Boron-containing compounds, light-emitting materials, organic electroluminescent elements, and electronic devices

Abstract

The present invention provides a boron-containing compound that is a multi-resonance thermally activated delayed fluorescence (MR-TADF) material capable of producing highly efficient and long-life elements, a light-emitting material made from the boron-containing compound, an organic electroluminescent element using the boron-containing compound, and an electronic device equipped with the organic electroluminescent element. [Solution] As a multi-resonance thermally activated delayed fluorescence (MR-TADF) material, a boron-containing compound with an asymmetric structure incorporating a phenoxazine skeleton was investigated. By extending the conjugation length of the phenoxazine moiety of the compound, the absorption wavelength was lengthened, thereby improving the energy transfer efficiency from the sensitizer.

Description

Technical Field

[0001] The present invention relates to a boron-containing compound, a luminescent material composed of a boron-containing compound, an organic electroluminescent device using a boron-containing compound, and an electronic device equipped with an organic electroluminescent device.

Background Art

[0002] Organic electroluminescent devices (hereinafter sometimes referred to as "organic EL devices") are being put into practical use as flat panel displays (FPDs). It is known that there are three types of luminescent materials for organic EL devices: fluorescent materials, phosphorescent materials, and thermally activated delayed fluorescence (TADF) materials.

[0003] One of the means to improve the practicality of organic EL devices is to increase the luminous efficiency. And thermally activated delayed fluorescence (TADF) materials are highly expected materials in terms of high luminous efficiency.

[0004] However, thermally activated delayed fluorescence (TADF) materials have a wide emission spectrum width, resulting in low color purity. In order to improve the color purity, it was necessary to remove unnecessary emission color components using an optical filter. And using an optical filter significantly reduced the luminous efficiency. Therefore, the development of a luminescent material with a narrow full width at half maximum (FWHM) of the emission spectrum and high color purity has been desired.

[0005] Under such circumstances, among thermally activated delayed fluorescence (TADF) materials, multiple resonance type thermally activated delayed fluorescence (MR-TADF) materials that utilize the multiple resonance effect between boron and nitrogen have attracted attention. Multiple resonance type thermally activated delayed fluorescence (MR-TADF) materials have a narrow full width at half maximum (FWHM) of the emission spectrum, so they have high color purity, and also have a high luminous efficiency because the internal quantum efficiency is 100%. Therefore, according to the multiple resonance type thermally activated delayed fluorescence (MR-TADF) materials, a high-definition and energy-saving display can be realized.

[0006] Non-patent document 1 discloses a compound having a triphenylborone skeleton, which is a blue thermally activated delayed fluorescence molecule with ultra-high color purity that increases the energy difference between HOMO and LUMO through multiple resonance effects. The compound has two nitrogen atoms bonded to the triphenylborone skeleton that are bonded to adjacent phenyl groups to form a rigid polycyclic aromatic structure.

[0007] The blue thermally activated delayed fluorescence molecule described in Non-Patent Literature 1 is said to exhibit narrow-band blue emission with a full width at half maximum of 28 nm at wavelengths of 459-467 nm.

[0008] Furthermore, in the molecular structure of multi-resonance thermally activated delayed fluorescence (MR-TADF) materials that utilize the multiple resonance effect of boron and nitrogen, compounds having a polycyclic aromatic structure in which one of the two nitrogen atoms is substituted by an oxygen atom have also been reported (see Non-Patent Literature 2).

[0009] The multi-resonance thermally activated delayed fluorescence (MR-TADF) material described in Non-Patent Literature 2 exhibits very efficient narrowband blue emission through multiple resonances, where nitrogen atoms in the boron-nitrogen condensation skeleton are replaced by oxygen atoms, resulting in weakened intramolecular charge transfer. As an example, Non-Patent Literature 2 reports a multi-resonance thermally activated delayed fluorescence (MR-TADF) material exhibiting blue emission with a full width at half maximum of 36 nm, and an organic EL device that achieved a maximum external quantum efficiency of 13.6%.

[0010] Non-patent document 3 discloses a molecule, ν-DABNA, as a multiple resonance thermally activated delayed fluorescence (MR-TADF) material, which has five benzene rings containing two boron atoms and four nitrogen atoms, and two diphenylamino groups. ν-DABNA is said to exhibit deep blue emission with ultra-high color purity and a full width at half maximum of 14 nm.

[0011] Non-patent document 3 reports that in ν-DABNA, the electron distribution in the HOMO-LUMO is localized due to the multiple resonance effect of boron and nitrogen, minimizing the vibratory interaction between the ground state (S0) and the excited singlet state (S1), as well as the energy difference between the excited singlet state (S1) and the excited triplet state (T1). Furthermore, emission with a full width at half maximum of 18 nm was observed at a wavelength of 469 nm, with an initial brightness of 1000 cdm. -2 It has been reported to exhibit an external quantum efficiency of 26.0% and a maximum of 34.4%. [Prior art documents] [Non-patent literature]

[0012] [Non-Patent Document 1] Takuji Hatakeyama et al., Advanced Materials, 28, 2777-2781 (2016) [Non-Patent Document 2] Jianmei Han et al., Advanced Optical Materials, 2021, 2102092 (2021) [Non-Patent Document 3] Yasuhiko Kondo et al., Nature Photonics 13, 678-682 (2019) [Non-Patent Document 4] Xin Xiong et al., Material Chemistry Frontiers 7,929-936(2023). [Overview of the project] [Problems that the invention aims to solve]

[0013] Multiple resonance thermally activated delayed fluorescence (MR-TADF) materials are highly promising as materials for forming organic electroluminescent devices because they exhibit a narrow full width at half maximum of the emission spectrum and achieve 100% emission quantum efficiency. However, when used in devices, MR-TADF materials have the problem of short device lifetime.

[0014] The present invention has been made in view of the above, and aims to provide a boron-containing compound that is a multi-resonance type thermally activated delayed fluorescence (MR-TADF) material capable of obtaining a highly efficient and long-life element, a light-emitting material made from a boron-containing compound, an organic electroluminescent element using a boron-containing compound, and an electronic device equipped with an organic electroluminescent element. [Means for solving the problem]

[0015] The inventors diligently conducted research to solve the above problems. They focused on hyperorganic electroluminescence technology using electrochemically robust thermally activated delayed fluorescence (TADF) materials and phosphorescent sensitizers. In hyperorganic electroluminescence technology, the sensitizer can convert all excitons into light, and energy transfer is used to ultimately make the material glow. In other words, they believed that if efficient energy transfer could be achieved from the sensitizer, a highly efficient and long-life device could be realized.

[0016] Furthermore, we investigated boron-containing compounds with an asymmetric structure incorporating a phenoxazine skeleton as multi-resonance thermally activated delayed fluorescence (MR-TADF) materials. We discovered that extending the conjugation length of the phenoxazine moiety in these compounds to lengthen the absorption wavelength improves the energy transfer efficiency from the sensitizer, thus completing the present invention.

[0017] In other words, the present invention includes the following embodiments.

