A Class of Organic Semiconductor Materials Containing Pyrazine, Preparation Methods Thereof and Applications

Abstract

The present invention belongs to the technical field of organic optoelectronic functional materials, and discloses a class of pyrazine-containing deep blue light and near ultraviolet light organic semiconductor materials, a preparation method thereof, and applications thereof. The pyrazine-containing organic semiconductor material has the following structure: #imgabs0# wherein, Ar1 and Ar2 are weak electron-donating groups. By connecting weak electron-donating groups to pyrazine, the present invention regulates the photophysical properties of pyrazine derivatives, so that the organic semiconductor material has a high triplet energy level in the solid state. The organic semiconductor material prepared by the present invention can be used as a guest material and a host material of a light-emitting layer; the energy level structure of the material has good regulation characteristics, so as to balance the electron / hole transport ability of the material, which is beneficial to the simplification of the device structure. When used as a host material, by selecting a suitable multiple resonance delayed fluorescence molecule as the guest material of the light-emitting layer, an organic electroluminescent device with excellent optoelectronic properties can be prepared, which has wide applications in the field of organic electroluminescence.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic optoelectronic functional materials, and particularly relates to a class of organic semiconductor materials containing pyrazine, a preparation method thereof, and applications thereof. Background Art

[0002] Organic Light Emitting Diode (OLED) has the characteristics of low driving voltage, fast response speed, high contrast, wide color gamut, thin and light, flexible, etc., and has broad application prospects in the fields of display and lighting. At present, based on the three primary colors of red, green, and blue organic light emitting materials, the commercial requirements have been met. However, in order to meet the requirements of a wider color gamut, richer display colors, and higher resolution, for blue light materials, it is necessary to satisfy deeper blue light emission and a narrower full width at half maximum. The light color and the full width at half maximum are two important factors determining the CIE y value.

[0003] On the one hand, to achieve short-wavelength emission, it is necessary to strictly limit the conjugation length of the molecule and avoid strong intramolecular charge transfer (CT) states. Generally, the effective conjugation length of the molecule can be limited by interrupting the conjugation through non-linear linkages. Secondly, weak donors and acceptors are selected to avoid the formation of strong intramolecular charge transfer. On the other hand, to achieve narrow emission, the molecule also needs to have an appropriate rigid structure to avoid the structural relaxation caused by too large conformational changes of the molecule in the excited state, thereby broadening the emission spectrum. For narrow-emission materials, in 2016, the Hatakeyama research group proposed the "multiple resonance (MR)" effect based on the B-N polycyclic structure. Such materials have a rigid polycyclic structure and the existence of non-bonding orbitals can suppress the vibrational coupling between the ground state and the excited state, successfully limiting the full width at half maximum of organic blue-light materials within 40 nm. This is a huge breakthrough compared to the wide full width at half maximum (70 - 100 nm) exhibited by traditional D-A type TADF materials. Since MR-TADF materials usually have a very rigid molecular structure, there are strong π-π interactions between molecules in the aggregated state, greatly quenching their solid-state luminescence quantum efficiency. Therefore, when such materials are applied to OLEDs, appropriate hosts are usually selected to prepare doped devices by doping MR-TADF materials at low concentrations to overcome the serious fluorescence quenching problem in the aggregated state (Jiang, P.; Miao, J.; Cao, X.; Xia, H.; Pan, K.; Hua, T.; Lv, X.; Huang, Z.; Zou, Y.; Yang, C. Quenching-Resistant Multiresonance TADF Emitter Realizes 40% External Quantum Efficiency in Narrowband Electroluminescence at High Doping Level. Adv. Mater. 2022, 34, 2106954.). However, sensitizing hosts for highly efficient MR-TADF are still scarce and urgently need to be developed.

