THERMALLY ACTIVATED DELAYED FLUORESCENCE MATERIAL AND METHOD FOR PREPARING THEREOF AND ORGANIC ELECTROLUMINESCENT DIODE DEVICE

Abstract

A thermally activated delayed fluorescent (TADF) compound, a method for preparing thereof, and an organic electroluminescent diode device are provided. The thermally activated delayed fluorescent compound includes a chemical structure of formula I:

##STR00001##

and R is an electron donating group. A trifluoromethyl group is used as a strong electron acceptor group, and an electron donor group is modified by combining different functional groups. An influence of the strength of the electron donor on material properties is researched to design a blue-light thermal activation delayed fluorescent compounds with significant TADF properties. The thermally activated delayed fluorescent compounds have a high reaction rate constant of reverse intersystem enthalpy constant (k.sub.RISC) and highly efficient blue-light TADF materials. When the thermally activated delayed fluorescent compounds are used as a light-emitting material for an organic light-emitting display device, and the organic light-emitting display device is improved to have high luminous efficiency.

Claims

1. A thermally activated delayed fluorescent compound, comprising a chemical structure of formula I: ##STR00013## wherein R is an electron donating group.

2. The thermally activated delayed fluorescent compound according to claim 1, wherein the electron donating group R is selected any one of following groups: ##STR00014## ##STR00015##

3. The thermally activated delayed fluorescent compound according to claim 2, wherein the thermally activated delayed fluorescent compound is compound 1, compound 2, or compound 3, and structure of formulas the compound 1, compound 2, and compound 3 are respectively represented as follows: ##STR00016##

4. A method for preparing a thermally activated delayed fluorescent compound, a chemical reaction is presented as follows: ##STR00017## adding a raw material 1, an electron donor compound, palladium acetate, and tri-tert-butylphosphine tetrafluoroborate to a reaction flask, wherein a molar ratio of the raw material, the electron donor compound, the palladium acetate, and the tri-tert-butylphosphine tetrafluoroborate is 1:3-4:0.1-0.2:0.3-0.4, and sodium tert-butoxide and raw material 1 are added to a glove box in a molar ratio of 3:4, and anhydrous, degassed toluene is added to the glove box under an argon atmosphere, and a reaction is performed at 120 C. for 24 hours; wherein reaction solution is cooled to room temperature and poured into ice water, and the reaction solution is extracted with dichloromethane for three times and combined with an organic phase, and the reaction solution is spun and dried, and the reaction solution is purified by column chromatography having a stationary phase of silica gel to obtain a product, and a yield is calculated; wherein a structural formula of the raw material 1 is ##STR00018## wherein a structural formula of an electron donating compound is represented as RH, and R is represented as an electron donating group.

5. The method for preparing the thermally activated delayed fluorescent compound according to claim 4, wherein the electron donating group R is selected any one of following groups: ##STR00019## ##STR00020##

6. The method for preparing the thermally activated delayed fluorescent compound according to claim 5, wherein the electron donating compound is 9,10-dihydro-9,9-dimethyl acridine, phenoxazine or phenothiazine.

7. An organic electroluminescent diode device, comprising: a substrate; a first electrode disposed on the substrate; an organic functional layer disposed on the first electrode; and a second electrode disposed on the organic functional layer of the first electrode; wherein the organic functional layer comprises an organic film or a multilayered organic film, and at least one of organic film is a luminescent layer; and wherein luminescent layer comprises the thermally activated delayed fluorescent compound of claim 1.

8. The organic electroluminescent diode device according to claim 7, wherein the luminescent layer is formed by vacuum evaporation or solution coating.

9. The organic electroluminescent diode device according to claim 7, wherein a material of the luminescent layer is a mixture of a host material and a guest material, and the guest material is selected from one or more of the thermally activated delayed fluorescent compounds of claim 1.

10. The organic electroluminescent diode device according to claim 7, wherein the substrate is a glass substrate, a material of the first electrode is indium tin oxide, and the second electrode is a two-layered composite structure made of a lithium fluoride layer and an aluminum layer; wherein the organic functional layer comprises a multilayered organic film, and the multilayered organic film comprises a hole injection layer, a hole transport layer, a luminescent layer, and an electron transport layer; wherein a material of the hole injection layer is molybdenum trioxide; wherein a material of the hole transport layer is Tris(4-carbazoyl-9-ylphenyl)amine (TCTA); wherein a material of the electron transport layer is 1,3,5-Tris(3-pyridyl-3-phenyl)benzene (Tm3PyPB); wherein a material of the luminescent layer is a mixture of a host material and a guest material, and the host material is Bis(2-(diphenylphosphino)phenyl)ether oxide (DPEPO); and wherein the guest material is selected from one or more of the thermally activated delayed fluorescent compounds of claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0024] The technical solutions and beneficial effects will be described in the following detailed description and drawings of embodiments.

