OLED blue light material and application thereof

Abstract

The patent discloses a kind of OLED blue light material and its application, the molecular structure formula of blue light material is, wherein, A is cyanophenyl electron acceptor, D is aromatic electron donor;The material has high thermal stability, good fluorescence quantum yield;By matching different electron donor and acceptor, the excitation state energy level is regulated, the energy of hot exciton transmission is promoted, the exciton utilization rate is improved, the external quantum efficiency of blue light OLED device is improved, and the OLED blue light material shows good electroluminescent performance.

Description

Technical Field

[0001] This invention belongs to the field of organic light-emitting diode (OLED) technology, and provides a class of OLED blue light materials and their applications. Background Technology

[0002] Compared to LCD display technology, OLED has advantages such as fast response, wide viewing angle, transparent display, and foldability, and has been widely used in televisions, smartphones, auto shows, laptops, and wearable devices. In 1987, Tang et al. of Kodak in the United States used 8-hydroxyquinoline aluminum as the luminescent material and aromatic diamine as the hole transport layer to fabricate a sandwich structure device. Under current driving, the device exhibited a brightness of 1000 cd cm⁻¹. -2 Luminous efficiency 1.5 lm W -1 It boasts excellent performance, including a driving voltage below 10 V and a lifespan exceeding 100 hours. This research achievement has garnered significant attention from both academia and industry, propelling OLED technology into a phase of rapid development.

[0003] Luminescent materials are the core functional layer of OLEDs. Among the three primary color luminescent materials, the development of blue light materials has been slower compared to green and red light materials, and high-efficiency blue light materials are relatively scarce. Under current drive, 25% singlet excitons and 75% triplet excitons are generated. Traditional fluorescent materials can only utilize 25% singlet excitons for emission, with a maximum external quantum efficiency of no more than 5%. The 75% triplet energy level becomes the source of improving exciton utilization. Metal phosphorescent materials emit light through radiative transitions of triplet energy levels, but metal phosphorescent materials are expensive; thermally excited delayed fluorescence (TEFF) involves the lowest excited triplet energy level T1 transferring energy to the singlet state for radiative emission. Thermally excited materials utilize higher triplet energy levels (T1). m (m>1) transfers energy to the singlet state for radiative emission, while avoiding the triplet-triplet annihilation problem caused by high concentration of T1. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a class of OLED blue light materials that, by matching different electron donors and acceptors at the 1,8-positions of the pyrene ring, regulate the excited state energy level, promote thermal exciton energy transfer, improve exciton utilization, improve the external quantum efficiency of OLED devices, and develop high-performance light-emitting materials.

[0005] The technical solution of the present invention is as follows: A class of OLED blue light materials has the following general molecular structure formula: Where A is a cyanophenyl electron acceptor The cyano group CN is one of the three bonding positions: ortho, meta, and para. D is an aromatic electron donor and can be one of the following groups: .

[0006] The OLED blue light material described herein has any one of the following molecular formulas: , .

[0007] The present invention also provides a method for preparing the above-mentioned type of OLED blue light material, comprising the following steps: chemical synthesis, separation and purification.

[0008] The chemical synthesis steps include: dispersing 1,8-dibromopyrene with a cyanophenylborone reagent (boric acid or borate ester), tetrakis(triphenylphosphine)palladium, and a base (potassium carbonate or cesium carbonate) in a mixed solvent of toluene, ethanol, and water; reacting at 80-95°C for more than 10 hours under a protective atmosphere (nitrogen or argon) to obtain the 1-bromo-8-p-cyanophenylpyrene intermediate. The intermediate, along with an aromatic electron donor boron reagent (boric acid or borate ester), tetrakis(triphenylphosphine)palladium, and a base (potassium carbonate or cesium carbonate), are dispersed in a mixed solvent of toluene, ethanol, and water. The reaction is carried out under a protective atmosphere (nitrogen or argon) at 80-95°C for at least 10 hours to obtain the OLED blue light material. .

[0009] .

[0010] The separation steps include: (1) cooling the reaction to room temperature and filtering to obtain the residual solid; (2) evaporating the reaction solution, extracting it with dichloromethane solvent, washing it with ultrapure water, collecting the dichloromethane organic phase, drying it, and evaporating it.

[0011] The purification steps include: using dichloromethane and petroleum ether as eluents, the collected solids are subjected to SiO2 column chromatography to obtain the OLED blue light material described above.

[0012] The present invention also provides an organic light-emitting diode device, comprising an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode.