[0004] As an electron-withdrawing group, pyrazine has the characteristics of easy structural modification and has been widely used in OLEDs. However, organic light-emitting materials that achieve highly efficient deep blue and near-ultraviolet light emission based on the pyrazine structure are still scarce. Therefore, by introducing a weak donor at the meta-position of pyrazine to construct D-A-D, the effective conjugation length of the molecule and the formation of strong CT states are limited, realizing deep blue and near-ultraviolet light emission, which is a light color that is difficult to achieve for TADF materials. In addition, such materials also have high exciton utilization efficiency and high-level molecular orientation mainly through the "hot exciton" channel, and have great application potential in highly efficient blue and near-ultraviolet OLEDs. Summary of the Invention

[0005] To overcome the above-mentioned deficiencies of the existing technologies, the object of the present invention is to provide a class of pyrazine-containing deep blue light and near-ultraviolet light organic semiconductor materials, their preparation methods and applications.

[0006] The object of the present invention is to provide a pyrazine-containing deep blue light and near-ultraviolet light organic semiconductor material system. This type of luminescent material has deep blue light and near-ultraviolet light emission; this type of luminescent material also has the characteristics of "hot excitons", which can break through the 25% exciton utilization rate limit of fluorescent materials, and highly efficient and low-efficiency roll-off deep blue light and near-ultraviolet organic electroluminescent devices can be prepared; in addition, this type of material can also be used as the host material for highly efficient green light and yellow light MR-TADF. Here, the green light MR-TADF molecule BN2 and the yellow light MR-TADF molecule BN3 reported in the literature are selected as the guest molecules respectively.

[0007] Another object of the present invention is to provide a preparation method for the above-mentioned pyrazine-containing deep blue light and near-ultraviolet light organic semiconductor materials. The method of the present invention has simple technology and easily available raw materials.

[0008] Another object of the present invention is to provide the application of the above-mentioned pyrazine-containing deep blue light and near-ultraviolet light organic semiconductor materials in the field of organic electroluminescence, especially in the application of preparing the light-emitting layer of organic light-emitting diodes.

[0009] The object of the present invention is achieved by at least one of the following technical solutions.

[0010] A class of pyrazine-containing deep blue light and near-ultraviolet light organic semiconductor materials provided by the present invention has the following chemical structural formula:

[0011]

[0012] Ar1 and Ar2 are weak electron-donating groups (where Ar1 and Ar2 can be the same or different).

[0013] Furthermore, the weak electron-donating groups of Ar1 and Ar2 are one of the following structural formulas 1-6:

[0014]

[0015] A preparation method for a class of pyrazine-containing deep blue light and near-ultraviolet light organic semiconductor materials provided by the present invention includes the following steps:

[0016] (1) When Ar1 and Ar2 are the same (the deep blue light and near-ultraviolet light organic semiconductor material is a symmetric compound),

[0017] Compound 1 is subjected to a cyclization reaction with ammonium acetate to obtain a dibromo-substituted compound containing pyrazine; the dibromo-substituted compound containing pyrazine is directly subjected to a one-step Suzuki cross-coupling with an arylboronic acid or borate ester to obtain an organic semiconductor material containing pyrazine.

[0018] (2) When Ar1 and Ar2 are different (the deep blue light and near ultraviolet light organic semiconductor materials are asymmetric compounds),

[0019] Compound 1 is subjected to a cyclization reaction with ammonium acetate to obtain a dibromo-substituted compound containing pyrazine; the dibromo-substituted compound containing pyrazine is subjected to a Suzuki cross-coupling with an arylboronic acid or borate ester to obtain an aryl bromide compound, and the aryl bromide compound is further subjected to a Suzuki cross-coupling with another arylboronic acid or borate ester to obtain an organic semiconductor material containing pyrazine;

[0020] The said Compound 1 is of Formula I, the structural formula of the dibromo-substituted compound containing pyrazine is of Formula II, and the structural formula of the aryl bromide compound is of Formula III:

[0021]

[0022] Further, the preparation method of Compound 1 in step (1) and step (2) is: using 4-bromopropiophenone and elemental iodine as raw materials, an α-keto oxidation reaction occurs in dimethyl sulfoxide solvent to obtain Compound 1;

[0023] Further preferably, the molar ratio of 4-bromopropiophenone to elemental iodine is 5:1 - 5:2; the conditions of the α-keto oxidation reaction are: heating at 70 - 80 °C for 12 - 24 h; after the reaction, sodium thiosulfate is used to quench the unreacted elemental iodine, and the reaction solution gradually changes from black-red to light yellow.

