Organic electroluminescent device and aromatic compound for use in organic electroluminescent device

Abstract

The present application relates to an organic electroluminescent device, comprising: a first electrode, a second electrode, and an emission layer between the first electrode and the second electrode and containing an aromatic compound, wherein the aromatic compound includes a benzene ring, two unsubstituted carbazole groups directly bonded to the benzene ring, two substituted carbazole groups directly bonded to the benzene ring and each substituted by a nitrogen-containing ring group, and a substituent directly bonded to the benzene ring and selected from a cyano group, fluorine, and a C1-C10 alkyl group substituted by fluorine. The organic electroluminescent device can obtain good luminous efficiency and long-life (long service life) characteristics while emitting blue light.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority and benefit of Korean Patent Application No. 10 - 2019 - 0142840, filed on November 8, 2019, the entire content of which is incorporated herein by reference. Technical field

[0003] One or more aspects of embodiments of the present disclosure relate to an organic electroluminescent device and an aromatic compound for an organic electroluminescent device. Background art

[0004] Recently, the development of organic electroluminescent displays as image display devices has been actively carried out. Different from liquid crystal display devices and the like, an organic electroluminescent display is a self - emitting display device, in which holes and electrons injected from a first electrode and a second electrode recombine in an emission layer, and thus a luminescent material including an organic compound in the emission layer emits light to realize the display of an image.

[0005] In the application of organic electroluminescent devices to display devices, there is a need (or expectation) for organic electroluminescent devices having high luminous efficiency and long life, and there is a continuous need for the development of materials for organic electroluminescent devices capable of stably achieving such characteristics.

[0006] In recent years, especially for realizing efficient organic electroluminescent devices, technologies involving phosphorescent emission using triplet energy or delayed fluorescence using triplet - triplet annihilation (TTA) (where singlet excitons are generated by the collision of triplet excitons) have been developed, and thermally activated delayed fluorescence (TADF) materials using the delayed fluorescence phenomenon have been developed. Summary of the invention

[0007] One or more aspects of embodiments of the present disclosure relate to efficient, long - life organic electroluminescent devices.

[0008] The present disclosure also provides an aromatic compound for an organic electroluminescent device having good efficiency.

[0009] Embodiments of the present disclosure provide an organic electroluminescent device, comprising: a first electrode, a second electrode on the first electrode, and an emission layer between the first electrode and the second electrode and containing an aromatic compound, wherein the first electrode and the second electrode each independently comprise at least one selected from the following: one selected from Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF / Ca, LiF / Al, Mo, Ti, In, Sn, and Zn; a compound of two or more selected from them; a mixture of two or more selected from them; and oxides thereof, wherein the aromatic compound includes a benzene ring, two unsubstituted carbazole groups directly bonded to the benzene ring, two substituted carbazole groups directly bonded to the benzene ring and substituted by a nitrogen-containing ring group, and a substituent directly bonded to the benzene ring and being a cyano group, fluorine, or a C1-C10 alkyl group substituted by fluorine.

[0010] The emission layer can emit delayed fluorescence.

[0011] The nitrogen-containing ring group can be a pyridine group or a pyrimidine group.

[0012] The two unsubstituted carbazole groups can be bonded to the benzene ring to be symmetric with respect to each other relative to the substituent, and the two substituted carbazole groups can be bonded to the benzene ring to be symmetric with respect to each other relative to the substituent.

[0013] The substituent and each of the two unsubstituted carbazole groups can be bonded to the benzene ring at the ortho position respectively, and the substituent and each of the two substituted carbazole groups can be bonded to the benzene ring at the meta position respectively.

[0014] The aromatic compound can be represented by Formula 1:

[0015] Formula 1

[0016]

[0017] In Formula 1, X can be a cyano group, fluorine, or a C1-C10 alkyl group substituted by fluorine; Y can be a hydrogen atom, a deuterium atom, a halogen atom, a cyano group, an unsubstituted heteroaryl group having 3 to 20 ring carbon atoms and at least one ring nitrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms; a to d can each independently be an integer from 1 to 4; at least one of R1 to R4 can be represented by Formula 2, and the remaining ones of R1 to R4 can each independently be a hydrogen atom, a deuterium atom, or a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms:

[0018] Formula 2

[0019]

[0020] In Formula 2, at least one of W1 to W5 may be a nitrogen atom, and the remaining ones of W1 to W5 may each independently be CR5; and R5 may be a hydrogen atom, a deuterium atom, or a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms.

[0021] Formula 2 may be represented by Formula 2-1 or Formula 2-2.

[0022] Formula 2-1

[0023]

[0024] Formula 2-2

[0025]

[0026] In an embodiment of the present disclosure, the organic electroluminescent device includes a first electrode, a second electrode on the first electrode, and an emission layer between the first electrode and the second electrode, wherein the first electrode and the second electrode each independently contain at least one selected from the following: one selected from Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF / Ca, LiF / Al, Mo, Ti, In, Sn, and Zn; a compound of two or more selected from them; a mixture of two or more selected from them; and their oxides, and the emission layer contains an aromatic compound represented by Formula 1.

[0027] The above-mentioned aromatic compound represented by Formula 1 may be laterally symmetric with respect to X and Y.

[0028] Y may be an unsubstituted phenyl group, an unsubstituted pyridine group, an unsubstituted carbazole group, or an unsubstituted alkyl group having 1 to 4 carbon atoms.

[0029] Formula 1 may be represented by Formula 3:

[0030] Formula 3

[0031]

[0032] In Formula 3, X, Y, and W1 to W5 are the same as those defined in Formula 1 and Formula 2.

[0033] The above-mentioned aromatic compound represented by Formula 1 may be a thermally activated delayed fluorescence emitting material. Description of the Drawings

[0034] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated into and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, are used to explain the principles of the present disclosure. In the drawings:

[0035] Figure 1 is a schematic cross-sectional view of an organic electroluminescent device according to an embodiment of the present disclosure;

[0036] Figure 2 is a schematic cross-sectional view of an organic electroluminescent device according to an embodiment of the present disclosure;

[0037] Figure 3 is a schematic cross-sectional view of an organic electroluminescent device according to an embodiment of the present disclosure; and

[0038] Figure 4 is a schematic cross-sectional view of an organic electroluminescent device according to an embodiment of the present disclosure. Detailed Description

[0039] The present disclosure may have various modifications and may be implemented in different forms, and exemplary embodiments will be explained in more detail with reference to the accompanying drawings. However, the present disclosure may be implemented in different forms and should not be construed as limited to the embodiments set forth herein. On the contrary, all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present disclosure should be included in the present disclosure.

[0040] It should be understood that when an element or layer is referred to as being "on", "connected to", or "coupled to" another element or layer, it can be directly on, connected to, or coupled to the other element or layer (without intervening elements and / or layers therebetween), or there can be intervening elements and / or layers.

[0041] The same numbers refer to the same elements throughout. In addition, in the drawings, for the purpose of effectively describing the technical content, the thickness, ratio, and dimensions of the elements are enlarged.

[0042] The term "and / or" includes all combinations of one or more of the things that the relevant configuration can define. Expressions such as "at least one (kind) of...", "one (kind) of...", and "selected from" when preceding a list of elements modify the entire list of elements, rather than a single element of the list. In addition, the use of "may" when describing embodiments of the present disclosure means "one or more embodiments of the present disclosure".

[0043] It should be understood that although the terms "first", "second", etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the exemplary embodiments of the present disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. The singular forms of the terms may include the plural forms unless the context clearly indicates otherwise.

