Thermally Activated Delayed Fluorescent Picolinonitrile Derivative and Organic Light-Emitting Device Containing the Same

Abstract

The present invention provides a picorinonitrile derivative that exhibits thermally activated delayed fluorescence characteristics by including an intramolecular electron donor unit and an electron acceptor unit, and an organic light-emitting device that exhibits excellent luminescence efficiency by including the same.

Description

Technology Field

[0001] The present invention relates to a thermally activated delayed fluorescent picolinonitrile derivative and an organic light-emitting device comprising the same. More specifically, the invention relates to a thermally activated delayed fluorescent picolinonitrile derivative comprising an electron donor unit and an electron acceptor unit, and an organic light-emitting device comprising the same that exhibits excellent photophysical properties. Background Technology

[0002] In general fluorescence, S1 is the singlet energy and T1 is the triplet energy, and singlet excitons are generated with a 25% probability, while the remaining 75% of triplet excitons disappear without emitting light; therefore, theoretically, fluorescence has an internal quantum efficiency of 25%. In the case of fluorescence, which is the main light emission method of currently used OLEDs, device stability is high, but the luminescence efficiency (25% based on internal quantum efficiency) is low.

[0003] In the case of phosphorescence capable of increasing internal quantum efficiency to 100%, material costs are currently high due to the use of platinum-based rare metals.

[0004] On the other hand, Thermally Activated Delayed Fluorescence (TADF), which has recently been attracting attention, is gaining interest because it has the advantage of being able to increase internal quantum efficiency to 100% even without using platinum-based rare metals. Specifically, by making the energy difference between S1 and T1 small, the state of the exciton can be changed from T1 to S1 using thermal energy present at room temperature, thereby enabling fluorescence with an internal quantum efficiency of 100%, which is called Thermally Activated Delayed Fluorescence (TADF).

[0005] Accordingly, there is a need for research on materials for Thermally Activated Delayed Fluorescence (TADF) that can achieve excellent luminescence efficiency. The problem to be solved

[0006] The object of the present invention is to provide a picolinonitrile derivative that exhibits thermally activated delayed fluorescence characteristics by including an intramolecular electron donor unit and an electron acceptor unit, and an organic light-emitting device that exhibits excellent photophysical properties by including the same.

[0007] However, the problem of the present invention is not limited thereto and includes parts that can be understood from the description below. means of solving the problem

[0008] The present invention provides a heat-activated delayed-fluorescent picorinonitrile derivative represented by the following chemical formula 1, having a structure in which an electron donor unit is coupled to an electron acceptor unit.

[0009] [Chemical Formula 1]

[0010]

[0011] In the above chemical formula 1,

[0012] A is nitrogen (N), B and E are hydrogen-bonded carbons (-CH), and

[0013] R1 is hydrogen; deuterium; a halogen group; -CN; a substituted or unsubstituted C1 to C40 alkyl group; and

[0014] Z1 and Z2 are different from each other and each independently has the structure of chemical formula 1A or 1B,

[0015] [Chemical Formula 1A]

[0016]

[0017] [Chemical Formula 1B]

[0018]

[0019] In the above chemical formulas 1A to 1B,

[0020] R2 to R5 are each independently selected from the group consisting of hydrogen; deuterium; a halogen group; -CN; a substituted or unsubstituted C1 to C40 alkyl group; a substituted or unsubstituted C2 to C40 alkenyl group; a substituted or unsubstituted C2 to C40 alkynyl group; a substituted or unsubstituted C3 to C40 monocyclic or polycyclic cycloalkyl group; a substituted or unsubstituted C2 to C40 monocyclic or polycyclic heterocycloalkyl group; a substituted or unsubstituted C6 to C60 monocyclic or polycyclic aryl group; a substituted or unsubstituted C2 to C40 monocyclic or polycyclic heteroaryl group; and

[0021] Ar1 to Ar2 are identical or different from one another and are each independently selected from the group consisting of hydrogen; deuterium, a substituted or unsubstituted C6 to C60 monocyclic or polycyclic aryl group; and a substituted or unsubstituted C2 to C40 monocyclic or polycyclic heteroaryl group; and form an aliphatic ring, a condensed aromatic ring, a condensed heteroaliphatic ring, or a condensed heteroaromatic ring fused with an adjacent group.

[0022] is the binding site with the compound of chemical formula 1.

[0023] The present invention provides an organic light-emitting device comprising an anode; a cathode; and a light-emitting layer disposed between the anode and the cathode, wherein the light-emitting layer comprises a thermally activated delayed fluorescent picorinonitrile derivative according to claim 1. Effects of the invention

[0024] The picolinonitrile derivative according to the present invention comprises a carbazole group as an electron donor unit and a picolinonitrile group as an electron acceptor unit, thereby possessing activated delayed fluorescence characteristics. The band gaps of the singlet and triplet phases are small, and the band gap energy exhibits a level similar to that of the triplet phase. Therefore, an organic light-emitting device incorporating the activated delayed fluorescence picolinonitrile derivative according to the present invention can exhibit excellent thermal stability, color purity, and luminescence efficiency. However, the effects of the present invention are not limited thereto and may include effects expected from the technical features of the present invention. Brief explanation of the drawing

[0025] Figure 1 is a UV spectrum of a picorinonitrile derivative green phosphorescent material according to an embodiment of the present invention. Specific details for implementing the invention

[0026] The terms of this specification are explained below. Except for those used in this specification, terms may have the meanings commonly understood by those skilled in the art.

[0027] The term "halogen group" means F, Cl, Br, or I.

