KR102164767B1 - Capping layer comprising an organic compound and organic electroluminescent device comprising the same - Google Patents

Abstract

The present application relates to a capping layer including a compound and an organic electroluminescent device including the same.

Description

A capping layer containing an organic compound and an organic electroluminescent device including the same {CAPPING LAYER COMPRISING AN ORGANIC COMPOUND AND ORGANIC ELECTROLUMINESCENT DEVICE COMPRISING THE SAME}

The present application relates to a capping layer including an organic compound and an organic electroluminescent device including the same. This application claims the benefit of the filing date of Korean Patent Application No. 10-2016-0045004 filed with the Korean Intellectual Property Office on April 12, 2016, all of which are incorporated in the specification.

An electroluminescent device is a type of self-luminous display device, and has the advantage of having a wide viewing angle, excellent contrast, and fast response speed.

The organic light emitting device has a structure in which an organic thin film is disposed between two electrodes. When a voltage is applied to the organic light-emitting device having such a structure, electrons and holes injected from the two electrodes are combined in the organic thin film to form a pair and then emit light while disappearing. The organic thin film may be composed of a single layer or multiple layers as needed, and a light extraction layer using a high refractive material is disposed on the opposite side of the electrode or a high heat-resistant organic layer for planarization is applied, and an organic material that can be used for the light extraction layer Research is ongoing to improve the refractive index and heat resistance.

Publication Patent Publication No. 2006-0059068

The present invention provides an organic electroluminescent device with high efficiency and long life by applying an organic compound having high refractive index and high heat resistance to a capping layer.

The present application provides a capping layer formed on a surface of a first electrode or a second electrode provided opposite to the first electrode, wherein the capping layer includes a compound represented by the following formula (1). .

[Formula 1]

In Formula 1,

X ₁ and X ₂ are the same as or different from each other, and each independently O or S,

L1 and L2 are the same as or different from each other, and each independently a direct bond; A substituted or unsubstituted secondary amine group; A substituted or unsubstituted arylene group; Or a substituted or unsubstituted heteroarylene group,

A is a substituted or unsubstituted secondary amine group; Or a substituted or unsubstituted heteroarylene group,

R1 to R8 are the same as or different from each other, and each independently hydrogen; heavy hydrogen; Halogen group; Nitrile group; Nitro group; Hydroxy group; Carbonyl group; Ester group; Imide group; Amide group; A substituted or unsubstituted alkyl group; A substituted or unsubstituted cycloalkyl group; A substituted or unsubstituted alkoxy group; A substituted or unsubstituted aryloxy group; A substituted or unsubstituted alkyl thioxy group; A substituted or unsubstituted arylthioxy group; A substituted or unsubstituted alkyl sulfoxy group; Substituted or unsubstituted arylsulfoxy group; A substituted or unsubstituted alkenyl group; A substituted or unsubstituted silyl group; A substituted or unsubstituted boron group; A substituted or unsubstituted amine group; A substituted or unsubstituted arylphosphine group; A substituted or unsubstituted phosphine oxide group; A substituted or unsubstituted aryl group; A substituted or unsubstituted heteroaryl group; Alternatively, adjacent groups may be bonded to each other to form a ring.

In addition, the present application is a first electrode; A second electrode provided to face the first electrode; At least one organic material layer provided between the first electrode and the second electrode; And a capping layer formed on a surface of the first electrode and/or the second electrode, wherein the organic electroluminescent device includes a capping layer including the compound according to Formula 1 above.

Since the capping layer according to the present invention includes the compound represented by Formula 1, it has high refractive index and high heat resistance.

In addition, the organic electroluminescent device according to the present invention provides an excellent light extraction effect by having a capping layer including the compound represented by Formula 1 above.

1 to 3 illustrate a stacking sequence of an electrode and an organic material layer of an organic light emitting device according to exemplary embodiments of the present invention.

Hereinafter, the present specification will be described in more detail.

An exemplary embodiment of the present specification provides a capping layer including the compound represented by Chemical Formula 1.

는 다른 치환기에 연결되는 부위를 의미한다.In this specification,

Means a moiety connected to another substituent.

In the present specification, the term "substituted or unsubstituted" refers to deuterium; Halogen group; Nitrile group; Nitro group; Amino group; Phosphine oxide group; Alkoxy group; Aryloxy group; Alkyl thioxy group; Arylthioxy group; Alkyl sulfoxy group; Arylsulfoxy group; Silyl group; Boron group; Alkyl group; Cycloalkyl group; Alkenyl group; Aryl group; Aralkyl group; Aralkenyl group; Alkylaryl group; Alkylamine group; Heteroarylamine group; Arylamine group; Or substituted or unsubstituted with one or more substituents selected from the group consisting of a heterocyclic group, or substituted or unsubstituted with a substituent to which two or more substituents are connected among the above-exemplified substituents. For example, "a substituent to which two or more substituents are connected" may be a biphenyl group. That is, the biphenyl group may be an aryl group or may be interpreted as a substituent to which two phenyl groups are connected.

In the present specification, examples of the halogen group include fluorine, chlorine, bromine or iodine.

In the present specification, the number of carbon atoms of the carbonyl group is not particularly limited, but from 1 to

It is preferably 40. Specifically, it may be a compound having the following structure, but is not limited thereto.

In the present specification, the ester group may be substituted with an oxygen of the ester group with a straight chain, branched or cyclic alkyl group having 1 to 25 carbon atoms or an aryl group having 6 to 25 carbon atoms. Specifically, it may be a compound of the following structural formula, but is not limited thereto.

In the present specification, the number of carbon atoms of the imide group is not particularly limited, but it is preferably 1 to 25 carbon atoms. Specifically, it may be a compound having the following structure, but is not limited thereto.

In the present specification, the silyl group is specifically trimethylsilyl group, triethylsilyl group, t-butyldimethylsilyl group, vinyldimethylsilyl group, propyldimethylsilyl group, triphenylsilyl group, diphenylsilyl group, phenylsilyl group, etc. However, it is not limited thereto.

In the present specification, the boron group specifically includes a trimethyl boron group, a triethyl boron group, a t-butyldimethyl boron group, a triphenyl boron group, and a phenyl boron group, but is not limited thereto.