[0044] In addition, terms such as "below", "lower", "above", "upper", etc. are used to describe the relationship of the configurations shown in the drawings. The terms are used as relative concepts and are described with reference to the directions indicated in the drawings.

[0045] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure pertains. It should also be understood that terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are explicitly defined herein, unless they are interpreted in an ideal or overly formal sense.

[0046] It should be understood that the terms "comprising" or "having" are intended to indicate the presence of the specified features, integers, steps, operations, elements, components, or combinations thereof in the disclosure, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

[0047] Hereinafter, an organic electroluminescent device according to an embodiment of the present disclosure and an aromatic compound included therein will be described with reference to the drawings.

[0048] Figures 1 to 4 is a cross-sectional view schematically illustrating an organic electroluminescent device according to an embodiment of the present disclosure. Referring to Figures 1 to 4 , in an organic electroluminescent device 10 according to an embodiment, a first electrode EL1 and a second electrode EL2 are provided to face each other, and an emission layer EML may be between the first electrode EL1 and the second electrode EL2.

[0049] In some embodiments, in addition to the emission layer EML, the organic electroluminescent device 10 of the embodiments may further include a plurality of functional layers between the first electrode EL1 and the second electrode EL2. The plurality of functional layers may include a hole transport region HTR and an electron transport region ETR. For example, the organic electroluminescent device 10 according to the embodiments may include the first electrode EL1, the hole transport region HTR, the emission layer EML, the electron transport region ETR, and the second electrode EL2 stacked in sequence. In some embodiments, the organic electroluminescent device 10 of the embodiments may include a cover layer CPL on the second electrode EL2.

[0050] The organic electroluminescent device 10 of the embodiments may include the aromatic compound (which will be described in more detail later) of the embodiments in the emission layer EML between the first electrode EL1 and the second electrode EL2.

[0051] Compared with Figure 1 In contrast, Figure 2 FIG. shows a cross-sectional view of the organic electroluminescent device 10 of the embodiments, where the hole transport region HTR includes a hole injection layer HIL and a hole transport layer HTL, and the electron transport region ETR includes an electron injection layer EIL and an electron transport layer ETL. Compared with Figure 1 In contrast, Figure 3 FIG. shows a cross-sectional view of the organic electroluminescent device 10 of the embodiments, where the hole transport region HTR includes a hole injection layer HIL, a hole transport layer HTL, and an electron blocking layer EBL, and the electron transport region ETR includes an electron injection layer EIL, an electron transport layer ETL, and a hole blocking layer HBL. Compared with Figure 2 In contrast, Figure 4 FIG. shows a cross-sectional view of the organic electroluminescent device 10 of the embodiments including a cover layer CPL on the second electrode EL2.

[0052] The first electrode EL1 has conductivity. The first electrode EL1 can be formed of a metal alloy or any suitable conductive compound. The first electrode EL1 can be an anode. In some embodiments, the first electrode EL1 can be a pixel electrode. The first electrode EL1 can be a transmissive electrode, a semi-transmissive reflective electrode, or a reflective electrode. When the first electrode EL1 is a transmissive electrode, the first electrode EL1 can include a transparent metal oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and / or indium tin zinc oxide (ITZO). When the first electrode EL1 is a semi-transmissive reflective electrode or a reflective electrode, the first electrode EL1 can include Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF / Ca, LiF / Al, Mo, Ti, their compounds, or their mixtures (e.g., a mixture of Ag and Mg). In some embodiments, the first electrode EL1 can have a multilayer structure that includes a reflective film or a semi-transmissive reflective film, and a transparent conductive film formed of ITO, IZO, ZnO, ITZO, etc. For example, the first electrode EL1 can have a three-layer structure of ITO / Ag / ITO, but is not limited thereto. The thickness of the first electrode EL1 can be about to about For example, about to about

[0053] A hole transport region HTR is provided on the first electrode EL1. The hole transport region HTR can include at least one of a hole injection layer HIL, a hole transport layer HTL, a hole buffer layer, and an electron blocking layer EBL. The thickness of the hole transport region HTR can be about to about

[0054] The hole transport region HTR can have a single layer formed of a single material, a single layer formed of multiple different materials, or a multilayer structure including multiple layers formed of multiple different materials.

[0055] For example, the hole transport region HTR can have a single layer structure of a hole injection layer HIL or a hole transport layer HTL, or can have a single layer structure formed of a hole injection material and a hole transport material. In some embodiments, the hole transport region HTR can have a single layer structure formed of multiple different materials, or a structure of a hole injection layer HIL / hole transport layer HTL, a hole injection layer HIL / hole transport layer HTL / hole buffer layer, a hole injection layer HIL / hole buffer layer, a hole transport layer HTL / hole buffer layer, or a hole injection layer HIL / hole transport layer HTL / electron blocking layer EBL stacked in sequence from the first electrode EL1, but the embodiments are not limited thereto.

[0056] The hole transport region HTR can be formed using one or more suitable methods (such as vacuum deposition, spin coating, casting, Langmuir-Blodgett (LB) method, inkjet printing, laser printing, and / or laser-induced thermal imaging (LITI) method).

[0057] The hole injection layer HIL can include, for example, phthalocyanine compounds (such as copper phthalocyanine); N,N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4'-diamine (DNTPD), 4,4',4”-[tris(3-methylphenyl)phenylamino]triphenylamine (m-MTDATA), 4,4',4”-tris(N,N-diphenylamino)triphenylamine (TDATA), 4,4',4”-tris{N-(2-naphthyl)-N-phenylamino}-triphenylamine (2-TNATA), poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate) (PEDOT / PSS), polyaniline / dodecylbenzenesulfonic acid (PANI / DBSA), polyaniline / camphorsulfonic acid (PANI / CSA), polyaniline / poly(4-styrenesulfonate) (PANI / PSS), N,N'-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine (NPD), triphenylamine-containing polyether ketone (TPAPEK), 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate, dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN), etc.

[0058] The hole transport layer HTL can further include, for example, carbazole derivatives (such as N-phenylcarbazole and / or polyvinylcarbazole), fluorene derivatives, N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), triphenylamine derivatives (such as 4,4',4”-tris(N-carbazolyl)triphenylamine (TCTA)), N,N'-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine (NPB), 4,4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)aniline] (TAPC), 4,4'-bis[N,N'-(3-tolyl)amino]-3,3'-dimethylbiphenyl (HMTPD), 1,3-bis(N-carbazolyl)benzene (mCP), etc.

[0059] The thickness of the hole transport region HTR can be about to about For example, about to about The thickness of the hole injection layer HIL can be, for example, about to about And the thickness of the hole transport layer (HTL) can be about to about For example, the thickness of the electron blocking layer (EBL) can be about to about If the thicknesses of the hole transport region (HTR), hole injection layer (HIL), hole transport layer (HTL), and electron blocking layer (EBL) each independently satisfy the ranges described above, satisfactory (or suitable) hole transport properties can be achieved without a significant increase in the driving voltage.

[0060] In addition to the materials described above, the hole transport region (HTR) can further include a charge generation material to increase conductivity. The charge generation material can be uniformly or non-uniformly dispersed in the hole transport region (HTR). The charge generation material can be, for example, a p-dopant. The p-dopant can be one of a quinone derivative, a metal oxide, and a compound containing a cyano group, but is not limited thereto. Non-limiting examples of the p-dopant can include quinone derivatives (e.g., tetracyanoquinodimethane (TCNQ) and / or 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ)), metal oxides (e.g., tungsten oxide and / or molybdenum oxide), etc.