[0028] The term "alkyl" refers to an aliphatic hydrocarbon group, meaning a "saturated alkyl" that does not contain any alkene or alkyne portions. The alkyl may include a branched or straight-chain form, and may also include structural isomers. Specifically, it may have 1 to 40 carbon atoms or 1 to 20 carbon atoms.

[0029] The term "alkenyl" means "unsaturated alkyl" comprising an alkene portion that is at least one carbon-carbon double bond. The alkenyl may include a branched or straight-chain form, and may also include structural isomers. Specifically, it may have 2 to 40 carbon atoms or 2 to 20 carbon atoms.

[0030] The term "alkynyl" means "unsaturated alkyl" comprising an alkyne portion that is at least one carbon-carbon triple bond. The alkynyl may include a branched or straight-chain form, and may also include structural isomers. Specifically, it may have 2 to 40 carbon atoms or 2 to 20 carbon atoms.

[0031] The term "cycloalkyl" means a fully saturated or partially unsaturated hydrocarbon ring of carbon atoms. Specifically, it may have 3 to 40 carbon atoms, or 3 to 20, or 3 to 10 carbon atoms.

[0032] The term "heterocycloalkyl" means a substituent in which a portion of a fully saturated or partially unsaturated hydrocarbon ring of carbon atoms is substituted with oxygen, nitrogen, sulfur, selenium, etc. Specifically, it may have 2 to 40 carbon atoms, or 2 to 20 carbon atoms, or 2 to 10 carbon atoms.

[0033] The term "aryl" means an aromatic substituent having at least one ring having a shared pi electron system. The substituent may be appropriately bonded to the ortho (o), meta (m), or para (p) positions. Specifically, it may be a ring having 6 to 60 carbon atoms, or an aromatic substituent having 6 to 30 carbon atoms.

[0034] The term "heteroaryl" means a substituent having at least one ring having a shared pi-electron system, wherein a portion of the carbons of the aromatic substituent are substituted with oxygen, nitrogen, sulfur, selenium, etc. Specifically, it may be a ring having 2 to 40 carbons, or an aromatic substituent having 5 to 20 carbons.

[0035] The term "monocyclic or polycyclic" refers to a mono- or poly-cyclic ring (i.e., rings that share adjacent pairs of carbon atoms). More specifically, it can form an aliphatic ring, a condensed aromatic ring, a condensed heteroaliphatic ring, or a condensed heteroaromatic ring fused with an adjacent group.

[0036] The term "substituted or unsubstituted" refers to a group consisting of one or more substituents selected from the group comprising deuterium; halogen group; nitrile group; nitro group; hydroxyl group; carbonyl group; ester group; imide group; amino group; phosphine oxide group; alkoxy group; aryloxy group; alkyl thioxy group; aryl thioxy group; alkyl sulfoxy group; aryl sulfoxy group; silyl group; boron group; alkyl group; cycloalkyl group; alkenyl group; aryl group; aralkyl group; aralkenyl group; alkylaryl group; alkylamine group; aralkylamine group; heteroarylamine group; arylamine group; arylphosphine group; or heterocyclic groups comprising one or more atoms of N, O, and S, which are substituted or unsubstituted with one or more substituents, or in which two or more of the said substituents are connected, and may be a biphenyl group.

[0037] The present invention provides a heat-activated delayed-fluorescent picorinonitrile derivative represented by the following chemical formula 1, having a structure in which an electron donor unit is coupled to an electron acceptor unit.

[0038] [Chemical Formula 1]

[0039]

[0040] In the above chemical formula 1,

[0041] A is nitrogen, and B and E are hydrogen-bonded carbons (-CH), and

[0042] R1 is hydrogen; deuterium; a halogen group; -CN; a substituted or unsubstituted C1 to C40 alkyl group; and

[0043] Z1 and Z2 are different from each other and each independently has the structure of chemical formula 1A or 1B,

[0044] [Chemical Formula 1A]

[0045]

[0046] [Chemical Formula 1B]

[0047]

[0048] In the above chemical formulas 1A to 1B,

[0049] R2 to R5 are each independently selected from the group consisting of hydrogen; deuterium; a halogen group; -CN; a substituted or unsubstituted C1 to C40 alkyl group; a substituted or unsubstituted C2 to C40 alkenyl group; a substituted or unsubstituted C2 to C40 alkynyl group; a substituted or unsubstituted C3 to C40 monocyclic or polycyclic cycloalkyl group; a substituted or unsubstituted C2 to C40 monocyclic or polycyclic heterocycloalkyl group; a substituted or unsubstituted C6 to C60 monocyclic or polycyclic aryl group; a substituted or unsubstituted C2 to C40 monocyclic or polycyclic heteroaryl group; and

[0050] Ar1 to Ar2 are identical or different from one another and are each independently selected from the group consisting of hydrogen; deuterium, a substituted or unsubstituted C6 to C60 monocyclic or polycyclic aryl group; and a substituted or unsubstituted C2 to C40 monocyclic or polycyclic heteroaryl group; and form a fused aliphatic ring, a condensed aromatic ring, a condensed heteroaliphatic ring, or a condensed heteroaromatic ring with an adjacent group.

[0051] is the binding site with the compound of chemical formula 1.

[0052] TADF (Thermally Activated Delayed Fluorescence) is a phenomenon in which electrons in the triplet state move to the singlet state using thermal energy and emit light. Since TADF molecules facilitate the transition from the triplet state to the singlet state, electrons in the triplet state can also contribute to light emission, which can ultimately significantly improve photophysical properties such as the luminous efficiency of organic light-emitting devices.