[0018] [1] A boron-containing compound having a phenoxazine skeleton represented by the following general formula (1); [Chemical formula] (In general formula (1), R 1 and R 2 are each independently a group selected from the group consisting of a hydrogen atom, an unsubstituted phenyl group, a phenyl group having a substituent, a biphenyl group, and a terphenyl group, and R 1 and R 2 are not both hydrogen atoms, R 3 is a hydrogen atom or a substituent, and R 4 and R 5 are each independently a hydrogen atom or a substituent.) [2] In the above R 1 and R 2 , the substituent is a methyl group, and the boron-containing compound according to aspect [1]. [3] [[ID=३३]]In the above R 1 and R 2 , the phenyl group having a substituent is a group selected from the group consisting of a 2-methylphenyl group, a 2,6-dimethylphenyl group, and a 2,4,6-trimethylphenyl group, and the boron-containing compound according to aspect [1]. [4] In the above R 1 and R 2 , the terphenyl group is a m-terphenyl group, and the boron-containing compound according to aspect [1]. [5] In the above R 3 , the substituent is an unsubstituted carbazole group or a carbazole group having a substituent, and the boron-containing compound according to aspect [1]. [6] In the above R 4 and R 5 , the substituent is a group selected from the group consisting of a t-butyl group, an unsubstituted phenyl group, a phenyl group having a substituent, a biphenyl group, and a terphenyl group, and the boron-containing compound according to aspect [1]. [7] A light-emitting material comprising a boron-containing compound according to any one embodiment of [1] to [6]. [8] An organic electroluminescent element comprising a boron-containing compound according to any one of embodiments [1] to [6] in the light-emitting layer. [9] The organic electroluminescent element according to embodiment [8], wherein the light-emitting layer further comprises a sensitizer.

[10] An electronic device equipped with the organic electroluminescent element described in embodiment [8]. [Effects of the Invention]

[0019] The boron-containing compound having a phenoxazine skeleton according to the present invention is a novel compound that exhibits green emission with a narrow full width at half maximum.

[0020] According to the boron-containing compound having a phenoxazine skeleton of the present invention, it is possible to obtain an organic electroluminescent element with high efficiency and long lifespan.

[0021] Furthermore, electronic devices such as flat displays that incorporate an organic electroluminescent element using a boron-containing compound having a phenoxazine skeleton according to the present invention will be high-definition, energy-efficient, and have a long lifespan. [Brief explanation of the drawing]

[0022] [Figure 1] These are the ultraviolet-visible (UV-vis) absorption spectra of the compounds prepared in the examples and comparative examples in toluene solutions. [Figure 2] These are the fluorescence spectra (PL spectra) of the compounds prepared in the examples and comparative examples in toluene solution. [Figure 3] These are the PYS measurement results for the solid thin film (single film) of the compound prepared in Example 1. [Figure 4] These are the PYS measurement results for the solid thin film (monofilm) of the compound prepared in Example 2. [Figure 5]These are the PYS measurement results for the solid thin film (single film) of the compound prepared in Comparative Example 1. [Figure 6] These are the ultraviolet-visible (UV-vis) absorption spectra of the solid thin films (monofilms) of the compounds prepared in the examples and comparative examples. [Figure 7] These are the UV-vis absorption spectra of binary co-evaporated films doped with 5 wt% of the compounds prepared in the examples and comparative examples. [Figure 8] These are the fluorescence spectra (PL spectra) of binary co-evaporated films doped with 5 wt% of the compounds prepared in the examples and comparative examples. [Figure 9] This figure shows the structure of the organic EL elements fabricated in the examples and comparative examples. [Figure 10] This is an energy diagram of the organic EL elements fabricated in the examples and comparative examples. [Figure 11] These are the EL spectra of the organic EL elements prepared in the examples and comparative examples. [Figure 12] These are the current density-voltage-luminance characteristics of the organic EL elements fabricated in the examples and comparative examples. [Figure 13] These are the external quantum efficiency-luminance characteristics of the organic EL elements fabricated in the examples and comparative examples. [Figure 14] These are the power efficiency-luminance characteristics of the organic EL elements fabricated in the examples and comparative examples. [Figure 15] This figure shows the luminance attenuation per unit time of the organic EL elements fabricated in the examples and comparative examples. [Figure 16] This figure shows the configuration of the organic electroluminescent element of the present invention. [Modes for carrying out the invention]

[0023] The present invention will be described in detail below. ≪Boron-containing compounds with a phenoxazine skeleton≫ The boron-containing compound having a phenoxazine skeleton according to the present invention is represented by the following general formula (1). [ka] (In general formula (1), R 1 and R 2 Each of these is independently selected from the group consisting of a hydrogen atom, an unsubstituted phenyl group, a substituted phenyl group, a biphenyl group, and a terphenyl group, and R 1 and R 2 None of them are hydrogen atoms, R 3 R is a hydrogen atom or substituent, 4 and R 5 Each of these is independently either a hydrogen atom or a substituent.

[0024] In general formula (1), R 1 and R 2 One of the groups may be a hydrogen atom, while the other is a group selected from the group consisting of an unsubstituted phenyl group, a substituted phenyl group, a biphenyl group, and a terphenyl group.

[0025] The boron-containing compound having a phenoxazine skeleton according to the present invention is R 1 and R 2 At least one of the groups is selected from the group consisting of an unsubstituted phenyl group, a substituted phenyl group, a biphenyl group, and a terphenyl group, thereby extending the conjugation length of the phenoxazine moiety. As a result, the boron-containing compound having the phenoxazine skeleton of the present invention has a longer absorption wavelength, which improves the energy transfer efficiency from the sensitizer, enabling the realization of a highly efficient and long-life device as a multi-resonance thermally activated delayed fluorescence (MR-TADF) material.

[0026] In general formula (1), R 1 and / or R 2 However, if the phenyl group has a substituent, the substituent on the phenyl group may be, for example, a methyl group. Furthermore, the phenyl group may have not just one methyl group, but two or three. That is, R 1 and / or R 2However, if the phenyl group has a substituent, it may be any of the following: a methylphenyl group (tolyl group), a dimethylphenyl group (xylyl group), or a trimethylphenyl group (mesityl group).

[0027] More specifically, in general formula (1), R 1 and / or R 2 However, if the phenyl group has a substituent, it may be a group selected from the group consisting of 2-methylphenyl, 2,6-dimethylphenyl, and 2,4,6-trimethylphenyl.

[0028] In general formula (1), R 1 and / or R 2 However, if it is a terphenyl group, it may be an m-terphenyl group.

[0029] In general formula (1), R 3 If the substituent is a substituent, the substituent may be an unsubstituted carbazole group or a substituted carbazole group.

[0030] In general formula (1), R 3 However, if the carbazole group has a substituent, the substituent on the carbazole group may be a group selected from the group consisting of, for example, a methyl group, a t-butyl group, a phenyl group, a biphenyl group, and a terphenyl group.

[0031] In general formula (1), R 3 However, if the carbazole group has a substituent and the substituent is a terphenyl group, it may be an m-terphenyl group.

[0032] In general formula (1), R 4 and / or R 5 If the substituent is a substituent, the substituent may be a group selected from the group consisting of a methyl group, a t-butyl group, a phenyl group, a biphenyl group, and a terphenyl group.

[0033] In general formula (1), R 4 and / or R 5If the substituent is a terphenyl group, it may also be an m-terphenyl group.

[0034] The boron-containing compound having the phenoxazine skeleton represented by the general formula (1) above may specifically be a compound having the following structural formula. However, the boron-containing compound of the present invention is not limited to the following. [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0035] <Method for producing boron-containing compounds having a phenoxazine skeleton> The boron-containing compounds having a phenoxazine skeleton according to the present invention can be synthesized by various known methods. As an example, the synthesis routes for PhPXZ-tCzBN and MesPXZ-tCzBN, which are two of the boron-containing compounds of the present invention, are shown below.

