JP6986737B2 - New isonicotinonitrile derivative and organic EL device using it - Google Patents

Description

The present invention relates to a novel isonicotinonitrile derivative having high luminous efficiency and an organic EL device using the novel isonicotinonitrile derivative.

In an organic EL (electronics) element, by applying a voltage between a pair of electrodes, holes from the anode and electrons from the cathode are injected into a light emitting layer containing an organic compound as a light emitting material, and the injected electrons and electrons and the injected electrons. By recombination of holes, excitons are formed in the luminescent organic compound, and light emission can be obtained from the excited organic compound.

One of the means for improving the practicality of such an organic EL element is to increase the luminous efficiency. The excitons organic compound forms, there are singlet excitons (E _S1) and triplet exciton (E _T1), and the fluorescence emission from singlet excitons (E _S1), triplet excitons (E _{There is phosphorescent emission from T1} ), but the statistical generation ratio of these in the element is E _S1 : E _T1 = 1: 3, and the internal quantum efficiency of 25% is the limit for organic EL elements using fluorescent emission. It is said that. Therefore, in order to improve the conversion efficiency from electrons to photons (internal quantum efficiency), a phosphorescent light emitting material capable of converting a triplet excited state into light emission has been developed, and recently, an organic substance using this phosphorescent light emission has been developed. EL elements have been reported.

Further, in using such a light emitting material in an organic EL device, a method of doping a host material with a dopant material is known. In the light emitting layer formed by the doping method, excitons can be efficiently generated from the electric charge injected into the host. Then, the exciton energy of the generated excitons can be transferred to the dopant, and high-efficiency light emission can be obtained from the dopant.

Here, in order to transfer intermolecular energy from the host to the phosphorescent phosphorescent dopant, it is necessary that the _{triplet energy E gH of the host is larger than the triplet energy E gD} of the phosphorescent dopant. ..

As a material having an effectively large triplet energy E _gH , for example, CBP (4,4'-bis (N-carbazolyl) biphenyl) and the like are known. If such a material is used as a host, a highly efficient light emitting element can be obtained by transferring energy between triplet excitons to a phosphorescent dopant having a predetermined light emitting wavelength (for example, red or green).

By the way, although the thermally activated delayed fluorescence (TADF) material described in Non-Patent Document 1 is a fluorescent material, it realizes a theoretically 100% exciton generation probability like a phosphorescent material. Is possible and useful for high efficiency. Furthermore, it is possible to reduce the cost due to the rare metal-free molecular design. Therefore, by developing a light-emitting material using this TADF, it is considered that a low-cost and high-efficiency light-emitting element can be obtained.

Patent Document 1 reports that a pyridinecarbonitrile compound containing a carbazole structure can be a TADF material as a light emitting material used for an organic EL element.

Further, Non-Patent Document 3 describes a blue organic EL element using a carbazole / pyridinedicarbonitrile derivative as a TADF material, and reports that it exhibits an external quantum efficiency of 21.2% and a luminous efficiency.

Japanese Unexamined Patent Publication No. 2015-172166

H. Uoyama, K. Goushi, K. Shizu, H. Nomura, C. Adachi, Nature 2012,492, 234. Wei Liu, Cai-Jun Zheng, Kai Wang, Zhan Chen, Dong-Yang Chen, Fan Li, Xue-Mei Ou, Yu-Ping Dong, and Xiao-Hong Zhang, Applied Materials & Interfaces 2015, 7, 18930

An object of the present invention is to provide a novel isonicotinonitrile derivative that emits light from light blue to green and emits light with high efficiency, and an organic EL device using the same.

（一般式（１）中、Ｒ¹及びＲ²はそれぞれ独立に水素原子、炭素原子数１〜６のアルキル基、炭素原子数１〜６のアルコキシ基、アリール基、又はアミノ基を表し、Ｒ³及びＲ⁴はそれぞれ独立に水素原子、メチル基、エチル基、プロピル基、イソプロピル基、メトキシ基、又はフェニル基を表し、ｎは１〜４の整数を表す。） The present invention comprises the following matters.
The isonicotinonitrile derivative of the present invention is characterized by being represented by the following general formula (1).

(In the general formula (1), R ¹ and R ² independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group, or an amino group, respectively, and R ³ and R ⁴ independently represent a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a methoxy group, or a phenyl group, and n represents an integer of 1 to 4).

In the general formula (1), n is preferably 1 or 2.
The isonicotinonitrile derivative is preferably a compound represented by the following structural formula.

The isonicotinonitrile derivative of the present invention is characterized by being represented by the following structural formula.

The organic EL device of the present invention is characterized by using the above-mentioned isonicotinonitrile derivative.

The isonicotinonitrile derivative of the present invention exhibits thermally activated delayed fluorescence (TADF) and emits light from light blue to green with high efficiency, so that it can be suitably used for an organic EL element.

FIG. 1 (a) shows the UV-vis absorption spectrum of the PXZINN single film and the 10 wt% CBP-doped co-deposited film, and FIG. 1 (b) shows the PL spectrum of the PXZINN single film and the 10 wt% CBP-doped co-deposited film. It is a figure showing. FIG. 2 (a) is a diagram showing the PL spectrum of the 10 wt% CBP-doped co-deposited film of PXZINN, and FIG. 2 (b) is a diagram showing the transient PL spectra of the 10 wt% CBP-doped co-deposited film of PXZINN at 300K and 5K. FIG. 3 shows the hole transport layer when the light emitting layer is a PXZINN 10 wt% CBP-doped co-deposited film (device 1) and a PXZINN 10 wt% TCTA-doped co-deposited film (device 2) in the device 1 or 2. It is an energy diagram of a light emitting layer and an electron transporting layer. FIG. 4A shows the current density-voltage characteristic relationship of the device 1 or 2, FIG. 4B shows the brightness-voltage characteristic relationship of the device 1 or 2, and FIG. 4C shows the relationship. The relationship between the external quantum efficiency of the device 1 or 2 and the brightness characteristic is shown, FIG. 4 (d) shows the relationship between the external quantum efficiency of the device 1 or 2 and the current density, and FIG. 4 (e) shows the relationship between the device 1 or 2 and the device 1 or 2. 4 (f) is a diagram showing the relationship between the power efficiency of the device 1 or 2 and the brightness characteristic. FIG. 5 (a) shows an EL spectrum when a current of 1 mA is passed through the device 1 or 2, and FIG. 5 (b) shows an exhibix (B3PyPB) in which the light emitting layer is CTTA only, B3PyPB only, or TCTA and B3PyPB. : TCTA) is a diagram comparing EL spectra of the device and the device 2 in each case. FIG. 6 shows the hole transport layer and light emission when the light emitting layer is a 10 wt% CBP-doped co-deposited film of PXZINN and the electron transport layer is B3PyPB (device 1) or B4PyPB (device 3) in the device 1 or 3. It is an energy diagram of a layer and an electron transport layer. 7 (a) shows the current density-voltage characteristic relationship of the device 1 or 3, FIG. 7 (b) shows the brightness-voltage characteristic relationship of the device 1 or 3, and FIG. 7 (c) shows the relationship. The relationship between the external quantum efficiency of the device 1 or 3 and the brightness characteristic is shown, FIG. 7 (d) shows the relationship between the external quantum efficiency of the device 1 or 3 and the current density, and FIG. 7 (e) shows the relationship between the device 1 or 3 and the device 1 or 3. 7 (f) is a diagram showing the relationship between the power efficiency of the device 1 or 3 and the brightness characteristic. FIG. 8 is a diagram showing an EL spectrum when a current of 1 mA is passed through the device 1 or 3. In FIG. 9, in the device 3 or 4, the light emitting layer is a 10 wt% CBP-doped co-deposited film (10 nm thick) of PXZINN (device 3), a 10 wt% TCTA-doped co-deposited film of PXZINN (5 nm thick), and PXZINN. It is an energy diagram of the hole transport layer, the light emitting layer and the electron transport layer when the 10 wt% CBP-doped co-deposited film (5 nm thickness) (device 4) is used. 10 (a) shows the current density-voltage characteristic relationship of the device 3 or 4, FIG. 10 (b) shows the brightness-voltage characteristic relationship of the device 3 or 4, and FIG. 10 (c) shows the relationship. The current density-brightness characteristic of the device 3 or 4 is shown, FIG. 10 (d) shows the power efficiency-brightness characteristic of the device 3 or 4, and FIG. 10 (e) shows the outside of the device 3 or 4. FIG. 10F shows the relationship between the quantum efficiency and the brightness characteristic, and FIG. 10F is a diagram showing the relationship between the external quantum efficiency and the current density of the device 3 or 4.