[0061] As described above, in addition to the hole injection layer (HIL) and the hole transport layer (HTL), the hole transport region (HTR) can further include at least one of a hole buffer layer and an electron blocking layer (EBL). The hole buffer layer can compensate for the resonance distance according to the wavelength of the light emitted from the emission layer (EML) and can increase the light emission efficiency. The materials that can be included in the hole transport region (HTR) can be used as the materials included in the hole buffer layer. The electron blocking layer (EBL) is a layer for preventing or reducing the injection of electrons from the electron transport region (ETR) into the hole transport region (HTR).

[0062] An emission layer (EML) is provided on the hole transport region (HTR). The thickness of the emission layer (EML) can be, for example, about to about or about to about The emission layer (EML) can have a single layer formed of a single material, a single layer formed of multiple different materials, or a multilayer structure having multiple layers formed of multiple different materials.

[0063] The emission layer (EML) of the organic electroluminescent device 10 of the embodiment can include the aromatic compound of the embodiment.

[0064] The aromatic compound of the embodiment may include a benzene ring, two unsubstituted carbazole groups directly bonded to the benzene ring, two substituted carbazole groups directly bonded to the benzene ring and substituted by a nitrogen-containing ring (cyclic) group, and a substituent directly bonded to the benzene ring and being a cyano group, fluorine, or a C1-C10 alkyl group substituted by fluorine.

[0065] According to the embodiment, the nitrogen-containing ring group may be an electron-withdrawing group containing at least one nitrogen atom in the benzene ring. For example, the nitrogen-containing ring group may be a pyridine group or a pyrimidine group. However, the embodiment is not limited thereto.

[0066] According to the embodiment, the two substituted carbazole groups may be symmetrically arranged with respect to the directly bonded substituent. In some embodiments, the two unsubstituted carbazole groups may be symmetrically arranged with respect to the directly bonded substituent.

[0067] The two unsubstituted carbazole groups included in the aromatic compound of the embodiment may be respectively bonded to the benzene ring at the ortho positions with respect to the directly bonded substituent. The two substituted carbazole groups may be respectively bonded to the benzene ring at the meta positions with respect to the directly bonded substituent.

[0068] In the description, the term "substituted or unsubstituted" may indicate an unsubstituted group or a group substituted by at least one substituent selected from the group consisting of a deuterium atom, a halogen atom, a cyano group, a nitro group, an amino group, a silyl group, an oxy group, a mercapto group, a sulfinyl group, a sulfonyl group, a carbonyl group, a boron group, a phosphine oxide group, a phosphine sulfide group, an alkyl group, an alkenyl group, an alkoxy group, a hydrocarbon ring group, an aryl group, and a heterocyclic group. In some embodiments, each of the substituents exemplified above may itself be substituted or unsubstituted. For example, a biphenyl group may be interpreted as an aryl group or a phenyl group substituted by a phenyl group.

[0069] In the description, examples of the halogen atom may include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0070] In the description, the alkyl group can be a straight-chain, branched-chain or cyclic alkyl group. The number of carbon atoms in the alkyl group is 1 to 50, 1 to 30, 1 to 20, 1 to 10, or 1 to 6. Examples of the alkyl group can include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl, 2-ethylbutyl, 3,3-dimethylbutyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, cyclopentyl, 1-methylpentyl, 3-methylpentyl, 2-ethylpentyl, 4-methyl-2-pentyl, n-hexyl, 1-methylhexyl, 2-ethylhexyl, 2-butylhexyl, cyclohexyl, 4-methylcyclohexyl, 4-tert-butylcyclohexyl, n-heptyl, 1-methylheptyl, 2,2-dimethylheptyl, 2-ethylheptyl, 2-butylheptyl, n-octyl, tert-octyl, 2-ethyloctyl, 2-butyl octyl, 2-hexyloctyl, 3,7-dimethyloctyl, cyclooctyl, n-nonyl, n-decyl, adamantyl, 2-ethyldecyl, 2-butyldecyl, 2-hexyldecyl, 2-octyldecyl, n-undecyl, n-dodecyl, 2-ethyldodecyl, 2-butyldodecyl, 2-hexyldodecyl, 2-octyldodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, 2-ethylhexadecyl, 2-butyldecyl, 2-hexyldecyl, 2-octyldecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl, 2-ethyleicosyl, 2-butyldecyl, 2-hexyldecyl, 2-octyldecyl, n-heneicosyl, n-docosyl, n-tricosyl, n-tetracosyl, n-pentacosyl, n-hexacosyl, n-heptacosyl, n-octacosyl, n-nonacosyl, n-triacontyl, etc., but not limited thereto.

[0071] In the description, the aryl group can refer to a functional group or substituent derived from an aromatic hydrocarbon ring. The aryl group can be a monocyclic aryl group or a polycyclic aryl group. The number of ring-forming carbon atoms in the aryl group can be 6 to 30, 6 to 20, or 6 to 15. Examples of the aryl group can include phenyl, naphthyl, fluorenyl, anthryl, phenanthryl, biphenyl, terphenyl, quaterphenyl, quinquephenyl, sexiphenyl, benzophenanthryl, pyrenyl, benzo[a]pyrenyl, groups, etc., but not limited thereto.

[0072] In the description, the heteroaryl group can contain at least one nitrogen atom as a ring-forming heteroatom. The number of ring-forming carbon atoms in the heteroaryl group can be 2 to 30, 2 to 20 or 2 to 10. In an embodiment, the number of heteroatoms in the heteroaryl group can be 1 to 6, such as 1, 2, 3, 4, 5 or 6, and the number of nitrogen atoms as ring-forming heteroatoms can be 1 to 6, such as 1, 2, 3, 4, 5 or 6.

[0073] Meanwhile, in the description, "-*" refers to the position to be connected (e.g., the binding site).

[0074] The aromatic compound of the embodiment contained in the organic electroluminescent device 10 of the embodiment can be represented by the following formula 1.

[0075] Formula 1

[0076]

[0077] In formula 1, X can be a cyano group, fluorine, or a C1-C10 alkyl group substituted with fluorine.

[0078] In formula 1, Y can be a hydrogen atom, a deuterium atom, a halogen atom, a cyano group, an unsubstituted heteroaryl group having 3 to 20 ring carbon atoms and containing a nitrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms.

[0079] For example, Y can be an unsubstituted phenyl group, an unsubstituted pyridine group, an unsubstituted carbazolyl group, or an unsubstituted alkyl group having 1 to 4 carbon atoms. However, the embodiment is not limited thereto.

[0080] a to d can each independently be an integer from 1 to 4. When a to d are each independently an integer of 2 or greater than 2, multiple of R1 to R4 can be the same as or different from each other. For example, when a is an integer of 2 or greater than 2, multiple R1 can all be the same as or different from each other.

[0081] In formula 1, the left and right parts of the compound can be laterally symmetric with respect to X and Y. For example, when a to d are all 1 and R1 to R4 are all the same, the left and right parts can be laterally symmetric with respect to X and Y. However, the embodiment is not limited thereto.

[0082] In formula 1, at least one of R1 to R4 can be represented by the following formula 2, and the rest can be a hydrogen atom, a deuterium atom, or a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms.

[0083] Formula 2

[0084]

[0085] In formula 2, at least one of W1 to W5 can be a nitrogen atom, and the rest can be CR5. R5 can be a hydrogen atom, a deuterium atom, or a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms.