[0036] [Synthesis pathway for PhPXZ-tCzBN] The synthesis route for PhPXZ-tCzBN is as follows: [ka]

[0037] [Synthesis pathway for MesPXZ-tCzBN] The synthesis route for MesPXZ-tCzBN is as follows: [ka]

[0038] ≪Luminescent Materials≫ The luminescent material of the present invention consists of a boron-containing compound having the phenoxazine skeleton of the present invention as described above.

[0039] The luminescent material of the present invention is a novel compound, a multi-resonance thermally activated delayed fluorescence (MR-TADF) material exhibiting green emission with a narrow full width at half maximum.

[0040] If the light-emitting material comprising the boron-containing compound having a phenoxazine skeleton of the present invention is used, for example, as a material for the light-emitting layer of an organic electroluminescent element, an organic electroluminescent element with high efficiency and a long lifespan can be obtained.

[0041] Organic electroluminescent elements The organic EL element of the present invention contains the boron-containing compound of the present invention. The boron-containing compound of the present invention functions as a light-emitting material included in the light-emitting band of the organic EL element. The light-emitting band is the region in which holes and electrons recombine and light emission occurs, and in many cases, this corresponds to the light-emitting layer. In other words, the boron-containing compound having a phenoxazine skeleton of the present invention can be suitably used as a material for forming the light-emitting layer of an organic electroluminescent element.

[0042] <Overall configuration of organic EL elements> Figure 16 shows a typical structure of the organic EL element of the present invention. The organic EL element is an element in which a hole injection layer 3, a hole transport layer 4, an emissive layer 5, an electron transport layer 6, an electron injection layer 7, and a cathode 8 are stacked in this order on an anode 2 deposited on a substrate 1.

[0043] In some organic EL devices, some layers in the multilayer structure may be omitted, or for example, the electron injection layer 7 may be an electron injection / transport layer that also functions as the electron transport layer 6. Alternatively, an electron blocking layer may be provided between the hole transport layer 4 and the light-emitting layer 5, or between the light-emitting layer 5 and the electron transport layer 6. These layers not only control the flow of injected holes and electrons within the device, but also play a role in efficiently radiating transitions to the ground state by confining excitons to the light-emitting layer 5 and preventing energy leakage of the electromer.

[0044] For example, 3,3'-di(9H-carbazole-9-yl)-1,1'-biphenyl (mCBP) is used as the electron blocking layer, and for example, 3,6-bis(diphenylformolyl)-9-phenylcarbazole (PO9) is used as the hole blocking layer.

[0045] The overall thickness of the organic EL layer may be, for example, 30 to 500 nm.

[0046] <Circuit board> As the substrate 1, for example, a transparent and smooth material having a total light transmittance of at least 70% is used. Specifically, examples include resin materials or glass materials with a thickness of 0.1 to 10 mm. Examples of resin materials include polyethylene terephthalate, polyethylene naphthalate, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, and polyarylate. Examples of glass materials include quartz glass and soda glass.

[0047] <Anode> Anode 2 has the function of injecting holes into the hole injection layer 3, the hole transport layer 4, and the light emission layer 5. Common materials for anode 2 include metal oxides, metals, alloys, and other conductive materials with a work function of 4.5 eV or higher. Of these, materials with a total light transmittance of 80% or higher are preferred from the viewpoint of transmitting emitted light. Specifically, examples include transparent conductive ceramics such as ITO (indium tin oxide) and ZnO (zinc oxide), poly(3,4-ethylenedioxythiophene) / poly(4-styrene sulfonic acid) (PEDOT / PSS), polyaniline, and other transparent conductive materials.

[0048] The film thickness of anode 2 may be 5 to 500 nm. Anode 2 is formed by methods such as vapor deposition, electron beam deposition, sputtering, chemical reaction, and coating.

[0049] <Hole Injection Layer: HIL> The hole injection layer 3 plays a role in improving luminescence efficiency by lowering the hole injection barrier from the anode 2 to the hole transport layer 4. Since the hole injection layer 3 is subjected to current at a low voltage, it is preferable that it be thin and uniform enough to prevent the formation of pinholes and other defects.

[0050] For example, a polymer buffer can be used as the hole injection layer 3. Examples of polymer buffers include polyether ketone (PEK), as well as triphenylamine-containing polyether ketone (TPAPEK) doped with 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl) borate (PPBI), tris(4-bromophenyl)aminium hexachloroantimonate (TBPAH), or tris(pentafluorophenyl) borane (PPB) as acceptors.

[0051] Alternatively, examples of hole-implantation materials include transition metal oxides, aromatic amines, and polymer compounds such as polythiophenes and polyanilines. Examples of transition metal oxides include molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide. Examples of aromatic amines include benzidine derivatives and phenylenediamine derivatives. A typical example of polymer compounds such as polythiophenes and polyanilines is poly(3,4-ethylenedioxythiophene) (PEDOT:PSS).

[0052] <Hole Transport Layer: HTL> The hole transport layer 4 is provided between the anode 2 and the light-emitting layer 5, and plays the role of efficiently transporting holes from the anode 2 to the light-emitting layer 5. As the hole transport material, one with a small ionization potential is used, that is, one in which electrons are easily excited from the HOMO and holes are easily generated. Specifically, examples include 4,4'-bis[phenyl(1-naphthyl)amino]biphenyl (NPB), hexaphenylbenzene derivatives (4DBTHPB), poly(9,9-dioctylfluorene-alto-N-(4-butylphenyl)diphenylamine) (TFB), 4,4'-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (α-NPD), 4,4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzeneamine] (TAPC), N,N'-diphenyl-N,N'-di(m-tolyl)benzidine (TPD), 4,4',4''-tri-9-carbazolyltriphenylamine (TCTA), and 4,4',4''-tris[phenyl(m-tolyl)amino]triphenylamine).

[0053] The hole-injection layer 3 described above may be a layer made of a composite material of a hole-transporting material and a material that exhibits electron-accepting properties for the hole-transporting material, or it may be a layer in which a layer made of an electron-accepting material and a layer made of a hole-transporting material are laminated. Examples of electron-accepting materials include compounds having electron-withdrawing groups such as 7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (F4-TCNQ) and hexaazatriphenylenecarbonitrate (HAT-CN), as well as oxides of transition metals from group 4 to group 8.

[0054] <Emitting layer: EML> The light-emitting layer 5 is generally a layer containing at least two components: a host material that transports electrons and holes, and a light-emitting material, i.e., a dopant. The boron-containing compound of the present invention is used as the dopant. The film thickness of the light-emitting layer 5 may typically be 2 to 100 nm.

[0055] Examples of host materials include mCBP, bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO), PO9, 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP), 2,8-bis(diphenylphosphoryl)dibenzothiophene (PPT), and DIC-TRZ (11-(4,6-diphenyl-1,3,5-triazine-2-yl)-12-phenylindoro[2,3-a]carbazole).

[0056] The dopant content in the light-emitting layer 5 is typically 0.1 to 30% by weight, preferably 0.5 to 10% by weight, relative to the host material, and the dopant is uniformly dispersed in the host material.