[0053] After numerous studies and efforts, the inventors of the present invention synthesized a picolinonitrile derivative having a structure in which a carbazole group is combined as an electron donor unit and a picolinonitrile group is combined as an electron acceptor unit. Since this molecule exhibits specific energy levels with the separation of HOMO and LUMO, the energy gap between the singlet and triplet states is minimized, allowing electrons in the triplet state to move to the singlet state and efficiently emit light. It was confirmed that this can improve the thermal stability, color purity, and luminous efficiency of organic light-emitting devices, leading to the completion of the present invention.

[0054] The compound of Formula 1 according to one embodiment may be selected from the compounds of Formula 2 and Formula 3 below.

[0055] [Chemical Formula 2]

[0056]

[0057] [Chemical Formula 3]

[0058]

[0059] In the above chemical formulas 2 to 3,

[0060] B and E are hydrogen-bonded carbons (-CH), and

[0061] R1 is a halogen group; -CN; a substituted or unsubstituted C1 to C40 alkyl group; and

[0062] R2 to R5 are each independently selected from the group consisting of hydrogen; deuterium; a halogen group; -CN; a substituted or unsubstituted C1 to C40 alkyl group; a substituted or unsubstituted C2 to C40 alkenyl group; and a substituted or unsubstituted C2 to C40 alkynyl group.

[0063] Ar1 to Ar2 are identical or different from one another and are each independently selected from the group consisting of hydrogen; deuterium; a substituted or unsubstituted C6 to C60 monocyclic or polycyclic aryl group; and a substituted or unsubstituted C2 to C40 monocyclic or polycyclic heteroaryl group; and form an aliphatic ring, a condensed aromatic ring, a condensed heteroaliphatic ring, or a condensed heteroaromatic ring fused with an adjacent group.

[0064] is the binding site with the compound of chemical formula 1.

[0065] The compound of Formula 1B according to one embodiment may be one or more selected from Formulas 1B-1 to 1B-6 below.

[0066]

[0067]

[0068] In the above chemical formulas 1B-1 to 1B-6,

[0069] G is selected from O, S, Se, and NH, and R6 and R7 are each independently selected from the group consisting of hydrogen; deuterium; halogen group; -CN; and substituted or unsubstituted C1 to C20 alkyl groups.

[0070] The compound of Formula 1B according to one embodiment may be selected from the following.

[0072]

[0073] In the above formula 1 according to one embodiment, R1 is selected from the group consisting of hydrogen; deuterium; a halogen group; and -CN, R2 and R3 are each hydrogen or deuterium, and R4 and R5 can each independently be selected from the group consisting of hydrogen; deuterium; and substituted or unsubstituted C1 to C40 alkyl groups.

[0074] The compound of Formula 1 according to one embodiment is one or more green thermally activated delayed fluorescent picorinonitrile derivatives selected from the following compounds GN-5-1 to GN-5-6, and may have excellent thermal stability, color purity, and light efficiency.

[0076]

[0077]

[0078] PL (photoluminescence) is a process in which a thermally activated delayed fluorescent picolinonitrile derivative emits light when energy of a specific wavelength is injected in the form of light, and the emission peak can determine the color of the emitted light.

[0079] In the present invention, the heat-activated delayed fluorescent picorinonitrile derivative may have a photoluminescence (PL) wavelength peak of 500 to 550 nm in the green color range.

[0080] PLQY (Photoluminescence Quantum Yield) is the ratio of the number of photons emitted by a material to the number of photons absorbed, representing the photoluminescence efficiency with respect to excitation light; a high PLQY indicates that a light-emitting device utilizing it can possess high efficiency.

[0081] In the present invention, the PLQY of the heat-activated delayed fluorescent picorinonitrile derivative may be 20 to 60%, and more specifically, the PLQY may be 23 to 55%.

[0082] HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) can represent the energy levels of a molecule's highest occupied molecular orbital and lowest unoccupied molecular orbital, respectively. HOMO and LUMO levels represent the electron transfer capabilities of a molecule and are related to the injection and transport of charge carriers in organic light-emitting diodes.

[0083] In the present invention, the HOMO (Highest Occupied Molecular Orbital) energy level of the heat-activated delayed fluorescent picorinonitrile derivative may be -5.1 eV to -4.9 eV, and the LUMO (Lowest Unoccupied Molecular Orbital) energy level may be -2.4 eV to -2.2 eV.

[0084] Meanwhile, the present invention comprises an anode; a cathode; and an organic layer disposed between the anode and the cathode, wherein the organic layer may include the thermally activated delayed fluorescent picorinonitrile derivative.

[0085] Organic light-emitting diodes emit light through the recombination of electrons and holes, but it is generally known that the luminescence efficiency is low in the triplet state. By using the thermally activated delayed fluorescent picolinonitrile derivative according to the present invention, electrons in the triplet state can also efficiently emit light, thereby exhibiting excellent thermal stability, color purity, and luminescence efficiency.

[0086] An organic light-emitting device according to one embodiment of the present invention is described below.

[0087] An organic light-emitting device according to an embodiment of the present invention comprises an anode; a cathode; and an organic layer disposed between the anode and the cathode, wherein the organic layer may comprise a thermally activated delayed fluorescent picorinonitrile derivative of the present invention.

[0088] The above anode is not limited to any material that can efficiently inject holes into an organic layer, but, for example, it can be formed from materials such as indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO2), zinc oxide (ZnO), and graphene, and these materials can have multiple layers either individually or in combination.

[0089] The above-mentioned cathode is not limited to any material capable of efficiently injecting electrons into an organic layer, but, for example, can be formed from a metal, alloy, electrically conductive compound, or a mixture thereof having a low work function. Specifically, it can be formed from lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag), etc., and these materials may have multiple layers either alone or in combination.