[0013] The OLED blue light material prepared by this invention has the following advantages and beneficial effects: (1) The structure of the blue light material is of type D-π-A, where π is the pyrene nucleus, A is the cyanophenyl electron acceptor, and D is the aromatic electron donor; (2) Regulate the excited state energy level to promote the transfer of thermal exciton energy and improve the exciton utilization rate; (3) Exhibits blue light emission with high external quantum efficiency; (4) It has excellent thermal stability. Attached Figure Description

[0014] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with examples of the invention to explain the invention and do not constitute a limitation thereof.

[0015] Figure 1 Thermogravimetric diagram of materials Figure 2 Excited state energy level distribution diagram Figure 3 EL spectrum of an undoped OLED device. Specific Implementation The present invention will be further described below with reference to specific embodiments and accompanying drawings. However, the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the principles of the present invention should be included within the scope of the present invention, and the described technical features or combinations of technical features should not be considered isolated; they can be combined and integrated with each other to achieve better technical effects.

[0017] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all materials and reagents used are commercially available.

[0018] Example 1: Chemical Synthesis of Materials Preparation of intermediate 1-bromo-8-p-cyanophenylpyrene:

[0019] 1,8-Dibromopyrene (2 mmol, 0.72 g), p-cyanobenzoboronic acid (2.2 mmol, 0.298 g), tetrakis(triphenylphosphine)palladium (0.1 mmol, 0.1 g), and potassium carbonate (10 mmol, 1.38 g) were added sequentially to 20 mL of a mixed solvent of toluene, ethanol, and water (volume ratio 2:1:1). The mixture was refluxed at 80-95 °C for at least 10 h under a protective atmosphere (nitrogen or argon) to confirm complete reaction of the starting material 1,8-dibromopyrene by thin-plate chromatography. Heating was stopped, and the system was cooled to room temperature. The mixture was then poured into water, and dichloromethane was added for extraction. The organic phase was dried over anhydrous sodium sulfate, and the solvent was removed by vacuum distillation. The crude product was purified by silica gel column chromatography (dichloromethane:petroleum ether = 4:1) to obtain a white solid in 43% yield. 1 H NMR (400 MHz, chloroform-d) δ: 8.43 (d, 1H), 8.29 (d, 1H), 8.27 (d, 1H), 8.13 (m, 4H), 7.98 (d, 1H), 7.87 (d, 2H), 7.75 (d, 2H).

[0020] Preparation of Material 1-1:

[0021] Intermediate 1-bromo-8-p-cyanophenylpyrene (2 mmol, 0.76 g), 1-naphthylboronic acid (3 mmol, 0.5 g), tetrakis(triphenylphosphine)palladium (0.1 mmol, 0.1 g), and cesium carbonate (16 mmol, 5.2 g) were added sequentially to a mixed solvent of 20 mL toluene, 10 mL water, and 10 mL ethanol. The mixture was refluxed at 80–95 °C for at least 10 h under a protective atmosphere (nitrogen or argon) to confirm complete reaction of 1-bromo-8-p-cyanophenylpyrene by thin-plate chromatography. After cooling to room temperature, the mixture was poured into water and extracted twice with dichloromethane, then dried over anhydrous sodium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the crude product was purified by silica gel column chromatography (dichloromethane: petroleum ether = 4:1) in 40% yield. 1H NMR (400 MHz, chloroform-d) δ: 8.33 (d, 1H), 8.28 (d, 1H), 8.22 (d, 1H), 8.17 (d, 1H), 8.06 (d, 1H), 7.98(t, 2H), 7.94 (d, 1H), 7.86 (d, 1H), 7.77 (d, 2H), 7.69 (d, 2H), 7.64 (m,2H), 7.58 (dd, 1H), 7.48 (m, 1H), 7.35 (d, 1H), 7.28 (d, 1H).

[0022] Preparation of materials 1-4:

[0023] The preparation method of Material 1-1 is adopted, except that 2-naphthylboronic acid reagent is used in the reaction. 1 ¹H NMR (400MHz, chloroform-d) δ: 8.31 (d, 1H), 8.27 (d, 1H), 8.20 (m, 2H), 8.13 (m, 2H), 8.07 (s, 1H), 8.01 (d, 1H), 7.99 (d, 1H), 7.94 (dd, 3H), 7.82 (d, 2H), 7.5 (m, 3H), 7.56 (dd, 2H).

[0024] Preparation of material 3-1:

[0025] The preparation method of Material 1-1 is adopted, except that (4-(9H-carbazole-9-yl)phenyl)boronic acid reagent is used in the reaction. 1 H NMR (400 MHz, chloroform-d) δ: 8.35 (d, 1H), 8.31 (t, 2H), 8.16 (m, 6H), 7.99(d, 1H), 7.86 (m, 4H), 7.77 (m, 4H), 7.59 (d, 2H), 7.47 (t, 2H), 7.34 (t, 2H).