[0057] [Sensitizer] The light-emitting layer in the organic EL element of the present invention comprises a host material and a dopant as essential components, and may further contain a sensitizer. The boron-containing compound with an asymmetric structure into which the phenoxazine skeleton of the present invention is introduced has an extended conjugation length of the phenoxazine moiety, resulting in a longer absorption wavelength. This improves the energy transfer efficiency from the sensitizer. Therefore, by using the boron-containing compound of the present invention in combination with a sensitizer, efficient energy transfer from the sensitizer can be achieved, resulting in a highly efficient and long-life organic EL element.

[0058] The sensitizer included in the light-emitting layer of the organic EL element of the present invention is not particularly limited, and any compound that can emit light at room temperature under optical or electrochemical excitation is acceptable.

[0059] Among the sensitizers, organometallic complexes, particularly transition metal complexes, are preferred. Furthermore, organometallic complexes containing copper, molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, gold, or europium are preferred as sensitizers, organometallic complexes containing copper, iridium, or platinum are even more preferred, and organometallic complexes containing iridium or platinum are particularly preferred.

[0060] As sensitizers included in the light-emitting layer of the organic EL element of the present invention, phosphorescent or thermally activated delayed fluorescence (TADF) sensitizers are particularly preferred. Specific phosphorescent sensitizers include, for example, Ir(ppy)3 and its derivatives. TADF sensitizers include, for example, 4CzIPN and its derivatives.

[0061] The content of the sensitizer in the light-emitting layer 5 is not particularly limited, but for example, it is 5 to 60% by weight, preferably 10 to 50% by weight, and most preferably 15 to 20% by weight, relative to the entire light-emitting layer.

[0062] <Electron transport layer: ETL> The electron transport layer 6 is provided between the cathode 8 and the light-emitting layer 5 and plays the role of efficiently transporting electrons from the cathode 8 to the light-emitting layer 5. Suitable materials for the electron transport layer 6 include those with high electron affinity, i.e., materials with a low LUMO energy and a high likelihood of excited electrons existing.

[0063] Examples of materials for the electron transport layer 6 include heterocyclic compounds having a pyridine skeleton such as 2,9-bis(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline (NBPhen), tris-1,3,5-(3'-(pyridine-3''-yl)phenyl)benzene (TmPyPhB), bathophenanthroline (BPhen), 2,4,6-tris(2-pyridyl)-1,3,5-triazine (2Py3Tzn), 2,9-di(2-naphthyl)-4,7-diphenyl-1,10-phenanthroline (ET1), 3,3”,5,5'-tetra(3-pyridyl)-1,1';3',1”-terphenyl (B3PyPB), Examples include 4,6-bis(3,5-di(pyridine-3-yl)phenyl)-2-methylpyrimidine (B3PyMPM), 2-(4-biphenylyl)-5-(pt-butylphenyl)-1,3,4-oxadiazole (tBu-PBD), 1,3-bis[5-(4-t-butylphenyl)-2-[1,3,4]oxadiazolyl]benzene (OXD-7), 3-(biphenyl-4-yl)-5-(4-t-butylphenyl)-4-phenyl-4H-1,2,4-triazole (TAZ), basocproine (BCP), and 1,3,5-tris(1-phenyl-1H-benzimidazole-2-yl)benzene (TPBi).

[0064] <Electron injection layer: EIL> The electron injection layer 7 is provided between the electron transport layer 6 and the cathode 8, and plays a role in reducing the difference in work functions and facilitating the transfer of electrons from the cathode 8 to the electron transport layer 6. Examples of materials for the electron injection layer 7 include lithium fluoride (LiF).

[0065] <Method for manufacturing a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and an electron injection layer> In an organic EL device, the hole injection layer 3, hole transport layer 4, light-emitting layer 5, electron transport layer 6, and electron injection layer 7 can be formed by vapor deposition or coating.

[0066] Examples of vapor deposition methods include resistance heating vapor deposition, electron beam vapor deposition, sputtering, and molecular stacking. In vapor deposition, the material for each layer is first converted to a gaseous state, deposited on a substrate, and then converted back to a solid. Vapor deposition is typically performed in 10 -3 The deposition process is carried out by heating the deposited material to 300-400°C in an atmosphere under reduced pressure below Pa.

[0067] When using a coating method, the material for each layer is dissolved in an ink, such as chloroform, methylene chloride, dichloroethane, tetrahydrofuran, toluene, xylene, acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, and ethyl cellulose acetate, and the film is formed by a known coating method. Examples of coating methods include bar coating, capillary coating, slit coating, inkjet, spray coating, nozzle coating, and printing. When using a coating method, the same coating method may be used for all layers, or the most suitable coating method may be selected according to the type of ink.

[0068] <Cathode> The cathode 8 has the function of injecting electrons into the light-emitting layer 5 via the electron injection layer 7 and the electron transport layer 6. Generally, metals or alloys with a work function of approximately 4 eV or less are suitable as materials for the cathode 8. Examples of metals that can be used for the cathode 8 include aluminum, lithium, sodium, potassium, calcium, and magnesium. Examples of cathodes using alloys include electrodes made of alloys of these low-work-function metals and metals such as aluminum or silver, or electrodes with a laminated structure of these low-work-function metals and metals such as aluminum or silver.

[0069] The film thickness of the cathode 8 may be, for example, 10 to 200 nm. The cathode 8 is formed by methods such as vapor deposition, electron beam irradiation, sputtering, chemical reaction, and coating. In addition to forming each layer of the organic EL element of the present invention using a single-wafer method, it may also be formed, for example, by a roll-to-roll method.

[0070] Electronic devices equipped with organic electroluminescent elements. Examples of electronic devices equipped with an organic electroluminescent element containing a light-emitting material made of a boron-containing compound having a phenoxazine skeleton according to the present invention include medium-sized displays such as tablets, mobile PCs, notebook PCs, medical monitors, and gaming monitors, as well as large displays such as televisions. [Examples]

[0071] The present invention will be described in more detail below based on examples, but the present invention is not limited in any way by the following examples.

[0072] <Measuring equipment> The instruments used for identifying the compounds in the examples and comparative examples are as follows: (1) 1 H nuclear magnetic resonance method ( 1 (H-NMR) JEOL Ltd., 400MHz, JNM-EX270FT-NMR (2) Mass spectrometry (MS) Waters SQD2 mass spectrometer The molecular weight was determined using a single quadrupole mass spectrometer (ASAP). (3)Elemental analyzer Perkin Elmer 2400II CHNS / O Analyzer Measurement mode: CHN mode

[0073] <Example 1> [Synthesis of PhPXZ-tCzBN] The boron-containing compound PhPXZ-tCzBN of Example 1 was synthesized using the following synthesis routes. The synthesis schemes for each route are shown below. [ka]

[0074] (Scheme 1: Synthesis scheme for 2Br-PXZ) [ka]

[0075] In a 500 mL four-necked flask, 5.50 g (30.0 mmol) of phenoxazine and 200 mL of THF were added and stirred, then cooled to 0°C in an ice bath. Next, 10.7 g (60.0 mmol) of N-bromosuccinimide was dissolved in 300 mL of THF and added dropwise while cooling in an ice bath, with stirring for 1 hour. Then, the mixture was allowed to return to room temperature and stirred for 12 hours.