[0090] The above organic layer is disposed between the anode and the cathode, and is specifically composed of a hole transport region, a light-emitting layer, and an electron transport region, so that an exciton formed through the recombination of a hole supplied from the anode and an electron supplied from the cathode can emit light during the process of transitioning to the ground state.

[0091] The light-emitting layer may include a host material and a dopant material as light-emitting materials. The host material can transfer charges supplied from the anode and the cathode to the dopant material, and the dopant material can generate light using the charges received from the host material.

[0092] In one embodiment of the present invention, the light-emitting layer may include a heat-activated delayed fluorescent picorinonitrile derivative according to the present invention described above as a dopant material, and a known light-emitting material selected from fluorescent materials, phosphorescent materials, delayed fluorescent materials, etc. as a host material, thereby exhibiting excellent thermal stability, color purity, and light-emitting efficiency.

[0093] The above dopant material may be in an amount of 0.01 to 20 parts by weight per 100 parts by weight of the host material. If the content of the dopant material is excessively small or large beyond the above range, it is undesirable as it may not be able to produce the effects intended by the present invention. Specifically, it may be 0.1 to 15, 1 to 15, or 5 to 12.

[0094] The hole transport region is disposed between the anode and the light-emitting layer and allows holes to be easily injected from the anode. The hole transport region may include a hole injection layer and a hole transport layer.

[0095] The hole injection layer above allows holes to be easily injected from the anode, and contains phthalocyanine compounds such as copper phthalocyanine, m-MTDATA [4,4',4''-tris (3-methylphenylphenylamino) triphenylamine], NPB (N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine)), TDATA, 2-TNATA, Pani / DBSA (Polyaniline / Dodecylbenzenesulfonic acid), PEDOT / PSS (Poly(3,4-ethylenedioxythiophene) / Poly(4-styrenesulfonate)), and Pani / CSA (Polyaniline / Camphor sulfonic acid It may be formed from a material selected from acid: polyaniline / camphorsulfonic acid), PANI / PSS (Polyaniline) / Poly (4-styrene sulfonate): polyaniline) / poly(4-styrene sulfonate)), HAT-CN (1,4,5,8,9,11-Hexaazatriphenylenehexacarbonitrile), etc., but is not limited thereto.

[0096] The hole transport layer described above can, for example, transport holes delivered through a hole injection layer to an emissive layer, and may include, for example, carbazole derivatives such as polyvinylcarbazole, fluorine derivatives, triphenylamine derivatives such as TPD (N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1-biphenyl]-4,4'-diamine), TCTA (4,4',4"-tris(Ncarbazolyl)triphenylamine), NPD (N,N'-di(naphthalene-l-yl)-N,N'-diplienyl-benzidine), TAPC (4,4-Cyclohexylidene bis[N,N-bis(4-methylphenyl)benzenamine]), HMTPD (4,4'-Bis[N,N'-(3-tolyl)amino]-3,3'-dimethylbiphenyl), It may be NPB (N,N'-Diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine), HT-1, two or more substances selected from these.

[0097] The electron transport region is disposed between the cathode and the light-emitting layer and allows electrons to be easily injected from the anode. The electron transport region may include an electron injection layer and an electron transport layer.

[0098] The above electron injection layer may be formed from one or more selected from, for example, LiF, NaCl, CsF, Li2O, BaO, etc., but is not limited thereto.

[0099] The electron transport layer is disposed between the light-emitting layer and the electron injection layer and can transport electrons delivered through the electron injection layer to the light-emitting layer. For example, the electron transport layer may be formed of quinoline derivatives such as tris(8-quinolinolate)aluminum, TAZ (3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole), C60, other fluorene series, etc., but is not limited thereto.

[0101] The present invention will be described in detail below with reference to embodiments. However, the following embodiments are merely illustrative of the present invention, and the scope of the present invention is not limited to the following embodiments.

[0103] <Example 1> Compound GN-5-1

[0104] (1) Intermediate (1-1): Preparation of 3-(2-nitrophenyl)dibenzo[b,d]thiophene

[0105]

[0106] 3-bromodibenzo[b,d]thiophene (5 g, 19 mmol), (2-nitrophenyl)boronic acid (6.34 g, 38 mmol), [1,1-Bis(diphenylphosphino)ferrocene]dichloropalladium(II) (0.776 g, 0.95 mmol), and potassium phosphate (12.1 g, 57 mmol) were added to 1,4-dioxane (80 ml) and H2O (1.8 ml) and refluxed under a nitrogen atmosphere for about 24 hours. After cooling to room temperature, the organic solvent layer was aliquoted and anhydrous with anhydrous Na2SO4. A solid column was prepared by adding silica gel to the organic layer and concentrating it in a concentrator. After removing impurities by column separation using a developing solvent (dichloromethane 10% / hexane 90%), 5g of 3-(2-nitrophenyl)dibenzo[b,d]thiophene (yield 86%) was obtained.

[0108] (2) Intermediate (1-2): Preparation of 12H-benzo[4,5]thieno[2,3-a]carbazole

[0109]

[0110] 3-(2-nitrophenyl)dibenzo[b,d]thiophene (5 g, 16.37 mmol), PPh3 (12.88 g, 49.12 mmol), and 1,2-Dichlorobenzene (81 ml) were added and refluxed under a nitrogen atmosphere for approximately 18 hours. After cooling to room temperature, the organic solvent layer was aliquoted and anhydrous with anhydrous Na2SO4. A solid column was prepared by adding silica gel to the organic layer and concentrating it in a concentrator. After removing impurities by column separation using a developing solvent (dichloromethane 20% / hexane 80%), 3-(2-nitrophenyl)dibenzo[b,d]thiophene 3.12 G (yield 70%) was obtained.