FIG. 11 is a diagram showing an EL spectrum when a current of 1 mA is passed through the device 3 or 4. FIG. 12 shows the hole transport layer and light emission when the hole transport layer is TAPC (25 nm thick) and TCTA (5 nm thickness) and the light emitting layer is a 10 wt% CBP-doped co-deposited film of PXZINN in devices 5 to 7. It is an energy diagram of a layer and an electron transport layer. 13 (a) shows the current density-voltage characteristic relationship of devices 5 to 7, FIG. 13 (b) shows the brightness-voltage characteristic relationship of devices 5 to 7, and FIG. 13 (c) shows the relationship. The current density-brightness characteristics of the devices 5 to 7 are shown, FIG. 13 (d) shows the power efficiency-brightness characteristics of the devices 5 to 7, and FIG. 13 (e) shows the outside of the devices 5 to 7. FIG. 13 (f) is a diagram showing the relationship between the quantum efficiency and the brightness characteristic, and FIG. 13 (f) shows the relationship between the external quantum efficiency and the current density of the devices 5 to 7. FIG. 14 is a diagram showing an EL spectrum when a current of 1 mA is passed through the devices 5 to 7. FIG. 15 is an energy diagram of a hole transport layer, a light emitting layer, and an electron transport layer when the light emitting layer is a 10 wt% DPEPO-doped co-deposited film of ACINN in the device 8. 16A shows the current density-voltage characteristic relationship of the device 8, FIG. 16B shows the brightness-voltage characteristic relationship of the device 8, and FIG. 16C shows the current of the device 8. The density-brightness characteristic is shown, FIG. 16 (d) shows the power efficiency-brightness characteristic of the device 8, and FIG. 16 (e) shows the external quantum efficiency-brightness characteristic of the device 8. FIG. 16 (f) is a diagram showing the relationship between the external quantum efficiency and the current density of the device 8. FIG. 17 is a diagram showing an EL spectrum when a current of 1 mA is passed through the device 8. FIG. 18 shows the UV-vis absorption spectra of (a): toluene solution ( ^10-5 M), (b): single film, and (c): 10 wt% DPEPO-doped co-deposited film of 2AcINN, 3AcINN, 2AcNN and 5AcNN. It is a figure which shows. FIG. 19 is a diagram showing the PL spectra of (a): toluene solution ( ^10-5 M), (b): single film, and (c): 10 wt% DPEPO-doped co-deposited film of 2AcINN, 3AcINN, 2AcNN and 5AcNN. be. FIG. 20 is a diagram showing transient PL spectra of a 5AcNN 10 wt% PyCN derivative: 30 wt% DPEPO-doped co-deposited film at 300K and 5K.

FIG. 21 is a diagram showing transient PL spectra of a 2AcNN 10 wt% PyCN derivative: 30 wt% DPEPO-doped co-deposited film at 300K and 5K. FIG. 22 is a diagram showing transient PL spectra of a 10 wt% PyCN derivative of 3AcINN: 30 wt% DPEPO-doped co-deposited film at 300K and 5K. FIG. 23 is a diagram showing a transient PL spectrum at 5K of a 5 AcNN 5 wt% Ir (ppz) ₃ : PyCN derivative (30 nm) -doped co-deposited film. FIG. 24 is a diagram showing a transient PL spectrum at 5K of a 5 wt% Ir (ppz) ₃ : PyCN derivative (30 nm) -doped co-deposited film of 2AcNN. FIG. 25 is a diagram showing a transient PL spectrum at 5K of a 5 wt% Ir (ppz) ₃ : PyCN derivative (30 nm) -doped co-deposited film of 3AcINN. FIG. 26 shows the hole transport layer in the device of Example 10 when the hole transport layer is TAPC (25 nm thick) and mCP (5 nm thickness) and the light emitting layer is a 10 wt% CBP-doped co-deposited film of each dopant. , Energy diagram of light emitting layer and electron transport layer. FIG. 27 shows the current density-voltage characteristic relationship (a), the brightness-voltage characteristic relationship (b), the current efficiency-brightness characteristic relationship (c), and the power efficiency-brightness characteristic relationship (a) of the device of the tenth embodiment. d) is a figure showing the relationship (e) of the external quantum efficiency-current density characteristic, and the relationship (f) of the external quantum efficiency-brightness characteristic. FIG. 28 is an EL spectrum when a current of 1 mA is passed through the device of Example 10. FIG. 29 is a diagram showing a typical configuration of an organic EL element.

Hereinafter, the present invention will be described in detail.
[Isonicotinonitrile derivative]
The isonicotinonitrile derivative of the present invention is represented by the following general formula (1).

In the general formula (1), R ¹ and R ² independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group, a phenyl group, or an amino group having 1 to 6 carbon atoms, respectively, and represent R 3 and ^{R 2.} R ⁴ independently represents a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, or a methoxy group, and n represents an integer of 1 to 4.

The isonicotinonitrile derivative has a π-conjugated system. It is known that molecules having a π-conjugated system have a light absorption band in the visible region, and many of them can function as dyes. Furthermore, the energy gap can be adjusted by appropriately adding a functional group to such a molecule to change its electronic properties. That is, in the present invention, in isonicotinonitrile derivatives, by molecular design to minimize the energy gap between the singlet excited state (E _S1) and a triplet excited state (E _T1), once a triplet excited state The energy transferred to can be returned to the singlet excited state again, and highly efficient fluorescence can be extracted.

The isonicotinonitrile derivative of the present invention is a thermally activated delayed fluorescent (TADF) molecule and is a compound that emits light in light blue to green (480 to 530 nm).
Further, when n is 1 or 2 in the general formula (1), the isonicotinonitrile derivative can stably maintain a π-conjugated system, and thus can exhibit long-life light blue to green light emission. ..

Specifically, the isonicotinonitrile derivative represented by the general formula (1) is preferably a compound represented by the following structural formula.

The isonicotinonitrile derivative represented by the general formula (1) is a compound represented by the following structural formula.

[Manufacturing method of isonicotinonitrile derivative]
The isonicotinonitrile derivative of the present invention can be produced, for example, by the method shown below. The manufacturing method of PXZINN is shown as an example.

2,6-Dichloroisonicotinonitrile, 4-chlorophenylboronic acid in a double molar amount with respect to the 2,6-dichloroisonicotinonitrile, and sodium carbonate are dissolved in water, and acetonitrile is further added. Then, 2ClPhINN is obtained by heating in the presence of bis (triphenylphosphine) palladium (II) dichloride (PdCl ₂ (PPh ₃ ) _{2) in a nitrogen atmosphere.} Next, 2ClPhINN, phenoxazine in a double molar amount with respect to the 2ClPhINN, and potassium carbonate (K ₂ CO ₃ ) were dissolved in toluene, and palladium (II) acetate (Pd (OAc) _{2) was dissolved in toluene.} ) And tri-t-butylphosphine (P (tBu) ₃ ) to give PXZINN in 96% yield.

However, the isonicotinonitrile derivative represented by the general formula (1) is not limited to the above-mentioned method, and can be produced by various known methods.

[Organic EL element]
The organic EL device of the present invention uses the above-mentioned isonicotinonitrile derivative.
Here, FIG. 29 shows a typical layer structure of the organic EL element.
In the organic EL element, for example, an ITO or the like is formed as an anode 2 on a substrate 1, and a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection are formed therein. The layers and cathodes are laminated in this order.

The substrate 1 is transparent and smooth, and has a total light transmittance of at least 70%. Specifically, it is a flexible transparent substrate, such as a glass substrate having a thickness of several μm or a special transparent substrate. Plastic or the like is used.