[0024] Further, the molar ratio of Compound 1 to ammonium acetate in step (1) and step (2) is 1:2.3 - 1:3;

[0025] Further, the molar ratio of the dibromo-substituted compound containing pyrazine to the arylboronic acid or borate ester in step (1) is 1:3 - 1:4.

[0026] Further, the molar ratio of the dibromo-substituted compound containing pyrazine to the arylboronic acid or borate ester in step (2) is 1:1 - 1:2, and the molar ratio of the aryl bromide compound to the arylboronic acid or borate ester is 1:1 - 1:2.

[0027] Furthermore, the reaction conditions for the cyclization reaction in steps (1) and (2) are as follows: using stannous chloride dihydrate as a catalyst, heating and stirring at 80 - 90 °C for 4 - 6 h; the conditions for the Suzuki cross-coupling reaction are: temperature 80 - 90 °C, time 8 - 12 h, the solvent is toluene, ethanol and water, and the catalysts required for the reaction are tetrakis(triphenylphosphine)palladium and potassium carbonate.

[0028] The application of a class of pyrazine-containing organic semiconductor materials provided by the present invention in the preparation of organic electroluminescent devices.

[0029] Furthermore, the pyrazine-containing organic semiconductor material is used as the guest material of the light-emitting layer; the organic electroluminescent device is a doped device.

[0030] Furthermore, the pyrazine-containing organic semiconductor material is used as the host material of the light-emitting layer; the organic electroluminescent device is a doped device. The light-emitting layer is formed by vacuum evaporation.

[0031] Further preferably, the guest material of the light-emitting layer of the organic electroluminescent device is an MR-TADF material; the MR-TADF material is green light BN2 or yellow light BN3. The light-emitting layer is formed by vacuum evaporation.

[0032] More preferably, the structural formula of the green light BN2 is Formula IV; the structural formula of the yellow light BN3 is Formula V;

[0033]

[0034] The present invention selects pyrazine as the building block of the material, so that the material can emit deep blue light and near-ultraviolet fluorescence; by connecting different weak electron-donating groups to pyrazine, the photophysical properties of pyrazine derivatives are regulated, so that the organic semiconductor material has a high triplet energy level in the solid state. The organic semiconductor material prepared by the present invention can be used as the host material of the light-emitting layer, and the energy level structure of the material has good regulation characteristics, so as to balance the electron / hole transport ability of the material, which is beneficial to the simplification of the device structure. Selecting a suitable multiple resonance delayed fluorescence molecule as the guest material of the light-emitting layer can prepare an organic electroluminescent device with excellent optoelectronic properties and has a wide application in the field of organic electroluminescence.

[0035] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0036] (1) The pyrazine-containing deep blue light and near ultraviolet light organic semiconductor material of the present invention can be used to prepare an organic electroluminescent device with high efficiency and low efficiency roll-off. The absorption and emission spectra can be adjusted and the luminescence physics and energy level characteristics can be regulated by changing the structure of the aryl unit, and there is a large operating space. In the embodiments of the present invention, an emission in the range of 387 - 417 nm is achieved through the construction of different structures;

[0037] (2) The synthesis method of the pyrazine-containing deep blue light and near ultraviolet light organic semiconductor material of the present invention is simple and the raw materials are easily available. The obtained material has good thermal stability, is easy to sublime, and has excellent electrochemical stability;