[0086] The aromatic compound of the embodiment represented by Formula 1 may include two unsubstituted carbazole groups and two substituted carbazole groups (substituted by a nitrogen-containing ring group). The carbazole groups substituted by R1 to R4 in Formula 1 may be two substituted carbazole groups, and the other carbazole groups may be two unsubstituted carbazole groups. In some embodiments, the nitrogen-containing ring group substituted at the carbazole group may be represented by Formula 2.

[0087] In the aromatic compound of the embodiment, the substituent (which is a cyano group, fluorine, or a C1-C10 alkyl group substituted by fluorine) may be represented by X in Formula 1.

[0088] Meanwhile, Formula 2 may be represented by Formula 2-1 or Formula 2-2.

[0089] Formula 2-1

[0090]

[0091] Formula 2-2

[0092]

[0093] Formula 2-1 shows the case of an unsubstituted pyridine group, and Formula 2-2 shows the case of an unsubstituted pyrimidine group.

[0094] Formula 1 may be represented by the following Formula 3.

[0095] Formula 3

[0096]

[0097] Formula 3 shows the case where a to d are all 1.

[0098] X, Y, and W1 to W5 in Formula 3 may be the same as those described in Formula 1 and Formula 2 above.

[0099] The aromatic compound of the embodiment may include at least four carbazole groups, which are directly bonded to the benzene ring and two of the four carbazole groups are unsubstituted carbazole groups, and the other two are substituted carbazole groups. The two substituted carbazole groups may be substituted by a nitrogen-containing ring group. The aromatic compound of the embodiment may be used as an emissive material that emits deep blue light having an emission center wavelength (λ max ) in the wavelength region of about 470 nm or less than 470 nm. For example, the aromatic compound of the embodiment may be an emissive material having an emission center wavelength in the wavelength region of about 430 nm to about 490 nm.

[0100] The aromatic compound of the embodiment may be any one of the compounds represented by the following Compound Group 1. The organic electroluminescent device 10 of the embodiment may include at least one aromatic compound represented by the compounds in Compound Group 1 in the emission layer EML.

[0101] Compound Group 1

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110]

[0111]

[0112]

[0113]

[0114]

[0115]

[0116] In the organic electroluminescent device 10 of the embodiment, the emission layer EML may emit delayed fluorescence. For example, the emission layer EML may emit thermally activated delayed fluorescence (TADF).

[0117] In some embodiments, the organic electroluminescent device 10 of the embodiment may include a plurality of emission layers. When the organic electroluminescent device 10 includes a plurality of emission layers, at least one emission layer EML may contain the aromatic compound of the above-described embodiment.

[0118] In an embodiment, the emission layer EML may include a host and a dopant, and may include the aromatic compound of the embodiment described above as the dopant. For example, in the organic electroluminescent device 10 of the embodiment, the emission layer EML may include a host for delayed fluorescence emission and a dopant for delayed fluorescence emission, and may include the aromatic compound of the embodiment described above as the dopant for delayed fluorescence emission. The emission layer EML may include at least one of the aromatic compounds represented by Compound Group 1 described above as a thermally activated delayed fluorescence dopant.

[0119] In an embodiment, the emission layer EML may be a delayed fluorescence emission layer, and the emission layer EML may include any suitable host material and the aromatic compound of the embodiment described above. For example, in an embodiment, the aromatic compound may be used as a TADF dopant.

[0120] Meanwhile, in an embodiment, the emission layer EML may include any suitable host material. For example, in an embodiment, the emission layer EML may include tris(8-hydroxyquinolinato)aluminum (Alq3), 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP), poly(N-vinylcarbazole) (PVK), 9,10-bis(naphthalen-2-yl)anthracene (ADN), 4,4',4"-tris(carbazol-9-yl)triphenylamine (TCTA), 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBi), 3-tert-butyl-9,10-bis(naphthalen-2-yl)anthracene (TBADN), stilbene-substituted arylide (DSA), 4,4'-bis(9-carbazolyl)-2,2'-dimethyl-biphenyl (CDBP), 2-methyl-9,10-bis(naphthalen-2-yl)anthracene (MADN), bis[2-(diphenylphosphino)phenyl]ether oxide (DPEPO), hexaphenylcyclotriphosphazene (CP1), 1,4-bis(triphenylsilyl)benzene (UGH2), hexaphenylcyclotrisiloxane (DPSiO3), octaphenylcyclotetrasiloxane (DPSiO4), 2,8-bis(diphenylphosphoryl)dibenzofuran (PPF), 3,3'-bis(N-carbazolyl)-1,1'-biphenyl (mCBP), and / or 1,3-bis(carbazol-9-yl)benzene (mCP) as the host material. However, the embodiments of the present disclosure are not limited thereto, and may include a suitable delayed fluorescence host material in addition to the presented host materials.

[0121] Meanwhile, in the organic electroluminescent device 10 of the embodiment, the emission layer EML may further include any suitable dopant material. In an embodiment, the emission layer EML may further include a styryl derivative as a dopant (e.g., 1,4-bis[2-(3-N-ethylcarbazolyl)vinyl]benzene (BCzVB), 4-(di-p-tolylamino)-4”-[(di-p-tolylamino)styryl]stilbene (DPAVB), and / or N-(4-((E)-2-(6-((E)-4-(diphenylamino)styryl)naphthalen-2-yl)vinyl)phenyl)-N-phenylaniline (N-BDAVBi)), perylene and / or its derivatives (e.g., 2,5,8,11-tetra-tert-butylperylene (TBP)), pyrene and / or its derivatives (e.g., 1,1'-dipyrene, 1,4-dipyrenylbenzene, 1,4-bis(N,N-diphenylamino)pyrene), etc.).

[0122] In some embodiments, the organic electroluminescent device 10 of the embodiment may include a plurality of emission layers. The plurality of emission layers may be stacked sequentially. For example, the organic electroluminescent device 10 including a plurality of emission layers may emit white light. The organic electroluminescent device including a plurality of emission layers may be an organic electroluminescent device having a tandem structure.

[0123] In Figures 1 to 4 the organic electroluminescent device 10 of the embodiment illustrated in, an electron transport region ETR is provided on the emission layer EML. The electron transport region ETR may include at least one of a hole blocking layer HBL, an electron transport layer ETL, and an electron injection layer EIL, but the embodiment is not limited thereto.

[0124] The electron transport region ETR may have a single layer formed of a single material, a single layer formed of a plurality of different materials, or a multilayer structure including a plurality of layers formed of a plurality of different materials.

[0125] For example, the electron transport region ETR may have a single layer structure of an electron injection layer EIL or an electron transport layer ETL, or may have a single layer structure formed of an electron injection material and an electron transport material. In some embodiments, the electron transport region ETR may have a single layer structure formed of a plurality of different materials, or may have a structure of an electron transport layer ETL / electron injection layer EIL, or a hole blocking layer HBL / electron transport layer ETL / electron injection layer EIL (where the layers are stacked sequentially from the emission layer EML), but is not limited thereto. The thickness of the electron transport region ETR may be, for example, about to about

[0126] One or more suitable methods (such as vacuum deposition, spin coating, casting, Langmuir-Blodgett (LB) method, inkjet printing, laser printing, laser-induced thermal imaging (LITI) method, etc.) can be used to form the electron transport region ETR.