The thin films such as the anode 2, the hole injection layer 3, the hole transport layer 4, the light emitting layer 5, the electron transport layer 6, the electron injection layer 7, and the cathode 8 formed on the substrate are laminated by a vacuum vapor deposition method or a coating method. Will be done. When the vacuum vapor deposition method is used, the vapor deposition is usually heated in an atmosphere reduced to ^{10 -3 Pa or less.} The film thickness of each layer varies depending on the type of layer and the material used, but usually, the anode 2 and the cathode 8 have a film thickness of about 100 nm, and the other layers including the light emitting layer 5 have a film thickness of less than 50 nm. The electron injection layer 7 and the like may be formed with a thickness of, for example, 1 nm or less.

As the anode 2, a anode having a large work function and a total light transmittance of 80% or more is usually used. Specifically, in order to transmit the light emitted from the anode 2, transparent conductive ceramics such as ITO and ZnO, transparent conductive polymers such as PEDOT / PSS and polyaniline, and other transparent conductive materials are used. The film thickness of the anode 2 is usually 10 to 200 nm.

As with other light emitting layers used in organic EL elements, it is preferable to use a host compound together with the isonicotinonitrile derivative which is the light emitting material of the present invention in the light emitting layer 5. The host compound is not limited as long as it does not impair the emission characteristics based on fluorescence and TADF, and is, for example, bis [2- (diphenylphosphino) phenyl] ether oxide (DPEPO), PO9, 4,4'-. Bis (N-carbazolyl) -1,1'-biphenyl (CBP), tris (4-carbazoyl-9-ylphenyl) amine (TCTA), 2,8-bis (diphenylphosphoryl) dibenzothiophene (PPT), adamantane. Examples include anthracene (Ad-Ant), rubrene, and 2,2'-bi (9,10-diphenylanthracene) (TPBA). The content of the light emitting material (isonicotinonitrile derivative) and the host compound of the present invention in the components constituting the light emitting layer 5 is 1 to 50 wt%, preferably 5 to 10 wt%.

A hole transport layer 4 is provided between the anode 2 and the light emitting layer 5 in order to efficiently transport holes from the anode 2 to the light emitting layer. Examples of the hole transport material forming the hole transport layer 4 include TAPC, N, N'-diphenyl-N, N'-di (m-tolyl) benzidine (TPD), N, N'-di (1). -Naphthyl) -N, N'-diphenylbenzidine (α-NPD), 1,3-di (carbazolyl-9-yl) benzene) (mCP) and 4,4', 4''-tris [phenyl (m-) Trill) Amino] Triphenylamine and the like can be mentioned.

An electron transport layer 6 is provided between the cathode 8 and the light emitting layer 5 in order to efficiently transport electrons from the cathode to the light emitting layer. Examples of the electron transport material forming the electron transport layer 6 include B3PymPm, B4PyPPm, 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), bathocuproine (BCP), 1,3,5-tris (1-phenyl-1H-benzimidazole-2-) Il) benzene (TPBi) and the like can be mentioned.

As the cathode 8, a cathode having a low work function (4 eV or less) and chemically stable is used.
Specifically, a cathode material such as an Al, MgAg alloy, or an alloy of Al and an alkali metal such as AlLi or AlCa is used. These cathode materials are formed by, for example, a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, or an ion plating method. The thickness of the cathode is usually 10 nm to 1 μm, preferably 50 to 500 nm.

Of the hole transport layer 4 and the electron transport layer 6, each of them has a function of improving the charge injection efficiency from the anode 2 or the cathode 8, and is positive as a layer that exerts the effect of lowering the drive voltage of the organic EL element. The hole injection layer 3 and the electron injection layer 7 may be provided. Further, layers such as a hole blocking layer, an electron blocking layer and an exciton blocking layer are formed as needed.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples.

[Synthesis of isonicotinonitrile derivative represented by the general formula (1)]
The equipment and measurement conditions used to identify the compound are as follows.
(1) ¹ H Nuclear Magnetic Resonance (NMR) Device JEM-EX270FT-NMR Type (2) Mass Spectrometry (MS) Device manufactured by JEOL Ltd. (400 MHz) JMS-K9 [Desktop GCQMS] manufactured by JEOL Ltd. Zspray manufactured by Waters Co., Ltd. (SQ detector 2)
(3) Sublimation refining equipment Temperature tilt type electric furnace, type: NPF80-500 type, company name: Cosmo Tech Co., Ltd.
Thermal constant flow rate device, type: MC-1A, company name: Koflock Co., Ltd.
Rotary pump, type: GLD-136C, company name: ULVAC Kiko Co., Ltd.
(4) Elemental analyzer PerkinElmer 2400II CHNS / O analyzer Measurement mode: CHN mode

[Example 1] Synthesis of PXZINN

(I) Synthesis of 2ClPhINN In a nitrogen-substituted 100 mL four-necked flask, 0.69 g (4.0 mmol) of 2,6-dichloroisonicotinonitrile, 1.37 g (8.8 mmol) of 4-chlorophenylboronic acid, and carbonic acid were added. _{A 1 MNa 2} CO ₃ aqueous solution prepared by dissolving 2.2 g of sodium (Na ₂ CO ₃ ) in 20 mL of water was added, 56 mL of acetonitrile was added, and nitrogen bubbling was performed for 1 hour. Then, _{0.14 g (0.2 mmol) of PdCl 2} (PPh ₃ ) ₂ was added, and the mixture was heated at 80 ° C. under a nitrogen atmosphere. After 1 hour, it was confirmed that the raw material was consumed by TLC, and the reaction was stopped. Suction filtration was performed, the filtrate was dissolved in 150 mL of chloroform, and washed twice with 100 mL of water and once with saturated brine in a liquid separation funnel. After dehydration with magnesium sulfate, it was concentrated. Further, it was thermally filtered with toluene to obtain 0.84 g (yield 65%) of a white solid.
^{1 1} H-NMR (400 MHz, DMSO-D6): δ8.46 (dd; J = 12.9, 9.3 Hz; 2H), 8.31 (dt; J = 9.2, 2.3 Hz; 4H), 7.73-7.52 (m; 4H) ppm
MS: [m / z] 325

(Ii) Synthesis of PXZINN In a nitrogen-substituted 50 mL four-necked flask, 0.54 g (1.6 mmol) of 2ClPh-INN, 0.67 g (3.6 mmol) of phenoxazine, and 1.52 g (11 mmol) of potassium carbonate. 50 mL of toluene was added and nitrogen bubbling was performed for 1 hour. Then, 25.0 mg (0.1 mmol) of Pd (OAc) _{2 and 0.097 mL (0.4 mmol) of P (tBu) 3} were added, and the mixture was heated under reflux at 110 ° C. under a nitrogen atmosphere. After 25 hours, the consumption of the raw material was confirmed by TLC (developing solvent dichloromethane: hexane = 1: 1), and the reaction was stopped. After confirming that the target product had a molecular weight by MS, it was dissolved in chloroform, separated twice with 100 mL of water and separated with 100 mL of saturated brine, dehydrated with magnesium sulfate, and concentrated. Then, thermal filtration was performed with toluene. Purification by silica gel column chromatography (developing solvent dichloromethane: hexane = 1: 2 → 1: 1) gave 0.99 g (yield 96%) of the target product as a yellow solid.
The results of ¹ H-NMR, MS, elemental analysis, thermogravimetric analysis (TGA), and vacuum TGA for PXZINN are shown below.
^{1 1} H-NMR (400 MHz, DMSO-D6): δ8.60 (d; J = 10.0 Hz; 6H), 7.63 (d; J = 8.2 Hz; 4H), 6.85-6.61 ( m; 12H), 6.08-5.88 (m; 4H) ppm
MS: [m / z] 618
Elemental analysis: Composition formula C ₄₂ H ₂₆ N ₄ O ₂
Theoretical value: C, 81.54%; H, 4.24%; N, 9.06%; O, 5.17%
Measured value: C, 81.51%; H, 4.25%; N, 9.05%
5% weight decay temperature: 463 ° C
Sublimation temperature (10 ^-4 Torr): 277 ° C