[0025] FIG. 1 is a distribution diagram of an electron level of the lowest unoccupied molecular orbital (LUMO) and an electron level of the highest occupied molecular orbital (HOMO) of compound 1, compound 2, and compound 3.

[0026] FIG. 2 is a photoluminescence spectrum of compounds 1-3 in a toluene solution at room temperature according to embodiments 1-3 of the present invention.

[0027] FIG. 3 is a schematic view of an organic electroluminescent device according one embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0028] Some of the unspecified raw materials used in the present invention are commercially available products. The preparation of some compounds will be described in the examples. The present invention will be further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

Example 1

[0029] A synthetic route of target compound 1 is described as follows:

##STR00010##

[0030] Raw material 1 (2.56 g, 5 mmol), 9,10-dihydro-9,9-dimethylacridine (3.76 g, 18 mmol), palladium acetate Pb(OAc) (135 mg, 0.6 mmol), and tri-tert-butylphosphine tetrafluoroborate (t-Bu).sub.3HPBF.sub.4 (0.51 g, 1.8 mmol) are added to a 100 mL two-neck bottle, and then sodium tert-butoxide NaOt-Bu (1.74 g, 18 mmol) is added to a glove box. Anhydrous, degassed toluene (40 mL) is added to the glove box under an argon atmosphere. A reaction is performed at 120 C. for 24 hours. After cooling to room temperature, this reaction solution is poured into 200 mL of ice water. The reaction solution is extracted with dichloromethane for three times and combined with an organic phase. The reaction solution is spun and dried, and then the reaction solution is purified by column chromatography (Dichloromethane:Hexane, v:v, 2:1) having a stationary phase of silica gel to obtain a 3.0 g compound 1 which is a blue-white powder, and a yield is 66%. 1HNMR (300 MHz, CD2Cl2, ): 7.19-7.14 (m, 18H), 6.95 (d, J=6.9 Hz, 6H), 1.69 (s, 18H).sub.o MS (EI) m/z: [M]+ calcd for C.sub.54H.sub.42F.sub.9N.sub.3, 903.32. found, 903.27.

Example 2

[0031] A synthetic route of target compound 2 is described as follows:

##STR00011##

[0032] Raw material 1 (2.56 g, 5 mmol), phenoxazine (3.30 g, 18 mmol), palladium acetate Pb(OAc) (135 mg, 0.6 mmol), and tri-tert-butylphosphine tetrafluoroborate (0.51 g, 1.8 mmol) are added to a 100 mL two-neck bottle, and then sodium tert-butoxide NaOt-Bu (1.74 g, 18 mmol) is added to a glove box. Anhydrous, degassed toluene (40 mL) is added to the glove box under an argon atmosphere. A reaction is performed at 120 C. for 24 hours. After cooling to room temperature, this reaction solution is poured into 200 mL of ice water. The reaction solution is extracted with dichloromethane for three times and combined with an organic phase. The reaction solution is spun and dried, and then the reaction solution is purified by column chromatography (Dichloromethane:Hexane, v:v, 2:1) having a stationary phase of silica gel to obtain a 2.7 g compound 2 which is a blue-white powder, and a yield is 65%. 1H NMR (300 MHz, CD2Cl2, ): 7.14 (d, J=7.2 Hz, 6H), 7.01-6.96 (m, 18H). MS (EI) m/z: [M]+ calcd for C.sub.45H.sub.24F.sub.9N.sub.3O.sub.3, 825.17. found, 825.13.

Example 3

[0033] The synthetic route of target compound 3 is described as follows:

##STR00012##

[0034] Raw material 1 (2.56 g, 5 mmol), phenothiazine (3.30 g, 18 mmol), palladium acetate Pb(OAc) (135 mg, 0.6 mmol), and tri-tert-butylphosphine tetrafluoroborate (0.51 g, 1.8 mmol) are added to a 100 mL two-neck bottle, and then sodium tert-butoxide NaOt-Bu (1.74 g, 18 mmol) is added to a glove box. Anhydrous, degassed toluene (40 mL) is added to the glove box under an argon atmosphere. A reaction is performed at 120 C. for 24 hours. After cooling to room temperature, this reaction solution is poured into 200 mL of ice water. The reaction solution is extracted with dichloromethane for three times and combined with an organic phase. The reaction solution is spun and dried, and then the reaction solution is purified by column chromatography (Dichloromethane:Hexane, v:v, 2:1) having a stationary phase of silica gel to obtain a 2.8 g compound 3 which is a blue-white powder, and a yield is 64%. .sup.1H NMR (300 MHz, CD.sub.2Cl.sub.2, ): 7.16-7.08 (m, 12H), 7.04-6.98 (m, 12H). MS (EI) m/z: [M].sup.+ calcd for C.sub.45H.sub.24F.sub.9N.sub.3S.sub.3, 873.10. found, 873.00.