In the present specification, the alkyl group may be a linear or branched chain, and the number of carbon atoms is not particularly limited, but is preferably 1 to 40. According to an exemplary embodiment, the alkyl group has 1 to 20 carbon atoms. According to another exemplary embodiment, the alkyl group has 1 to 10 carbon atoms. According to another exemplary embodiment, the alkyl group has 1 to 6 carbon atoms. According to another exemplary embodiment, the alkyl group has 3 or more carbon atoms. Specific examples of the alkyl group include methyl, ethyl, propyl, n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethyl-butyl, pentyl, n -Pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, heptyl , n-heptyl, 1-methylhexyl, cyclopentylmethyl, cycloheptylmethyl, octyl, n-octyl, tert-octyl, 1-methylhexyl, 2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2 -Dimethylheptyl, 1-ethyl-propyl, 1,1-dimethyl-propyl, isohexyl, 2-methylhexyl, 4-methylhexyl, 5-methylhexyl, and the like, but are not limited thereto.

In the present specification, the cycloalkyl group is not particularly limited, but is preferably 3 to 60 carbon atoms, and according to an exemplary embodiment, the cycloalkyl group has 3 to 30 carbon atoms. According to another exemplary embodiment, the number of carbon atoms of the cycloalkyl group is 3 to 20. According to another exemplary embodiment, the cycloalkyl group has 3 to 6 carbon atoms. Specifically, cyclopropyl, cyclobutyl, cyclopentyl, 3-methylcyclopentyl, 2,3-dimethylcyclopentyl, cyclohexyl, 3-methylcyclohexyl, 4-methylcyclohexyl, 2,3-dimethylcyclohexyl, 3, 4,5-trimethylcyclohexyl, 4-tert-butylcyclohexyl, cycloheptyl, cyclooctyl, and the like, but are not limited thereto.

In the present specification, the alkoxy group may be linear, branched or cyclic. The number of carbon atoms of the alkoxy group is not particularly limited, but it is preferably 1 to 20 carbon atoms. Specifically, methoxy, ethoxy, n-propoxy, isopropoxy, i-propyloxy, n-butoxy, isobutoxy, tert-butoxy, sec-butoxy, n-pentyloxy, neopentyloxy, Isopentyloxy, n-hexyloxy, 3,3-dimethylbutyloxy, 2-ethylbutyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, benzyloxy, p-methylbenzyloxy, etc. May be, but is not limited thereto.

In the present specification, the alkenyl group may be a linear or branched chain, and the number of carbon atoms is not particularly limited, but is preferably 2 to 40. According to an exemplary embodiment, the alkenyl group has 2 to 20 carbon atoms. According to another exemplary embodiment, the alkenyl group has 2 to 10 carbon atoms. According to another exemplary embodiment, the alkenyl group has 2 to 6 carbon atoms. Specific examples include vinyl, 1-propenyl, isopropenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 3-methyl-1- Butenyl, 1,3-butadienyl, allyl, 1-phenylvinyl-1-yl, 2-phenylvinyl-1-yl, 2,2-diphenylvinyl-1-yl, 2-phenyl-2-( Naphthyl-1-yl)vinyl-1-yl, 2,2-bis(diphenyl-1-yl)vinyl-1-yl, stilbenyl group, styrenyl group, and the like, but are not limited thereto.

In the present specification, the number of carbon atoms in the amine group is not particularly limited, but is preferably 1 to 30 carbon atoms. Specific examples of the amine group include, but are not limited to, a methylamine group, a dimethylamine group, an ethylamine group, and a diethylamine group.

In the present specification, the aryl group is not particularly limited, but is preferably 6 to 60 carbon atoms, and may be a monocyclic aryl group or a polycyclic aryl group. According to an exemplary embodiment, the aryl group has 6 to 30 carbon atoms. According to an exemplary embodiment, the aryl group has 6 to 20 carbon atoms. The aryl group may be a phenyl group, a biphenyl group, or a terphenyl group, but the monocyclic aryl group is not limited thereto. The polycyclic aryl group may be a naphthyl group, an anthracenyl group, a phenanthryl group, a pyrenyl group, a perylenyl group, a chrysenyl group, a fluorenyl group, and the like, but is not limited thereto.

In the present specification, the fluorenyl group may be substituted, and two substituents may be bonded to each other to form a spiro structure.

,

,

, 및

등이 될 수 있다. 다만, 이에 한정되는 것은 아니다.When the fluorenyl group is substituted,

,

,

, And

Etc. However, it is not limited thereto.

In the present specification, the heterocyclic group is a heterocyclic group containing at least one of O, N and S as a heterogeneous element, and the number of carbon atoms is not particularly limited, but it is preferably 2 to 60 carbon atoms. Examples of heterocyclic groups include thiophene group, furan group, pyrrole group, imidazole group, thiazole group, oxazole group, oxadiazole group, triazole group, pyridyl group, bipyridyl group, pyrimidyl group, triazine group, triazole group, Acridyl group, pyridazine group, pyrazinyl group, quinolinyl group, quinazoline group, quinoxalinyl group, phthalazinyl group, pyrido pyrimidinyl group, pyrido pyrazinyl group, pyrazino pyrazinyl group, isoquinoline group , Indole group, carbazole group, benzoxazole group, benzoimidazole group, benzothiazole group, benzocarbazole group, benzothiophene group, dibenzothiophene group, benzofuranyl group, phenanthroline group, thiazolyl group, Isoxazolyl group, oxadiazolyl group, thiadiazolyl group, benzothiazolyl group, phenothiazinyl group, dibenzofuranyl group, and the like, but are not limited thereto.

In the present specification, the aryl group among the aryloxy group, arylthioxy group, arylsulfoxy group, arylphosphine group, aralkyl group, aralkylamine group, aralkenyl group, alkylaryl group, and arylamine group same.

In the present specification, among the alkyl thioxy group, alkyl sulfoxy group, aralkyl group, aralkylamine group, alkylaryl group, and alkylamine group, the alkyl group is the same as the exemplary alkyl group described above.

In the present specification, the heteroaryl group among the heteroarylamine groups may be described above for the heterocyclic group.

In the present specification, the alkenyl group of the aralkenyl group is the same as the example of the alkenyl group described above.