[0112] (3) Intermediate (1-3): Preparation of 5-bromo-3-(9,9-dimethylacridin-10(9H)-yl)picolinonitrile

[0114]

[0115] NaH (1.08 g, 22.5 mmol) was suspended in DMF (30 ml) in an ice bath. Under a nitrogen atmosphere, 9,9-dimethyl-9,10-dihydroacridine (3.4 g, 16.4 mmol) was diluted in DMF (30 ml) and slowly added dropwise. After stirring for 30 minutes, 5-bromo-3-fluoropicolinonitrile (3 g, 14.9 mmol) was diluted in DMF (30 ml) and slowly added dropwise. The mixture was stirred at room temperature for approximately 18 hours. After cooling the reaction mixture in an ice bath and adding water to terminate the reaction, the organic solvent layer was aliquoted and anhydrous with anhydrous Na2SO4. Silica gel was added to the organic layer, and the mixture was concentrated in a concentrator to prepare a solid column. After removing impurities by column separation using a developing solvent (dichloromethane 10% / hexane 90%), 3.6 g of 5-bromo-3-(9,9-dimethylacridin-10(9H)-yl)picolinonitrile (yield 61%) was obtained.

[0117] (4) Preparation of compound GN-5-1 (5-(12H-benzo[4,5]thieno[2,3-a]carbazol-12-yl)-3-(9,9-dimethylacridin-10(9H)-yl)picolinonitrile)

[0118]

[0119] 5-bromo-3-(9,9-dimethylacridin-10(9H)-yl)picolinonitrile (300 mg, 0.77 mmol), 12H-benzo[4,5]thieno[2,3-a]carbazole (252 mg, 0.92 mmol), Tris(dibenzylideneacetone)dipalladium(0) (70 mg, 0.077 mmol), Tri-tert-butylphosphonium tetrafluoroborate (45 mg, 0.154 mmol), and Sodium tert-butoxide (148 mg, 1.54 mmol) were added, along with Toluene (24 ml), and the mixture was refluxed and stirred under a nitrogen atmosphere for approximately 18 hours. After cooling to room temperature, the organic solvent layer was aliquoted and anhydrous with anhydrous Na2SO4. A solid column was prepared by adding silica gel to the organic layer and concentrating it in a concentrator. After removing impurities by column separation using a developing solvent (dichloromethane 50% / hexane 50%), 290 mg of GN-5-1 (yield 65%) was obtained.

[0121] <Example 2> Compound GN-5-2

[0122] (1) Preparation of compound GN-5-2: 5-(5H-benzofuro[3,2-c]carbazol-5-yl)-3-(9,9-dimethylacridin-10(9H)-yl)picolinonitrile

[0123]

[0124] The intermediates 5-bromo-3-(9,9-dimethylacridin-10(9H)-yl)picolinonitrile (300 mg, 0.77 mmol), 5H-benzofuro[3,2-c]carbazole (218 mg, 0.847 mmol), Tris(dibenzylideneacetone)dipalladium(0) (70 mg, 0.077 mmol), Tri-tert-butylphosphonium tetrafluoroborate (45 mg, 0.154 mmol), and Sodium tert-butoxide (148 mg, 1.54 mmol) were added, along with Toluene (24 ml), and the mixture was refluxed and stirred under a nitrogen atmosphere for approximately 18 hours. After cooling to room temperature, the organic solvent layer was aliquoted and anhydrous with anhydrous Na2SO4. A solid column was prepared by adding silica gel to the organic layer and concentrating it in a concentrator. After removing impurities by column separation using a developing solvent (dichloromethane 50% / hexane 50%), 251 mg of GN-5-2 (yield 58%) was obtained.

[0126] <Example 3> Compound GN-5-3

[0127] (1) Preparation of compound GN-5-3: 5-(12H-benzofuro[2,3-a]carbazol-12-yl)-3-(9,9-dimethylacridin-10(9H)-yl)picolinonitrile

[0128]

[0129] The intermediates 5-bromo-3-(9,9-dimethylacridin-10(9H)-yl)picolinonitrile (300 mg, 0.77 mmol), 12H-benzofuro[2,3-a]carbazole (218 mg, 0.847 mmol), Tris(dibenzylideneacetone)dipalladium(0) (70 mg, 0.077 mmol), Tri-tert-butylphosphonium tetrafluoroborate (45 mg, 0.154 mmol), and Sodium tert-butoxide (148 mg, 1.54 mmol) were added, along with Toluene (24 ml), and the mixture was refluxed and stirred under a nitrogen atmosphere for approximately 18 hours. After cooling to room temperature, the organic solvent layer was aliquoted and anhydrous with anhydrous Na2SO4. A solid column was prepared by adding silica gel to the organic layer and concentrating it in a concentrator. After removing impurities by column separation using a developing solvent (dichloromethane 50% / hexane 50%), 314 mg of GN-5-3 (yield 72%) was obtained.

[0131] <Example 4> Compound GN-5-4

[0132] (1) Preparation of the intermediate 3-(12H-benzo[4,5]thieno[2,3-a]carbazol-12-yl)-5-bromopicolinonitrile

[0133]

[0134] NaH (108 mg, 2.25 mmol) was suspended in DMF (3 ml) in an ice bath. Under a nitrogen atmosphere, 12H-benzo[4,5]thieno[2,3-a]carbazole (492 mg, 1.8 mmol) was diluted in DMF (3 ml) and slowly added dropwise. After stirring for 30 minutes, 5-bromo-3-fluoropicolinonitrile (300 mg, 1.5 mmol) was diluted in DMF (3 ml) and slowly added dropwise. The mixture was stirred at room temperature for approximately 18 hours. After cooling the reaction mixture in an ice bath and adding water to terminate the reaction, the organic solvent layer was aliquoted and anhydrous with anhydrous Na2SO4. Silica gel was added to the organic layer, and the mixture was concentrated in a concentrator to prepare a solid column. After removing impurities by column separation using a developing solvent (dichloromethane 10% / hexane 90%), 3-(12H-benzo[4,5]thieno[2,3-a]carbazol-12-yl)-5-bromopicolinonitrile 512 mg (yield 75%) was obtained.

