Thermally activated delayed fluorescence compound and organic electroluminescent device

Abstract

The present invention relates to the field of electronic materials technology, and more specifically to a thermally activated delayed fluorescent compound and an organic electroluminescent device. The present invention provides a thermally activated delayed fluorescent compound having the structure shown in Formula 1: #imgabs0#, which enables an organic electroluminescent device containing this material to achieve both high external quantum efficiency and low efficiency roll-off.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic materials, and in particular to a thermally activated delayed fluorescence compound and an organic electroluminescent device. Background Art

[0002] Organic light-emitting diodes (OLEDs) offer advantages such as low cost, low power consumption, and flexibility, making them widely used in display and lighting applications. In 2012, Adachi's group reported high-efficiency OLEDs based on pure organic thermally activated delayed fluorescence (TADF) materials. These materials boast near-100% internal quantum efficiency, simple construction, and low cost. Currently, devices based on TADF materials are comparable to those based on phosphorescent materials.

[0003] Current technologies use TADF materials to effectively convert triplet excitons into singlet excitons by effectively separating frontier molecular orbitals, reducing the singlet-triplet energy level difference and achieving rapid reverse intersystem crossing. However, this separation of frontier orbitals reduces the radiative transition rate, thus affecting the photoluminescence efficiency of the molecules, making it difficult to simultaneously achieve high external quantum efficiency and low efficiency roll-off. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that OLEDs prepared using TADF materials are difficult to achieve both high external quantum efficiency and low efficiency roll-off, thereby providing a thermally activated delayed fluorescence compound and an organic electroluminescent device.

[0005] The scheme adopted by the present invention is as follows:

[0006] The present invention provides a thermally activated delayed fluorescence compound having the following structure:

[0007]

[0008] Wherein, A is selected from substituted or unsubstituted C5-C60 aryl, substituted or unsubstituted C3-C60 heteroaryl;

[0009] R is selected from -O-, -S-, -SO2-, -Si(R1R2)-, -N(R1)-, -Se-; R1-R2 are each independently selected from substituted or unsubstituted C5-C60 aryl, substituted or unsubstituted C3-C60 heteroaryl;

[0010] R T1 -RT16 are the same or different and are independently selected from hydrogen, deuterium, sulfone, cyano, alkyl, alkoxy, substituted or unsubstituted C6-C60 aryl, substituted or unsubstituted C3-C60 heteroaryl, or R T1 -RT 16 Adjacent groups are linked to each other to form a C5-C60 aryl group or a C3-C60 heteroaryl group.

[0011] Preferably, the substituents of the substituted C5-C60 aryl, substituted C3-C60 heteroaryl, substituted C6-C60 aryl, and substituted C3-C60 heteroaryl are selected from deuterium, halogen, cyano, C1-C6 alkyl, C3-C30 cycloalkyl, C6-C30 aryl, and C3-C30 heteroaryl.

[0012] Preferably, A is selected from group Q, and group Q is selected from one of the following structures:

[0013]

[0014]

[0015] Preferably, R1 and R2 are each independently selected from one of the following structures:

[0016]

[0017]

[0018] In the present invention, --- represents a connecting bond.

[0019] Preferably, R is selected from -O-, -N(R1)-; R1 is selected from one of the following groups:

[0020]

[0021] Preferably, R T1 -RT 16 The same or different, each independently selected from hydrogen, methyl, phenyl, pyridyl, carbazolyl, triazinyl, tolyl or having Structural groups.

[0022] The substituted methyl, the substituted phenyl, the substituted pyridyl, the substituted carbazolyl, the substituted triazine, the substituted tolyl, and the substituted The substituent of the group of the structure is selected from one or a combination of two of deuterium, cyano, C1-C6 alkyl, C3-C30 cycloalkyl, C6-C30 aryl, and C3-C30 heteroaryl;

[0023] Preferably, the substituted methyl, the substituted phenyl, the substituted pyridyl, the substituted carbazolyl, the substituted triazine, the substituted tolyl, and the substituted The substituents of the structural group include phenyl, methyl, and cyano.

[0024] Preferably, R T1 -R T16 Adjacent groups are linked to each other to form one of the following structures:

[0025]

[0026] In the present invention, · is a connection point.

[0027] Preferably, the thermally activated delayed fluorescence compound has any of the following structures:

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034] The present invention also provides an organic electroluminescent device, comprising a first electrode, a second electrode, and a light-emitting layer located between the first electrode and the second electrode, wherein the light-emitting layer comprises any one of the thermally activated delayed fluorescent compounds described above.