In the present specification, the meaning of bonding with adjacent groups to form a ring means a substituted or unsubstituted aliphatic hydrocarbon ring by bonding with adjacent groups; A substituted or unsubstituted aromatic hydrocarbon ring; Substituted or unsubstituted aliphatic heterocycle; Or it means to form a substituted or unsubstituted aromatic heterocycle.

In the present specification, the "adjacent group" refers to a substituent substituted on an atom directly connected to the atom where the corresponding substituent is substituted, a substituent positioned three-dimensionally closest to the corresponding substituent, or another substituent substituted on the atom where the corresponding substituent is substituted. It can mean. For example, two substituents substituted with an ortho position in a benzene ring and two substituents substituted with the same carbon in an aliphatic ring may be interpreted as "adjacent groups".

In the present specification, the aliphatic hydrocarbon ring is a ring that is not aromatic and refers to a ring consisting only of carbon and hydrogen atoms.

In the present specification, examples of the aromatic hydrocarbon ring include a phenyl group, a naphthyl group, and an anthracenyl group, but are not limited thereto.

In the present specification, the aliphatic heterocycle refers to an aliphatic ring including one or more of N, O, or S atoms as a heteroatom.

In the present specification, the aromatic heterocycle refers to an aromatic ring including at least one of N, O, or S atoms as a heteroatom.

In the present specification, the aliphatic hydrocarbon ring, aromatic hydrocarbon ring, aliphatic hetero ring and aromatic hetero ring may be monocyclic or polycyclic.

In the exemplary embodiment of the present specification, X ₁ and X ₂ are O.

In the exemplary embodiment of the present specification, X ₁ and X ₂ are S.

In the exemplary embodiment of the present specification, one of X ₁ and X ₂ is O, and the other is S.

In the exemplary embodiment of the present specification, L1 and L2 are the same as or different from each other, and each independently a direct bond; A substituted or unsubstituted arylene group; Or a substituted or unsubstituted heteroarylene group.

In the exemplary embodiment of the present specification, L1 and L2 are the same as or different from each other, and each independently a direct bond; A substituted or unsubstituted arylene group having 6 to 30 carbon atoms; Or a substituted or unsubstituted heteroarylene group having 2 to 30 carbon atoms.

In the exemplary embodiment of the present specification, L1 and L2 are the same as or different from each other, and each independently a direct bond; Arylene group; Or a heteroarylene group.

In the exemplary embodiment of the present specification, L1 and L2 are the same as or different from each other, and each independently a substituted or unsubstituted arylene group.

In the exemplary embodiment of the present specification, L1 and L2 are the same as or different from each other, and each independently a direct bond; A substituted or unsubstituted phenylene group; A substituted or unsubstituted biphenyl group; A substituted or unsubstituted terphenyl group; A substituted or unsubstituted naphthalene group; A substituted or unsubstituted fluorene group; A substituted or unsubstituted anthracene group; A substituted or unsubstituted phenanthrene group; Or a substituted or unsubstituted triphenylene group.

In the exemplary embodiment of the present specification, L1 and L2 are the same as or different from each other, and each independently a substituted or unsubstituted phenylene group; A substituted or unsubstituted biphenyl group; A substituted or unsubstituted terphenyl group; A substituted or unsubstituted naphthalene group; A substituted or unsubstituted fluorene group; A substituted or unsubstituted anthracene group; A substituted or unsubstituted phenanthrene group; Or a substituted or unsubstituted triphenylene group.

In the exemplary embodiment of the present specification, L1 and L2 are the same as or different from each other, and each independently a phenylene group; Biphenyl group; Terphenyl group; Naphthalene group; Fluorene group; Anthracene group; Phenanthrene group; Or a triphenylene group.

In the exemplary embodiment of the present specification, L1 and L2 are the same as or different from each other, and each independently a phenylene group; Or it is a naphthalene group..

In the exemplary embodiment of the present specification, L1 and L2 are the same as each other.

In the exemplary embodiment of the present specification, A is -NH-; Carbon number is 1 to 60 inch ring or unsubstituted alkylamine group; A substituted or unsubstituted arylamine group having 6 to 60 carbon atoms; The number of carbon atoms is a substituted or unsubstituted heteroarylamine group having 2 to 60 carbon atoms or a substituted or unsubstituted heterocyclic group having 2 to 60 carbon atoms including at least one atom selected from the group consisting of O, N, S, and Se.

In the exemplary embodiment of the present specification, A is -NH-; A substituted or unsubstituted alkylamine group having 1 to 30 carbon atoms; A substituted or unsubstituted arylamine group having 6 to 30 carbon atoms; The number of carbon atoms is a substituted or unsubstituted heteroarylamine group having 2 to 30 carbon atoms or a substituted or unsubstituted heterocyclic group having 2 to 30 carbon atoms including at least one atom selected from the group consisting of O, N, S, and Se.

In the exemplary embodiment of the present specification, A is a substituted or unsubstituted arylamine group having 6 to 30 carbon atoms; Or a substituted or unsubstituted heterocyclic group having 2 to 30 carbon atoms including one or more atoms selected from the group consisting of O, N, S, and Se.

In the exemplary embodiment of the present specification, A is a substituted or unsubstituted phenylamine group; A substituted or unsubstituted biphenylamine group; A substituted or unsubstituted triazine group; A substituted or unsubstituted dibenzofuran group; A substituted or unsubstituted carbazole group; A substituted or unsubstituted dibenzothiophene group; Or a substituted or unsubstituted benzocarbazole group.

In the exemplary embodiment of the present specification, A is a phenylamine group; Biphenylamine group; A triazine group unsubstituted or substituted with an aryl group; Dibenzofuran group; A carbazole group unsubstituted or substituted with an aryl group; Dibenzothiophene group; Or a benzocarbazole group unsubstituted or substituted with an aryl group.

In the exemplary embodiment of the present specification, A is a phenylamine group; Biphenylamine group; A triazine group unsubstituted or substituted with a substituent selected from the group consisting of a phenyl group, a biphenyl group, and a naphthyl group; Dibenzofuran group; A carbazole group unsubstituted or substituted with a substituent selected from the group consisting of a phenyl group, a biphenyl group, and a naphthyl group; Dibenzothiophene group; Or a benzocarbazole group unsubstituted or substituted with a substituent selected from the group consisting of a phenyl group, a biphenyl group, and a naphthyl group.

