WO2020211121A1 - Thermally activated delayed fluorescence material, preparation method therefor, and organic electroluminescent diode device - Google Patents

Abstract

The present invention relates to a thermally activated delayed fluorescence material, a preparation method therefor, and an organic electroluminescent diode device, the structural general formula of the thermally activated delayed fluorescence material being shown in the following formula: (I), wherein R₁represents a chemical group acting as an electron donor and R₂ represents a chemical group acting as an electron acceptor. The thermally activated delayed fluorescence material of the present invention is a blue-light TADF material with significant TADF characteristics and has an ultra-fast reverse inter-system crossing rate and high light emission efficiency and, when used as a light emitting layer guest material in an organic electroluminescent device, can effectively improve the light emission efficiency of the organic electroluminescent device; an organic electroluminescent device based on the thermally activated delayed fluorescence material of the present invention has extremely high device efficiency.

Description

Thermally activated delayed fluorescent material and preparation method thereof and organic electroluminescent diode device Technical field

The invention belongs to the technical field of electroluminescent materials, and particularly relates to a thermally activated delayed fluorescent material, a preparation method thereof, and an organic electroluminescent diode device.

Background technique

Organic Light-Emitting Diode (OLED) display panels have active light emission without backlight, high luminous efficiency, large viewing angle, fast response speed, large temperature adaptation range, relatively simple production and processing technology, and drive The advantages of low voltage, low energy consumption, lighter and thinner, flexible display and huge application prospects have attracted the attention of many researchers.

The principle of the OLED device is that under the action of an electric field, holes and electrons are injected from the anode and the cathode respectively, through the hole injection layer, the hole transport layer, the electron injection layer, and the electron transport layer, respectively, to form excitons in the light emitting layer. Exciton radiation attenuates luminescence.

As the core component of OLED devices, organic electroluminescent materials have a great impact on the performance of the devices. The light-emitting layer of an OLED device generally contains a host material and a guest material, and the light-emitting guest material that plays a leading role is very important. The light-emitting guest materials used in early OLED devices were fluorescent materials. Since the ratio of singlet and triplet excitons in OLED devices is 1:3, the theoretical internal quantum efficiency (IQE) of OLED devices based on fluorescent materials is only It can reach 25%, which greatly limits the application of fluorescent electroluminescent devices. Due to the spin-orbit coupling of heavy atoms, heavy metal complex phosphorescent materials can simultaneously use singlet and triplet excitons to achieve 100% IQE. However, the commonly used heavy metals are precious metals such as iridium (Ir) and platinum (Pt), and the phosphorescent materials of heavy metal complexes still need a breakthrough in blue light materials. The pure organic thermally activated delayed fluorescence (TADF) material has a molecular structure combining electron donor (D) and electron acceptor (A). Through clever molecular design, the molecule has a small minimum single triplet energy difference (ΔE) _ST ), so that the triplet excitons can return to the singlet state through the reverse intersystem crossing (RISC), and then through the radiation transition to the ground state to emit light, so that the singlet and triplet excitons can be used at the same time, and 100% can also be achieved IQE.

For TADF materials, fast reverse intersystem crossing constant (k _RISC ) and high photoluminescence quantum yield (PLQY) are necessary conditions for the preparation of high-efficiency OLED devices. At present, TADF materials with the above conditions are still relatively scarce compared to heavy metal Ir complexes.

Summary of the invention

The purpose of the present invention is to provide a thermally activated delayed fluorescent material, which has an ultrafast reverse inter-system crossing rate and high luminous efficiency, is a blue TADF compound with remarkable TADF characteristics, and can be used as a guest of the light-emitting layer of an organic electroluminescent diode material.

Another object of the present invention is to provide a method for preparing a thermally activated delayed fluorescent material, which is easy to operate and has a high yield of the target product.

Another object of the present invention is to provide an organic electroluminescent diode device, which uses the thermally activated delayed fluorescent material as the guest material of the light-emitting layer, thereby improving the light-emitting efficiency of the device.

