BLUE THERMALLY ACTIVATED DELAYED FLUORESCENCE MATERIAL, SYNTHESIS METHOD THEREOF, AND USE THEREOF

Abstract

The present disclosure relates to the field of organic light-emitting materials, and more particularly, to a blue thermally activated delayed fluorescence material, a synthesis method thereof, and use thereof. The blue thermally activated delayed fluorescence material has a following structural formula:

##STR00001##

the present disclosure provides a novel blue thermally activated delayed fluorescence material which has a lower singlet triplet energy level difference, a high RISC rate constant (kRISC), and a high photoluminescence quantum yield (PLQY) by finely adjusting a structure of electron acceptor units, making them have different abilities to accept electrons, thereby realizing fine adjustment of spectrum in the deep blue range.

Claims

1. A blue thermally activated delayed fluorescence material, having a following structural formula: ##STR00009## wherein, R is selected from one of following structural formulas: ##STR00010## ##STR00011##

2. A synthesis method of a blue thermally activated delayed fluorescence material, comprising following steps: under an inert gas environment, performing a Buchwald-Hartwig coupling reaction between a raw material 1 and a raw material 2 under an effect of a palladium catalyst to obtain the blue thermally activated delayed fluorescence material; wherein, the raw material 1 has a following structural formula: ##STR00012## the raw material 2 is selected from one of 9,9-diphenyl-9,10-dihydroacridine, phenoxazine, 3,6-dimethyl-9H-carbazole, 10H-spiro[acridine-9,9′-fluorene], 9,9-dimethyl-9,10-dihydroacridine, 9,10-dihydro-9,9-diphenylsila acridine, 3,7-dimethoxy-10H-phenoxazine, 10H-silaspiro[acridine-9,9′-fluorene], 7H-benzo[C]phenoxazine, 9-phenyl-7H-benzo[C]phenoxazine, 3, 6-di-tert-butyl-9H-carbazole, 1,3,6,8-tetramethyl-9H-carbazole, or 2-(tert-butyl)-5H-benzo[b]carbazole; and a molar ratio of the raw material 1 to the raw material 2 ranges from 1:2 to 1:6.

3. The synthesis method of the blue thermally activated delayed fluorescence material according to claim 2, wherein a reaction temperature of the Buchwald-Hartwig coupling reaction ranges from 80° C. to 160° C., and a reaction time thereof ranges from 12 hours to 48 hours.

4. The synthesis method of the blue thermally activated delayed fluorescence material according to claim 2, wherein a reaction solvent of the Buchwald-Hartwig coupling reaction is dehydrated and deoxygenated toluene; the palladium catalyst is selected from one of palladium acetate, palladium nitrate, palladium chloride, or palladium sulfate.

5. The synthesis method of the blue thermally activated delayed fluorescence material according to claim 2, wherein, after finishing the Buchwald-Hartwig coupling reaction, a reaction product is subjected to cooling, extraction, column chromatography separation, and purification in sequence to obtain the blue thermally activated delayed fluorescence material.

6. A use of a blue thermally activated delayed fluorescence material in organic electroluminescence; wherein the blue thermally activated delayed fluorescence material has the following structural formula: ##STR00013## wherein, R is selected from one of the following structural formulas: ##STR00014## ##STR00015##

7. The use according to claim 6, wherein the blue thermally activated delayed fluorescence material is used in an electrothermally activated delayed fluorescent device.

8. The use according to claim 7, wherein the electrothermally activated delayed fluorescent device comprises a substrate layer, a light-emitting layer, and a cathode layer in a stack, and a light-emitting material of the light-emitting layer is the blue thermally activated delayed fluorescence material.

9. The use according to claim 8, wherein the electrothermally activated delayed fluorescent device further comprises a hole injection layer disposed on the substrate layer, a transport layer disposed on the hole injection layer, and an electron transport layer disposed between the light-emitting layer and the cathode layer.

10. (canceled)

Description

DESCRIPTION OF DRAWINGS

[0021] The accompanying figures to be used in the description of embodiments of the present disclosure or prior art will be described in brief to more clearly illustrate the technical solutions of the embodiments or the prior art. The accompanying figures described below are only part of the embodiments of the present disclosure, from which those skilled in the art can derive further figures without making any inventive efforts.

[0022] FIG. 1 is photoluminescence spectrums of compound 1 to compound 3 in a toluene solution at room temperature obtained according to embodiment 1 to embodiment 3 of the present disclosure.

[0023] FIG. 2 is a schematic structural diagram of an electrothermally activated delayed fluorescent device according to an application embodiment of the present disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0024] The present disclosure will be further described below in conjunction with embodiments 1 to 3 and application embodiments 1 to 3.