[0035] FIG. 1 is an orbital distribution diagram of compound 1, compound 2, and compound 3. As shown in FIG. 1, an electron level of the highest occupied molecular orbital (HOMO) and an electron level of the lowest unoccupied molecular orbital (LUMO) of compound 1, compound 2, and compound 3 are individually arranged on different units, and thus HOMO and LUMO of compound 1, compound 2, and compound 3 are completely separated. Therefore, the intersystem energy difference (EST) is reduced, thereby improving a reverse intersystem crossing ability. FIG. 2 is a photoluminescence spectrum of compounds 1-3 in a toluene solution at room temperature. As for the compounds 1-3, the lowest singlet energy level S1 and the lowest triplet energy level T1 of the molecule are calculated by simulation.

[0036] The relevant data of Examples 1-3 are shown in Table 1. It can be seen from Table 1 that all compounds have a Est of less than 0.3 ev, thereby achieving a less singlet energy level and triplet energy level difference with a significant delayed fluorescence effect.

TABLE-US-00001 TABLE 1 Photophysical properties of compounds 1-3 PL Peak S1 T1 EST HOMO LUMO (nm) (eV) (eV) (eV) (eV) (eV) Compound 1 474 2.62 2.57 0.05 5.42 2.28 Compound2 474 2.62 2.56 0.06 5.56 2.28 Compound 3 477 2.60 2.54 0.06 5.58 2.28

[0037] In Table 1, PL Peak represents a photoluminescence peak. S1 represents a singlet energy level. T1 represents a triplet energy level. EST represents a singlet and triplet energy level difference.

Example 4

[0038] A method for fabricating an organic light-emitting diode (OLED) device is described as follows. Referring to FIG. 1, the thermally activated delayed fluorescent compounds according to embodiments of the present invention are used as a guest material of light-emitting layer in the organic light-emitting diode device. The organic light-emitting diode device includes a substrate 9, an anode layer 1, a hole injection layer 2, a hole transport layer 3, a light-emitting layer 4, an electron transport layer 5, and a cathode layer 6 that are disposed in order from bottom to top. The substrate 9 is a glass substrate, and the anode 1 is made of indium tin oxide (ITO). The substrate 9 and the anode 1 are configured to an ITO glass, and the ITO glass has a sheet resistance of is 10 /cm.sup.2. The hole injection layer 2 is made of molybdenum trioxide (MoO.sub.3). The hole transport layer 3 is made of TCTA, and the light-emitting layer is made of a mixture of the activated delayed fluorescent compounds provided by the embodiments and DPEPO. The electron transport layer 5 is made of Tm3PyPB. The cathode is a two-layered structure composed of a lithium fluoride (LiF) layer and an aluminum (Al) layer. TCTA is 4,4,4-tris(carbazol-9-yl)triphenylamine, DPEPO is bis[2-((oxo)diphenylphosphino)phenyl]ether, and Tm3PyPB is 1,3, 5-tris(3-(3-pyridyl)phenyl)benzene.

[0039] Specifically, a method for fabricating the organic light-emitting diode device includes sequentially depositing a MoO.sub.3 film (2 nm), a TCTA film (35 nm), a mixture of DPEPO and thermally activated delayed fluorescent compounds, a Tm3PyPB film (40 nm), a LiF film (1 nm), and an Al film (100 nm) on the clean ITO glass under high vacuum conditions. A device as shown in FIG. 1 is obtained by the method, and various specific device structures are described as follows:

[0040] Device 1: ITO/MoO.sub.3 (2 nm)/TCTA (35 nm)/DPEPO: compound 1 (3% 40 nm)/TmPyPB (40 nm)/LiF (1 nm)/Al (100 nm)

[0041] Device 2: ITO/MoO.sub.3 (2 nm)/TCTA (35 nm)/DPEPO: compound 2 (3% 40 nm)/TmPyPB (40 nm)/LiF (1 nm)/Al (100 nm)

[0042] Device 3: ITO/MoO.sub.3 (2 nm)/TCTA (35 nm)/DPEPO: compound 3 (3% 40 nm)/TmPyPB (40 nm)/LiF (1 nm)/Al (100 nm)

[0043] Furthermore, each of the above devices 1-3 performances is measured, and current-brightness-voltage characteristics of the devices are achieved by a Keithley source measurement system (Keithley 2400 Sourcemeter, Keithley 2000 Currentmeter) with a silicon photodiode which is calibrated. An electroluminescence spectrum is measured by the French JY SPEX CCD3000 spectrometer, and all measurements are performed at room temperature in the atmosphere.

[0044] The data of each of the devices 1-3 are shown in Table 2:

TABLE-US-00002 TABLE 2 Maximum current Maximum external efficiency quantum efficiency Device (cd/A) CIEy (%) Device 1 56.7 0.25 26.6 Device 2 55.6 0.25 25.9 Device 3 29.4 0.29 25.1
In Table 2, CIEy is the y-coordinate value in standard CIE color space.

[0045] In the above, the present application has been described in the above preferred embodiments, but the preferred embodiments are not intended to limit the scope of the invention, and a person skilled in the art may make various modifications without departing from the spirit and scope of the application. The scope of the present application is determined by claims.