In order to achieve the above-mentioned object of the invention, the present invention provides a thermally activated delayed fluorescent material, which has a chemical structure shown in the following formula 1:

Formula one

In the above formula 1, R ₁ represents a chemical group as an electron donor, and R ₂ represents a chemical group as an electron acceptor.

The chemical group R _{1 of} the electron donor is selected from any one of the following groups:

The chemical group R _{2 of} the electron acceptor is selected from any one of the following groups:

The thermally activated delayed fluorescent material is compound 1, compound 2 or compound 3. The structural formulas of compound 1, compound 2 and compound 3 are as follows:

The present invention also provides a preparation method of thermally activated delayed fluorescent material, and its chemical synthesis route is as follows:

Specifically: add halogenated raw materials, electron donor compounds, palladium acetate and tri-tert-butylphosphine tetrafluoroborate with a molar ratio of 1:1-2:0.02-0.1:0.1-0.2 to the reaction flask, and then In an anhydrous and oxygen-free environment, add sodium tert-butoxide at a molar ratio of 1-2:1 to the halogenated raw materials. In an argon atmosphere, drive in toluene for removing water and oxygen, and react at 110-130℃ for 20-30 Hours; cool to room temperature, pour the reaction solution into ice water, combine the organic phases after extraction, spin into silica gel, separate and purify by column chromatography to obtain the product, calculate the yield;

The general structural formula of the halogenated raw material is

Wherein, R ₂ represents a chemical group as an electron acceptor;

The general structural formula of the electron-donor-containing compound is R ₁ -H, wherein R ₁ represents a chemical group as an electron donor.

The chemical group R _{1 of} the electron donor is selected from any one of the following groups:

The chemical group R _{2 of} the electron acceptor is selected from any one of the following groups:

The structural formula of the halogenated raw material is

The electron donor compound is 9,10-dihydro-9,9-dimethylacridine, phenoxazine or phenothiazine.

The present invention also provides an organic electroluminescent diode device including a substrate, a first electrode provided on the substrate, an organic functional layer provided on the first electrode, and a second electrode provided on the organic functional layer ；

The organic functional layer includes one or more organic film layers, and at least one organic film layer is a light-emitting layer;

The material of the light-emitting layer includes a mixed host material and a guest material, and the guest material is selected from one or more of the thermally activated delayed fluorescent materials described above.

The light-emitting layer is formed by vacuum evaporation or solution coating.

The main body material is DPEPO.

The substrate is a glass substrate, the material of the first electrode is indium tin oxide, and the second electrode is a double-layer composite structure composed of a lithium fluoride layer and an aluminum layer;

The organic functional layer includes a multilayer organic film layer, the multilayer organic film layer includes a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer, wherein the material of the hole injection layer is molybdenum trioxide The material of the hole transport layer is TCTA, and the material of the electron transport layer is TmPyPB.

Compared with existing materials and technologies, the present invention has the following advantages and beneficial effects:

The thermally activated delayed fluorescent material of the present invention is a blue TADF compound with a lower single triplet energy level difference, an ultrafast reverse intersystem crossing rate and high luminous efficiency. When it is used as a blue guest material in an organic light emitting display device , The luminous efficiency of the organic light-emitting display device can be improved, and the organic electroluminescent diode devices based on the thermally activated delayed fluorescent material of the present invention have achieved very high device efficiency.

Description of the drawings

The technical solutions and other beneficial effects of the present invention will be made obvious by describing in detail the specific embodiments of the present invention in conjunction with the accompanying drawings.