[Example 2] Synthesis of 2AcINN

(I) Synthesis of ClPhINN 1.38 g (8.0 mmol) of 2-chloroisonicotinonitrile, 1.37 g (8.8 mmol) of 4-chlorophenylboronic acid, and sodium carbonate 4 in a nitrogen-substituted 200 mL four-necked flask. A 1 M aqueous sodium carbonate solution in which 4 g was dissolved in 40 mL of water was added, 112 mL of acetonitrile was added, and nitrogen bubbling was performed for 1 hour. Then, _{0.14 g (0.2 mmol) of PdCl 2} (PPh ₃ ) ₂ was added, and the mixture was heated at 80 ° C. under a nitrogen atmosphere to initiate the reaction. After confirming that the raw material was consumed by TLC, the reaction was stopped. It was washed twice with 50 mL of water and once with 50 mL of saturated saline in a separating funnel. After dehydration with magnesium sulfate, it was concentrated. Since a small amount of toluene was used when transferring to a separating funnel and filtering, only acetonitrile was skipped for concentration, and then only a small amount of toluene solution was left. Column purification was performed using 12 mL of this solution as injection. A Φ4.2 cm column tube was filled with silica gel to a height of 10 cm. The developing solvent was toluene (Rf value: 0.20). Fractions from which the target product was isolated by collecting 100 mL each were collected and concentrated. The obtained colorless viscous body was dried under reduced pressure to obtain 1.68 g (yield 98%) of a white solid.
^{1 1} H-NMR (400 MHz, DMSO-D6): δ8.91 (d; J = 5.0 Hz; 1H), 8.53 (s; 1H), 8.19 (dt; J = 8.9, 2. 3Hz; 2H), 7.84 (dd; J = 5.0, 1.4Hz; 1H), 7.60 (dt; J = 9.2, 2.3Hz; 2H) ppm
MS: [m / z] 214

(Ii) Synthesis of 2AcINN 1.49 g (6.96 mmol) of ClPhINN, 1.60 g (7.66 mmol) of 9,10-dihydro-9,9-dimethylacridine and carbonic acid in a nitrogen-substituted 50 mL four-necked flask. 1.92 g (13.9 mmol) of potassium and 35 mL of toluene were added, and nitrogen bubbling was performed for 1 hour. Then, 79.0 mg (0.35 mmol) of Pd (OAc) _{2 and 308 mg (1.05 mmol) of [(tBu) 3} PH] BF ₄ were added, and the mixture was heated under reflux at 110 ° C. under a nitrogen atmosphere. Consumption of the raw material was confirmed by TLC (developing solvent dichloromethane), and the reaction was stopped. After suction filtration, the mixture was separated twice with 50 mL of water and 50 mL of saturated brine, dehydrated with magnesium sulfate, and concentrated. Silica gel was filled in a Φ4.2 cm column tube to a height of 15 cm, and the target product was isolated by silica gel column chromatography (developing solvent toluene) (Rf value: 0.2). This was recovered, concentrated, and dried under reduced pressure to obtain 2.09 g (yield 77%) of a white to pale yellow solid.
The results of ¹ H-NMR, MS, elemental analysis, thermogravimetric analysis (TGA), and vacuum TGA for 2AcINN are shown below.
^{1 1} H-NMR (400 MHz, DMSO-D6): δ8.97 (dd; J = 5.0, 0.9 Hz; 1H), 8.63 (s; 1H), 8.47 (dd; J = 6. 8, 1.8Hz; 2H), 7.88 (dd; J = 5.0, 1.4Hz; 1H), 7.52 (td; J = 8.4, 2.0Hz; 4H), 6.95 (Dtd; J = 27.6, 7.5, 1.4Hz; 4H), 6.22 (dd; J = 7.9, 1.1Hz; 2H), 1.63 (s; 6H) ppm
MS: [m / z] 214
Elemental analysis: C ₂₇ H ₂₁ N ₃
Theoretical value: C, 83.69%; H, 5.46%; N, 10.84%
Measured value: C, 83.69%; H, 5.34%; N, 10.84%
5% weight decay temperature: 312 ° C
Sublimation temperature (10 ^-4 Torr): 156 ° C

[Example 3] Synthesis of PXZINN-MPA

(I) Synthesis of ClPhPXZ In a nitrogen-substituted 50 mL four-necked flask, 1.83 g (10 mmol) of phenoxazine, 1.92 g (10 mmol) of 1-bromo-4-chlorobenzene, 2.76 g (20 mmol) of potassium carbonate, and the like. And 50 mL of toluene was added, and nitrogen bubbling was performed for 1 hour. Then, 0.44 g (1.5 mmol) of [(tBu) ₃ PH] BF _{4 and 0.11 g (0.5 mmol) of Pd (OAc) 2} were added, and the mixture was heated and stirred at 110 ° C. under a nitrogen atmosphere. The reaction was started. After 3.5 hours, it was confirmed that the raw material phenoxazine was almost consumed by TLC, and the reaction was stopped after another 1 hour. A peak derived from the target substance was observed by MS. Then, salts and the like were removed by suction filtration, and washing was performed twice with 50 mL of water and once with 50 mL of saturated saline in a liquid separation funnel. It was dehydrated with sodium sulfate, removed, and then concentrated. 2.9 g of a yellow to gray solid was obtained. Next, purification was performed by column chromatography. Since there was only one spot on the TLC, it was about a blank column. A Φ4.2 cm column tube was filled with silica gel equivalent to 140 cc (height about 10 cm), and the process was carried out with a developing solvent (toluene: hexane = 1: 4). The spot of interest was recovered and concentrated to obtain 3.0 g of a white solid. After drying in a vacuum dryer, the white solid weighed 2.51 g (yield 85%).
^{1 1} H-NMR (400 MHz, DMSO-D6): δ7.72 (dt; J = 9.4, 2.6 Hz; 2H), 7.47 (dt; J = 9.2, 2.5 Hz; 2H), 6.85-6.56 (m; 6H) 5.96-5.76 (m; 2H) ppm
MS: [m / z] 293

(Ii) Synthesis of ClPhPXZ-Br In a nitrogen-substituted four-necked flask, 3.12 g (1.06 mmol) of ClPhPXZ and 20 to 30 mL of methylene chloride were placed, and nitrogen flow was performed at 0 ° C. or lower. Then, 1.88 g (1.06 mmol) of N-bromosuccinimide (NBS) was dissolved in the remaining 90 to 100 mL of methylene chloride and placed in a dropping funnel. The entire system was shielded from light with aluminum foil, dripping was started, and the reaction was started. After dropping all of them, it was judged that the spot of the monosubstituted product was dark and the raw material was thin and almost no, and the reaction was terminated. A peak derived from the target substance was observed by MS. Then, it was washed twice with 50 mL of water and once with 50 mL of saturated saline in a separating funnel. It was dehydrated with magnesium sulfate, and the origin was removed with silica gel. The decolorized solution was concentrated and dried under reduced pressure to obtain 3.90 g (yield 98%) of a white to pale yellow solid.
The same operation was carried out to obtain a total of 5.91 g of the target product, ClPhPXZ-Br.
^{1 1} H-NMR (400 MHz, DMSO-D6): δ7.70 (dd; J = 6.3, 2.3 Hz; 2H), 7.48-7.40 (m; 2H), 6.92 (t; J = 2.0Hz; 1H), 6.82 (td; J = 9.3, 2.3Hz; 1H), 6.75-6.61 (m; 3H), 5.84 (td; J = 3) .5, 2.1Hz; 1H) 5.76 (dd; J = 8.6, 2.7Hz; 1H) ppm
MS: [m / z] 373