[0076] Thin-layer chromatography (TLC) confirmed the disappearance of the starting materials, so the reaction was stopped, and the solvent was removed under reduced pressure to obtain the reaction mixture. The reaction mixture was dissolved in ethyl acetate, washed with a 5% aqueous sodium thiosulfate solution and saturated brine, and the organic layer was dehydrated with anhydrous magnesium sulfate, after which the solvent was removed under reduced pressure.

[0077] Separation and purification were performed by silica gel chromatography (600cc silica gel, developing solvent = hexane:ethyl acetate = 5:1). Then, recrystallization was performed with toluene and hexane, and after drying under reduced pressure, the target product, a deep blue solid, was obtained. The yield was 6.44g, with a yield of 63.7%. Identification was performed as follows: 1 The analysis was performed using 1H-NMR. 1 H-NMR(400MHz,DMSO-d6)δ7.67(s,1H),6.06(dd,J=8.2,1.8Hz,2H),5.94(d,J=2.3Hz,2H),5.54(d,J=8.2Hz,2H)ppm.

[0078] (Scheme2:2Ph-PXZ synthesis scheme) [ka]

[0079] In a 100 mL four-necked flask fitted with a reflux condenser and a nitrogen inlet tube, 5.08 g (15.0 mmol) of 2Br-PXZ, 5.48 g (45.0 mmol) of phenylboronic acid, 100 mL of toluene, and 12.7 g of potassium phosphate were added, and nitrogen bubbling was performed for 1 hour. Then, 687 mg (0.75 mmol) of Tris(dibenzylideneacetone)dipalladium(0) and 616 mg (1.5 mmol) of SPhos were added, and the mixture was refluxed under nitrogen and stirred for 12 hours.

[0080] Thin-layer chromatography confirmed the consumption of the raw materials and the formation of the target product, so the reaction was terminated. After cooling to room temperature, the filtrate was filtered and concentrated.

[0081] Separation and purification were performed by silica gel chromatography (500cc silica gel, developing solvent = hexane:toluene = 3:1). Recrystallization was then performed using toluene and hexane. The yield was 2.72g, with a yield of 53.9%. Identification was performed as follows: 1 The analysis was performed using 1H-NMR. 1 H-NMR(400MHz,DMSO-d6)δ8.52(s,1H),7.56(d,J=7.8Hz,4H),7.39(t,J=7.5Hz,4H),7.27(t ,J=7.3Hz,2H),7.09(dd,J=8.2,1.4Hz,2H),6.96(d,J=1.4Hz,2H),6.56(d,J=8.2Hz,2H)ppm.

[0082] (Scheme3: 2Br-tCz synthesis scheme) [ka]

[0083] In a 200 mL two-necked flask, 4.19 g (15.0 mmol) of 3,6-di-tert-butylcarbazole, 9.77 g (30.0 mmol) of cesium carbonate, and 120 mL of DMF were added and the mixture was stirred for 1 hour. Then, 2.02 mL (16.0 mmol) of 1,2-dibromo-3-fluorobenzene was added and the mixture was heated and stirred at 160 °C for 12 hours.

[0084] Thin-layer chromatography (TLC) confirmed the disappearance of the starting materials, so the reaction was stopped and the mixture was allowed to return to room temperature. The reaction mixture was then filtered off. The filtrate was dissolved in methylene chloride, and the solution was dehydrated with anhydrous magnesium sulfate, after which the solvent was removed under reduced pressure.

[0085] Separation and purification were performed by silica gel chromatography (450cc silica gel, developing solvent = hexane:dichloromethane = 15:1). Subsequently, dispersion washing with methanol was performed to obtain the target white solid. The yield was 4.06g, 53.0%. Identification was performed as follows: 1 The analysis was performed using 1H-NMR. 1 H-NMR(400MHz,CDCl3)δ8.13(d,J=1.8Hz,2H),7.79(dd,J=7.1,2.5Hz,1H),7.43( dd,J=8.7,1.8Hz,2H),7.37-7.35(m,2H),6.95(d,J=8.7Hz,2H),1.45(s,18H)ppm.

[0086] (Scheme 4: Synthetic scheme for PhPXZ-Br-tCz) [ka]

[0087] In a 100 mL four-necked flask equipped with a reflux condenser and a nitrogen inlet tube, 3.0 g (9.0 mmol) of Ph-PXZ, 3.83 g (7.5 mmol) of 2Br-tCz, 2.88 g (30.0 mmol) of sodium-tert-butoxide, and 75 mL of anhydrous toluene were added, and nitrogen bubbling was performed for 1 hour. Then, 84 mg (0.375 mmol) of palladium acetate and 218 mg (0.75 mmol) of tri-tert-butylphosnium tetrafluoroborate were added, and the mixture was refluxed under nitrogen and stirred for 12 hours.

[0088] Thin-layer chromatography confirmed the consumption of the starting materials and the formation of the target product, so the reaction was terminated. The reaction mixture was filtered off, and the solvent was removed from the filtrate by distillation.

[0089] Next, separation and purification were performed by silica gel column chromatography (700cc silica gel, developing solvent = hexane:toluene = 7:1) to obtain the target yellow solid. The yield was 3.87g, and the yield was 67%. Identification was performed as follows: 1 The analysis was performed using 1H-NMR. 1 H-NMR(400MHz,CDCl3)δ8.15(s,2H),7.75(t,J=7.8Hz,1H),7.67-7.62(m,2H),7.53-7.47(m,6H),7.39(t,J=7.8Hz,4H),7.29( t,J=7.3Hz,2H),7.16(d,J=7.3Hz,1H),7.06-7.04(m,4H),6.98(dd,J=8.2,1.8Hz,2H),6.04(d,J=8.2Hz,2H),1.46(s,18H)ppm.

[0090] (Scheme 5: PhPXZ-tCzBN synthesis scheme) [ka]

[0091] A 50 mL Schlenk tube was degassed, and 2.12 g (2.8 mmol) of PhPXZ-Br-tCz and 20 mL of anhydrous xylene were added and stirred to dissolve. The mixture was then cooled to -40°C with liquid nitrogen, and 2.15 mL (2.6 M) of n-butyllithium hexane solution was added dropwise. The mixture was stirred at -40°C for 5 minutes, then stirred at room temperature for 30 minutes. The mixture was then stirred at 60°C for 1 hour. After cooling to room temperature, the hexane was removed by distillation under reduced pressure using a pump.

[0092] Next, the mixture was cooled again to -40°C with liquid nitrogen, 5.6 mL (1.0 M) of boron tribromide was added dropwise, and the mixture was stirred for 5 minutes. Then, it was stirred at room temperature for 1 hour.

[0093] Next, the mixture was cooled again to -40°C with liquid nitrogen, 0.98 mL of N,N-diisopropylethylamine was added dropwise, and the mixture was stirred at room temperature for 30 minutes. Then, heating and stirring were started at 100°C. After 12 hours, the reaction was stopped, and after cooling to room temperature, the reaction mixture was dissolved in ethyl acetate, washed with water and saturated brine, the organic layer was dehydrated with anhydrous magnesium sulfate, and the solvent was removed under reduced pressure.

