chemical Formula 4]

In Formula 4,

Represents an arylene group having 6 to 12 carbon atoms which is substituted or unsubstituted with an alkyl group having 1 to 6 carbon atoms,
D is represented by any one of the following formulas (5) to (11).
[Chemical Formula 5]

[Chemical Formula 6]

(7)

[Chemical Formula 8]

[Chemical Formula 9]

[Chemical formula 10]

(11)

4. The compound according to claim 3, wherein in Formula 4,

Represents an arylene group having 6 to 12 carbon atoms which is substituted or unsubstituted with an alkyl group having 1 to 6 carbon atoms,
D is a triarylboron compound represented by the following general formula (5), (7) or (10)
[Chemical Formula 5]

(7)

[Chemical formula 10]

The method according to claim 1,
Wherein the difference in energy between singlet state and triplet state of the triarylboron compound is in the range of 0.001 to 0.3 eV.
The compound according to claim 1, wherein in formula (1)
The one side of D

And the angle of the back surface is in the range of 70 to 90 DEG.
An anode, a cathode, and an organic layer between both electrodes,
Wherein the organic layer comprises the triarylboron compound according to claim 1.
8. The method of claim 7,
Wherein the organic layer is a light emitting layer.
8. The method of claim 7,
And a first charge transport layer on the anode and the organic layer.
10. The method of claim 9,
Wherein the first charge transporting layer comprises at least one selected from the group consisting of a hole injecting layer and a hole transporting layer.
8. The method of claim 7,
And a second charge transport layer between the cathode and the organic layer.
12. The method of claim 11,
And the second charge transporting layer comprises at least one selected from the group consisting of an electron transporting layer and an electron injecting layer.
10. The method of claim 9,
And an electron blocking layer between the organic layer and the first charge transporting layer.
12. The method of claim 11,
And a hole blocking layer between the organic layer and the second charge transporting layer.

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