(Iii) Synthesis of ClPhPXZ-MPA In a nitrogen-substituted four-necked flask, 1.00 g (2.68 mmol) of 3-bromo-10- (4-chlorophenyl) phenoxazine (ClPhPXZ-Br) and 0.74 g (5) of potassium carbonate were placed. .36 mmol) and 20 mL of toluene were added and nitrogen bubbling was performed for 1 hour. Then, N- methylaniline 0.29 mL (2.68 mmol), was added the _{[(tBu) 3 PH] BF} 4 0.11g (0.40mmol), and _{Pd (OAc) 2 0.03g (0.13mmol} ) , 110 ° C., stirring while heating in a nitrogen atmosphere. On the way, the same amount of catalyst and ligand as above were added, and 24 hours after the addition, it was confirmed by TLC that the raw material was consumed, and the reaction was stopped. After cooling to room temperature, suction filtration was performed, and the filtrate was washed twice with 50 mL of water and once with 50 mL of saturated saline in a separate solution funnel. Further, the aqueous layer was extracted with 20 mL of toluene. It was dehydrated with magnesium sulfate, removed by filtration, and then concentrated. Obtained a yellow viscous body. The column tube was filled with hexane to a height of silica gel of about 15 cm. The developing solvent was set to dichloromethane: hexane = 1: 3 (object: Rf value 0.25). Injection was created by diluting the yellow viscous body with a small amount of toluene. After the spots appeared, 50 mL each was collected. Up to the second fraction, dust spots were mixed thinly, but after that, only the target object was isolated. Since the target substance was contained up to the sixth fraction, this was concentrated. 0.85 g (yield 79%) of yellow viscous substance was obtained.
The same operation was carried out to obtain a total of 3.65 g of ClPhPXZ-MPA, which is the target product.
MS: [m / z] 399

(Iv) Synthesis of BPinPhPXZ-MPA In a nitrogen-substituted 25 mL four-necked flask, 280 g (7.02 mmol) of ClPhPXZ-MPA, 3.55 g (8.42 mmol) of bis (pinacolato) diboron, and 2.08 g (21.2 mmol) of KOAc. ) And 66 mL of 1,4-dioxane were added and nitrogen bubbling was performed for 1 hour. Then, 2-dicyclohexyl phosphino-2,6'-dimethoxy biphenyl (S-Phos) 148mg (0.33mmol ), and the addition of _{Pd (OAc) 2 79mg (0.33mmol} ), 100 ℃, under a nitrogen atmosphere The reaction was started by heating and stirring. The next day, after confirming the consumption of the raw material by TLC, the reaction was stopped. After returning to room temperature, suction filtration was performed, and the filtrate was washed twice with 50 mL of water and once with 50 mL of saturated saline in a separate solution funnel. Further, the aqueous layer was extracted with toluene. It was dehydrated with magnesium sulfate and concentrated to obtain a yellow viscous body.
The column tube was filled with silica gel to a height of about 20 cm. The developing solvent was set to dichloromethane: hexane = 1: 2 (object: Rf value 0.25). The solution of the fraction recovered by silica gallam column chromatography was concentrated and dried under reduced pressure to obtain 2.62 g (yield: 72%) of a yellow solid.
The same operation was carried out to obtain a total of 3.14 g of the target product, BPinPhPXZ-MPA.
^{1 1} H-NMR (400 MHz, DMSO-D6): δ7.94 (dd; J = 8.2, 2.7 Hz; 2H), 7.45-7.38 (m; 2H), 7.25-7. 13. (m; 2H), 6.88-6.79 (m; 2H), 6.77-6.56 (m; 4H), 6.49 (d; J = 2.7Hz; 1H), 6. 39 (dd; J = 8.6, 2.3Hz; 1H), 5.91-5.81 (m; 2H), 3.12 (d; J = 13.1Hz; 3H), 1.31 (d) J = 12.7Hz; 12H) ppm
MS: [m / z] 490

(V) Synthesis of PXZINN-MPA In a nitrogen-substituted four-necked flask, 2.62 g (5.34 mmol) of BPinPhPXZ-MPA, 440 mg (2.54 mmol) of 2,6-dichloroisonicotinonitrile, 1,4-dioxane 31 Nitrogen bubbling was performed for 1 hour by adding an aqueous solution prepared by dissolving 1.6 mL of K ₃ PO _{4 in 6.6 mL of water.} Then, _{209 mg (0.51 mmol) of Pd 2} (dba) ₃ and 476 mg (0.51 mmol) of SPhos were added, and the mixture was heated and stirred at 100 ° C. under a nitrogen atmosphere. After 22 hours, it was confirmed that BPinPhPXZ-MPA was consumed by TLC, and the reaction was stopped. After returning to room temperature, suction filtration was performed, and the filtrate was washed twice with water and once with saturated brine in a separate funnel. It was dehydrated with magnesium sulfate, removed by filtration, and then concentrated. 0.7 g of orange solid was obtained. The column tube Φ4.2 cm was filled with silica gel (height about 20 cm) with hexane. It was prepared by dissolving the injection in toluene. The developing solvent was set to toluene: hexane = 3: 1 (Rf: 2.0). 50 mL each was collected and isolated from the 7th bottle. This was poured until there were no spots, collected, and concentrated. 1.32 g (yield 63%) of an orange solid was obtained.
The same operation was performed to obtain a total of 1.54 g of the target product, PXZINN-MPA.
^{The results of 1} H-NMR, MS, thermogravimetric analysis (TGA), and vacuum TGA for PXZINN-MPA are shown below.
^{1 1} H-NMR (400 MHz, DMSO-D6): δ8.70-8.50 (m; 6H), 7.64 (d; J = 8.2Hz; 4H), 7.27-7.15 (m) 4H), 6.96-6.62 (m; 12H), 6.59-6.36 (m; 4H), 6.09-5.89 (m; 4H), 3.17 (d; J) = 15.4Hz; 6H) ppm
MS: [m / z] 829
5% weight decay temperature: 435 ° C
Sublimation temperature (× 10 ^-4 Torr): 333 ° C

[Example 4] Synthesis of 3AcINN

1.16 g (2.83 mmol) of 4- (dioxaborolane) phenyl-9,9-dimethylacridine and 0.39 g (2.83 mmol) of 3-chloro-4-cyanopyridine in a nitrogen-substituted 50 mL four-necked flask. , 1,4-dioxane (35.4 mL) and K ₃ PO _{4 (} 1.81 g) were added, and 7.4 mL of water was added to dissolve the mixture, and nitrogen bubbling was performed for 1 hour. Then, _{0.13 g (0.14 mmol) of Pd 2} (dba) ₃ and 0.057 g (0.14 mmol) of SPhos were added, and the mixture was heated and stirred at 100 ° C. Sampling was performed after 1 hour, and it was confirmed by TLC that a new spot was generated. A peak derived from the target product was confirmed by Mass. After 14 hours, it was confirmed by TLC that the raw material was consumed, and the reaction was stopped. Then, 10 cm of silica gel was filled in a Φ4.2 cm column tube, and the target product was isolated by column chromatography using dichloromethane as the developing solvent (Rf value: 0.1). After concentration and drying under reduced pressure, 0.7 g of a white to pale yellow solid was obtained. Yield 77%.
^{1 1} H-NMR (400 MHz, DMSO-D6) δ9.08 (s, 1H), 8.88 (d, J = 5.4 Hz, 1H), 8.12-7.91 (m, 3H), 7. 68-7.43 (m, 4H), 7.11-6.84 (m, 4H), 6.22 (dd, J = 8.2, 1.4Hz, 2H), 1.64 (s, 6H) ) Ppm
MS: [m / z] 388
5% weight decay temperature: 300.7 ° C
Elemental analysis: Composition formula C ₂₇ H ₂₁ N ₃
Theoretical value: C, 83.69%; H, 5.46%; N, 10.84%
Measured value: C, 83.83%; H, 5.62%; N, 10.91%