[0136] (2) Preparation of compound GN-5-4: 3-(12H-benzo[4,5]thieno[2,3-a]carbazol-12-yl)-5-(9,9-dimethylacridin-10(9H)-yl)picolinonitrile

[0137]

[0138] The intermediates 3-(12H-benzo[4,5]thieno[2,3-a]carbazol-12-yl)-5-bromopicolinonitrile (500 mg, 1.1 mmol), 9,9-dimethyl-9,10-dihydroacridine (253 mg, 1.21 mmol), Tris(dibenzylideneacetone)dipalladium(0) (100 mg, 0.11 mmol), Tri-tert-butylphosphonium tetrafluoroborate (64 mg, 0.22 mmol), and Sodium tert-butoxide (211 mg, 2.2 mmol) were added, along with Toluene (40 ml), and the mixture was refluxed and stirred under a nitrogen atmosphere for approximately 18 hours. After cooling to room temperature, the organic solvent layer was aliquoted and anhydrous with anhydrous Na2SO4. A solid column was prepared by adding silica gel to the organic layer and concentrating it in a concentrator. After removing impurities by column separation using a developing solvent (dichloromethane 60% / hexane 40%), 460 mg of GN-5-4 (yield 74%) was obtained.

[0140] <Example 5> Compound GN-5-5

[0141] (1) Preparation of the intermediate 3-(5H-benzofuro[3,2-c]carbazol-5-yl)-5-bromopicolinonitrile

[0142]

[0143] NaH (179 mg, 3.73 mmol) was suspended in DMF (3 ml) in an ice bath. Under a nitrogen atmosphere, 5H-benzofuro[3,2-c]carbazole (705 mg, 2.74 mmol) was diluted in DMF (3 ml) and slowly added dropwise. After stirring for 30 minutes, 5-bromo-3-fluoropicolinonitrile (500 mg, 2.49 mmol) was diluted in DMF (3 ml) and slowly added dropwise. The mixture was stirred at room temperature for approximately 18 hours. After cooling the reaction mixture in an ice bath and adding water to terminate the reaction, the organic solvent layer was aliquoted and anhydrous with anhydrous Na2SO4. Silica gel was added to the organic layer, and the mixture was concentrated in a concentrator to prepare a solid column. After removing impurities by column separation using a developing solvent (dichloromethane 10% / hexane 90%), 3-(5H-benzofuro[3,2-c]carbazol-5-yl)-5-bromopicolinonitrile 773 mg (yield 71%) was obtained.

[0145] (2) Preparation of compound GN-5-5: 3-(5H-benzofuro[3,2-c]carbazol-5-yl)-5-(9,9-dimethylacridin-10(9H)-yl)picolinonitrile

[0147]

[0148] The intermediates 3-(5H-benzofuro[3,2-c]carbazol-5-yl)-5-bromopicolinonitrile (400 mg, 0.91 mmol), 9,9-dimethyl-9,10-dihydroacridine (209 mg, 1 mmol), Tris(dibenzylideneacetone) dipalladium (0) (83 mg, 0.091 mmol), Tri-tert-butylphosphonium tetrafluoroborate (53 mg, 0.182 mmol), and Sodium tert-butoxide (175 mg, 1.82 mmol) were added, along with Toluene (24 ml), and the mixture was refluxed and stirred under a nitrogen atmosphere for approximately 18 hours. After cooling to room temperature, the organic solvent layer was aliquoted and anhydrous with anhydrous Na2SO4. A solid column was prepared by adding silica gel to the organic layer and concentrating it in a concentrator. After removing impurities by column separation using a developing solvent (dichloromethane 50% / hexane 50%), 430 mg of GN-5-5 (yield 83%) was obtained.

[0150] <Example 6> Compound GN-5-6

[0151] (1) Preparation of the intermediate 3-(12H-benzofuro[2,3-a]carbazol-12-yl)-5-bromopicolinonitrile

[0152]

[0153] NaH (179 mg, 3.73 mmol) was suspended in DMF (3 ml) in an ice bath. Under a nitrogen atmosphere, 12H-benzofuro[2,3-a]carbazole (705 mg, 2.74 mmol) was diluted in DMF (3 ml) and slowly added dropwise. After stirring for 30 minutes, 5-bromo-3-fluoropicolinonitrile (500 mg, 2.49 mmol) was diluted in DMF (3 ml) and slowly added dropwise. The mixture was stirred at room temperature for approximately 18 hours. After cooling the reaction mixture in an ice bath and adding water to terminate the reaction, the organic solvent layer was aliquoted and anhydrous with anhydrous Na2SO4. Silica gel was added to the organic layer, and the mixture was concentrated in a concentrator to prepare a solid column. After removing impurities by column separation using a developing solvent (dichloromethane 60% / hexane 40%), 3-(12H-benzofuro[2,3-a]carbazol-12-yl)-5-bromopicolinonitrile 756 mg (yield 69%) was obtained.