[0038] (3) The pyrazine-containing deep blue light and near ultraviolet light organic semiconductor material of the present invention is used in the light-emitting layer of an organic light-emitting diode, and can be used as a sensitizing host for high-efficiency green and yellow MR-TADF materials. Its comprehensive performance is excellent and it can be widely used in the fields of organic electroluminescence, etc. For example, in Example 3 of the present invention, the maximum external quantum efficiency of the doped device of compound VDMP-TPA reached 9.03%, and it had a maximum brightness of 10810 cd m -2 At the same time, as a sensitizing host for the BN3 yellow MR-TADF material, the prepared doped device only showed the emission of the guest molecule BN3, indicating that the Forster energy transfer was very complete, and the maximum external quantum efficiency reached 37.16%, and the maximum brightness was as high as 36870 cd m -2 . Description of the Drawings

[0039] Figure 1a is the photoluminescence spectrum of the compound VDMP-PhCz prepared in Example 1 in toluene solution and doped film state;

[0040] Figure 1b is the photoluminescence spectrum of the compound VDMP-36PhCz prepared in Example 2 in toluene solution and doped film state;

[0041] Figure 1c is the photoluminescence spectrum of the compound VDMP-TPA prepared in Example 3 in toluene solution and doped film state;

[0042] Figure 2a is the electroluminescence spectrum of the doped OLEDs device obtained from the compound VDMP-PhCz prepared in Example 1;

[0043] Figure 2b is the J-V-L curve of the doped OLEDs device obtained from the compound VDMP-PhCz prepared in Example 1;

[0044] Figure 2cThe graph showing the variation of the efficiency of the doped OLEDs device obtained with the compound VDMP-PhCz prepared in Example 1 with respect to brightness;

[0045] Figure 3a The electroluminescence spectrum of the doped OLEDs device obtained with the compound VDMP-36PhCz prepared in Example 2;

[0046] Figure 3b The J-V-L curve of the doped OLEDs device obtained with the compound VDMP-36PhCz prepared in Example 2;

[0047] Figure 3c The graph showing the variation of the efficiency of the doped OLEDs device obtained with the compound VDMP-36PhCz prepared in Example 2 with respect to brightness;

[0048] Figure 4a The electroluminescence spectrum of the doped OLEDs device obtained with the compound VDMP-TPA prepared in Example 3;

[0049] Figure 4b The J-V-L curve of the doped OLEDs device obtained with the compound VDMP-TPA prepared in Example 3;

[0050] Figure 4c The graph showing the variation of the efficiency of the doped OLEDs device obtained with the compound VDMP-TPA prepared in Example 3 with respect to brightness;

[0051] Figure 5a The electroluminescence spectrum of the doped OLEDs device obtained with the compound VDMP-PhCz prepared in Example 1 as the sensitizing host and the green light MR-TADF material BN2 as the guest;

[0052] Figure 5b The J-V-L curve of the doped OLEDs device obtained with the compound VDMP-PhCz prepared in Example 1 as the sensitizing host and the green light MR-TADF material BN2 as the guest;

[0053] Figure 5c The graph showing the variation of the efficiency of the doped OLEDs device obtained with the compound VDMP-PhCz prepared in Example 1 as the sensitizing host and the green light MR-TADF material BN2 as the guest with respect to brightness;

[0054] Figure 6a The electroluminescence spectrum of the doped OLEDs device obtained with the compound VDMP-36PhCz prepared in Example 2 as the sensitizing host and the yellow light MR-TADF material BN3 as the guest;

[0055] Figure 6b The J-V-L curve diagram of the doped OLEDs device obtained by using the compound VDMP-36PhCz prepared in Example 2 as the sensitizing host and the yellow MR-TADF material BN3 as the guest;

[0056] Figure 6c The curve diagram showing the change of the efficiency of the doped OLEDs device with luminance, obtained by using the compound VDMP-36PhCz prepared in Example 2 as the sensitizing host and the yellow MR-TADF material BN3 as the guest;