[0094] Separation and purification were performed by silica gel column chromatography (450cc silica gel, developing solvent = hexane:ethyl acetate = 15:1). Subsequently, recrystallization was performed in a mixed solvent of toluene and methanol to obtain an orange solid. The yield was 737 mg, with a yield of 38%. Identification was performed as follows: 1 Analysis was performed using 1H-NMR, mass spectrometry, and elemental analysis after sublimation purification. 1 H-NMR(400MHz,CD2Cl2)δ8.92(d,J=1.8Hz,1H),8.64(d,J=1.8Hz,1H),8.52(d,J =1.8Hz,1H),8.39(d,J=8.7Hz,1H),8.31(d,J=1.8Hz,1H),8.24(dd,J=7.3,1.4H z,1H),7.92-7.86(m,2H),7.82-7.79(m,3H),7.71-7.65(m,3H),7.55-7.44(m,6 H),7.41-7.36(m,2H),7.31(dd,J=8.5,2.1Hz,1H),1.63(s,9H),1.53(s,9H)ppm. MS:[M + ]=780.43m / z Elementalanalysis(%)calculatedforC 50 H 41 BN2O:C86.20,H5.93,N4.02; Found: C86.04, H6.17, N3.99.

[0095] <Example 2> [Synthesis of MesPXZ-tCzBN] The boron-containing compound MesPXZ-tCzBN of Example 2 was synthesized using the following synthesis routes. The synthesis schemes for each route are shown below. [ka]

[0096] (Scheme 6: 2Br-PXZ synthesis scheme) [ka]

[0097] The synthesis scheme for 2Br-PXZ is the same as Scheme 1 described above.

[0098] (Scheme7:2Mes-PXZ synthesis scheme) [ka]

[0099] In a 100 mL four-necked flask, 5.08 g (15.0 mmol) of 2Br-PXZ, 7.38 g (45.0 mmol) of 2,4,6-trimethylphenylboronic acid, 12.7 g (60.0 mmol) of potassium phosphate, and 100 mL of toluene were added, and nitrogen bubbling was performed for 1 hour. Then, 687 mg (0.75 mmol) of Tris(dibenzylideneacetone)dipalladium(0) and 616 mg (1.5 mmol) of S-Phos were added, and the mixture was heated under nitrogen and refluxed for 12 hours.

[0100] Thin-layer chromatography confirmed the consumption of the starting materials and the formation of the target product, so the reaction was terminated. After cooling to room temperature, the mixture was concentrated. The reaction mixture was dissolved in ethyl acetate, washed with water and saturated brine, and the organic layer was dehydrated with anhydrous magnesium sulfate. The solvent was then removed under reduced pressure.

[0101] The product was separated and purified by silica gel column chromatography (600cc silica gel, developing solvent = hexane:toluene = 5:1), followed by dispersion washing with methanol to obtain the target pink solid. The yield was 2.26g, with a yield of 36%. Identification was performed as follows: 1 The analysis was performed using 1H-NMR. 1 H-NMR(400MHz,DMSO-d6)δ8.33(s,1H),6.89(d,J=14.6Hz,4H),6.54(d,J=7. 8Hz,2H),6.46(d,J=8.2Hz,2H),6.33(s,2H),2.23(s,6H),1.98(s,12H)ppm.

[0102] (Scheme 8: 2Br-tCz synthesis scheme) [ka]

[0103] The synthesis scheme for 2Br-tCz is the same as Scheme 3 described above.

[0104] (Scheme9: MesPXZ-Br-tCz synthesis scheme) [ka]

[0105] In a 25 mL four-necked flask equipped with a reflux condenser and a nitrogen inlet tube, 1.26 g (3.0 mmol) of 2Mes-PXZ, 1.27 g (2.5 mmol) of 2Br-tCz, 961 mg (10.0 mmol) of sodium-tert-butoxide, and 25 mL of anhydrous toluene were added, and nitrogen bubbling was performed for 1 hour. Then, 28 mg (0.125 mmol) of palladium acetate and 73 mg (0.250 mmol) of tri-tert-butylphosnium tetrafluoroborate were added, and the mixture was refluxed under nitrogen and stirred for 12 hours.

[0106] Thin-layer chromatography confirmed the consumption of the starting materials and the formation of the target product, so the reaction was terminated. The reaction mixture was filtered off, and the solvent in the filtrate was removed under reduced pressure.

[0107] The product was separated and purified by silica gel column chromatography (300cc silica gel, developing solvent = hexane:toluene = 7:1), followed by dispersion washing with methanol to obtain the target white solid. The yield was 1.3g, with a yield of 61%. Identification was performed as follows: 1 The analysis was performed using 1H-NMR. 1 H-NMR(400MHz,CDCl3)δ8.17(d,J=1.8Hz,2H),7.77-7.74(m,2H),7.60(dd,J=5.7,3.9Hz,1H),7.49(dd,J=8.5,2.1Hz,2H),7.06(d,J=8.2Hz,2H) ,6.92(s,4H),6.56(d,J=1.8Hz,2H),6.49(dd,J=8.2,1.8Hz,2H),6.03(d ,J=8.2Hz,2H),2.32(s,6H),2.10(s,6H),2.07(s,6H),1.47(s,18H)ppm.

[0108] (Scheme10: MesPXZ-tCzBN synthesis scheme) [ka]

[0109] A 50 mL Schlenk tube was degassed, and 1.27 g (1.5 mmol) of PhPXZ-Br-tCz and 15 mL of anhydrous xylene were added and stirred to dissolve. The mixture was then cooled to -40°C with liquid nitrogen, and 1.15 mL (2.6 M) of n-butyllithium hexane solution was added dropwise. The mixture was stirred at -40°C for 5 minutes, then stirred at room temperature for 30 minutes. Next, it was stirred at 60°C for 1 hour. After cooling to room temperature, the hexane was removed by distillation under reduced pressure using a pump.

[0110] Next, the mixture was cooled again to -40°C with liquid nitrogen, 3.0 mL (1.0 M) of boron tribromide was added dropwise, and the mixture was stirred for 5 minutes. Then, it was stirred at room temperature for 1 hour.

[0111] Next, the mixture was cooled again to -40°C with liquid nitrogen, 0.52 mL of N,N-diisopropylethylamine was added dropwise, and the mixture was stirred at room temperature for 30 minutes. Then, heating and stirring were started at 100°C. After 12 hours, the reaction was stopped, and after cooling to room temperature, the reaction mixture was dissolved in ethyl acetate. The mixture was washed with water and saturated brine, and the organic layer was dehydrated with anhydrous magnesium sulfate, after which the organic solvent was removed under reduced pressure.

[0112] The sample was purified by silica gel column chromatography (450cc silica gel, developing solvent = hexane:ethyl acetate = 20:1), and then recrystallized in a mixed solvent of toluene and methanol to obtain an orange solid. The yield was 480 mg, with a yield of 47%. Identification was performed as follows: 1 Elemental analysis was performed using H-NMR, mass spectrometry, and sublimation purification. 1 H-NMR(400MHz,CD2Cl2)δ8.69(s,1H),8.49(s,1H),8.39(d,J=8.7Hz,1H),8.30( s,1H),8.24(d,J=8.2Hz,1H),8.07(s,1H),7.98(d,J=8.2Hz,1H),7.89(t,J=8.2H z,1H),7.77(d,J=8.2Hz,1H),7.70(d,J=8.7Hz,1H),7.04(s,2H),6.95(s,4H),6. 82(d,J=8.2Hz,1H),2.36-2.27(m,9H),2.17-2.01(m,9H),1.54(q,J=1.2Hz,18H) MS:[M + ]=780.43m / z Elementalanalysis(%)calculatedforC 56 H 53 BN2O:C86.14,H6.84,N3.59; Found: C86.09, H7.03, N3.64.