In the exemplary embodiment of the present specification, R1 to R8 are the same as or different from each other, and each independently hydrogen; Or deuterium.

In an exemplary embodiment of the present specification, R1 to R8 are hydrogen.

In an exemplary embodiment of the present specification, the compound of Formula 1 may be selected from the following structural formulas.

In addition, the present specification provides an organic electroluminescent device including the capping layer described above.

In one embodiment of the present specification, the first electrode; A second electrode provided to face the first electrode; At least one organic material layer provided between the first electrode and the second electrode; And a capping layer formed on the surface of the first electrode and/or the second electrode, wherein the organic electroluminescent device includes a capping layer containing the compound of Formula 1 above.

The organic material layer of the organic light emitting device of the present specification may have a single-layer structure, but may have a multilayer structure in which two or more organic material layers are stacked. For example, the organic electroluminescent device of the present invention may have a structure including a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and the like as an organic material layer. However, the structure of the organic light emitting device is not limited thereto, and may include a smaller number of organic material layers.

In the exemplary embodiment of the present specification, the organic material layer further includes one or two or more layers from the group consisting of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer.

In an exemplary embodiment, the organic material layer includes an emission layer, and the emission layer includes a compound represented by Formula A-1 below.

[Formula A-1]

In the formula A-1,

n is an integer greater than or equal to 1,

Ar1 is a substituted or unsubstituted monovalent or more benzofluorene group; A substituted or unsubstituted monovalent or more fluoranthene group; A substituted or unsubstituted monovalent or higher pyrene group; Or a substituted or unsubstituted monovalent or higher chrysene group,

L3 is a direct bond; A substituted or unsubstituted arylene group; Or a substituted or unsubstituted heteroarylene group,

Ar2 and Ar3 are the same as or different from each other, and each independently a substituted or unsubstituted aryl group; A substituted or unsubstituted silyl group; A substituted or unsubstituted alkyl group; A substituted or unsubstituted arylalkyl group; Or a substituted or unsubstituted heteroaryl group, or may be bonded to each other to form a substituted or unsubstituted ring,

When n is 2 or more, the structures in parentheses are the same as or different from each other.

In an exemplary embodiment, the organic material layer includes an emission layer, and the emission layer includes the compound represented by Formula A-1 as a dopant of the emission layer.

According to an exemplary embodiment, L3 is a direct bond.

According to an exemplary embodiment, n is 2.

In an exemplary embodiment, Ar1 is a divalent pyrene group unsubstituted or substituted with deuterium, methyl group, ethyl group, isopropyl group, or tert-butyl group; Or a divalent chrysene group unsubstituted or substituted with deuterium, methyl group, ethyl group, isopropyl group, or tert-butyl group.

In an exemplary embodiment, Ar1 is a divalent pyrene group unsubstituted or substituted with a methyl group.

According to an exemplary embodiment, Ar2 and Ar3 are the same as or different from each other, and each independently a substituted or unsubstituted aryl group having 6 to 30 carbon atoms.

According to an exemplary embodiment, Ar2 and Ar3 are the same as or different from each other, and are each independently an aryl group unsubstituted or substituted with an alkyl group.

In one embodiment, Ar2 and Ar3 are the same as or different from each other, and each independently a methyl group, an ethyl group, or an isopropyl group substituted or unsubstituted aryl group.

According to an exemplary embodiment, Ar2 and Ar3 are the same as or different from each other, and each independently a phenyl group unsubstituted or substituted with a methyl group.

According to an exemplary embodiment, Ar2 and Ar3 are the same as or different from each other, and are each independently a biphenyl group unsubstituted or substituted with a methyl group.

According to an exemplary embodiment, Ar2 and Ar3 are the same as or different from each other, and each independently a methyl group substituted or unsubstituted terphenyl group.

In one embodiment, Formula A-1 is selected from the following compounds.

In an exemplary embodiment, the organic material layer includes an emission layer, and the emission layer includes a compound represented by Formula A-2 below.

[Formula A-2]

In Formula A-2,

Ar4 and Ar5 are the same as or different from each other, and each independently a substituted or unsubstituted monocyclic aryl group; Or a substituted or unsubstituted polycyclic aryl group,

G1 to G8 are the same as or different from each other, and each independently hydrogen; A substituted or unsubstituted monocyclic aryl group; Or a substituted or unsubstituted polycyclic aryl group.

In one embodiment, the organic material layer includes an emission layer, and the emission layer includes the compound represented by Formula A-2 as a host of the emission layer.

In an exemplary embodiment of the present invention, Ar4 and Ar5 are the same as or different from each other, and each independently a substituted or unsubstituted polycyclic aryl group.

In an exemplary embodiment, Ar4 and Ar5 are the same as or different from each other, and each independently a substituted or unsubstituted naphthyl group.

In an exemplary embodiment of the present invention, Ar4 and Ar5 are the same as or different from each other, and each independently a substituted or unsubstituted 2-naphthyl group.

According to an exemplary embodiment, Ar4 and Ar5 are 2-naphthyl groups.

In an exemplary embodiment, G1 to G8 are the same as or different from each other, and each independently hydrogen; Or a substituted or unsubstituted polycyclic aryl group.

According to an exemplary embodiment, G1 to G8 are hydrogen.

In an exemplary embodiment of the present invention, Formula A-2 is selected from the following compounds.

In an exemplary embodiment, the organic material layer includes an emission layer, the emission layer includes the compound represented by Formula A-1 as a dopant of the emission layer, and the compound represented by Formula A-2 as a host of the emission layer. .

In another exemplary embodiment, the organic light emitting device may be a normal type organic light emitting device in which an anode, one or more organic material layers, and a cathode are sequentially stacked on a substrate.

In another embodiment, the organic light emitting device may be an inverted type organic light emitting device in which a cathode, one or more organic material layers, and an anode are sequentially stacked on a substrate.

1 to 3 illustrate a stacking sequence of an electrode and an organic material layer of an organic light emitting device according to exemplary embodiments of the present invention. However, it is not intended that the scope of the present invention be limited by these drawings, and the structure of an organic electroluminescent device known in the art can be applied to the present invention.