[0155] (2) Preparation of compound GN-5-6: 3-(12H-benzofuro[2,3-a]carbazol-12-yl)-5-(9,9-dimethylacridin-10(9H)-yl)picolinonitrile

[0157]

[0158] The intermediates 3-(12H-benzofuro[2,3-a]carbazol-12-yl)-5-bromopicolinonitrile (400 mg, 0.91 mmol), 9,9-dimethyl-9,10-dihydroacridine (209 mg, 1 mmol), Tris(dibenzylideneacetone) dipalladium (0) (83 mg, 0.091 mmol), Tri-tert-butylphosphonium tetrafluoroborate (53 mg, 0.182 mmol), and Sodium tert-butoxide (175 mg, 1.82 mmol) were added, along with Toluene (24 ml), and the mixture was refluxed and stirred under a nitrogen atmosphere for approximately 18 hours. After cooling to room temperature, the organic solvent layer was aliquoted and anhydrous with anhydrous Na2SO4. A solid column was prepared by adding silica gel to the organic layer and concentrating it in a concentrator. After removing impurities by column separation using a developing solvent (dichloromethane 50% / hexane 50%), 409 mg of GN-5-6 (yield 79%) was obtained.

[0160] <Experimental Example 1>

[0161] The NMR spectra of the green heat-activated delayed fluorescent compounds synthesized in Examples 1 to 6 are shown in Table 1 below.

[0164] Example / Compound Number 1 H NMR (400 MHz, CDCl3) Example 1 / GN-5-1 9.21 (d, 1H), 8.26~8.22 (m, 3H), 8.19~8.17 (m, 2H), 8.01~7.98(m, 2H), 7.75 (d, 1H), 7.43(t, 2H), 7.14(dt, 2H), 7.08 (dt, 2H), 6.43 (dd, 2H), 1.74 (s, 6H). Example 2 / GN-5-2 9.31 (d, 1H), 8.59~8.57 (m, 1H), 8.27 (d, 1H), 7.83(dd, 1H), 7.61~7.59(m, 1H), 7.56~7.49(m, 5H), 7.48(dd, 1H), 7.42 (dt, 1H), 7.11~7.06 (m, 4H), 7.62 (dd, 2H), 6.29 (d, 2H), 1.75 (s, 6H). Example 3 / GN-5-3 9.37 (d, 1H), 8.36 (d, 1H), 8.24 (d, 1H), 8.14(d, 1H), 8.01~7.99(m, 1H), 7.95(d, 1H), 7.69(d, 1H), 7.56~7.52 (m, 3H), 7.48 (t, 1H), 7.37~7.35 (m, 2H), 7.27(m, 1H), 7.15~7.05 (m, 4H), 6.42(d, 2H), 1.75 (s, 6H). Example 4 / GN-5-4 9.09 (d, 1H), 8.26~8.20 (m, 3H), 8.16 (d, 1H), 7.90 (d, 1H), 7.76(d, 1H), 7.52~7.50 (m, 3H), 7.48~7.46(m, 1H), 7.44~7.38 (m, 2H), 7.27~7.23 (m, 3H), 7.22~7.14 (m, 4H), 1.61 (s, 6H). Example 5 / GN-5-5 8.96 (d, 1H), 8.57 (d, 1H), 8.02~7.99 (m, 2H), 7.95 (d, 1H), 7.76 (d, 1H), 7.54~7.47(m, 5H), 7.42 (t, 1H), 7.33(d, 1H), 7.26~7.23 (m, 3H), 7.22~7.16 (m, 4H), 1.61 (s, 6H). Example 6 / GN-5-6 9.00 (d, 1H), 8.21 (d, 1H), 8.12 (d, 1H), 8.04~8.01 (m, 2H), 7.92 (d, 1H), 7.55~7.48(m, 3H), 7.44~7.38 (m, 5H), 7.12~7.10(m, 4H), 7.06~7.03 (m, 2H), 1.61 (s, 6H).

[0165] <Experimental Example 2>

[0166] Organic light-emitting diodes were fabricated using the green thermally activated delayed fluorescent compounds synthesized in Examples 1 to 6 as the light-emitting layer material, and PL (nm) was measured under low temperature (-77℃) conditions in liquid nitrogen. Additionally, UV absorption spectra, PLQY (%), HOMO (eV), and LUMO (eV) were measured and are shown in Table 2 below.

[0167] The organic light-emitting diode (OLED) was fabricated under the following conditions. An ITO substrate was patterned to have a light-emitting area of ​​2 mm x 2 mm. The ITO substrate was then mounted in the substrate holder of a vacuum deposition apparatus, and the pressure was applied to a vacuum level of 1 x 10⁻⁷ torr. Subsequently, a HAT-CN compound was vacuum-deposited to a thickness of 5 nm. This compound acts as the hole injection layer. On top of this, NPB material was formed as the first hole transport layer to a thickness of 50 nm. Next, HT-1 material was formed as the second hole transport layer to a thickness of 10 nm. Afterward, a green light-emitting layer was formed by co-depositing a synthetic material as a dopant to a thickness of 30 nm at a mass ratio of approximately 10%. An electron transport layer of ET-1 compound was formed to a thickness of 35 nm on top of this light-emitting layer. Subsequently, LiF material was deposited to form an electron injection layer to a thickness of 1 nm. Finally, Al was deposited to a thickness of 100 nm to form the cathode, thereby fabricating the organic EL device.