In the attached picture,

Figure 1 is a diagram of HOMO and LUMO energy levels of compounds 1-3 prepared in specific examples 1-3 of the present invention;

Figure 2 is a photoluminescence spectrum of compound 1-3 prepared in specific examples 1-3 of the present invention in a toluene solution at room temperature;

Fig. 3 is a schematic diagram of the structure of the organic electroluminescent diode device of the present invention.

detailed description

Some unspecified raw materials used in the present invention are all commercially available products. The preparation methods of some compounds will be described in the implementation case. The present invention will be further described in detail below in conjunction with specific examples, but the implementation of the present invention is not limited thereto.

Example 1:

The synthetic route of target compound 1 is as follows:

Add raw material 1 (2.00g, 5mmol), 9,10-dihydro-9,9-dimethylacridine (1.25g, 6mmol), palladium acetate Pb(OAc) (45mg, 0.2mmol) into a 100mL two-neck flask ) And tri-tert-butylphosphine tetrafluoroborate (t-Bu) ₃ HPBF ₄ (0.17g, 0.6mmol), and then add sodium tert-butoxide NaOt-Bu (0.58g, 6mmol) in the glove box. 40 mL of toluene that had been previously dewatered and deoxygenated was injected under an air atmosphere, and reacted at 120°C for 24 hours. Cool to room temperature, pour the reaction solution into 200 mL ice water, extract three times with dichloromethane, combine the organic phases, spin into silica gel, and separate and purify by column chromatography (dichloromethane: n-hexane, v: v, 1:1) to obtain 1.7 g of compound 1 as a white powder, with a yield of 64%.

1HNMR (300MHz, CD ₂ Cl ₂ , δ): 7.20-7.14 (m, 6H), 6.95-6.90 (m, 2H), 1.69 (s, 6H).

Example 2:

The synthetic route of target compound 2 is as follows:

To a 100mL two-neck flask was added raw material 1 (2.00g, 5mmol), phenoxazine (1.10g, 6mmol), palladium acetate (45mg, 0.2mmol) and tri-tert-butylphosphine tetrafluoroborate (0.17g, 0.6 mmol), and then add sodium tert-butoxide (0.58 g, 6 mmol) into the glove box, and drive 40 mL of toluene previously dewatered and deoxygenated under an argon atmosphere, and react at 120° C. for 24 hours. Cool to room temperature, pour the reaction solution into 200 mL ice water, extract three times with dichloromethane, combine the organic phases, spin into silica gel, and separate and purify by column chromatography (dichloromethane: n-hexane, v: v, 1:1) to obtain 1.3 g of compound 2 as a light blue powder with a yield of 52%.

¹ H NMR (300MHz, CD ₂ Cl ₂ , δ): 7.19-7.14 (m, 2H), 7.05-6.96 (m, 6H).

Example 3:

The synthetic route of target compound 3 is as follows:

To a 100mL two-neck flask was added raw material 1 (2.00g, 5mmol), phenothiazine (1.19g, 6mmol), palladium acetate (45mg, 0.2mmol) and tri-tert-butylphosphine tetrafluoroborate (0.17g, 0.6 mmol), and then add sodium tert-butoxide (0.58 g, 6 mmol) into the glove box, and drive 40 mL of toluene previously dewatered and deoxygenated under an argon atmosphere, and react at 120° C. for 24 hours. Cool to room temperature, pour the reaction solution into 200 mL ice water, extract three times with dichloromethane, combine the organic phases, spin into silica gel, and separate and purify by column chromatography (dichloromethane: n-hexane, v: v, 1:1) to obtain 1.1 g of compound 3 as a light blue powder with a yield of 42%.

¹ H NMR (300MHz, CD ₂ Cl ₂ , δ): 7.20-7.14 (m, 6H), 6.96-6.89 (m, 2H).

Figure 1 shows the orbital arrangement of compound 1-3. It can be clearly seen from Figure 1 that the highest electron occupied orbital (HOMO) and lowest electron unoccupied orbital (LUMO) of compound 1-3 are arranged in In different units, complete separation is achieved, which helps to reduce the energy difference ΔEST between systems, thereby improving the ability of reverse intersystem crossing. Figure 2 shows the photoluminescence spectra of Compound 1-3 in a toluene solution at room temperature. For compounds 1-3, the lowest singlet energy level S1 and the lowest triplet energy level T1 of the molecule were simulated and calculated.