Referring to FIG. 1, an organic light emitting device in which an anode 200, an organic material layer 300, a cathode 400, and a capping layer 500 are sequentially stacked on a substrate 100 is shown. However, it is not limited to such a structure, and as shown in FIG. 2, an organic light emitting device in which a cathode, an organic material layer, an anode, and a doping layer are sequentially stacked on a substrate may be implemented.

3 illustrates a case in which the organic material layer is a multilayer. The organic electroluminescent device according to FIG. 3 includes a hole injection layer 301, a hole transport layer 302, a light emitting layer 303, an electron transport layer 304, and an electron injection layer 305. However, the scope of the present invention is not limited by such a lamination structure, and other layers other than the light emitting layer may be omitted, or other necessary functional layers may be further added as necessary.

Except that the organic electroluminescent device capping layer of the present specification includes the compound represented by Formula 1 above, it may be manufactured by materials and methods known in the art.

The capping layer of the present specification is formed by laminating a high refractive organic material to a predetermined thickness.

In one embodiment of the present specification, the thickness of the capping layer is 100Å to 2000Å.

The capping layer may be formed of one selected from materials consisting of an arylene amine derivative, a triamine derivative, CBP or a quinoline-aluminum complex (Alq ₃ ).

For example, the organic electroluminescent device of the present specification may be manufactured by sequentially laminating a first electrode, an organic material layer, and a second electrode on a substrate. At this time, using a PVD (Physical Vapor Deposition) method such as sputtering or e-beam evaporation, the anode is formed by depositing a metal or a conductive metal oxide or an alloy thereof on the substrate. Then, after forming an organic material layer including a hole injection layer, a hole transport layer, a light emitting layer and an electron transport layer thereon, a material that can be used as a cathode is deposited thereon, and then a capping layer is formed thereon. In addition to such a method, an organic light emitting device may be manufactured by sequentially depositing a cathode material, an organic material layer, an anode material, and a capping layer on a substrate.

In addition, the compound of Formula 1 may be formed as an organic material layer by a solution coating method as well as a vacuum deposition method when the organic electroluminescent device is manufactured. Here, the solution coating method refers to spin coating, dip coating, doctor blading, inkjet printing, screen printing, spray method, roll coating, and the like, but is not limited thereto.

In addition to this method, an organic light emitting device may be manufactured by sequentially depositing an organic material layer, an anode material, and a capping layer from a cathode material on a substrate. However, the manufacturing method is not limited thereto.

In the exemplary embodiment of the present specification, the first electrode is an anode, the second electrode is a cathode, and the capping layer is formed on a surface of the first electrode.

In another exemplary embodiment, the first electrode is a cathode, the second electrode is an anode, and the capping layer is formed on a surface of the first electrode.

As the anode material, a material having a large work function is preferable so that holes can be smoothly injected into the organic material layer. Specific examples of the cathode material that can be used in the present invention include metals such as vanadium, chromium, copper, zinc, and gold, or alloys thereof; Metal oxides such as zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); A combination of a metal and oxide such as ZnO:Al or SnO2:Sb; Poly(3-methylthiophene), poly[3,4-(ethylene-1,2-dioxy)thiophene] (PEDOT), conductive polymers such as polypyrrole and polyaniline, and the like, but are not limited thereto.

It is preferable that the cathode material is a material having a small work function to facilitate electron injection into the organic material layer. Specific examples of the negative electrode material include metals such as magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin, and lead, or alloys thereof; There are a multilayered material such as LiF/Al or LiO2/Al, but are not limited thereto.

The hole injection layer is a layer that injects holes from the electrode, and has the ability to transport holes as a hole injection material, and thus has a hole injection effect at the anode, an excellent hole injection effect for the light emitting layer or the light emitting material, and is generated from the light emitting layer. A compound that prevents the movement of excitons to the electron injection layer or the electron injection material and has excellent ability to form a thin film is preferable. It is preferable that the HOMO (highest occupied molecular orbital) of the hole injection material is between the work function of the positive electrode material and the HOMO of the surrounding organic material layer. Specific examples of hole injection materials include metal porphyrin, oligothiophene, arylamine-based organic substances, hexanitrile hexaazatriphenylene-based organic substances, quinacridone-based organic substances, and perylene-based organic substances. Organic substances, anthraquinone, polyaniline, and polythiophene-based conductive polymers, but are not limited thereto.

The hole transport layer is a layer that receives holes from the hole injection layer and transports holes to the emission layer, and the hole transport material is a material capable of transporting holes from the anode or the hole injection layer to the emission layer, and has high mobility for holes. The material is suitable. Specific examples include an arylamine-based organic material, a conductive polymer, and a block copolymer including a conjugated portion and a non-conjugated portion, but are not limited thereto.

The light-emitting material is a material capable of emitting light in a visible light region by transporting and bonding holes and electrons from the hole transport layer and the electron transport layer, respectively, and a material having good quantum efficiency for fluorescence or phosphorescence is preferable. Specific examples include 8-hydroxy-quinoline aluminum complex (Alq ₃ ); Carbazole-based compounds; Dimerized styryl compounds; BAlq; 10-hydroxybenzo quinoline-metal compound; Benzoxazole, benzthiazole, and benzimidazole-based compounds; Poly(p-phenylenevinylene) (PPV)-based polymer; Spiro compounds; Polyfluorene, rubrene, and the like, but are not limited thereto.

The emission layer may include a host material and a dopant material. Host materials include condensed aromatic ring derivatives or heterocyclic-containing compounds. Specifically, condensed aromatic ring derivatives include anthracene derivatives, pyrene derivatives, naphthalene derivatives, pentacene derivatives, phenanthrene compounds, and fluoranthene compounds, and heterocycle-containing compounds include carbazole derivatives, dibenzofuran derivatives, ladder type Furan compounds, pyrimidine derivatives, and the like, but are not limited thereto.

Dopant materials include aromatic amine derivatives, styrylamine compounds, boron complexes, fluoranthene compounds, and metal complexes. Specifically, the aromatic amine derivative is a condensed aromatic ring derivative having a substituted or unsubstituted arylamino group, and includes pyrene, anthracene, chrysene, and periflanthene having an arylamino group, and the styrylamine compound is substituted or unsubstituted A compound in which at least one arylvinyl group is substituted on the arylamine, and one or two or more substituents selected from the group consisting of aryl group, silyl group, alkyl group, cycloalkyl group and arylamino group are substituted or unsubstituted. Specifically, there are styrylamine, styryldiamine, styryltriamine, styryltetraamine, and the like, but are not limited thereto. In addition, the metal complex includes an iridium complex, a platinum complex, and the like, but is not limited thereto.