Embodiment 1: Synthesis of a Blue Thermally Activated Delayed Fluorescence Material

[0025] The reaction formula is as follows:

##STR00006##

[0026] Weigh 3.19 g of raw material 1 (5 mmol), 4.00 g of 9,9-diphenyl-9, 10-dihydroacridine (12 mmol), 0.18 g of palladium acetate (0.8 mmol) and 0.68 g of tri-tert-butylphosphine tetrafluoroborate (2.4 mmol) respectively, and pour into a 250 mL two-necked flask. Transfer the two-necked flask which contains the reaction raw material to a glove box, then add 2.34 g of NaOt-Bu (24 mmol) to the two-necked flask in the glove box, then inject 100 mL of toluene which is dehydrated and deoxygenated under an argon atmosphere, and then react at 120° C. for 24 hours. Cool to room temperature, the reaction solution is poured into 200 mL of ice water, and is extracted three times with dichloromethane. Combine the organic phase to spin to a silica gel column chromatography (volume of dichloromethane:volume of n-hexane, 1:3) to separate and purify to obtain 2.3 g of light blue powders. The yield is 51%.

[0027] The nuclear magnetic resonance spectrum of the obtained product (compound 1) is: 1H NMR (300 MHz, CD2Cl2, δ): 8.18 (s, 1H), 7.91 (s, 1H), 7.75-7.63 (m, 4H), 7.51-7.40 (m, 14H), 7.30-7.18 (m, 17H), 6.95-6.89 (m, 2H), 1.69 (s, 12H).

Embodiment 2: Synthesis of a Blue Thermally Activated Delayed Fluorescence Material

[0028] The reaction formula is as follows:

##STR00007##

[0029] Weigh 3.19 g of raw material 1 (5 mmol), 2.20 g of phenoxazine (12 mmol), 0.18 g of palladium acetate (0.8 mmol) and 0.68 g of tri-tert-butylphosphine tetrafluoroborate (2.4 mmol) respectively, and pour into a 250 mL two-necked flask. Transfer the two-necked flask which contains the reaction raw material to a glove box, then add 2.34 g of NaOt-Bu (24 mmol) to the two-necked flask in the glove box, then inject 100 mL of toluene which is dehydrated and deoxygenated under an argon atmosphere, and then react at 120° C. for 24 hours. Cool to room temperature, the reaction solution is poured into 200 mL of ice water, and is extracted three times with dichloromethane. Combine the organic phase to spin to a silica gel column chromatography (volume of dichloromethane:volume of n-hexane, 1:3) to separate and purify to obtain 2.1 g of light blue powders. The yield is 49%.

[0030] The nuclear magnetic resonance spectrum of the obtained product (compound 2) is: 1H NMR (300 MHz, CD2Cl2, δ): 8.18 (s, 1H), 7.91 (s, 1H), 7.75-7.63 (m, 4H), 7.51-7.40 (m, 14H), 7.30-7.18 (m, 13H), 6.93-6.89 (m, 6H).

Embodiment 3: Synthesis of a Blue Thermally Activated Delayed Fluorescence Material

[0031] The reaction formula is as follows:

##STR00008##

[0032] Weigh 3.19 g of raw material 1 (5 mmol), 2.34 g of 3,6-Dimethyl-9H-carbazole (12 mmol), 0.18 g of palladium acetate (0.8 mmol) and 0.68 g of tri-tert-butylphosphine tetrafluoroborate (2.4 mmol) respectively, and pour into a 250 mL two-necked flask. Transfer the two-necked flask which contains the reaction raw material to a glove box, then add 2.34 g of NaOt-Bu (24 mmol) to the two-necked flask in the glove box, then inject 100 mL of toluene which is dehydrated and deoxygenated under an argon atmosphere, and then react at 120° C. for 24 hours. Cool to room temperature, the reaction solution is poured into 200 mL of ice water, and is extracted three times with dichloromethane. Combine the organic phase to spin to a silica gel column chromatography (volume of dichloromethane:volume of n-hexane, 1:3) to separate and purify to obtain 2.6 g of light blue powders. The yield is 60%.

[0033] The nuclear magnetic resonance spectrum of the obtained product (compound 3) is: 1H NMR (300 MHz, CD2Cl2, δ): 8.80 (s, 4H), 8.18 (s, 1H), 7.89 (d, J=6.3 Hz, 1H), 7.75-7.63 (m, 4H), 7.51-7.46 (m, 4H), 7.36-7.21 (m, 10H), 7.17-7.10 (m, 4H), 6.98 (d, J=6.6 Hz, 4H), 2.46 (s, 12H). (Using a nuclear magnetic resonance frequency of 300 MHz, the solvent is deuterated dichloromethane, and cooling by liquid nitrogen.)