[0057] Figure 7a The electroluminescence spectrum diagram of the doped OLEDs device obtained by using the compound VDMP-TPA prepared in Example 3 as the sensitizing host and the yellow MR-TADF material BN3 as the guest;

[0058] Figure 7b The J-V-L curve diagram of the doped OLEDs device obtained by using the compound VDMP-TPA prepared in Example 3 as the sensitizing host and the yellow MR-TADF material BN3 as the guest;

[0059] Figure 7c The curve diagram showing the change of the efficiency of the doped OLEDs device with luminance, obtained by using the compound VDMP-TPA prepared in Example 3 as the sensitizing host and the yellow MR-TADF material BN3 as the guest. Detailed implementation manners

[0060] The following further illustrates the specific implementation of the present invention in combination with examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that for the processes not specifically described in detail below, those skilled in the art can implement or understand them with reference to the prior art. The reagents or instruments not indicating the manufacturer are regarded as conventional products that can be obtained through commercial purchase.

[0061] Example 1: Preparation of near-ultraviolet organic semiconductor material (VDMP-PhCz) containing pyrazine

[0062]

[0063] Reaction equation (1):

[0064]

[0065] (1) Synthesis of Intermediate 2: Weigh (6.39 g, 30 mmol) of 4-bromopropiophenone and elemental iodine (1.524 g, 6 mmol) into a 250 ml single-necked flask, add 60 ml of DMSO and dissolve it completely. After complete dissolution, start stirring and heat at 70 °C for 24 h. After the reaction is completed, add an excessive amount of saturated aqueous sodium thiosulfate solution to quench the unreacted iodine. The reaction solution gradually changes from dark red to light yellow. Then, extract it with EA and distilled water, combine the organic phases, concentrate by rotary evaporation, add silica gel powder, and separate by column chromatography. The eluent is DCM / PE (volume ratio: 1:1) to obtain a light yellow oily product with a yield of 66.7%;

[0066] (2) Synthesis of Intermediate 3: Weigh Intermediate 2 (4.56 g, 20 mmol) and ammonium acetate (3.542 g, 46 mmol) into a 100 ml single-necked flask, add the catalyst stannous chloride dihydrate (0.45 g, 2 mmol), heat and stir at 80 °C for 4 h. After the reaction is completed, it is orange-yellow and viscous. Then, add DCM and distilled water for extraction, combine the organic phases, concentrate by rotary evaporation to remove DCM, add anhydrous ethanol to wash the precipitated yellowish-white solid, filter by suction. Dissolve the obtained filter cake completely in a small amount of DCM, add silica gel powder and spin dry, and separate by column chromatography. The eluent is DCM / PE (volume ratio: 1:6) to obtain a white solid with a yield of 11.7%;

[0067] (3) Synthesis of VDMP-PhCz: Add Intermediate 3 (0.416 g, 1 mmol), Intermediate 4 (1.148 g, 4 mmol), tetrakis(triphenylphosphine)palladium (0.12 g, 0.1 mmol) and potassium carbonate (1.10 g, 8 mmol) into a 250 ml two-necked round-bottom flask, evacuate, and replace with nitrogen three times to make the reaction proceed under a nitrogen atmosphere to prevent the tetrakis(triphenylphosphine)palladium catalyst from deteriorating. Then, add the solvent (toluene:ethanol:water = 3:1:1 (volume ratio)) to dissolve it with a syringe, heat and stir at 90 °C for 12 h. After the reaction is completed, evaporate to remove toluene and ethanol in the reaction system by rotary evaporation, extract with DCM and distilled water, combine the organic phases, add anhydrous sodium sulfate for drying, concentrate by rotary evaporation, add silica gel powder and spin dry, and separate by column chromatography. The eluent is DCM / PE (volume ratio is 1:4) to obtain a white powder with a yield of 86%; 1 H NMR (400 MHz, CD2Cl2) δ 8.21–8.14 (m, 4H), 7.99–7.85 (m, 12H), 7.73 (d, J = 7.9 Hz, 4H), 7.55–7.42 (m, 8H), 7.32 (dd, J = 11.8, 6.9 Hz, 4H), 3.01 (s, 6H) (It should be noted that: 13 13C NMR could not be obtained because the product has poor solubility in organic solvents).