The electron transport layer is a layer that receives electrons from the electron injection layer and transports electrons to the emission layer. As an electron transport material, a material capable of receiving electrons from the cathode and transferring them to the emission layer. Suitable. Specific examples include the Al complex of 8-hydroxyquinoline; Complexes including Alq3; Organic radical compounds; Hydroxyflavone-metal complexes and the like, but are not limited thereto. The electron transport layer can be used with any desired cathode material as used according to the prior art. In particular, examples of suitable cathode materials are conventional materials that have a low work function and are followed by an aluminum layer or a silver layer. Specifically, they are cesium, barium, calcium, ytterbium, and samarium, and in each case an aluminum layer or a silver layer follows.

The electron injection layer is a layer that injects electrons from the electrode, has the ability to transport electrons, has an electron injection effect from the cathode, an excellent electron injection effect on the light emitting layer or light emitting material, and injects holes of excitons generated from the light emitting layer. A compound that prevents migration to the layer and has excellent thin film formation ability is preferable. Specifically, fluorenone, anthraquinodimethane, diphenoquinone, thiopyran dioxide, oxazole, oxadiazole, triazole, imidazole, perylenetetracarboxylic acid, preorenylidene methane, anthrone, and their derivatives, metals Complex compounds and nitrogen-containing 5-membered ring derivatives, but are not limited thereto.

Examples of the metal complex compound include lithium 8-hydroxyquinolinato, bis(8-hydroxyquinolinato)zinc, bis(8-hydroxyquinolinato)copper, bis(8-hydroxyquinolinato)manganese, Tris(8-hydroxyquinolinato)aluminum, tris(2-methyl-8-hydroxyquinolinato)aluminum, tris(8-hydroxyquinolinato)gallium, bis(10-hydroxybenzo[h] Quinolinato)beryllium, bis(10-hydroxybenzo[h]quinolinato)zinc, bis(2-methyl-8-quinolinato)chlorogallium, bis(2-methyl-8-quinolinato)( o-cresolato)gallium, bis(2-methyl-8-quinolinato)(1-naphtholato)aluminum, bis(2-methyl-8-quinolinato)(2-naphtholato)gallium, etc. It is not limited to this.

The organic electroluminescent device according to the present specification may be a top emission type, a bottom emission type, or a double-sided emission type depending on the material used.

In the exemplary embodiment of the present specification, the compound of Formula 1 may be included in an organic solar cell or an organic transistor in addition to the organic electroluminescent device.

Hereinafter, the present specification will be described in detail with reference to understanding examples. However, the embodiments according to the present specification may be modified in various forms, and the scope of the present application is not construed as being limited to the embodiments described below. The embodiments of the present application are provided to more completely describe the present specification to those of ordinary skill in the art.

<Preparation Example 1> Preparation of Formula A

[Formula A]

2-(4-bromophenyl)-benzoxazole (10g, 36.5mmol), bis(pinacolato)diboron (9.7g, 38.3mmol) and potassium acetate (10.7g, 109.4mmol) were 1,4- After adding to dioxane (383ml, 0.1M) and stirring the suspension. Pd(dppf)Cl ₂ (267mg, 0.36mmol) was added and heated and stirred at 100°C for 8 hours. After the reaction solution was cooled to room temperature, H ₂ O (300ml) was added, stirred for 10 minutes, extracted with THF, the water layer was removed, and the organic layer was treated with MgSO ₄ and concentrated. After crystallization with ethanol (150ml), the resultant was filtered to obtain formula A (10.1g, yield 86%).

MS:[M+H]+=322

<Production Example 2> Preparation of Formula B

[Formula B]

Formula B was synthesized in the same manner as in Formula A, except that 2-(4-bromophenyl)-benzthiazole was used instead of 2-(4-bromophenyl)-benzoxazole.

MS:[M+H]+=338

<Preparation Example 3> Preparation of Chemical Formula C

[화학식 C]

[Formula C]

Formula C was synthesized in the same manner as in Formula A, except that 2-(6-bromonaphthyl)-benzoxazole was used instead of 2-(4-bromophenyl)-benzoxazole.

MS:[M+H]+=372

<Preparation Example 4> Preparation of Formula D

[Formula D]

Formula D was synthesized in the same manner as in Formula A, except that 2-(6-bromonaphthyl)-benzthiazole was used instead of 2-(4-bromophenyl)-benzoxazole.

MS:[M+H]+=388

<Preparation Example 5> Preparation of Formulas E and F

[Formula E] [Formula F]

4-bromophenol (20g, 115.6mmol), aniline (5.4g, 57.8mmol) and sodium

tert-butoxide (16.7g, 173.4mmol) was added to toluene (578ml, 0.1 M), suspended and stirred for 10 minutes, bis(tri-tertbutylphosphine) palladium (591mg, 1.16mmol) was added and heated and stirred for 4 hours. I did. After the reaction was completed, the temperature was lowered to room temperature, filtered, washed several times with H ₂ O and ethanol, and purified by column with THF/hexane: 1/6 to obtain Formula E (7.2 g, yield: 45%).

MS:[M+H]+=278

Formula E (7g, 25.2mmol) was added to methylene chloride (252ml, 0.1M) and an ice bath was set to set the internal temperature to 0, followed by pyridine (4.4g, 55.5mmol) and stirred for 10 minutes. . Cryfluoromethanesulphonic anhydride (15.6g. 55.5mmol) was slowly added for 15 minutes, followed by stirring for 1 hour. After raising the temperature to room temperature, a 1M solution of sodium bicarbonate (150ml) was added and stirred for 5 minutes. The water layer was removed, and the organic layer was treated with MgSO ₄ and concentrated. After crystallization with ethanol (150ml), the resultant was filtered to obtain Formula F (12.7g, yield 93%).