[0127] When the electron transport region ETR includes an electron transport layer ETL, the electron transport layer ETL can contain anthracene-based compounds. However, the present disclosure is not limited thereto, and the electron transport region can contain, for example, tris(8-hydroxyquinolinato)aluminum (Alq3), 1,3,5-tris[(3-pyridinyl)-benzene-3-yl]benzene, 2,4,6-tris(3'-(pyridin-3-yl)biphenyl-3-yl)-1,3,5-triazine, 2-(4-(N-phenylbenzimidazol-1-yl)phenyl)-9,10-dinaphthylanthracene, 1,3,5-tris(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBi), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl-1,10-phenanthroline (Bphen), 3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ), 4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole (NTAZ), 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD), bis(2-methyl-8-quinolinato-N1,O8)-(1,1'-biphenyl-4-yl)aluminum (BAlq), bis(benzoquinolinato-10)beryllium (Bebq2), 9,10-di(naphthalen-2-yl)anthracene (ADN), 1,3-bis[3,5-bis(pyridin-3-yl)phenyl]benzene (BmPyPhB), or a mixture thereof. The thickness of the electron transport layer ETL can be about to about and can be, for example, about to about When the thickness of the electron transport layer ETL satisfies the range described above, satisfactory (or suitable) electron transport properties can be obtained without a significant increase in the driving voltage.

[0128] When the electron transport region (ETR) includes an electron injection layer (EIL), the electron injection layer (EIL) can be a metal halide (such as LiF, NaCl, CsF, RbCl, RbI, and / or CuI), a lanthanide metal (such as Yb), a metal oxide (such as Li2O and BaO), and / or lithium 8-hydroxyquinoline (LiQ), but is not limited thereto. The electron injection layer (EIL) can also be formed of a mixture material of an electron injection material and an insulating organometallic salt. The organometallic salt can be a material having a band gap of about 4 eV or greater than 4 eV. In some embodiments, the organometallic salt can include, for example, metal acetates, metal benzoates, metal acetoacetates, metal acetylacetonates, and / or metal stearates. The thickness of the electron injection layer (EIL) can be about to about For example, about to about When the thickness of the electron injection layer (EIL) satisfies the range described above, satisfactory (or suitable) electron injection properties can be obtained without a significant increase in the driving voltage.

[0129] The electron transport region (ETR) can include a hole blocking layer (HBL). The hole blocking layer (HBL) can contain at least one of, for example, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), bis[2-(diphenylphosphino)phenyl]ether oxide (DPEPO), and 4,7-diphenyl-1,10-phenanthroline (Bphen), but is not limited thereto.

[0130] A second electrode (EL2) is provided on the electron transport region (ETR). The second electrode (EL2) can be a common electrode and / or a cathode. The second electrode (EL2) can be a transmissive electrode, a semi-transmissive reflective electrode, or a reflective electrode. If the second electrode (EL2) is a transmissive electrode, the second electrode (EL2) can contain a transparent metal oxide, such as, for example, ITO, IZO, ZnO, ITZO, etc.

[0131] If the second electrode (EL2) is a semi-transmissive reflective electrode or a reflective electrode, the second electrode (EL2) can contain Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF / Ca, LiF / Al, Mo, Ti, their compounds, or their mixtures (such as a mixture of Ag and Mg). In some embodiments, the second electrode (EL2) can have a multilayer structure, the multilayer structure including a reflective film or a semi-transmissive reflective film formed of any one of the materials described above and a transparent conductive film formed of ITO, IZO, ZnO, ITZO, etc.

[0132] In some embodiments, the second electrode (EL2) can be connected to an auxiliary electrode. If the second electrode (EL2) is connected to the auxiliary electrode, the resistance of the second electrode (EL2) can be reduced.

[0133] Meanwhile, the organic electroluminescent device 10 according to the embodiment may further include a cover layer CPL on the second electrode EL2. The cover layer CPL may contain, for example, α-NPD, NPB, TPD, m-MTDATA, Alq3, CuPc, N4,N4,N4',N4'-tetrakis(biphenyl-4-yl)biphenyl-4,4'-diamine (TPD15), 4,4',4"-tris(carbazol-9-yl)triphenylamine (TCTA), etc.

[0134] The organic electroluminescent device 10 according to the embodiment contains the aromatic compound of the above-described embodiment in the emission layer EML between the first electrode EL1 and the second electrode EL2, thereby providing good luminous efficiency and long-life characteristics. In some embodiments, the aromatic compound according to the embodiment may be a thermally activated delayed fluorescence dopant, and the emission layer EML may contain the aromatic compound of the embodiment to emit thermally activated delayed fluorescence, thereby obtaining good luminous efficiency characteristics.

[0135] Hereinafter, with reference to Examples and Comparative Examples, the compounds of the embodiments according to the present disclosure and the organic electroluminescent devices of the embodiments will be described in more detail. However, the Examples shown below are merely illustrative to help understand the present disclosure, and the scope of the present disclosure is not limited thereto.

[0136] Examples

[0137] 1. Synthesis of the Aromatic Compounds of the Examples

[0138] First, by exemplifying the methods for synthesizing Compound 1, Compound 2, Compound 11, and Compound 21, the method for synthesizing the aromatic compounds according to these embodiments will be described in more detail. However, it should be understood that the method for synthesizing the aromatic compounds described below is provided as an example, and thus the method for synthesizing the compounds according to the embodiments of the present disclosure is not limited to the following examples.

[0139] (1) Synthesis of Compound 1

[0140] Compound 1 according to the example can be synthesized, for example, by the following Reaction Schemes 1-1 to 1-4.

[0141] Synthesis of Intermediate Compound A-1

[0142] Intermediate Compound A-1 is synthesized by the following Reaction Scheme 1-1.

[0143] Reaction Scheme 1-1

[0144]

[0145] 2,3,4,5,6-Pentafluorobenzonitrile (20.0 g, 103.6 mmol), carbazole (60.6 g, 362.5 mmol), and NaH (8.7 g, 362.5 mmol) were added to a three-necked flask purged with argon (Ar), and then tetrahydrofuran (THF, 1600 mL) was added and stirred at room temperature for 16 hours. After adding water to the reaction solution, the organic layer was extracted with THF and dried over magnesium sulfate to remove the solvent. The obtained crude product was purified by silica gel column chromatography (hexane / toluene mixed solvent) and recrystallization solvent (ethanol / toluene mixed solvent) to obtain a pale yellow solid (19.9 g, yield 30%). The obtained pale yellow solid was confirmed to have a molecular weight of 634 as measured by fast atom bombardment mass spectrometry (FAB MS), and it was confirmed to be intermediate compound A-1 as the target object.

[0146] Synthesis of Intermediate Compound A-2

[0147] Intermediate compound A-2 was synthesized according to the following Reaction Scheme 1-2.

[0148] Reaction Scheme 1-2

[0149]

[0150] 3,6-Dibromocarbazole (25.0 g, 76.9 mmol), bis(pinacolato)diboron (58.0 g, 230.1 mmol), [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (12.6 g, 15.4 mmol), and potassium acetate (90.0 g, 923 mmol) were added to a three-necked flask purged with argon (Ar), and then 1,4-dioxane (500 mL) was added and stirred at 100 °C for 3 hours. After adding water to the reaction solution, the organic layer was extracted with dichloromethane and dried over magnesium sulfate to remove the solvent. The obtained crude product was purified by silica gel column chromatography (hexane / toluene mixed solvent) and recrystallization solvent (ethanol / toluene mixed solvent) to obtain a white solid (17.3 g, yield 54%). The obtained white solid was confirmed to have a molecular weight of 419 as measured by FAB MS, and it was confirmed to be intermediate compound A-2 as the target object.

[0151] Synthesis of Intermediate Compound A-3

[0152] Intermediate compound A-3 was synthesized according to the following Reaction Scheme 1-3.