[0026] Preparation of materials 3-4:

[0027] The preparation method of Material 1-1 is adopted, except that (3-(9H-carbazole-9-yl)-phenyl)boronic acid reagent is used in the reaction. 1 H NMR (400 MHz, chloroform-d) δ: 8.31 (d, 1H), 8.29 (s, 1H), 8.26 (d, 1H), 8.16(m, 5H), 8.05 (d, 1H), 7.96 (d, 1H), 7.83 (m, 3H), 7.79 (d, 1H), 7.74 (m,3H), 7.71 (d, 1H), 7.56 (d, 2H), 7.43 (t, 2H), 7.30 (t, 2H).

[0028] Preparation of materials 3-7:

[0029] The preparation method of Material 1-1 is adopted, except that (2-(9H-carbazole-9-yl)-phenyl)boronic acid reagent is used in the reaction. 1 H NMR (400 MHz, chloroform-d) δ: 8.18 (d, 1H), 8.14 (d, 1H), 7.95 (d, 1H), 7.91(d, 1H), 7.86 (m, 5H), 7.80 (m, 2H), 7.76 (d, 1H), 7.69 (m, 5H), 7.63 (d,1H), 7.34 (m, 2H), 7.17 (t, 1H), 7.02 (m, 1H), 6.90 (m, 2H).

[0030] Example 2: Thermal, photophysical and electrochemical properties of materials and theoretical calculations These OLED blue light materials exhibit high thermal stability; as shown in Figure 1 and Table 1, their thermal decomposition temperature is greater than 410℃. The fluorescence emission of the material solution and the 30 nm evaporated thin film is located at 425-431 nm and 444-474 nm, respectively, and is blue light emission. They possess high fluorescence quantum yield and high radiative velocity, with a quantum yield of 92% for the solution and 80% for the thin film.

[0031] Table 1: Photophysical properties and energy level parameters of the materials Material <![CDATA[T d,5% (℃) a ]]> <![CDATA[λ abs (nm) b ]]> <![CDATA[λ em (nm) c ]]> <![CDATA[PLQY (%) c ]]> <![CDATA[HOMO / LUMO / Eg (eV) d ]]> <![CDATA[τ F (ns) c ]]> <![CDATA[K r / K nr (x10 8 s -1 ) e ]]> 1-1 416 356 425 / 444 74.0 / 61.0 -5.33 / -2.18 / 3.15 3.90 / 4.80 1.27 / 0.81 1-4 425 365 431 / 474 92.0 / 80.0 -5.30 / -2.23 / 3.07 13.8 / 13.7 0.58 / 0.15 3-1 470 363 439 / 466 83.2 / 54.5 -5.71 / -2.65 / 3.06 5.40 / 13.1 0.42 / 0.35 3-4 467 362 425 / 465 80.2 / 71.6 -5.46 / -2.34 / 3.12 4.70 / 6.70 1.07 / 0.42 3-7 448 362 427 / 449 66.8 / 47.4 -5.54 / -2.46 / 3.08 4.0 / 13.2 0.36 / 0.40 a The thermal decomposition temperature of a material corresponds to the temperature at which it loses 5% of its weight when heated. b Concentration of 10 -5 UV absorption λ of mol / L tetrahydrofuran solution abs ; c Concentration of 10 -5 Fluorescence emission λ of mol / L tetrahydrofuran solution and 30 nm thick vapor-deposited thin film em Fluorescence quantum yield PLQY and lifetime τ F ; d Using a platinum wire as the auxiliary electrode, a glassy carbon disk as the working electrode, and Ag / Ag+ as the reference electrode, cyclic voltammetry (CV) was performed on CHI 660E A14297 in a 0.1 M tetrabutylammonium hexafluorophosphate (Bu4NPF6) dichloromethane solution at a scan rate of 100 mV / s. -1 HOMO = [E ox -E 1 / 2 (Fc / Fc + ) + 4.8] eV, the band gap width Eg is the energy initially absorbed by the tetrahydrofuran solution, LUMO = HOMO – Eg; e The radiative velocity K of a 30 nm thick vapor-deposited thin film r With nonradiative velocity K nr .

[0032] Appendix Figure 2The results are obtained using function theory calculations based on the B3LYP / 6-311G(d) basis set. The energy difference between T1 and S1 in the material is greater than 1.10 eV, and the probability of reverse intersystem crossing from T1 to S1 is small. However, the triplet energy level located at the higher position is close to the excited singlet energy level. The energy difference between T2 and S1 in 1-1 is 0.04 eV, the energy difference between T5 and S2 in 1-4 is 0.08 eV, the energy difference between T2 and S1 in 3-1 is 0.04 eV, the energy difference between T3 and S2 in 3-4 is 0, and the energy difference between T3 and S2 in 3-7 is 0.05 eV. Thermal exciton energy transfer can be achieved between these energy levels through reverse intersystem crossing, which is beneficial to improving exciton utilization.