[0035] Preferably, the light-emitting layer comprises the thermally activated delayed fluorescent compound and the organic functional material, and in terms of mass percentage, the thermally activated delayed fluorescent compound accounts for 0.01%-100%, and the organic functional material accounts for 0-99.9%.

[0036] The present invention provides application of the organic electroluminescent device described above in electronic equipment.

[0037] It should be noted that the application of the thermally activated delayed fluorescence compound of the present invention is not limited to the device configuration described above, and the film thickness or constituent materials of each layer can be appropriately changed according to the basic physical properties of the specific compound structure of the present invention.

[0038] The method for preparing the organic device of the present invention is a conventional method in the art. Optionally, the preparation of the organic electroluminescent device includes the following steps: using a glass substrate with ITO vapor-deposited thereon as a transparent support substrate, and sequentially vapor-depositing the organic layers and metal electrodes on the ITO film on the transparent support substrate.

[0039] Functional materials include hole injection materials, hole transport materials, hole blocking materials, electron injection materials, electron transport materials, electron blocking materials, exciton blocking materials, fluorescent materials, phosphorescent materials, host materials and organic dyes.

[0040] The present invention also provides a method for preparing the above-mentioned thermally activated delayed fluorescence compound:

[0041] The synthesis route of the thermally activated delayed fluorescence compound of the present invention is as follows:

[0042]

[0043]

[0044] Wherein, R1 and R2 are defined the same as above.

[0045] The specific steps of synthesis include:

[0046] To one equivalent of a substituted or unsubstituted m-dibromobenzene derivative M1-1 and an appropriate amount of tetrahydrofuran solvent, 1.2 equivalents of lithium diisopropylamide (LDA) were added dropwise at -78°C and incubated for 30 minutes. Then, 1.1 equivalents of a substituted or unsubstituted benzaldehyde compound M1-2 was added. The mixture was incubated at -78°C for 30 minutes, then brought to room temperature (25°C) and stirred for 12 hours. The solvent in the flask was then separated and removed by rotary evaporation. An appropriate amount of dichloromethane solvent and 2.5 equivalents of pyridinium chlorochromate (PCC) were added, and the reaction was continued at room temperature (25°C) for 12 hours. The organic solvent was then evaporated, and the remaining mixture was separated by column chromatography to obtain M1-3. M1-3 was then reacted with an equal amount of a substituted or unsubstituted aniline (M1-4) via Buchwald-Hartwig coupling to prepare intermediate M1-5. M1-5 is reacted with an equimolar amount of P1 via Ullmann coupling via reaction route i to prepare intermediate M1-6, or is reacted with 1.2 equivalents of magnesium to prepare a Grignard reagent via reaction route ii and then reacted with P2 to prepare intermediate M1-6. One equivalent of M1-6 is placed in a two-necked flask, heated to 120° C., and then 0.2 equivalents of p-toluenesulfonic acid monohydrate are added. The temperature is raised to 160° C. and kept warm for 15 minutes, then cooled to 40° C., dichloromethane is added, and the organic phase is evaporated and separated by column chromatography to obtain intermediate M1-7. An equimolar amount of M1-7 is coupled with A-Br via Buchwald-Hartwig coupling, and after the reaction, the reaction is filtered through diatomaceous earth and purified by column chromatography to obtain the compound shown in Formula 1.

[0047] Beneficial effects of the present invention:

[0048] The present invention provides a thermally activated delayed fluorescent compound having a structure of formula 1. A luminescent molecule is prepared by constructing a tetrahedral donor unit and combining it with an acceptor unit at a specific position. Due to the steric effect, the tetrahedral donor has both planar and bent structures. The planar structure combines with the acceptor to produce a larger torsion angle between the donor unit and the acceptor unit, reducing the overlap of the molecular frontier orbitals, thereby reducing the lowest excited singlet-triplet energy level difference and increasing the reverse intersystem crossing rate of the molecule; the bent configuration can increase the delocalization of the highest occupied molecular orbital, and can increase the molecular radiation transition rate while maintaining the overlap of the smaller molecular frontier orbitals, thereby improving the photoluminescence efficiency of the molecule. The simultaneously improved radiation transition rate and reverse intersystem crossing rate can improve the exciton utilization rate of the TADF material, thereby enabling the organic electroluminescent device containing the material to achieve high external quantum efficiency and low efficiency roll-off at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0050] Figure 1 Structural diagram of the organic electroluminescent device in device embodiments 1-5 of the present invention;

[0051] Figure 2 This is the H NMR spectrum of the thermally activated delayed fluorescence compound 36 prepared in Example 1 of the present invention;

[0052] Figure 3 This is the NMR carbon spectrum of the thermally activated delayed fluorescence compound 36 prepared in Example 1 of the present invention.