[0153] Reaction Scheme 1-3

[0154]

[0155] Intermediate compound A-2 (15.0 g, 35.7 mmol), 2-bromopyridine (17.0 g, 107.4 mmol), tetrakis(triphenylphosphine)palladium(0) (18.6 g, 16.1 mmol), and cesium carbonate (104.9 g, 322.1 mmol) were added to a three-necked flask purged with argon (Ar), and then toluene (388 mL), ethanol (258 mL), and water (258 mL) were added, and the mixture was stirred at 100 °C for 3 hours. After adding water to the reaction solution, the organic layer was extracted with ethyl acetate and dried over magnesium sulfate to remove the solvent. The obtained crude product was purified by silica gel column chromatography (hexane / toluene mixed solvent) and recrystallization solvent (ethanol / toluene mixed solvent) to obtain a white solid (4.4 g, yield 38%). The obtained white solid was confirmed to have a molecular weight of 321 as measured by FAB MS, and it was confirmed to be intermediate compound A-3 as the target object.

[0156] Synthesis of Compound 1

[0157] Compound 1 was synthesized according to the following Reaction Scheme 1-4.

[0158] Reaction Scheme 1-4

[0159]

[0160] Intermediate compound A-1 (3.0 g, 4.7 mmol), intermediate compound A-3 (3.8 g, 12.0 mmol), and NaH (0.3 g, 12.0 mmol) were added to a three-necked flask purged with argon (Ar), and then dimethylformamide (DMF, 75 mL) was added and the mixture was stirred at 90 °C for 5 hours. After adding water to the reaction solution, the organic layer was extracted with dichloromethane and dried over magnesium sulfate to remove the solvent. The obtained crude product was purified by silica gel column chromatography (hexane / toluene mixed solvent) and recrystallization solvent (ethanol / toluene mixed solvent) to obtain a light yellow solid (3.5 g, yield 60%). The obtained light yellow solid was confirmed to have a molecular weight of 1233 as measured by FAB MS, and it was confirmed to be Compound 1 as the target object.

[0161] (2) Synthesis of Compound 2

[0162] For example, Compound 2 according to the embodiment can be synthesized by Reaction Scheme 2-1 and Reaction Scheme 2-2.

[0163] Synthesis of Intermediate Compound B

[0164] Intermediate compound B was synthesized according to the following Reaction Scheme 2-1.

[0165] Reaction Scheme 2-1

[0166]

[0167] Intermediate compound A-2 (15.0 g, 35.7 mmol), 3-bromopyridine (17.0 g, 107.4 mmol), tetrakis(triphenylphosphine)palladium(0) (18.6 g, 16.1 mmol), and cesium carbonate (104.9 g, 322.1 mmol) were added to a three-necked flask purged with argon (Ar), and then toluene (388 mL), ethanol (258 mL), and water (258 mL) were added, and the mixture was stirred at 100 °C for 3 hours. After adding water to the reaction solution, the organic layer was extracted with ethyl acetate and dried over magnesium sulfate to remove the solvent. The obtained crude product was purified by silica gel column chromatography (hexane / toluene mixed solvent) and recrystallization solvent (ethanol / toluene mixed solvent) to obtain a white solid (3.5 g, yield 31%). The obtained white solid was confirmed to have a molecular weight of 321 as measured by FAB MS, and it was confirmed to be intermediate compound B as the target object.

[0168] Synthesis of Compound 2

[0169] Compound 2 was synthesized according to the following Reaction Scheme 2-2.

[0170] Reaction Scheme 2-2

[0171]

[0172] Intermediate compound A-1 (3.0 g, 4.7 mmol), intermediate compound B (3.8 g, 12.0 mmol), and NaH (0.3 g, 12.0 mmol) were added to a three-necked flask purged with argon (Ar), and then dimethylformamide (DMF, 75 mL) was added, and the mixture was stirred at 90 °C for 5 hours. After adding water to the reaction solution, the organic layer was extracted with dichloromethane and dried over magnesium sulfate to remove the solvent. The obtained crude product was purified by silica gel column chromatography (hexane / toluene mixed solvent) and recrystallization solvent (ethanol / toluene mixed solvent) to obtain a light yellow solid (2.5 g, yield 43%). The obtained light yellow solid was confirmed to have a molecular weight of 1233 as measured by FAB MS, and it was confirmed to be compound 2 as the target object.

[0173] (3) Synthesis of Compound 11

[0174] For example, compound 11 according to the embodiment can be synthesized by the following Reaction Schemes 3-1 to 3-3.

[0175] Synthesis of Intermediate Compound C-1

[0176] The intermediate compound C-1 was synthesized through the following Reaction Scheme 3-1.

[0177] Reaction Scheme 3-1

[0178]

[0179] 4-Bromotetrafluorobenzonitrile (10.0 g, 39.4 mmol), phenylboronic acid (5.8 g, 47.3 mmol), palladium(II) acetate (18.6 g, 16.1 mmol), tripotassium phosphate (16.7 g, 78.8 mmol) and SPhos (2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl) (1.6 g, 3.9 mmol) were added to a three-necked flask purged with argon (Ar), and then toluene (394 mL), ethanol (16 mL) and water (16 mL) were added, and the mixture was stirred at 100 °C for 3 hours. After adding water to the reaction solution, the organic layer was extracted with ethyl acetate and dried over magnesium sulfate to remove the solvent. The obtained crude product was purified by silica gel column chromatography (hexane / toluene mixed solvent) and recrystallization solvent (ethanol / toluene mixed solvent) to obtain a white solid (7.0 g, yield 62%). The obtained white solid was confirmed to have a molecular weight of 287 as measured by FAB MS, and it was confirmed to be the intermediate compound C-1 as the target object.

[0180] Synthesis of Intermediate Compound C-2

[0181] The intermediate compound C-2 was synthesized through the following Reaction Scheme 3-2.

[0182] Reaction Scheme 3-2

[0183]

[0184] The intermediate compound C-1 (7.0 g, 27.9 mmol), carbazole (9.3 g, 55.7 mmol) and NaH (1.3 g, 55.7 mmol) were added to a three-necked flask purged with argon (Ar), and then THF (450 mL) was added, and the mixture was stirred at room temperature for 2 hours. After adding water to the reaction solution, the organic layer was extracted with toluene and dried over magnesium sulfate to remove the solvent. The obtained crude product was purified by silica gel column chromatography (hexane / toluene mixed solvent) and recrystallization solvent (ethanol / toluene mixed solvent) to obtain a light yellow solid (5.5 g, yield 36%). The obtained light yellow solid was confirmed to have a molecular weight of 545 as measured by FAB MS, and it was confirmed to be the intermediate compound C-2 as the target object.

[0185] Synthesis of Compound 11

[0186] Compound 11 was synthesized through the following Reaction Scheme 3-3.

[0187] Reaction Scheme 3-3

[0188]

[0189] The intermediate compound C-2 (7.0 g, 12.8 mmol), intermediate compound A-3 (10.3 g, 32.1 mmol) and NaH (0.8 g, 32.1 mmol) were added to a three-necked flask purged with argon (Ar), and then DMF (200 mL) was added, and the mixture was stirred at 100 °C for 6 hours. After adding water to the reaction solution, the organic layer was extracted with dichloromethane and dried over magnesium sulfate to remove the solvent. The obtained crude product was purified by silica gel column chromatography (hexane / toluene mixed solvent) and recrystallization solvent (ethanol / toluene mixed solvent) to obtain a light yellow solid (9.8 g, yield 67%). The obtained light yellow solid was confirmed to have a molecular weight of 1148 as measured by FAB MS, and it was confirmed to be Compound 11 as the target object.