[0034] Electrochemical energy levels and other parameters of compounds 1 to 3 obtained according to embodiments 1 to 3 are tested, the results are as shown in the following table 1:

TABLE-US-00001 TABLE 1 the lowest singlet state (S1), the lowest triplet state (T1), and electrochemical energy levels of compound 1 to compound 3. PL Peak S.sub.1 T.sub.1 E.sub.ST HOMO LUMO (nm) (eV) (eV) (eV) (eV) (eV) Compound 1 458 2.71 2.61 0.10 −5.46 −2.43 Compound 2 473 2.62 2.53 0.09 −5.56 −2.43 Compound 3 451 2.75 2.70 0.05 −5.41 −2.43

[0035] Results of photoluminescence spectrums of compound 1 to compound 3 in a toluene solution at room temperature obtained according to embodiment 1 to embodiment 3 are as shown in FIG. 1. In FIG. 1, waveforms from left to right are respectively photoluminescence spectrums of compound 2, compound 1, and compound 3. It can be known from FIG. 1: emission spectrums of compounds 1 to 3 all fall within the blue light range, particularly compound 1 and compound 3, which are deep blue light having an emission peak of less than 460 nm.

Application Embodiment 1: An Electrothermally Activated Delayed Fluorescent Device 1

[0036] An electrothermally activated delayed fluorescent device can be prepared according to methods known in the art, such as a method disclosed in the reference of Adv. Mater. 2003, 15, 277. The specific method is: vapor depositing MoO3, TCTA, DPEPO+a blue thermally activated delayed fluorescence material, TmPyPB, 1 nm of LiF, and 100 nm of Al on a cleaned conductive glass substrate (ITO) under a high vacuum condition in sequence.

[0037] A structure of the electrothermally activated delayed fluorescent device is as shown in FIG. 2, which comprises: a substrate layer 1, a hole injection layer 2 disposed on the substrate layer 1, a transport layer 3 disposed on the hole injection layer 2, a light-emitting layer 4 disposed on the transport layer 3, an electron transport layer 5 disposed on the light-emitting layer 4, and a cathode layer 6 disposed on the electron transport layer 5. The substrate layer 1 is a glass or a conductive glass (ITO), the hole injection layer 2 is made of MoO3, the transport layer 3 is made of Tris(4-carbazoyl-9-ylphenyl)amine (TCTA), the light-emitting layer 4 is made of the compound 1 obtained according to embodiment 1, the transport layer 5 is made of 1,3,5-tris(3-(3-pyridyl)phenyl)benzene (TmPyPB), and the cathode layer 6 is made of lithium fluoride/aluminum. The structure of formed device 1 is: ITO/MoO3 (2 nm)/TCTA (35 nm)/DPEPO:compound 1 (3%, 20 nm)/TmPyPB (40 nm)/LiF (1 nm)/Al (100 nm).

Application Embodiment 2: An Electrothermally Activated Delayed Fluorescent Device 2

[0038] Application embodiment 2 uses the same method as application embodiment 1. The difference is that the light-emitting layer 4 is made of the compound 2 obtained according to embodiment 2. A structure of formed device 2 is: ITO/MoO3 (2 nm)/TCTA (35 nm)/DPEPO: compound 2 (3%, 20 nm)/TmPyPB (40 nm)/LiF (1 nm)/Al (100 nm).

Application Embodiment 3: An Electrothermally Activated Delayed Fluorescent Device 3

[0039] Application embodiment 3 uses the same method as application embodiment 1. The difference is that the light-emitting layer 4 is made of the compound 3 obtained according to embodiment 3. A structure of formed device 3 is: ITO/MoO3 (2 nm)/TCTA (35 nm)/DPEPO: compound 3 (3%, 20 nm)/TmPyPB (40 nm)/LiF (1 nm)/Al (100 nm).

[0040] Performances of the devices 1 to 3 obtained according to application embodiments 1 to 3 are tested. Current-brightness-voltage characteristics of the device are measured by Keithley source measurement system with a calibrated silicon photodiode (Keithley 2400 Sourcemeter, Keithley 2000 Currentmeter). Electroluminescence spectrums are measured by SPEX CCD3000 spectrometer (from JY company, French) at room temperature under atmospheric environment. The test results are as shown in table 2.

TABLE-US-00002 TABLE 2 tested performances of devices. Maximum current Maximum external Device efficiency (cd/A) CIEy quantum efficiency (%) Device 1 33.1 0.15 21.3% Device 2 32.3 0.21 21.7% Device 3 29.3 0.13 18.4% Industrial applicability: The subject matter of the present disclosure can be manufactured and used in the industry, thereby having industrial applicability.