[0053] Reference numerals:

[0054] 10-conductive glass substrate, 1-hole injection layer, 2-first hole transport layer, 3-second hole transport layer, 4-electron blocking layer, 5-light-emitting layer, 6-hole blocking layer, 7-electron transport layer, 8-electron injection layer, 9-cathode. DETAILED DESCRIPTION

[0055] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0056] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0057] In some specific embodiments, the preparation of the following five compounds is taken as an example:

[0058]

[0059] Example 1

[0060] This embodiment provides a method for preparing a thermally activated delayed fluorescent compound 36, comprising the following steps:

[0061]

[0062] 1 mmol of QAC, 1 mmol of iodobenzene, and xylene (5 ml) were placed in a 50 ml reaction flask. After purging with argon for 10 min, trisdibenzylideneacetone dipalladium (46 mg, 0.05 mmol), tri-tert-butylphosphine tetrafluoroborate (38 mg, 0.13 mmol), and sodium tert-butoxide (192 mg, 2 mmol) were added. The temperature was raised to 110°C and the reaction was carried out for 12 hours. The intermediate Ph-QAC was obtained by column chromatography. 1 mmol of Ph-QAC, 1 mmol of 2-(4-bromophenyl)-4,6-diphenyl-1,3,5-triazine, and xylene (10 ml) were placed in a 50 ml reaction flask. After purging with argon for 10 minutes, trisdibenzylideneacetone dipalladium (46 mg, 0.05 mmol), tri-tert-butylphosphine tetrafluoroborate (38 mg, 0.13 mmol), and sodium tert-butoxide (192 mg, 2 mmol) were added. The temperature was raised to 110°C for 12 hours. The product was separated by column chromatography to obtain a light green powder, namely compound 36 (yield 63%). MS (MALDI-TOF): m / z 729.89 [M + ].

[0063] Figure 2 is the H NMR spectrum of thermally activated delayed fluorescence compound 36,

[0064] Figure 3 This is the C NMR spectrum of thermally activated delayed fluorescence compound 36.

[0065] Example 2

[0066] This embodiment provides a method for preparing a thermally activated delayed fluorescent compound 17, comprising the following steps:

[0067]

[0068] QAC (346 mg, 1 mmol) was first placed in a 50 ml reaction flask with 10-(4-bromophenyl)-9,9-dimethyl-9,10-dihydroacridine (364 mg, 1 mmol) and xylene (10 ml). After purging with argon for 10 minutes, trisdibenzylideneacetone dipalladium (46 mg, 0.05 mmol), tri-tert-butylphosphine tetrafluoroborate (38 mg, 0.13 mmol) and sodium tert-butoxide (192 mg, 2 mmol) were added. The temperature was raised to 110 ° C and the reaction was carried out for 12 hours to obtain the product MA-QAC. MA-QAC (629 mg, 1 mmol), 2-(3-bromophenyl)-4,6-diphenyl-1,3,5-triazine (388 mg, 1 mmol), and reaction xylene (10 ml) were placed in a 50 ml reaction flask. After purging with argon for 10 minutes, trisdibenzylideneacetone dipalladium (46 mg, 0.05 mmol), tri-tert-butylphosphine tetrafluoroborate (38 mg, 0.13 mmol), and sodium tert-butoxide (192 mg, 2 mmol) were added. The temperature was raised to 110°C and the reaction was allowed to proceed for 12 hours. After the reaction, the mixture was filtered through celite, the organic solvent was evaporated from the filtrate, and the product was separated by column chromatography (petroleum ether / dichloromethane = 4 / 1). The product was a yellow powder, namely, thermally activated delayed fluorescent compound 17 (yield 48%). MS (MALDI-TOF): m / z 937.16 [M + ].

[0069] Example 3

[0070] This embodiment provides a method for preparing a thermally activated delayed fluorescent compound 62, comprising the following steps:

[0071]

[0072] 1 mmol of Cz-QAc, 2 mmol of 2-(3-bromophenyl)-4,6-diphenyl-1,3,5-triazine, and xylene (15 ml) were placed in a 50 ml reaction flask. After purging with argon for 10 minutes, trisdibenzylideneacetone dipalladium (92 mg, 0.1 mmol), tri-tert-butylphosphine tetrafluoroborate (76 mg, 0.26 mmol), and sodium tert-butoxide (384 mg, 4 mmol) were added. The temperature was raised to 110°C and the reaction was allowed to proceed for 12 hours. After the reaction, the mixture was filtered through celite, the organic solvent was evaporated from the filtrate, and the mixture was separated by column chromatography (petroleum ether / dichloromethane = 4 / 1). The product was a green powder, namely, the thermally activated delayed fluorescent compound Compound 62 (yield 40%). MS (MALDI-TOF): m / z 1126.34 [M + ].