[Example 5] Synthesis of 2AcNN

1.16 g (2.83 mmol) of 4- (dioxaborolane) phenyl-9,9-dimethylacridine and 0.39 g (2.83 mmol) of 2-chloro-3-cyanopyridine in a nitrogen-substituted 50 mL four-necked flask. , 1,4-dioxane (35.4 mL) and K ₃ PO _{4 (} 1.81 g) were added, and 7.4 mL of water was added to dissolve the mixture, and nitrogen bubbling was performed for 1 hour. Then, _{0.13 g (0.14 mmol) of Pd 2} (dba) ₃ and 0.057 g (0.14 mmol) of SPhos were added, and the mixture was heated and stirred at 100 ° C. Sampling was performed after 1 hour, and it was confirmed by TLC that a new spot was generated. A peak derived from the target product was confirmed by Mass. After 14 hours, it was confirmed by TLC that the raw material was consumed, and the reaction was stopped. Then, 10 cm of silica gel was filled in a Φ4.2 cm column tube, and the target product was isolated by column chromatography using dichloromethane as the developing solvent (Rf value: 0.1). After concentration and drying under reduced pressure, 0.74 g of a white to pale yellow solid was obtained. Yield 67%.
^{1 1} H-NMR (400 MHz, DMSO-D6) δ9.08 (s, 1H), 8.88 (d, J = 5.4 Hz, 1H), 8.12-7.91 (m, 3H), 7. 68-7.43 (m, 4H), 7.11-6.84 (m, 4H), 6.22 (dd, J = 8.2, 1.4Hz, 2H), 1.64 (s, 6H) ) Ppm
MS: [m / z] 388
5% weight decay temperature: 303.9 ° C
Elemental analysis: Composition formula C ₂₇ H ₂₁ N ₃
Theoretical value: C, 83.69%; H, 5.46%; N, 10.84%
Measured value: C, 83.82%; H, 5.39%; N, 10.81%

[Example 6] Synthesis of 5AcNN

0.89 g (2.18 mmol) of 4- (dioxaborolane) phenyl-9,9-dimethylacridine and 0.40 g of 5-bromo-3-pyridinecarbonitrile in a nitrogen-substituted 50 mL four-necked flask (50 mL) ( 2.18 mmol), 27.3 mL of 1,4-dioxane and _{1.39 g of K 3} PO ₄ were added, and 5.7 mL of water was added to dissolve the mixture, and nitrogen bubbling was performed for 1 hour. Then, _{0.20 g (0.22 mmol) of Pd 2} (dba) ₃ and 0.09 g (0.22 mmol) of SPhos were added, and the mixture was heated and stirred at 100 ° C. Sampling was performed after 1 hour, and it was confirmed by TLC that a new spot was generated. A peak derived from the target product was confirmed by Mass. After 41 hours, it was confirmed by TLC that the raw material was consumed, and the reaction was stopped. Column purification was performed. Injection was prepared with dichloromethane in 20 mL. Then, 10 cm of silica gel was filled in a Φ4.2 cm column tube, and the target product was isolated by column chromatography using dichloromethane as the developing solvent (Rf value: 0.1). After concentration and drying under reduced pressure, 0.7 g of a white to pale yellow solid was obtained. Yield 83%.
^{1 1} H-NMR (400MHz, DMSO-D6) δ9.34 (d, J = 2.3Hz, 1H), 9.07 (d, J = 1.8Hz, 1H), 8.80 (t, J = 2) .0Hz, 1H), 8.16 (d, J = 8.2Hz, 2H), 7.59-7.44 (m, 4H), 7.03-6.82 (m, 4H), 6.21 (D, J = 8.2Hz, 2H), 1.60 (d, J = 27.2Hz, 6H) ppm
MS: [m / z] 388
5% weight decay temperature: 306.8 ° C
Elemental analysis: Composition formula C ₂₇ H ₂₁ N ₃
Theoretical value: C, 83.69%; H, 5.46%; N, 10.84%
Measured value: C, 83.78%; H, 5.39%; N, 10.82%

[Evaluation of optical characteristics]
The equipment and measurement conditions used for the optical characteristic evaluation are as follows.
(1) Ultraviolet / visible (UV-vis) spectrophotometer UV-3150 manufactured by Shimadzu Corporation
Measurement conditions; Scan speed Medium speed, Measurement range 200 to 800 nm Sampling pitch 0.5 nm, Slit width 0.5 nm
(2) Photoluminescence (PL) measuring device Fluoro MAX-2 manufactured by HORIBA, Ltd.
The PL spectrum and the time-resolved PL spectrum (transient PL spectrum) using a streak camera (C4334 manufactured by Hamamatsu Photonics Co., Ltd.) were measured at room temperature and low temperature.
(3) Photoelectron yield spectroscopy (PYS) device Ionization potential measuring device manufactured by Sumitomo Heavy Industries, Ltd. Ionization potential (Ip) was measured in vacuum using an ionization potential measuring device.
The electron affinity _{(E a)} was calculated by estimating the energy gap _{(E g)} than the absorption edge of the UV-vis absorption spectra.

[Example 7] Evaluation of optical characteristics The optical characteristics of the PXZINN synthesized in Example 1 were evaluated in the film state. A single film of PXZINN and a film obtained by doping CBP with 10 wt% of PXZINN were prepared using a fluorescent glass chamber and evaluated.
In addition, the optical characteristics of 2AcINN, 3AcINN, 2AcNN, and 5AcNN synthesized in Examples 2 and 4 to 6 in a toluene diluted solution ( ^10-5 M) and a thin film were evaluated. As the thin film, a single film of 2AcINN, 3AcINN, 2AcNN, and 5AcNN and a co-deposited film (10 wt% in DPEPO) of these and DPEPO were prepared using a fluorescent glass chamber and evaluated.

(1) UV-vis absorption spectrum, PL spectrum, and PLQY measurement Optical characteristic evaluation of PXZINN From the results of UV-vis absorption spectrum measurement, peaks derived from absorption of PXZINN and CBP were observed in the dope film.
In the PL spectrum measurement, the single film showed yellow emission with an _{emission wavelength of λ max = 560 nm.} In the CBP-doped film, since PXZINN was dispersed, no red shift due to aggregation was observed _{, and green emission at λ max} = 520 nm was exhibited.
Further, when each PLQY was measured, it was about 32% for the single film and about 79% for the doped film, and a high quantum yield was obtained for the doped film.
The results are shown in FIGS. 1 (a) and 1 (b).

Optical characterization of 2AcINN, 3AcINN, 2AcNN, 5AcNN As a result of measuring UV-vis absorption spectra, CT absorption (around 360 to 390 nm) derived from these dopants did not show strong absorption in any molecule and did not shift significantly. became. Since the PL spectrum, which will be described later, shows a large shortening of wavelength by 5 AcNN, it was thought that CT absorption was weaker than the others, but no significant difference was observed. Therefore, it can be said that 5AcNN is the molecule with the smallest Stokes shift among these derivatives.
As a result of measuring the PL spectrum, luminescence from pure blue to bluish green of 450 to 510 nm was observed. In the co-deposited film, 5AcNN showed pure blue emission, and the others showed equivalent light blue emission. As a result of verifying the change in the characteristics depending on the substitution position of the cyano group and the position of the N atom of pyridine, it was found that the one in which the cyano group was modified to the para position with respect to the N atom showed stronger CT properties. Among them, the one in which the cyano group having a stronger electron donating property is modified on the donor site side than the pyridine has stronger CT property and causes a long wavelength shift. Further, even if the N atom and the cyano group are modified to the meta position, the one closer to the donor site side as in the para position is considered to have stronger CT property and shift to a longer wavelength.

(2) PYS and transient PL measurement Optical characteristic evaluation of PXZINN A single film of PXZINN was used for PYS, and a film obtained by doping CBP with 10 wt% of PXZINN was used for transient PL measurement.
As a result of PYS measurement, _{it was found that the ionization potential (I p} ) was about 5.63 eV, which was much deeper than the calculated value of 5.16 eV in the state of the membrane. The electron affinity (E _a ) was calculated _{from the energy gap (E g} ) estimated from the UV-vis spectrum.
Transient PL measurements using a streak camera, to measure the light emission life of the actual measurement values and the variable temperature Delta] E _ST. As a result, ΔE _ST was estimated to be 0.06 eV. It was found that this value is larger than the calculated value of 0.004 eV, but has a relatively small ΔE _{ST of 0.1 eV or less.} However, the emission lifetime of the delayed component was 26.9 μs, which was rather long.

The measurement results and optical characteristics are shown in Table 1 and FIGS. 2 (a) and 2 (b).