The relevant data of Examples 1-3 are shown in Table 1. It can be seen from Table 1 that the ΔEst of all the compounds is less than 0.3ev, which achieves a small singlet and triplet energy level difference, and has an obvious delayed fluorescence effect.

Table 1. Results of photophysical properties of compounds 1-3

In Table 1, PL Peak represents the photoluminescence peak, S1 represents the singlet energy level, T1 represents the triplet energy level, and ΔEST represents the difference between the singlet and triplet energy levels.

Example 4:

Preparation of organic electroluminescent diode (OLED) devices:

As shown in FIG. 1, the thermally activated delayed fluorescent material of the present invention is used as the organic electroluminescent diode device of the blue guest material in the light-emitting layer, and may include a substrate 9, an anode layer 1, and a hole injection layer 2 which are sequentially arranged from bottom to top. , The hole transport layer 3, the light emitting layer 4, the electron transport layer 5, and the cathode layer 6. Wherein, the substrate 9 is a glass substrate, the material of the anode 1 is indium tin oxide (ITO), and the substrate 9 and the anode 1 together constitute ITO glass. The material of the hole injection layer 2 is molybdenum trioxide (MoO ₃ ), the material of the hole transport layer 3 is TCTA, and the material of the light-emitting layer is the thermally activated delayed fluorescent material and the blue light host material DPEPO of the present invention The material of the electron transport layer 5 is TmPyPB. The cathode has a double-layer structure composed of a lithium fluoride (LiF) layer and an aluminum (Al) layer.

Among them, TCTA refers to 4,4',4”-tris(carbazol-9-yl)triphenylamine, DPEPO refers to bis[2-((oxo)diphenylphosphino)phenyl]ether, TmPyPB refers to 1, 3,5-Tris(3-(3-pyridyl)phenyl)benzene.

The organic electroluminescent diode device can be manufactured according to a method known in the art, and the specific method is: sequentially vapor-depositing a 2nm thick MoO ₃ film, a 35nm thick TCTA film, and a DPEPO on the cleaned ITO glass under high vacuum conditions. Add the thermally activated delayed fluorescence compound of the present invention, a 40nm thick TmPyPB film, a 1nm thick LiF film and a 100nm thick Al film. The device as shown in Figure 3 is made by this method, and the specific device structures are as follows:

Device 1:

ITO/MoO ₃ (2nm)/TCTA(35nm)/DPEPO: Compound 1(10%20nm)/TmPyPB(40nm)/LiF(1nm)/Al(100nm)

Device 2:

ITO/MoO ₃ (2nm)/TCTA(35nm)/DPEPO: Compound 2(10%20nm)/TmPyPB(40nm)/LiF(1nm)/Al(100nm)

Device 3:

ITO/MoO ₃ (2nm)/TCTA(35nm)/DPEPO: Compound 3(10%20nm)/TmPyPB(40nm)/LiF(1nm)/Al(100nm)

The current-brightness-voltage characteristics of devices 1-3 are completed by the Keithley source measurement system (Keithley 2400 Sourcemeter, Keithley 2000 Currentmeter) with a calibrated silicon photodiode, and the electroluminescence spectrum is performed by the French JY company SPEX CCD3000 spectrometer All measurements are done in room temperature atmosphere. The performance data of devices 1-3 are shown in Table 2 below.

Table 2. Performance results of devices based on compounds 1-3 as guest materials for the light-emitting layer

In Table 2, CIEy is the y coordinate value of the standard CIE color space.