[0073] Example 4

[0074] This embodiment provides a method for preparing a thermally activated delayed fluorescent compound 14, the synthesis path of which is as follows:

[0075]

[0076] The preparation method of compound 14 comprises the following steps:

[0077] QAC (13b-phenyl-9,13b-dihydro-5H-quinolino[2,3,4-kl]acridine) (346 mg, 1 mmol), 7-bromo-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (768 mg, 2.2 mmol) and xylene (10 ml) were placed in a 50 ml reaction bottle, and after passing argon for 10 min, trisdibenzylideneacetone dipalladium (92 mg, 0.1 mmol) was added. ), 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (124 mg, 0.26 mmol), and sodium tert-butoxide (384 mg, 4 mmol) were heated to 110°C for 12 hours. After the reaction, the mixture was filtered through celite, and the organic solvent was evaporated from the filtrate. The mixture was separated by column chromatography (petroleum ether / dichloromethane = 4 / 1) to obtain a light yellow powder, which was the thermally activated delayed fluorescent compound Compound 14 (494 mg, yield 56%). MS (MALDI-TOF): m / z 882.59 [M + ].

[0078] Example 5

[0079] This embodiment provides a method for preparing a thermally activated delayed fluorescent compound 4, comprising the following steps:

[0080]

[0081] 1 mmol of 9b-phenyl-1,9b-dihydrobenzopyrano[4,3,2-mn]acridine (OAC), 1 mmol of 2-(4-bromophenyl)-4,6-diphenyl-1,3,5-triazine, and xylene (5 ml) were placed in a 50 ml reaction flask. After purging with argon for 10 minutes, trisdibenzylideneacetone dipalladium (46 mg, 0.05 mmol), tri-tert-butylphosphine tetrafluoroborate (38 mg, 0.13 mmol), and sodium tert-butoxide (192 mg, 2 mmol) were added. The temperature was raised to 110°C and the reaction was allowed to proceed for 12 hours. After column chromatography, a light yellow powder was obtained, which was thermally activated delayed fluorescent compound 4 (yield 44%). MS (MALDI-TOF): m / z 654.77 [M + ].

[0082] Device Example 1

[0083] This embodiment provides an organic electroluminescent device, such as Figure 1 As shown, from bottom to top are a conductive glass substrate 10, a hole injection layer 1, a first hole transport layer 2, a second hole transport layer 3, an electron blocking layer 4, a light-emitting layer 5, a hole blocking layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode 9; its device structure is: indium tin oxide conductive glass substrate (ITO) / hole injection layer (HIL) / first hole transport layer (HTL1) / second hole transport layer (HTL2) / electron blocking layer (EBL) / light-emitting layer (EML) / hole blocking layer (HBL) / electron transport layer (ETL) / electron injection layer (EIL) / cathode.

[0084] The materials used to manufacture the organic electroluminescent device are as follows:

[0085]

[0086] The preparation method of the organic electroluminescent device is as follows:

[0087] 1) Substrate cleaning

[0088] Indium tin oxide conductive glass (ITO) was used as the conductive glass substrate 1. The indium tin oxide conductive glass (ITO) was ultrasonically cleaned with deionized water, acetone and isopropyl alcohol for 30 minutes in sequence, and then dried and treated with O2 plasma for 10 minutes.

[0089] 2) Preparation of organic layer:

[0090] Transfer the indium tin oxide conductive glass (ITO) to the evaporation equipment and evacuate to 5×10 -4 Pa, sequentially deposited 5nm hole injection layer (HIL) / 30nm first hole transport layer (HTL1) / 15nm second hole transport layer 2 (HTL2) / 10nm electron blocking layer (EBL) / 12nm light emitting layer (EML) / 10nm hole blocking layer (HBL) / 30nm electron transport layer (ETL) / 3nm electron injection layer (EIL) / 100nm thick cathode;

[0091] in:

[0092] The material of the hole injection layer (HIL) is HATCN (1,4,5,8,9,11-hexaazabenzonitrile)

[0093] The material of the first hole transport layer (HTL1) is TAPC (1,1-bis[4-[N,N-di-p-toluylamino]phenyl]cyclohexane)

[0094] The material of the second hole transport layer (HTL2) is TCTA (tris(4-carbazol-9-yl-phenyl)amine)

[0095] The material of the electron blocking layer (EBL) is mCBP (3,3-di(carbazolyl)biphenyl)

[0096] The materials of the light-emitting layer (EML) include a host material (organic functional material PPF (2,8-bis(diphenylphosphoryl)dibenzo[b,d]furan)) and a guest material (thermally activated delayed fluorescence compound 36). The doping amount of the guest material in the light-emitting layer accounts for 20% of the total mass of the host and guest materials.