[0168] Example / Compound Number Code molecular weight UV(nm) PL(nm) PLQY(%) HOMO(eV) LUMO(eV) Example 1 / GN-5-1 GN-5-1 582.73 282.45 / 321.13 541.6 25 -5.06 -2.35 Example 2 / GN-5-2 GN-5-2 566.66 283.56 / 302.24 533.6 33 -5.05 -2.27 Example 3 / GN-5-3 GN-5-3 566.66 283.26 / 315.95 526.5 36 -5.05 -2.26 Example 4 / GN-5-4 GN-5-4 582.73 294.27 / 319.83 515.6 33 -4.99 -2.31 Example 5 / GN-5-5 GN-5-5 566.66 284.85 / 302.26 515.3 37 -4.96 -2.27 Example 6 / GN-5-6 GN-5-6 566.66 283.31 / 310.6 507.8 53 -4.98 -2.25

[0169] According to Table 2, the thermally activated delayed fluorescent picolinonitrile derivative according to the present invention is a green molecule exhibiting excellent photoluminescence yield, color purity, and thermal stability, and it can be seen that when used in an organic light-emitting device, it will ultimately exhibit excellent photophysical properties.

Claims

Claim 1 A heat-activated delayed-fluorescent picolinonitrile derivative represented by the following chemical formula 1, having a structure in which an electron donor unit is bonded to an electron acceptor unit: [Chemical Formula 1] In the above Chemical Formula 1, A is nitrogen, B and E are hydrogen-bonded carbons (-CH), R1 is -CN, Z1 and Z2 are different from each other and each independently have the structure of Chemical Formula 1A or 1B, [Chemical Formula 1A] (However, in the above Formula 1 A, R2 and R3 are each independently hydrogen, deuterium, or a C1 to C4 alkyl group, and R4 and R5 are each independently hydrogen, a halogen group, or a methyl group.)[Formula 1 B] (However, in the above formula 1B, Ar1 and Ar2 are identical or different from each other and are each independently selected from the group consisting of (i) hydrogen or deuterium, (ii) a substituted or unsubstituted C6 to C60 monocyclic or polycyclic aryl group, or a substituted or unsubstituted C2 to C40 monocyclic or polycyclic heteroaryl group, and may form an aliphatic ring, an aromatic ring, a heteroaliphatic ring, or a heteroaromatic ring condensed with an adjacent group, is the binding site with the compound of Chemical Formula 1.) Claim 2 In claim 1, the compound of Formula 1 is a heat-activated delayed-fluorescent picolinonitrile derivative selected from the compounds of Formula 2 and Formula 3 below: [Formula 2] [Chemical Formula 3] In the above chemical formulas 2 to 3, B and E are hydrogen-bonded carbons (-CH); R1 is a halogen group; -CN; a substituted or unsubstituted C1 to C40 alkyl group; R2 to R5 are each independently selected from the group consisting of hydrogen; deuterium; a halogen group; -CN; a substituted or unsubstituted C1 to C40 alkyl group; a substituted or unsubstituted C2 to C40 alkenyl group; and a substituted or unsubstituted C2 to C40 alkynyl group; Ar1 ​​to Ar2 are the same or different from each other and each independently hydrogen; deuterium; a substituted or unsubstituted C6 to C60 monocyclic or polycyclic aryl group; Selected from the group consisting of substituted or unsubstituted C2 to C40 monocyclic or polycyclic heteroaryl groups, and forming an aliphatic ring, a condensed aromatic ring, a condensed heteroaliphatic ring, or a condensed heteroaromatic ring fused with an adjacent group, is the binding site with the compound of chemical formula 1. Claim 3 In claim 2, the compound of formula 1B is a heat-activated delayed-fluorescence picolinonitrile derivative selected from the following formulas 1B-1 to 1B-6: In the above chemical formulas 1B-1 to 1B-6, G is selected from O, S, Se, and NH, and R6 and R7 are each independently selected from the group consisting of hydrogen; deuterium; halogen group; -CN; and substituted or unsubstituted C1 to C20 alkyl groups. Claim 4 In claim 3, the compound of Formula 1B is a heat-activated delayed-fluorescence picolinonitrile derivative selected from the following: Claim 5 A heat-activated delayed-fluorescent picolinonitrile derivative according to claim 1, wherein in the above formula 1, R1 is selected from the group consisting of hydrogen; deuterium; a halogen group; and -CN, R2 and R3 are each hydrogen or deuterium, and R4 and R5 are each independently selected from the group consisting of hydrogen; deuterium; and a substituted or unsubstituted C1 to C40 alkyl group. Claim 6 In claim 1, the compound of Formula 1 is a heat-activated delayed-fluorescence picolinonitrile derivative selected from the following compounds. Claim 7 In claim 1, the picorinonitrile derivative is a thermally activated delayed fluorescent picorinonitrile derivative having a photoluminescence (PL) wavelength peak of 500 to 550 nm in the green spectrum. Claim 8 A heat-activated delayed-fluorescent picolinonitrile derivative according to claim 1, wherein the PLQY (Photoluminescence Quantum Yield) of the picolinonitrile derivative is 20 to 60%. Claim 9 A heat-activated delayed-fluorescent picorinonitrile derivative according to claim 1, wherein the HOMO (Highest Occupied Molecular Orbital) energy level of the heat-activated delayed-fluorescent picorinonitrile derivative is -5.1 eV to -4.9 eV and the LUMO (Lowest Unoccupied Molecular Orbital) energy level is -2.4 eV to -2.2 eV. Claim 10 An organic light-emitting device comprising an anode; a cathode; and a light-emitting layer disposed between the anode and the cathode, wherein the light-emitting layer comprises a thermally activated delayed fluorescent picolinonitrile derivative according to claim 1. Claim 11 An organic light-emitting device according to claim 10, wherein the light-emitting layer comprises a thermally activated delayed fluorescent picolinonitrile derivative as a dopant, and the dopant is in an amount of 0.01 to 20 parts by weight per 100 parts by weight of a host.

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