[0068] Example 2: Preparation of Near-ultraviolet Organic Semiconductor Material (VDMP-3,6PhCz) Containing Pyrazine

[0069]

[0070] Reaction Equation (2):

[0071]

[0072] (1) The same as Example 1;

[0073] (2) The same as Example 1;

[0074] (3) Synthesis of VDMP-3,6PhCz: Add intermediate 3 (0.416 g, 1 mmol), intermediate 4 (1.148 g, 4 mmol), tetrakis(triphenylphosphine)palladium (0.12 g, 0.1 mmol) and potassium carbonate (1.10 g, 8 mmol) into a 250 ml two-necked round-bottom flask. Evacuate the flask and replace the gas with nitrogen three times to make the reaction under a nitrogen atmosphere to prevent the deterioration of the tetrakis(triphenylphosphine)palladium catalyst. Then add the solvent (toluene:ethanol:water = 3:1:1 (volume ratio)) to dissolve with a syringe, heat and stir at 90 °C for 12 h. After the reaction is completed, rotary evaporate to remove toluene and ethanol in the reaction system, extract with DCM and distilled water, combine the organic phases, add anhydrous sodium sulfate for drying, rotary evaporate and concentrate, then add silica gel powder and rotary dry. Separate by column chromatography with an eluent of DCM / PE (volume ratio of 1:4) to obtain a white powder with a yield of 83%; 1 H NMR (400 MHz, CD2Cl2) δ 8.48 (s, 2H), 8.24 (d, J = 7.7 Hz, 2H), 7.96–7.74 (m, 10H), 7.73–7.58 (m, 8H), 7.57–7.40 (m, 8H), 7.33 (dt, J = 7.9, 4.1 Hz, 2H), 2.89 (s, 6H) (It should be noted that: 13 13C NMR could not be obtained because the product has poor solubility in organic solvents).

[0075] Example 3: Preparation of Deep Blue Light-emitting Organic Semiconductor Material (VDMP-TPA) Containing Pyrazine

[0076]

[0077] Reaction Equation (3):

[0078]

[0079] (1) The same as Example 1;

[0080] (2)Same as Example 1;

[0081] (3)Synthesis of VDMP-TPA: Add intermediate 3 (0.416 g, 1 mmol), intermediate 4 (1.148 g, 4 mmol), tetrakis(triphenylphosphine)palladium (0.12 g, 0.1 mmol) and potassium carbonate (1.10 g, 8 mmol) into a 250 ml two-necked round-bottom flask. Evacuate the air and replace it with nitrogen three times to make the reaction under a nitrogen atmosphere to prevent the deterioration of the tetrakis(triphenylphosphine)palladium catalyst. Then add the solvent (toluene:ethanol:water = 3:1:1 (volume ratio)) to dissolve with a syringe, heat and stir at 90 °C for 12 h. After the reaction is completed, rotary evaporate to remove toluene and ethanol in the reaction system, extract with DCM and distilled water, combine the organic phases, add anhydrous sodium sulfate for drying, rotary evaporate and concentrate, then add silica gel powder and rotary dry. Separate by column chromatography with an eluent of DCM / PE (volume ratio 1:4) to obtain a white powder with a yield of 85%; 1 H NMR (500 MHz, CD2Cl2) δ 7.79–7.66 (m, 8H), 7.62–7.52 (m, 4H), 7.36–7.22 (m, 8H), 7.18–7.10 (m, 12H), 7.06 (t, J = 7.4 Hz, 4H), 2.73 (s, 6H). 13 C NMR (101 MHz, CD2Cl2) δ 150.65, 148.59, 148.19, 148.14, 141.20, 137.75, 134.72, 130.21, 129.87, 128.26, 126.87, 125.10, 124.24, 123.67, 22.92.