MS:[M+H]+=542

<Preparation Example 6> Preparation of Chemical Formula 1-9

Formula F (10g, 18.5mmol), Formula A (10.6g, 38.8mmol) was dissolved in tetrahydrofuran (185mL, 0.1M), and K ₂ CO ₃ /H ₂ O 0.5M aqueous solution (200 mL) and Pd( PPh ₃ ) ₄ (641mg, 0.56mmol) was added and refluxed for 5 hours. After the reaction was completed, the aqueous layer was separated and filtered. The filtered solid was purified by column with tetrahydrofuran/hexane = 1/2 to obtain Chemical Formula 1-9 (8.8g, yield 75%).

MS: {M+H}+ = 632

<Preparation Example 7> Preparation of Chemical Formula 1-16

Formula 1-16 was prepared in the same manner as in Formula 1-9 except that 2,4-dichloro-6-(biphenyl-4-yl)-1,3,5-triazine was used instead of Formula F. .

MS: {M+H}+ = 620

<Preparation Example 8> Preparation of Chemical Formula 1-24

Formula 1-24 was prepared in the same manner as in Formula 1-9 except that 3,6-dibromobenzofuran was used instead of Formula F and Formula B was used instead of Formula A.

MS: {M+H}+ = 587

<Preparation Example 9> Preparation of Chemical Formula 1-30

Chemical formula 1-30 in the same manner as in the preparation method of Chemical Formula 1-9, except that 3,6-dibromo-N-(biphenyl-4-yl)-carbazole is used instead of Chemical Formula F and Chemical Formula B is used instead of Chemical Formula A. Was prepared.

MS: {M+H}+ = 738

<Preparation Example 10> Preparation of Chemical Formula 1-31

Formula 1-31 was prepared in the same manner as in Formula 1-9 except that 3,6-dibromo-N-(2-naphthyl)-carbazole was used instead of Formula F.

MS: {M+H}+ = 680

<Preparation Example 11> Preparation of Chemical Formula 1-46

Formula 1-46 was prepared in the same manner as in Formula 1-9 except that 3,6-dibromo-N-phenylcarbazole was used instead of Formula F and Formula C was used instead of Formula A.

MS: {M+H}+ = 730

<Preparation Example 12> Preparation of Chemical Formula 1-56

[Chemical Formula G]

Formula G was prepared in the same manner as in Formula 1-9 except that 3-bromo-N-(phenyl)-benzocarbazole was used instead of Formula F and Formula C was used instead of Formula A.

MS: {M+H}+ = 537

[Formula H]

Formula G (10g, 18.6mmol) was added to methylene chloride (186ml, 0.1M), stirred at room temperature to dissolve, and then N-bromosuccinimide (3.3g, 18.6mmol) was slowly added dropwise and stirred at room temperature for 3 minutes. I did. An aqueous solution in which an excess of sodium phosphate dihydrate was added to water (300ml) was slowly added dropwise, followed by stirring for 30 minutes. After removing the water layer, MgSO ₄ treatment, and the organic layer was distilled under reduced pressure. The distilled solid was purified by column with tetrahydrofuran/hexane = 1/2 to obtain Chemical Formula H (10.2 g, yield 89%).

MS: {M+H}+ = 616

Formula 1-56 was prepared in the same manner as in Formula 1-9 except that Formula H instead of Formula F and Formula D instead of Formula A were used.

MS: {M+H}+ = 796

<Comparative Example 1>

A glass substrate coated with a thin film of 1,500Å of ITO (indium tin oxide) was placed in distilled water dissolved in a detergent and washed with ultrasonic waves. At this time, a product made by Fisher Co. was used as a detergent, and distilled water secondarily filtered with a filter made by Millipore Co. was used. After washing the ITO for 30 minutes, it was repeated twice with distilled water to perform ultrasonic cleaning for 10 minutes. After washing with distilled water, ultrasonic cleaning was performed with a solvent of isopropyl alcohol, acetone, and methanol, dried, and then transported to a plasma cleaner. After cleaning the substrate for 5 minutes using oxygen plasma, the substrate was transported to a vacuum evaporator.

On the thus prepared ITO transparent electrode, hexanitrile hexaazatriphenylene was thermally vacuum deposited to a thickness of 500 Å to form a hole injection layer. After vacuum deposition of NPB (400 Å), which is a material for transporting holes, thereon, a dopant D1 (4 wt%) was deposited (300 Å) with the following compound H1 to form a light emitting layer.

[Hexanitrile hexaazatriphenylene]

[NPB]

[D1] [H1]

[E1] [Alq ₃ ]

Compound E1 was vacuum-deposited to a thickness of 200 Å on the emission layer to form an electron injection and transport layer. Lithium fluoride (LiF) having a thickness of 12 Å and aluminum having a thickness of 2,000 Å were sequentially deposited on the electron injection and transport layer to form a cathode.

In the above process, the deposition rate of the organic material was maintained at 1 Å/sec, the deposition rate of lithium fluoride was 0.2 Å/sec, and the deposition rate was 3 to 7 Å/sec for aluminum.

As a result of applying a forward electric field of 7.6V to the organic electroluminescent device manufactured above, blue light emission of 3.1 cd/A corresponding to x=0.154 and y=0.192 based on 1931 CIE color coordination was observed at a current density of 10mA/cm2. Became.

<Comparative Example 2>

After fabricating an organic electroluminescent device in the same manner as in Comparative Example 1, Alq ₃ was vacuum-deposited on an aluminum cathode at 600 Å to form a capping layer.

As a result of applying a forward electric field of 7.6V to the organic electroluminescent device manufactured above, blue light emission of 4.0cd/A corresponding to x=0.135 and y=0.098 based on 1931 CIE color coordination at a current density of 9.3mA/cm2 Was observed.

<Experimental Example 1-1>

After fabricating an organic electroluminescent device in the same manner as in Comparative Example 1, formula 1-9 was vacuum-deposited at 600 Å on an aluminum cathode to form a capping layer.

As a result of applying a forward electric field of 7.6V to the organic electroluminescent device manufactured above, blue light emission of 3.4cd/A corresponding to x=0.145 and y=0.158 based on 1931 CIE color coordination at a current density of 9.4mA/cm2 Was observed.

<Experimental Example 1-2>

After fabricating an organic electroluminescent device in the same manner as in Comparative Example 1, formula 1-16 was vacuum-deposited on an aluminum cathode at 600 Å to form a capping layer.

As a result of applying a forward electric field of 7.6V to the organic electroluminescent device manufactured above, blue light emission of 3.7cd/A corresponding to x=0.145 and y=0.138 based on 1931 CIE color coordination at a current density of 9.4mA/cm2 Was observed.