[0190] (4) Synthesis of Compound 21

[0191] For example, Compound 21 can be synthesized through the following Reaction Scheme 4-1 and Reaction Scheme 4-2.

[0192] Synthesis of Intermediate Compound D

[0193] Intermediate compound D was synthesized through the following Reaction Scheme 4-1.

[0194] Reaction Scheme 4-1

[0195]

[0196] 2,3,5,6-Tetrafluoro-4-methylbenzonitrile (10.0 g, 52.9 mmol), carbazole (17.7 g, 105.8 mmol) and NaH (2.5 g, 105.8 mmol) were added to a three-necked flask purged with argon (Ar), and then THF (800 mL) was added, and the mixture was stirred at room temperature for 5 hours. After adding water to the reaction solution, the organic layer was extracted with toluene and dried over magnesium sulfate to remove the solvent. The obtained crude product was purified by silica gel column chromatography (hexane / toluene mixed solvent) and recrystallization solvent (ethanol / toluene mixed solvent) to obtain a light yellow solid (5.2 g, yield 45%). The obtained light yellow solid was confirmed to have a molecular weight of 483 as measured by FAB MS, and it was confirmed to be Intermediate Compound D as the target object.

[0197] Synthesis of Compound 21

[0198] Compound 21 was synthesized through the following Reaction Formula 4-2.

[0199] Reaction Formula 4-2

[0200]

[0201] Intermediate compound D (5.0 g, 9.2 mmol), intermediate compound A-3 (7.4 g, 22.9 mmol), and NaH (0.6 g, 22.9 mmol) were added to a three-necked flask purged with argon (Ar), and then DMF (200 mL) was added, followed by stirring at 100 °C for 6 hours. After adding water to the reaction solution, the organic layer was extracted with toluene and dried over magnesium sulfate to remove the solvent. The obtained crude product was purified by silica gel column chromatography (hexane / toluene mixed solvent) and recrystallization solvent (ethanol / toluene mixed solvent) to obtain a light yellow solid (4.1 g, yield 64%). The obtained light yellow solid was confirmed to have a molecular weight of 1088 as measured by FAB MS, and it was confirmed to be compound 21 as the target object.

[0202] 2. Evaluation of the energy levels of the compounds

[0203] Table 2 below shows the lowest singlet excitation energy level (S1 level), the lowest triplet excitation energy level (T1 level), and ΔE of the following compounds 1, 2, 11, and 21, as well as Comparative Example Compounds N1 to N3. ST Value.

[0204] The compounds used in Comparative Examples 1 to 3 are shown in Table 1.

[0205] Table 1

[0206]

[0207]

[0208] The energy level values in Table 2 were calculated by the ab initio molecular orbital method. Specifically, it was calculated using Gaussian 09 from Gaussian by B3LYP / 6-31G(d). ΔE ST represents the difference between the lowest singlet excitation energy level (S1 level) and the lowest triplet excitation energy level (T1 level).

[0209] Table 2

[0210] Type of compound S1 level (eV) T1 level (eV) <![CDATA[ΔE ST (eV)]]> Compound 1 2.64 2.48 0.16 Compound 2 2.67 2.50 0.17 Compound 11 2.73 2.64 0.09 Compound 21 2.85 2.76 0.09 Comparative example compound N1 2.60 2.46 0.14 Comparative example compound N2 2.61 2.51 0.10 Comparative example compound N3 2.68 2.59 0.09

[0211] Referring to the results in Table 2, Compounds 1, 2, 11, and 21 have a ΔE of 0.25 eV or less than 0.25 eV.ST Value. It is assumed that Compound 1, Compound 2, Compound 11, and Compound 21 can be used as thermally activated delayed fluorescence dopant materials. Comparative Example Compounds N1 to N3 also have a low ΔE ST value and are considered to be usable as thermally activated delayed fluorescence dopant materials

[0212] 3. Evaluation of the Luminescent Properties of Compounds

[0213] The fluorescence properties were evaluated using a V-670 spectrometer from JASCO Corporation, Japan. After deposition, an organic layer was formed on quartz glass using the following PPF shown respectively as the host material and using Compound 1, Compound 2, Compound 11, Compound 21, and Comparative Example Compounds N1 to N3 as dopant materials.

[0214]

[0215] The ratio of the deposited host and dopant was 80:20. The fluorescence emission spectrum was measured for the fabricated organic layer. The fluorescence quantum yield was measured using an ILF-835 integrating sphere system from JASCO Corporation, Japan.

[0216] Table 3 below shows the fluorescence emission characteristics of the examples and comparative examples, and in the evaluation of the fluorescence emission characteristics, λ max represents the emission center wavelength at the maximum emission intensity at the representative emission peak.

[0217] Table 3

[0218] Example Dopant material <![CDATA[λ max (nm)]]> Fluorescence quantum yield (%) Example 1 Compound 1 470 75.1 Example 2 Compound 2 469 72.6 Example 3 Compound 11 463 76.0 Example 4 Compound 21 459 74.2 Comparative example 1 Comparative example compound N1 495 80.0 Comparative example 2 Comparative example compound N2 496 73.2 Comparative example 3 Comparative example compound N3 485 65.0

[0219] Referring to the results in Table 3, Examples 1 to 4 and Comparative Examples 1 and 2 have similar values in terms of the fluorescence quantum yield. It is found that the emission center wavelengths λ of Examples 1 to 4 are in the short wavelength region compared to those of Comparative Examples 1 to 3. max That is, the results in Table 3 show that Compound 1, Compound 2, Compound 11, and Compound 21 emit blue light in the short wavelength region compared to the comparative example compounds.

[0220] 4. Fabrication and Evaluation of Organic Electroluminescent Devices

[0221] (Fabrication of Organic Electroluminescent Devices)

[0222] An organic electroluminescent device according to an embodiment containing the compound according to the embodiment in the emission layer is manufactured by the following method. The organic electroluminescent devices of Examples 1 to 4 are manufactured using Compound 1, Compound 2, Compound 11, and Compound 21 of the above-described examples as dopant materials for the emission layer, respectively. The organic electroluminescent devices of Comparative Examples 1 to 3 are manufactured using Comparative Compound N1 to Comparative Compound N3 as dopant materials for the emission layer, respectively.

[0223] ITO having a thickness is patterned on a glass substrate, washed with ultrapure water, and subjected to ozone treatment after being irradiated with UV for 10 minutes. Thereafter, HAT-CN is deposited to a thickness to form a hole injection layer, and α-NPD is deposited to a thickness to form a hole transport layer. Then, mCP is deposited to a thickness to form an electron blocking layer.

[0224] Then, mCBP and the compound of the embodiment or the comparative compound are co-deposited on the electron blocking layer at a ratio of 1:99, respectively, to form an emission layer having a thickness. That is, the emission layers formed by co-deposition in Examples 1 to 4 are deposited by mixing Compound 1, Compound 2, Compound 11, and Compound 21 with mCBP, respectively, and the emission layers in Comparative Examples 1 to 3 are deposited by mixing Comparative Compound N1 to Comparative Compound N3 with mCBP, respectively.

[0225] An electron transport layer having a thickness is formed on the emission layer from 2,2',2"-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzoimidazole) (TPBi). Thereafter, an electron injection layer having a thickness is formed from LiF. Then, a second electrode having a thickness is formed from aluminum (Al).

[0226] In the embodiment, a hole injection layer, a hole transport layer, an electron blocking layer, an emission layer, an electron transport layer, an electron injection layer, and a second electrode are formed using a vacuum deposition apparatus.