[0113] <Comparative Example 1> [Synthesis of PXZ-tCzBN] PXZ-tCzBN, a boron-containing compound with the following structure, was synthesized by the method described in Xin Xiong et al., Material Chemistry Frontiers 7,929-936 (2023) (Non-Patent Literature 4). Note that PXZ-tCzBN is a boron-containing compound having a phenoxazine skeleton represented by the general formula (1) above, where R 1 and R 2 All of these are compounds in which the atom is hydrogen.

[0114] [ka]

[0115] <Evaluation of physical properties> The glass transition temperature (Tg), melting point (Tm), and 5% decay temperature (Td5) of the PhPXZ-tCzBN prepared in Example 1, the MesPXZ-tCzBN prepared in Example 2, and the PXZ-tCzBN prepared in Comparative Example 1 were measured using the following method. The results are shown in Table 1.

[0116] [Glass transition temperature (Tg) and melting point (Tm)] Each compound was confined in an aluminum pan, and its glass transition temperature (Tg) and melting point (Tm) were measured in nitrogen gas at a heating rate of 10°C / min using a differential scanning calorimetry device (product name: DSCDTA, manufactured by PerkinElmer).

[0117] [5% decay temperature (Td5)] Each compound that had undergone sublimation purification was weighed into an aluminum pan and subjected to thermogravimetric analysis (TGA) in nitrogen gas at a heating rate of 10°C / min using a thermogravimetric analyzer (product name: TGA Diamond, manufactured by PerkinElmer). The 5% decay temperature (Td5) was then measured.

[0118] [Table 1]

[0119] <Evaluation of optical properties in toluene solution> The ultraviolet-visible (UV-vis) absorption spectra, fluorescence spectra (PL spectra), and PLQY values ​​were measured for the PhPXZ-tCzBN prepared in Example 1, the MesPXZ-tCzBN prepared in Example 2, and the PXZ-tCzBN prepared in Comparative Example 1, using the following method. The UV-vis absorption spectra are shown in Figure 1, the fluorescence spectra (PL spectra) in Figure 2, and the PLQY values ​​in Table 2.

[0120] [UV-visible absorption spectrum measurement] A dilute solution of toluene (concentration: 10) is placed in a quartz cell (10 x 10 mm). -5 Sample M was prepared and measured. A Shimadzu UV-2600 was used as the measuring instrument, and the measurement conditions were as follows. Scan speed: Medium Measurement range: 200~800nm Sampling pitch: 3nm Slit width: 3nm

[0121] [Fluorescence Spectrum (PL Spectrum) Measurement] A dilute solution of toluene (concentration: 10) is placed in a quartz cell (10 x 10 mm). -5 Sample M was prepared and measured after 5 minutes of nitrogen bubbling. The FluoroMAX-2 manufactured by Instruments S.A. was used as the measuring instrument, and the measurement conditions were as follows. Excitation side slit width: 3nm Detector-side slit width: 3nm

[0122] [PLQY measurement] A dilute solution of toluene (concentration: 10) is placed in a quartz cell (10 x 10 mm). -5 Sample M was prepared and measured after 5 minutes of nitrogen bubbling. The excitation light irradiation device (ABSOLUTEPLQUANTUMYIELDSPECTROMETER C11347Quantaurus-QY, manufactured by Hamamatsu Photonics Co., Ltd.) was used as the measurement instrument.

[0123] [Table 2]

[0124] <Evaluation of Optical Properties of Solid Thin Films> For the PhPXZ-tCzBN prepared in Example 1, the MesPXZ-tCzBN prepared in Example 2, and the PXZ-tCzBN prepared in Comparative Example 1, single films (100 nm) were prepared, and their ionization potential (Ip) was measured using the following method. The UV-vis absorption spectra were also measured, and the energy gap (Eg) was estimated. Then, the electron affinity (Ea) was determined from the obtained ionization potential (Ip) and energy gap (Eg).

[0125] The measurement results of the ionization potential (Ip) are shown in Figures 3-5, the ultraviolet-visible (UV-vis) absorption spectrum is shown in Figure 6, and the ionization potential (Ip), energy gap (Eg), and electron affinity (Ea) are shown in Table 3.

[0126] [Ionization potential (Ip)] The measurement was performed using Photoelectron Yield Spectroscopy (PYS). An ionization potential analyzer manufactured by Sumitomo Heavy Industries, Ltd. was used as the measuring instrument, under vacuum (vacuum degree ~10°C). -3 Measurements were taken at Pa.

[0127] [UV-visible absorption spectrum] For each of the fabricated solid thin films, measurements were performed using a Shimadzu UV-2600 as the measuring instrument, under the following conditions. Scan speed: Medium Measurement range: 200~800nm Sampling pitch: 3nm Slit width: 3nm

[0128] [Energy gap (Eg)] The energy gap (Eg) was estimated from the absorption edge of the UV-vis absorption spectrum shown above.

[0129] [Electron affinity (Ea)] The electron affinity (Ea) was calculated using the ionization potential (Ip) and energy gap (Eg) obtained above, according to the following formula. Ea = Ip - Eg

[0130] [Table 3]

[0131] <Fabrication and evaluation of a binary co-evaporated film obtained by doping DIC-TRZ with 5 wt% luminescent material> Using DIC-TRZ, a carbazole derivative with the following chemical formula, as the host molecule, binary co-evaporated films (30 nm) were prepared by doping DIC-TRZ with 5 wt% of PhPXZ-tCzBN prepared in Example 1, MesPXZ-tCzBN prepared in Example 2, and PXZ-tCzBN prepared in Comparative Example 1. The ultraviolet-visible (UV-vis) absorption spectra, fluorescence spectra (PL spectra), and PLQY were measured using the following method.

[0132] [ka]

[0133] The ultraviolet-visible (UV-vis) absorption spectrum is shown in Figure 7, the fluorescence spectrum (PL spectrum) in Figure 8, and PLQY in Table 4.

[0134] [UV-vis absorption spectrum measurement] Single films and co-deposited films deposited on a round quartz substrate under vacuum using ULVACSINKUKIKOU's VPC-1100KO and VPC-1100KOT were measured. As mentioned above, DIC-TRZ, a carbazole derivative, was used as the host molecule. A Shimadzu Corporation UV-2600 was used as the measurement instrument, and the measurement conditions were as follows. Scan speed: Medium Measurement range: 200~800nm Sampling pitch: 3nm Slit width: 3nm

[0135] [Fluorescence Spectrum (PL Spectrum) Measurement] Single films and co-deposited films deposited on a round quartz substrate under vacuum using ULVACSINKUKIKOU's VPC-1100KO and VPC-1100KOT were measured. As mentioned above, DIC-TRZ, a carbazole derivative, was used as the host molecule. The measurement instrument used was InstrumentsS.A.'s FluoroMAX-2, and the measurement conditions were as follows. Excitation side slit width: 3nm Detector-side slit width: 3nm

[0136] [PLQY measurement] Measurements were taken of co-evaporated films deposited on a circular quartz substrate under vacuum using a glass chamber deposition apparatus. As mentioned above, the carbazole derivative DIC-TRZ was used as the host molecule. The measurement instrument used was the Hamamatsu Photonics K.K. ABSOLUTEPLQUANTUMYIELDSPECTROMETER C11347Quantaurus-QY excitation light irradiation device.