[0097] The hole blocking layer (HBL) is made of PPF (2,8-bis(diphenylphosphoryl)dibenzo[b,d]furan)

[0098] The material of the electron transport layer (ETL) is ANT-BIZ (3,6-bis(N-phenylcarbazole-3-yl)-N-phenylcarbazole)

[0099] The material of the electron injection layer (EIL) is Liq (8-hydroxyquinoline lithium)

[0100] The cathode is Al.

[0101] Device Example 2

[0102] This embodiment provides an organic electroluminescent device, which differs from the device embodiment 1 in that the guest material thermally activated delayed fluorescent compound 36 in the light-emitting layer is replaced by the thermally activated delayed fluorescent compound 17, and the doping amount of the guest material in the light-emitting layer accounts for 20% of the total mass of the host material and the guest material.

[0103] Device Example 3

[0104] This embodiment provides an organic electroluminescent device, which differs from the device embodiment 1 in that the guest material thermally activated delayed fluorescent compound 36 in the light-emitting layer is replaced by a thermally activated delayed fluorescent compound 62, and the doping amount of the guest material in the light-emitting layer accounts for 20% of the total mass of the host material and the guest material.

[0105] Device Example 4

[0106] This embodiment provides an organic electroluminescent device, which differs from the device embodiment 1 in that the guest material thermally activated delayed fluorescent compound 36 in the light-emitting layer is replaced by the thermally activated delayed fluorescent compound 14, and the doping amount of the guest material in the light-emitting layer accounts for 20% of the total mass of the host material and the guest material.

[0107] Device Example 5

[0108] This embodiment provides an organic electroluminescent device, which differs from the device embodiment 1 in that the guest material thermally activated delayed fluorescent compound 36 in the light-emitting layer is replaced by the thermally activated delayed fluorescent compound 4, and the doping amount of the guest material in the light-emitting layer accounts for 20% of the total mass of the host material and the guest material.

[0109] Test Example 1

[0110] The organic electroluminescent devices provided in Device Examples 1-5 were tested. Current-luminance-voltage characteristics were measured using a Keithley 2450 Sourcemeter with a calibrated silicon photodiode, and electroluminescence spectra were measured using a SpectraScan PR-745 spectrometer. All measurements were performed at room temperature in atmospheric air. The test results are shown in Table 1.

[0111] Table 1

[0112]

[0113] ((1) At 100 cd m -2 Efficiency roll-off measured at 1000 cd m -2 Efficiency roll-off measured under

[0114] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A thermally activated delayed fluorescence compound, characterized in that Has the following structure: Wherein, A is selected from one of the following groups: R is selected from -O-, -S-, -N(R1)-, -Se-; R1 is selected from one of the following groups: R T1 -R T16 The same or different, each independently selected from hydrogen, phenyl, methyl, carbazolyl, tolyl.

2. The thermally activated delayed fluorescent compound according to claim 1, wherein R1 is selected from one of the following groups:

3. The thermally activated delayed fluorescent compound according to claim 1, wherein R T1 -R T9 、R T11 -R T16 is selected from hydrogen; R T10 Selected from hydrogen and carbazolyl.

4. A thermally activated delayed fluorescence compound, characterized in that The thermally activated delayed fluorescent compound has any of the following structures:

5. An organic electroluminescent device, characterized in that: The organic electroluminescent device comprises a first electrode, a second electrode and a light-emitting layer located between the first electrode and the second electrode, wherein the light-emitting layer comprises any one of the thermally activated delayed fluorescent compounds according to any one of claims 1 to 4.

6. The organic electroluminescent device according to claim 5, characterized in that: The light-emitting layer comprises the thermally activated delayed fluorescent compound according to any one of claims 1 to 4 and an organic functional material, wherein, by mass percentage, the thermally activated delayed fluorescent compound accounts for 0.01% to 100%, and the organic functional material accounts for 0 to 99.9%.

7. Use of the organic electroluminescent device according to claim 5 or 6 in electronic devices.

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