[0227] (Evaluation of Organic Electroluminescent Device Characteristics)

[0228] Table 4 shows the evaluation results of the organic electroluminescent devices of Examples 1 to 4 and Comparative Examples 1 to 3. The λ of the organic light-emitting devices was compared max(It is the emission center wavelength), luminous efficiency, and service life. In the characteristic evaluation results of the examples and comparative examples shown in Table 4, a source meter (2400 series from Keithley Instruments) was used to measure voltage and current density, and an external quantum efficiency measurement device (C9920-12 from HAMAMATSU Photonics) was used to measure luminance and external quantum efficiency. The luminous efficiency represents the current efficiency value for a current density of 10 mA / cm 2 and the service life represents the half-life at 1.0 mA / cm 2 .

[0229] In Table 4, the luminous efficiency and service life were compared and shown as relative values. The luminous efficiency and service life in Comparative Example 1 were set to 1, and the luminous efficiency and service life of the comparative examples and examples were shown in a relative sense.

[0230] Table 4

[0231] Example Dopant material <![CDATA[λ max (nm)]]> Luminescence efficiency Service life Example 1 Compound 1 475 1.25 2.50 Example 2 Compound 2 470 1.10 2.20 Example 3 Compound 11 466 1.15 2.30 Example 4 Compound 21 463 1.20 2.15 Comparative example 1 Comparative example compound N1 497 1.00 1.00 Comparative example 2 Comparative example compound N2 499 0.82 0.95 Comparative example 3 Comparative example compound N3 488 0.76 0.57

[0232] Referring to the results in Table 4, it was confirmed that the organic electroluminescent devices of Examples 1 to 4 had good luminous efficiency and long device characteristics when compared with the organic electroluminescent devices of Comparative Examples 1 to 3. In addition, when compared with the organic electroluminescent devices of Comparative Examples 1 to 3, the organic electroluminescent devices of Examples 1 to 4 had a maximum emission λ max in the short wavelength region, and thus it was seen that the organic electroluminescent devices of Examples 1 to 4 emitted dark blue light, which was short blue light, when compared with Comparative Examples 1 to 3.

[0233] It is considered that the nitrogen-containing ring group contained in the carbazole group of the compound of the example weakens the electron donation of the carbazole group, thereby emitting short, dark blue light. In addition, the inclusion of the nitrogen-containing ring group expands the conjugation range of the carbazole group, and thus the nitrogen-containing ring group contributes to the stability of the compound by forming intramolecular or intermolecular hydrogen bonds.

[0234] Meanwhile, Comparative Example Compound N2 contains a nitrogen-containing ring group connected to a carbazole group, similar to the compound of the present disclosure, but has a longer wavelength value when compared with the compound of the example. It is considered that the electron-withdrawing methyl group substituted on the carbazole group that does not include the nitrogen-containing ring group can make the wavelength longer. In addition, since the methyl group causes steric distortion of the compound and the stability of the compound is reduced, the device service life is lower than that of the device using the compound of the example.

[0235] Referring to the evaluation results of the reference compounds and the examples of the organic electroluminescent devices, it can be seen that the compounds of the embodiments can be used as luminescent materials that emit deep blue light and have long-life characteristics. In addition, it can be seen that the organic electroluminescent devices of the embodiments that contain the compounds of the embodiments to emit deep blue light have good luminous efficiency and long-life characteristics.

[0236] The aromatic compounds of the embodiments may include a nitrogen-containing ring group linked to a carbazole group directly bonded to a benzene ring, and can be used as a material that emits deep blue light while having long-life characteristics. The organic electroluminescent devices containing the aromatic compounds of the embodiments can emit deep blue light while having good luminous efficiency and long-life device characteristics.

[0237] The organic electroluminescent devices of the embodiments may have improved device characteristics, such as high efficiency and long life in the blue wavelength region.

[0238] The aromatic compounds of the embodiments may be included in the emission layer of the organic electroluminescent device to provide an organic electroluminescent device with high efficiency.

[0239] As used herein, the terms "use", "using", and "used" may be considered to be synonymous with the terms "utilize", "utilizing", and "utilized", respectively.

[0240] In addition, the terms "substantially", "about", and similar terms are used as approximate terms and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by a person of ordinary skill in the art.

[0241] In addition, any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, the range of "1.0 to 10.0" is intended to include all sub-ranges between the recited minimum value of 1.0 and the recited maximum value of 10.0 (and including the end values), that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein, and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein. Accordingly, the applicant reserves the right to modify this specification (including the claims) to expressly recite any sub-ranges subsumed within the ranges expressly recited herein.

[0242] Although the present disclosure has been described with reference to exemplary embodiments thereof, it should be understood that the present disclosure should not be limited to these embodiments, but rather various changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the present disclosure.

[0243] Therefore, the technical scope of the present disclosure is not intended to be limited to what is set forth in the detailed description of the specification, but rather is intended to be defined by the appended claims and their equivalents.

Claims

1. An organic electroluminescent device, comprising: A first electrode; A second electrode on the first electrode; And An emission layer between the first electrode and the second electrode, Wherein the first electrode and the second electrode each independently comprise at least one selected from the following: one selected from Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF / Ca, LiF / Al, Mo, Ti, In, Sn, and Zn; a compound of two or more selected from them; a mixture of two or more selected from them; and their oxides, Wherein the emission layer comprises an aromatic compound represented by Formula 1: Formula 1 Wherein in Formula 1, X is a cyano group, fluorine, or a C1-C10 alkyl group substituted with fluorine, Y is a hydrogen atom, a deuterium atom, a halogen atom, a cyano group, an unsubstituted heteroaryl group having 3 to 20 ring carbon atoms and at least one ring nitrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a to d are each independently an integer from 1 to 4, and At least one of R1 to R4 is represented by Formula 2, and the remaining ones of R1 to R4 are each independently a hydrogen atom, a deuterium atom, or a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, Formula 2 Wherein in Formula 2, At least one of W1 to W5 is a nitrogen atom, and the remaining ones of W1 to W5 are each independently CR5, R5 is a hydrogen atom, a deuterium atom, or a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, and -* is a binding site, Wherein the substituents for the substitution are selected from the group consisting of a deuterium atom, a halogen atom, a cyano group, a nitro group, an amino group, a silyl group, an oxy group, a mercapto group, a sulfinyl group, a sulfonyl group, a carbonyl group, a boron group, a phosphine oxide group, a phosphine sulfide group, and a C1-C10 alkyl group.

2. The organic electroluminescent device according to claim 1, wherein the aromatic compound represented by Formula 1 is a thermally activated delayed fluorescence emitting material.

3. The organic electroluminescent device according to claim 1, wherein Formula 2 is represented by Formula 2-1 or Formula 2-2: Formula 2-1 Formula 2-2 4. The organic electroluminescent device according to claim 1, wherein a to d are all 1, and R1 to R4 are all the same.

5. The organic electroluminescent device according to claim 1, wherein the aromatic compound represented by Formula 1 is laterally symmetric with respect to X and Y.

6. The organic electroluminescent device according to claim 1, wherein Y is an unsubstituted phenyl group, an unsubstituted pyridine group, an unsubstituted carbazole group, or an unsubstituted alkyl group having 1 to 4 carbon atoms.

7. The organic electroluminescent device according to claim 1, wherein Formula 1 is represented by Formula 3: Formula 3 Wherein in Formula 3, X, Y, and W1 to W5 are the same as those defined in Formula 1 and Formula 2.

8. The organic electroluminescent device according to claim 1, wherein Formula 1 is any one of the compounds represented by Compound Group 1: Compound Group 1

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