Optical characterization of 2AcINN, 3AcINN, 2AcNN, 5AcNN 3AcINN, 2AcNN, 5AcNN to verify whether the isonicotinonitrile derivative is a light emitting material with TADF properties and how long its light emitting life is. The time-resolved transient PL attenuation spectrum was measured. The measurement was carried out under the temperature conditions of 300K and 5K by preparing a film of 10 wt% PyCN (4-cyanopyridine) derivative: DPEPO (30 nm).
As shown in FIGS. 20 to 22, in all the derivatives, the emission intensity of the delayed component was higher under the condition of 300K than at 5K, suggesting that the emission is derived from thermal activated delayed fluorescence due to temperature dependence. Was done. However, it was found that the emission lifetime under 300K conditions was 250 to 460 μs, which was a very long emission lifetime. Considering that the emission lifetime of 2AcINN was also very long, about 450 μs, it is considered that this pyridinecarbonitrile derivative tends to have a longer emission lifetime as compared with a normal TADF material. The cause may be agglutination between CN groups.
_{Subsequently, the low-temperature phosphorescence spectrum was measured, S 1} and T ₁ were estimated from the rise of the fluorescent component and the phosphorescence component, respectively, and the magnitude of _{DE ST} , which is an important parameter for the TADF material, was calculated. The temperature conditions were the same as for the time-resolved transient PL attenuation spectrum, but the phosphorescence component was not observed in the above-mentioned co-deposited film, so the _{measurement was performed with 5 wt% Ir (ppz) 3} : PyCN derivative (30 nm). ..
As shown in FIGS. 23 to 25, the energy level of _{T 1} is higher in all of 3AcINN, 2AcNN, and 5AcNN as compared with _{2AcINN (S 1} 2.97 eV / T ₁ 2.67 eV / DE _{ST 0.30 eV).} It can be seen that it has improved and the DE _{ST has also become smaller.} It is probable that the energy level of _{T 1} was low because 2AcINN had the most planar structure because the N atom was present on the donor group side and the CN group was not oriented toward the donor group side. However, these derivatives, those obtained by introducing a bulky CN group to the donor group side or both that were designed molecules that are not facing the donor group side, of T ₁ to have a twisted structure It is considered that the energy level has improved. As a result, more efficient TADF characteristics can be expected normally, but it is considered that the TADF characteristics are equivalent to 2AcINN because the emission lifetime of the delayed component is long according to the previous experiment. The results are shown in Table 2.

[Manufacturing and evaluation of organic EL elements]
The equipment used for the evaluation of the organic EL element is as follows.
EL (Electroluminescence) Spectrum Device; Hamamatsu Photonics Co., Ltd. PHOTONIC MULTI-CHANNEL ANALYZER PMA-1

[Example 8] Device evaluation of PXZINN (1) Verification of host material Using the PXZINN synthesized in Example 1, the device structures (Devices 1 and 2) shown below were produced.

(I) Device 1
[ITO / KLHIP: PPBI (20 nm) / TAPC (30 nm) / 10 wt% PXZINN: CBP (10 nm) / B3PyPB (50 nm) / LiF / Al]
(Ii) Device 2
[ITO / KLHIP: PPBI (20 nm) / TAPC (30 nm) / 10 wt% PXZINN: TCTA (10 nm) / B3PyPB (50 nm) / LiF / Al]

That is, in Device 1, the host material is CBP, and in Device 2, the host material is CTTA, which can be expected to be driven at a lower voltage than CBP. The energy diagram of these element structures and the energy value in the initial state are shown in FIG.
The characteristics of Devices 1 and 2 are shown in FIGS. 4 and 5. Table 3 also shows the voltage (V), power efficiency (PE), current efficiency (CE), and external of Devices 1 and 2 when the luminance is 1 cd / m ² , 100 cd / m ² and 1000 cd / m ^2. Quantum efficiency (EQE) is shown.

As a result of using CBP and TCTA as host materials, CBP showed higher efficiency with an external quantum efficiency of about 22% at ^{100 cd / m 2.} However, looking at the current density-voltage characteristics, the voltage is lowered in the high current density region (FIG. 4A). It is probable that this was caused by the efficient transport of holes because _{TCTA has a lower energy level of I p.}

Further, when the EL spectra were compared, in Device 2 using TCTA, light emission not derived from the dopant was observed weakly in the vicinity of 400 nm (FIG. 5 (a)). For this verification, a comparison was made between the emission spectra of the peripheral materials TCTA and B3PyPB and the case where TCTA and B3PyPB form an exciplex (B3PyPB: TCTA) (FIG. 5 (b)). The emission spectra of TCTA and B3PyPB: TCTA almost overlap, but the emission of B3PyPB: TCTA-derived emission has a peak top overlap with the EL spectrum of Device 2 slightly closer. Therefore, it is considered that excitons were recombined at the interface between TCTA and B3PyPB, and emission derived from exciplex was observed. This also leads to factors that reduce efficiency. Therefore, although it is better to use CBP in terms of efficiency, it is considered desirable to use both of them to form a double light emitting layer in order to optimize it because it is driven at a lower voltage by using TCTA.

(2) Verification of electron transport material The device structures (Devices 1 and 3) shown below were prepared, and the electron transport material was examined.
(I) Device 1
[ITO / KLHIP: PPBI (20 nm) / TAPC (30 nm) / 10 wt% PXZINN: CBP (10 nm) / B3PyPB (50 nm) / LiF / Al]
(Ii) Device 3
[ITO / KLHIP: PPBI (20 nm) / TAPC (30 nm) / 10 wt% PXZINN: CBP (10 nm) / B4PyPPM (50 nm) / LiF / Al]

That is, by changing the electron transport material from B3PyPB to B4PyPPM having a deeper LUMO level, the voltage was lowered and the power efficiency was improved. As the host material, CBP showing high efficiency was used in "(1) Verification of host material". The energy diagram of these element structures and the energy value in the initial state are shown in FIG.
The characteristics of Devices 1 and 3 are shown in FIGS. 7 and 8. Table 4 also shows the voltage (V), power efficiency (PE), current efficiency (CE), and external of Devices 1 and 3 when the luminance is 1 cd / m ² , 100 cd / m ² and 1000 cd / m ^2. Quantum efficiency (EQE) is shown.

In Device 3 using B4PyPPM, the external quantum efficiency decreased to about 20% at the maximum. It is considered that this is because the carrier balance is lost as compared with the case where B3PyPB is used. However, since the emission start voltage at 1 cd / m ² was 0.5 V lower than 2.8 V to 2.3 V compared to Device 1, the maximum power efficiency was 89 lm / W, which is the highest among devices using this dopant. It showed a high value (FIG. 7 (f)). Therefore, for further device optimization, B4PyPPM is used as the electron transport material, a double light emitting layer using both TCTA and CBP is used, and excitons are generated at the interface of these host materials to achieve carrier balance. It is possible to make adjustments. Furthermore, by sandwiching the TCTA, it is considered that hole transportability can be improved and low voltage and high power efficiency can be expected.

(3) Verification of double light emitting layer An element structure (Device 4) having a double light emitting layer using both TCTA and CBP as a host was prepared, and further improvement in efficiency was examined in comparison with Device 3. That is, it was expected that by using TCTA, the holes would be transported more efficiently and the voltage would be lowered, and exciton generation at the interface between TCTA and CBP would be induced to improve the carrier balance.

(I) Device 3
[ITO / KLHIP: PPBI (20 nm) / TAPC (30 nm) / 10 wt% PXZINN: CBP (10 nm) / B4PyPPM (50 nm) / LiF / Al]
(Ii) Device 4
[ITO / KLHIP: PPBI (20 nm) / TAPC (30 nm) / 10 wt% PXZINN: TCTA (5 nm) / 10 wt% PXZINN: CBP (5 nm) / B4PyPPM (50 nm) / LiF / Al]

The energy diagram of these element structures and the energy value in the initial state are shown in FIG.
The characteristics of Devices 3 and 4 are shown in FIGS. 10 and 11. Table 5 also shows the voltage (V), power efficiency (PE), current efficiency (CE), and external of Devices 3 and 4 when the luminance is 1 cd / m ² , 100 cd / m ² and 1000 cd / m ^2. Quantum efficiency (EQE) is shown.