[0137] [Table 4]

[0138] [Consideration] Fluorescence spectrum (PL spectrum) measurements revealed that the emission wavelengths of the compounds prepared in Example 1, Example 2, and Comparative Example 1 were 532 nm, 522 nm, and 518 nm, respectively, and green emission was confirmed in all compounds.

[0139] The PLQY measurement results for the compounds in Example 1, Example 2, and Comparative Example 1 were 94%, 96%, and 75%, respectively. The introduction of substituents to the phenoxazine moiety, which resulted in longer wavelengths, promoted energy transfer, leading to high PLQY values ​​exceeding 90% for the compounds in Example 1 and Example 2.

[0140] <Fabrication and Evaluation of Organic EL Devices> [Fabrication of organic EL elements] Vapor deposition organic EL devices were fabricated using a three-component system with PhPXZ-tCzBN prepared in Example 1, MesPXZ-tCzBN prepared in Example 2, and PXZ-tCzBN prepared in Comparative Example 1, each with the phosphorescent sensitizer Ir(ppy)3 as the sensitizer and DIC-TRZ as the host molecule. Figure 9 shows the structure of the fabricated organic EL devices. Figure 10 shows the energy diagram for the fabricated organic EL devices.

[0141] (Element structure) ITO(100nm) / PolymerBuffer(20nm) / NPD(10nm) / 4DBFHPB(10nm) / EML(30nm) / DBF-TRZ(10nm) / T3PyTRZ_20wt%Lig(40nm) / Liq(1nm) / Al(100nm)

[0142] [Performance evaluation of organic EL elements] (Current density, voltage, brightness) For the fabricated organic EL elements, current density, voltage, and brightness were measured using a Keithley 2400 series source meter and a Konica Minolta CS200 luminance meter as electroluminescence (EL) measurement devices.

[0143] (Power efficiency (PE), current efficiency (CE), external quantum efficiency (EQE)) EL spectra were measured using a PHOTONIC MULTI-CHANNEL ANALYZER PMA-11 manufactured by Hamamatsu Photonics Ltd., and power efficiency (PE), current efficiency (CE), and external quantum efficiency (EQE) were calculated.

[0144] (Lifespan of OLED displays) The lifespan of the organic EL display was measured using the OLED lifespan evaluation device EAS-203, manufactured by System Giken Co., Ltd.

[0145] The obtained EL spectrum is shown in Figure 11, the current density-voltage-luminance characteristics in Figure 12, the external quantum efficiency-luminance characteristics in Figure 13, the power efficiency-luminance characteristics in Figure 14, the luminance decay per unit time in Figure 15, and the measurement results in Table 5. The initial luminance for the compound device in Example 1 was 8141 cd / m². 2 The element using the compound of Example 2 had a density of 7605 cd / m². 2 The element using the compound of Comparative Example 1 had a density of 5545 cd / m². 2 That was the case.

[0146] [Table 5]

[0147] [Consideration] From the EL spectra, no emission from the surrounding material was observed in any of the elements, and green emission originating from the light-emitting material was confirmed, with an emission wavelength of 520-533 nm and a full width at half maximum of 52-60 nm.

[0148] Based on the current density-voltage-luminance characteristics, the devices using the compounds fabricated in Example 1 and Example 2 achieved the lowest turn-on voltages (Von) of 2.15V and 2.11V, respectively, which is lower than the device using the compound fabricated in Comparative Example 1.

[0149] This suggests that the compounds in Example 1 and Example 2 have a deeper electron affinity (Ea) compared to the compound in Comparative Example 1, which facilitates carrier injection into the luminescent layer (EML), resulting in a lower turn-on voltage (Von). It also suggests that the lower voltage may be due to enhanced energy transfer from the phosphorescent sensitizer Ir(ppy)3.

[0150] Based on the external quantum efficiency-brightness characteristics, the devices using the compounds from Example 1 and Example 2 achieved a high maximum external quantum efficiency of 27.6%. Furthermore, the devices using the compounds from Example 1 and Example 2 successfully suppressed the efficiency roll-off at high brightness levels compared to other devices.

[0151] This is thought to be due to the introduction of substituents to the phenoxazine moiety, which further promotes energy transfer and facilitates the recovery of triplet excitons by the phosphorescent sensitizer Ir(ppy)3.

[0152] On the other hand, the device using the compound of Comparative Example 1 showed a low maximum external quantum efficiency of 20.7%, which is thought to be mainly due to the low energy transfer efficiency from PLQY and the phosphorescent sensitizer Ir(ppy)3.

[0153] Furthermore, based on power efficiency-luminance characteristics, the devices using the compounds from Example 1 and Example 2 achieved maximum power efficiencies of 150.3 m / W and 145.4 lm / W. These values ​​are among the highest reported for green organic EL devices.

[0154] Furthermore, the element using the compound from Example 1 showed an initial brightness of 8141 cd / m². 2 The brightness decay time was measured and found to be 220 hours. 95 @1000cdm -2 =LT 95 @8141cdm -2 x(8141cdm –2 / 1000cdm -2 ) 1.75 From the conversion formula, 1000 cd / m 2 When converted to lifetime, the device using the compound of Example 1 has a lifetime of LT 90 @1000cd / m 2 It has achieved a long lifespan of over 3000 hours. This is equivalent to the operating life of an Ir(ppy)3 device using only phosphorescent sensitizer. [Explanation of symbols]

[0155] 1 circuit board 2 Anode 3. High-intensity injection layer (HIL) 4. Hole Transport Layer (HTL) 5. Emitting Layer (EML) 6 Electron transport layer (ETL) 7 Electron injection layer (EIL) 8 cathode

Claims

1. Boron-containing compounds having a phenoxazine skeleton represented by the following general formula (1); 【Chemistry 1】 (In general formula (1), R １ and R ２ Each of these is independently selected from the group consisting of a hydrogen atom, an unsubstituted phenyl group, a substituted phenyl group, a biphenyl group, and a terphenyl group, R １ and R ２ None of them are hydrogen atoms, R ３ R is a hydrogen atom or substituent, ４ and R ５ Each of these is independently either a hydrogen atom or a substituent.

2. The above R １ and R ２ In the above, the substituent is a methyl group. The boron-containing compound according to claim 1.

3. The aforementioned R １ and R ２ The boron-containing compound according to claim 1, wherein the substituted phenyl group is a group selected from the group consisting of 2-methylphenyl group, 2,6-dimethylphenyl group, and 2,4,6-trimethylphenyl group.

4. The aforementioned R １ and R ２ The boron-containing compound according to claim 1, wherein the terphenyl group is an m-terphenyl group.

5. The aforementioned R ３ The boron-containing compound according to claim 1, wherein the substituent is an unsubstituted carbazole group or a substituted carbazole group.

6. The aforementioned R ４ and R ５ The boron-containing compound according to claim 1, wherein the substituent is a group selected from the group consisting of a t-butyl group, an unsubstituted phenyl group, a substituted phenyl group, a biphenyl group, and a terphenyl group.

7. A light-emitting material comprising a boron-containing compound according to any one of claims 1 to 6.

8. An organic electroluminescent element comprising a boron-containing compound according to any one of claims 1 to 6 in its light-emitting layer.

9. The organic electroluminescent element according to claim 8, wherein the light-emitting layer further comprises a sensitizer.

10. An electronic device equipped with the organic electroluminescent element described in claim 8.

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