[0033] Example 3: Application of OLED Blue Light Materials The structure of an undoped organic light-emitting diode (OLED) device is ITO / PEDOT:PSS (~40 nm) / TCTA (~40 nm) / EML (~25 nm) / TPBi (~30 nm) / LiF (~1 nm) / Al (~100 nm), and the fabrication process includes: (1) Cleaning: First, use acetone, deionized water and ethanol to ultrasonically clean the ITO glass substrate for 15 minutes in sequence. Then use N2 air gun to blow dry the residual solvent on the ITO surface. Then perform oxygen plasma treatment for 10 minutes. After that, transfer the ITO glass substrate to the N2 glove box and vacuum evaporation chamber to prepare the functional layer. (2) Preparation of hole injection layer: In an N2 glove box, polystyrene sulfonate (PEDOT:PSS) (~40 nm) was spin-coated onto ITO; (3) Preparation of hole transport layer: TCTA (~40 nm) was deposited on hole injection layer in vacuum evaporation chamber; (4) Preparation of the light-emitting layer: In a vacuum evaporation chamber, the above-mentioned blue light material (~25 nm) is deposited on the hole transport layer; (5) Preparation of electron transport layer: TPBi (~30 nm) was deposited on organic light-emitting layer in vacuum evaporation chamber; (6) Electrode preparation: Lithium fluoride (~1 nm) and aluminum (~100 nm) were deposited on the electron transport layer in the vacuum evaporation chamber.

[0034] OLED performance: Current was passed through the above OLED devices to test their electroluminescence performance. Figure 3 The EL spectrum shows that the device emits blue light in the 444-476 nm range, all originating from the emissive layer material. Table 2 shows the OLED performance parameters, with exciton utilization far exceeding 25%, achieving a significant improvement in external quantum efficiency. The external quantum efficiency of OLEDs 1-4 reaches as high as 12.5%.

[0035] Table 2: Performance parameters of undoped OLEDs Devices EL / nm Turn-on voltage / V <![CDATA[Maximum brightness / cd m -2 > Maximum external quantum efficiency / % Exciton utilization rate / % 1-1 444 4.2 3567 10.5 86 1-4 460 4.2 7166 12.5 79 3-1 460 4.4 11000 8.08 74 3-4 476 4.8 6048 7.38 52 3-7 468 4.8 9441 8.64 91 .

[0036] In summary, it can be shown that in the D-π-A type structure, π is the pyrene nucleus, A is the cyanophenyl electron acceptor, and D is the aromatic electron donor. By matching different electron acceptors and donors, the excited state energy level can be regulated, promoting thermal exciton energy transfer, improving exciton utilization, and enhancing the external quantum efficiency of blue OLED devices. This type of OLED blue light material exhibits excellent electroluminescence performance.

[0037] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes, substitutions or simple modifications that can be easily conceived by those skilled in the art within the scope of the present invention should be included within the scope of protection of the present invention.

Claims

1. A type of OLED blue light material, characterized in that: Its general molecular formula is as follows: Where A is a cyanophenyl electron acceptor The cyano group CN can be one of the three bonding positions: ortho, meta, or para. D is an aromatic electron donor and can be one of the following groups: 。 2. The OLED blue light material according to claim 1, characterized in that, The molecular structural formula can be any of the following: ， 。 3. A method for preparing a type of OLED blue light material, characterized in that, 1,8-Dibromopyrene reacts with cyanophenylborone reagent, tetrakis(triphenylphosphine)palladium, and a base in a mixed solvent of toluene, ethanol, and water to give a 1-bromo-8-p-cyanophenylpyrene intermediate. The intermediate, along with an aromatic electron donor boron reagent, tetra(triphenylphosphine)palladium, and a base, were dispersed in a mixed solvent of toluene, ethanol, and water. Under a protective atmosphere, the reaction yielded an OLED blue light material. .

4. The method for preparing OLED blue light material according to claim 3, characterized in that, The protective atmosphere is nitrogen or argon.

5. The method for preparing OLED blue light material according to claim 3, characterized in that, The reaction is carried out at 80-95℃ for more than 10 hours.

6. The method for preparing OLED blue light material according to claim 3, characterized in that, The boron reagent is boric acid or borate ester.

7. The method for preparing OLED blue light material according to claim 3, characterized in that, The alkali mentioned is potassium carbonate or cesium carbonate.

8. An OLED light-emitting device, characterized in that, The anode / hole injection layer / hole transport layer / light emission layer / electron transport layer / electron injection layer / cathode, wherein the light emission layer is made of any of the OLED blue light materials described in claims 1-2, exhibiting high-performance blue light emission.

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