In summary, the present invention fine-tunes the structure of the electron donor groups to make them have different electron donating abilities, designs a blue thermally activated delayed fluorescent material with significant TADF characteristics, and realizes the material's emission spectrum from deep blue to dark blue. Fine adjustment in the range of sky blue light; the thermally activated delayed fluorescent material of the present invention is a blue TADF compound with lower single triplet energy level difference, ultrafast reverse intersystem crossing rate and high luminous efficiency, when it is used as a blue guest material When applied to an organic light-emitting display device, the light-emitting efficiency of the organic light-emitting display device can be improved. The organic electroluminescent diode device based on the thermally activated delayed fluorescent material of the present invention has achieved very high device efficiency.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, etc. made without departing from the spirit and principle of the present invention Simplified, all should be equivalent replacement methods, and they are all included in the protection scope of the present invention.

Claims (10)

1. A thermally activated delayed fluorescent material has a chemical structure shown in the following formula 1:

   

   In the above formula 1, R ₁ represents a chemical group as an electron donor, and R ₂ represents a chemical group as an electron acceptor.
2. The thermally activated delayed fluorescent material according to claim 1, wherein the chemical group R _{1 of} the electron donor is selected from any one of the following groups:

   

   The chemical group R _{2 of} the electron acceptor is selected from any one of the following groups:

   
3. The thermally activated delayed fluorescent material of claim 2 is compound 1, compound 2, or compound 3. The structural formulas of compound 1, compound 2 and compound 3 are as follows:

   
4. A preparation method of thermally activated delayed fluorescent material, the chemical synthesis route is as follows:

   

   Specifically: add halogenated raw materials, electron donor compounds, palladium acetate and tri-tert-butylphosphine tetrafluoroborate with a molar ratio of 1:1-2:0.02-0.1:0.1-0.2 to the reaction flask, and then In an anhydrous and oxygen-free environment, add sodium tert-butoxide at a molar ratio of 1-2:1 to the halogenated raw materials. In an argon atmosphere, drive in toluene for removing water and oxygen, and react at 110-130℃ for 20-30 Hours; cool to room temperature, pour the reaction solution into ice water, combine the organic phases after extraction, spin into silica gel, separate and purify by column chromatography to obtain the product, calculate the yield;

   The general structural formula of the halogenated raw material is

   

   Wherein, R ₂ represents a chemical group as an electron acceptor;

   The general structural formula of the electron-donor-containing compound is R ₁ -H, wherein R ₁ represents a chemical group as an electron donor.
5. The method for preparing a thermally activated delayed fluorescent material according to claim 4, wherein the chemical group R _{1 of} the electron donor is selected from any one of the following groups:

   

   

   The chemical group R _{2 of} the electron acceptor is selected from any one of the following groups:

   
6. The method for preparing a thermally activated delayed fluorescent material according to claim 5, wherein the structural formula of the halogenated raw material is

   

   The electron donor compound is 9,10-dihydro-9,9-dimethylacridine, phenoxazine or phenothiazine.
7. An organic electroluminescent diode device, comprising a substrate, a first electrode provided on the substrate, an organic functional layer provided on the first electrode, and a second electrode provided on the organic functional layer;

   The organic functional layer includes one or more organic film layers, and at least one organic film layer is a light-emitting layer;

   The material of the light-emitting layer comprises a mixed host material and a guest material, and the guest material is selected from one or more of the thermally activated delayed fluorescent materials according to claim 1.
8. 8. The organic electroluminescent diode device of claim 7, wherein the light-emitting layer is formed by vacuum evaporation or solution coating.
9. 8. The organic electroluminescent diode device of claim 7, wherein the host material is DPEPO.
10. The organic electroluminescent diode device of claim 7, wherein the substrate is a glass substrate, the material of the first electrode is indium tin oxide, and the second electrode is composed of a lithium fluoride layer and an aluminum layer Double-layer composite structure;

    The organic functional layer includes a multilayer organic film layer, the multilayer organic film layer includes a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer, wherein the material of the hole injection layer is molybdenum trioxide The material of the hole transport layer is TCTA, and the material of the electron transport layer is TmPyPB.

Images