In Device 4, the voltage was lower than that in Device 3 in which only CBP was used as the host material, and the voltage dropped by 0.3 V at ^{1000 cd / m 2.} On the other hand, the external quantum efficiency (EQE) and power efficiency (PE) have been sluggish. It is probable that the efficiency was reduced because the PLQY in the part where TCTA was used was lower than that of CBP. However, there is room for measuring and verifying PLQY in the co-deposited film with TCTA.
From the results of Table 4 and FIGS. 10 and 11, it is considered that the host should be only CBP because the efficiency on the TCTA side is lowered in the double light emitting layer of TCTA and CBP.

(4) Verification of TCTA insertion element and doping concentration In "(3) Verification of double light emitting layer", the efficiency of Device 4 was lowered probably because the PLQY of the TCTA host was low. However, it is considered that the hole transportability from TAPC to CBP was improved because the drive voltage was lowered. Therefore, instead of using TCTA as a host material for the light emitting layer, we investigated maintaining efficiency and reducing the voltage by inserting it between the hole transport layer and the light emitting layer.

Further, in Device 5 (doping concentration: 10 wt%), an element in which the doping concentration was changed to 20 wt% and 30 wt% was produced, and the doping concentration was optimized.
(I) Device 5
[ITO / KLHIP: PPBI (20 nm) / TAPC (25 nm) / TCTA (5 nm) / 10 wt% PXZINN: CBP (10 nm) / B4PyPPM (50 nm) / LiF / Al]
(Ii) Device 6
[ITO / KLHIP: PPBI (20 nm) / TAPC (25 nm) / TCTA (5 nm) / 20 wt% PXZINN: CBP (10 nm) / B4PyPPM (50 nm) / LiF / Al]
(Iii) Device 7
[ITO / KLHIP: PPBI (20 nm) / TAPC (25 nm) / TCTA (5 nm) / 30 wt% PXZINN: CBP (10 nm) / B4PyPPM (50 nm) / LiF / Al]

The energy diagram of these element structures and the energy value in the initial state are shown in FIG.
The characteristics of Devices 5 to 7 are shown in FIGS. 13 and 14. Table 6 also shows the voltage (V), power efficiency (PE), current efficiency (CE), and external of Devices 5 to 7 when the luminance is 1 cd / m ² , 100 cd / m ² and 1000 cd / m ^2. Quantum efficiency (EQE) is shown.

Instead of using a double light emitting layer, only CBP is used as the host material, and TCTA is inserted between the hole transport layer (TAPC) and the light emitting layer (PXZINN: CBP) to maintain high efficiency while maintaining high efficiency. It was possible to reduce the voltage. In Device 5 having a doping concentration of 10 wt%, the drive voltage was 2.3 V, the maximum external quantum efficiency was 21.0%, and the maximum power efficiency was 89.2 lm / W (Table 5 and FIG. 13 (d)). (E)). When the doping concentration was set to 20 wt%, the drive voltage was 2.2 V, the maximum external quantum efficiency was 22.2%, and the maximum power efficiency was 99.0 lm / W. Table 5 and FIGS. 13 (d) and 13 (e)). When the doping concentration was further increased to 30 wt%, a decrease in the driving voltage was observed due to the good charge transportability of the dopant, which is a bipolar molecule. However, the power efficiency did not increase because the efficiency decreased (Table 5 and FIG. 13 (d)). It is considered that this is because the concentration of the dopant was quenched at the doping concentration of 30 wt%.

すなわち、発光層のホスト材料にＤＰＥＰＯを使用し、正孔輸送層にＴＡＰＣ、励起子ブロック層にｍＣＰ、電子輸送層にＢ３ＰｙＰＢを使用した。この素子構造のエネルギーダイアグラム及び初期状態のエネルギー値を図１５に示す。
Ｄｅｖｉｃｅ ８の特性を図１６及び１７に示す。また、表７に、輝度が１ｃｄ／ｍ²、１００ｃｄ／ｍ²及び１０００ｃｄ／ｍ²である場合のＤｅｖｉｃｅ ８の電圧（Ｖ）、電力効率（ＰＥ）、電流効率（ＣＥ）、及び外部量子効率（ＥＱＥ）を示す。 [Example 9] Device evaluation of 2AcINN Using the 2AcINN synthesized in Example 2, the device structure (Device 8) shown below was prepared and device evaluation was performed.
Device 8
[ITO / KLHIP: PPBI (20 nm) / TAPC (25 nm) / mCP (5 nm) / 10 wt% 2AcINN: DPEPO (10 nm) / B3PyPB (50 nm) / LiF / Al]

That is, DPEPO was used as the host material of the light emitting layer, TAPC was used as the hole transport layer, mCP was used as the exciton block layer, and B3PyPB was used as the electron transport layer. The energy diagram of this device structure and the energy value in the initial state are shown in FIG.
The characteristics of Device 8 are shown in FIGS. 16 and 17. Table 7 also shows the voltage (V), power efficiency (PE), current efficiency (CE), and external quantum efficiency of Device 8 when the luminance is 1 cd / m ² , 100 cd / m ² and 1000 cd / m ^2. (EQE) is shown.

λ_EL＝４８６ｎｍとドーパント由来の発光が確認された（図１７）。０．１ｃｄ／ｍ²時に最大外部量子効率（ＥＱＥ）１５．２％を示した（図１６（ｅ））。しかし、１００ｃｄ／ｍ²時では６．９％、１０００ｃｄ／ｍ²時では２．９％と、非常にロールオフが大きい結果となった（図１６（ｅ））。キャリアバランスの調整によってロールオフを抑制できる可能性がある。

Emission derived from the dopant was confirmed at λ _EL = 486 nm (Fig. 17). The maximum external quantum efficiency (EQE) of 15.2% was shown at 0.1 cd / m ^{2 (FIG. 16 (e)).} However, 6.9% in at 100 cd / m ^2, and 2.9% at times 1000 cd / m ^2, was a very results rolloff is large (FIG. 16 (e)). Roll-off may be suppressed by adjusting the carrier balance.

[Example 10] Device evaluation of 2AcINN, 3AcINN, 2AcNN, 5AcNN Using 2AcINN, 3AcINN, 2AcNN, and 5AcNN synthesized in Examples 2, 4 to 6, four types of devices having the element structure shown below were produced.

ITO / KLHIP: PPBI (20nm) / TAPC (25nm) / mCP (5nm) / 10wt% dopant: DPEPO (20nm) / B3PyPB (50nm) / LiF (0.5nm) / Al (100nm)
The dopant represents 2AcINN, 3AcINN, 2AcNN, or 5AcNN.

The characteristics of the device are shown in FIGS. 27 and 28. In addition, Table 8 shows the voltage (V), power efficiency (PE), and current efficiency (CE) of the above-mentioned devices when the ^{brightness is 1 cd / m 2} , 100 cd / m ² and 1000 cd / m ^{2, and the maximum brightness.} , And external quantum efficiency (EQE).

As a result of device evaluation, only the light emission derived from the dopant was obtained from the EL spectrum. Therefore, it is considered that the energy transfer from the host material is performed efficiently. 5AcNN emitted at the shortest wavelength _{showed pure blue emission of λ EL} = 454 nm and CIE (0.16, 0.19), but EQE was 6.7% at maximum, which did not exceed the theoretical limit of fluorescence. .. It is considered that this is because the PLQY of the dopant is about 35% and the emission characteristics are weakened in the first place. However, the EQE estimated from PLQY is 2.6% in the case of fluorescence, so it is considered that triplet excitons contribute to emission by TADF or other processes. This also applies to other dopants. Of the four types of devices, 3AcINN, which emitted blue-green light, showed the highest efficiency. Focusing on the overall efficiency graph here, they all show a similarly violent roll-off. It is considered that 2AcNN and 3AcINN have a cyano group introduced on the phenyl group side, thereby inducing a twist due to steric hindrance, thereby breaking the conjugation and increasing the energy level of the triplet state. However, since the roll-off shows a similar downward trend, _{the magnitude of DE ST} cannot be discussed, but it is considered that the emission lifetime is about the same. Although a correct argument cannot be made based on the results of streak measurement, it may be difficult to shorten the emission lifetime of this derivative with DPEPO, which is the host material.

1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Electron transport layer 7 Electron injection layer 8 Cathode

Claims (2)

An isonicotinonitrile derivative represented by the following structural formula.

An organic EL device using the isonicotinonitrile derivative according to claim 1.

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