<Experimental Example 1-3>

After fabricating an organic electroluminescent device in the same manner as in Comparative Example 1, formula 1-24 was vacuum-deposited on an aluminum cathode at 600 Å to form a capping layer.

As a result of applying a forward electric field of 7.6V to the organic electroluminescent device manufactured above, blue light emission of 5.0 cd/A corresponding to x=0.138 and y=0.105 based on 1931 CIE color coordination at a current density of 9.3mA/cm2 Was observed.

<Experimental Example 1-4>

After fabricating an organic light-emitting device in the same manner as in Comparative Example 1, Formula 1-30 was vacuum-deposited at 600 Å on an aluminum cathode to form a capping layer.

As a result of applying a forward electric field of 7.6V to the organic electroluminescent device manufactured above, blue light emission of 4.9 cd/A corresponding to x=0.141 and y=0.112 based on 1931 CIE color coordination at a current density of 8.8mA/cm2 Was observed.

<Experimental Example 1-5>

After fabricating an organic light-emitting device in the same manner as in Comparative Example 1, Formula 1-31 was vacuum-deposited at 600 Å on an aluminum cathode to form a capping layer.

As a result of applying a forward electric field of 7.7V to the organic electroluminescent device manufactured above, blue light emission of 5.1cd/A corresponding to x=0.138 and y=0.096 based on 1931 CIE color coordination at a current density of 8.6mA/cm2 Was observed.

<Experimental Example 1-6>

After fabricating an organic electroluminescent device in the same manner as in Comparative Example 1, formula 1-46 was vacuum-deposited at 600 Å on an aluminum cathode to form a capping layer.

As a result of applying a forward electric field of 7.7V to the organic light emitting device manufactured above, blue light emission of 5.4 cd/A corresponding to x=0.135 and y=0.094 based on 1931 CIE color coordination at a current density of 8.6mA/cm2 was observed. Became.

<Experimental Example 1-7>

After fabricating an organic light-emitting device in the same manner as in Comparative Example 1, formula 1-56 was vacuum-deposited at 600 Å on an aluminum cathode to form a capping layer.

As a result of applying a forward electric field of 7.7V to the organic electroluminescent device manufactured above, blue light emission of 5.8cd/A corresponding to x=0.134 and y=0.094 based on 1931 CIE color coordination at a current density of 8.3mA/cm2 Was observed.

100: substrate
200: anode
300: organic material layer
301: hole injection layer
302: hole transport layer
303: light emitting layer
304: electron transport layer
305: electron injection layer
400: cathode
500: capping layer

Claims (14)

In the capping layer formed on the surface of the first electrode or the second electrode provided to face the first electrode,
The capping layer is a capping layer, characterized in that it comprises a compound represented by the following formula (1):
[Formula 1]

In Formula 1,
X ₁ and X ₂ are the same as or different from each other, and each independently O or S,
L1 and L2 are the same as or different from each other, and each independently an arylene group,
A is a triazine group substituted with an aryl group,
R1 to R8 are hydrogen. delete delete The method according to claim 1,
Wherein L1 and L2 are the same as or different from each other, and each independently a capping layer comprising a compound of an arylene group having 6 to 30 carbon atoms. delete delete The method according to claim 1,
The compound represented by Formula 1 is a capping layer comprising a compound selected from the following structural formulas:

A first electrode; A second electrode provided to face the first electrode; At least one organic material layer provided between the first electrode and the second electrode; And a capping layer formed on the surface of the first electrode and the second electrode, wherein the organic electroluminescent device comprises a capping layer according to any one of claims 1, 4 and 7. The organic electroluminescent device of claim 8, wherein the organic material layer further comprises one or two or more layers from the group consisting of a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and an electron injection layer. The organic electroluminescent device of claim 8, wherein the organic material layer includes an emission layer, and the emission layer includes a compound represented by Formula A-1:
[Formula A-1]

In the formula A-1,
n is an integer greater than or equal to 1,
Ar1 is a substituted or unsubstituted monovalent or more benzofluorene group; A substituted or unsubstituted monovalent or more fluoranthene group; A substituted or unsubstituted monovalent or higher pyrene group; Or a substituted or unsubstituted monovalent or higher chrysene group,
L3 is a direct bond; A substituted or unsubstituted arylene group; Or a substituted or unsubstituted heteroarylene group,
Ar2 and Ar3 are the same as or different from each other, and each independently a substituted or unsubstituted aryl group; A substituted or unsubstituted silyl group; A substituted or unsubstituted alkyl group; A substituted or unsubstituted arylalkyl group; Or a substituted or unsubstituted heteroaryl group, or may be bonded to each other to form a substituted or unsubstituted ring,
When n is 2 or more, the structures in parentheses are the same as or different from each other. The method according to claim 10, wherein L3 is a direct bond, Ar1 is a substituted or unsubstituted divalent pyrene group, Ar2 and Ar3 are the same as or different from each other, and each independently an aryl group unsubstituted or substituted with an alkyl group, n is An organic electroluminescent device of 2. The organic electroluminescent device of claim 8, wherein the organic material layer includes an emission layer, and the emission layer includes a compound represented by Formula A-2:
[Formula A-2]

In Formula A-2,
Ar4 and Ar5 are the same as or different from each other, and each independently a substituted or unsubstituted monocyclic aryl group; Or a substituted or unsubstituted polycyclic aryl group,
G1 to G8 are the same as or different from each other, and each independently hydrogen; A substituted or unsubstituted monocyclic aryl group; Or a substituted or unsubstituted polycyclic aryl group. The organic electroluminescent device according to claim 12, wherein Ar4 and Ar5 are 2-naphthyl groups, and G1 to G8 are hydrogen. The organic electroluminescent device according to claim 10, wherein the emission layer further comprises a compound represented by the following Formula A-2:
[Formula A-2]

In Formula A-2,
Ar4 and Ar5 are the same as or different from each other, and each independently a substituted or unsubstituted monocyclic aryl group; Or a substituted or unsubstituted polycyclic aryl group,
G1 to G8 are the same as or different from each other, and each independently hydrogen; A substituted or unsubstituted monocyclic aryl group; Or a substituted or unsubstituted polycyclic aryl group.

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