[0082] Example 4: Photoluminescence spectrum test of pyrazine-containing near-ultraviolet organic semiconductor materials in toluene solution and doped film state

[0083] Weigh 3.71 mg of the VDMP-PhCz compound prepared in Example 1 and dissolve it in 5 mL of spectroscopic pure toluene (Tol) to prepare a solution with a concentration of 10 -3The test sample was at a concentration of mol / L. 30 μL of the VDMP-PhCz test sample was added to a 5 mL centrifuge tube, and then 2970 μL of spectroscopically pure toluene was added. The emission spectrum of the test sample was measured at the corresponding excitation wavelength, and through data processing, the photoluminescence spectrum of the compound VDMP-PhCz in solution was obtained. Then, through a temperature-raising procedure in a glove box, it was vacuum-evaporated onto a 1x1 quartz wafer together with the common host material 2,8-bis(diphenylphosphoryl)dibenz[b,d]furan (PPF) to form a film. The doping concentration was 30 wt%, and the emission spectrum of the test sample was measured at the corresponding excitation wavelength. Through data processing, the photoluminescence spectrum of the compound VDMP-PhCz in the doped thin film state was obtained. The photoluminescence spectrum of the near-ultraviolet organic semiconductor material containing pyrazine is shown in Figure 1a . It can be seen from Figure 1a that the solution emission peak of the near-ultraviolet organic semiconductor material containing pyrazine is 387 nm, the full width at half maximum is only 50 nm, and the absolute quantum efficiency is 62.3%. The emission peak of its doped thin film is 404 nm, showing a red shift of about 17 nm compared to the solution state, and the full width at half maximum is slightly broadened to 60 nm, probably due to the relatively large polarity of the selected host material PPF.

[0084] The compound VDMP-36PhCz prepared in Example 2 and the compound VDMP-TPA prepared in Example 3 were also tested as above. The testing method was the same as that of the compound VDMP-PhCz. The photoluminescence spectra of the compound VDMP-36PhCz and the compound VDMP-TPA in Tol solution and doped thin film states were obtained respectively. The results are as shown in Figure 1b and Figure 1c . For the compound VDMP-36PhCz (solution emission peak is 390 nm, full width at half maximum is only 49 nm, absolute quantum efficiency is 62.4%, and its thin film emission peak is 412 nm), and the compound VDMP-TPA (solution emission peak is 417 nm, full width at half maximum is only 54 nm, absolute quantum efficiency is 75.9%, and the thin film emission peak is 444 nm), there are red shifts of about 22 nm and 27 nm respectively in the thin film state.

[0085] Example 5: OLED device performance of the near-ultraviolet organic semiconductor material (VDMP-PhCz) containing pyrazine

[0086] Using the near-ultraviolet organic semiconductor material VDMP-PhCz (near-ultraviolet wavelength = 387 nm, full width at half maximum is 50 nm) prepared in Example 1 as the light-emitting material, a doped device was prepared, and its device performance was tested and characterized. The results are shown in Figure 2a and Figure 2b and Figure 2c .

[0087] Doped device structure: ITO / HATCN(5nm) / TAPC(40nm) / TcTa(5nm) / mcp(5nm) / EML(20nm) / PPF(5nm) / TmPyPB(30nm) / LiF(1nm) / Al(120nm), where EML is PPF:30wt% VDMP-PhCz.

[0088] Figure 2a It is the electroluminescence spectrum diagram of the doped OLEDs device prepared by using the near-ultraviolet organic semiconductor material containing pyrazine in Example 1. It can be seen from the figure that the electroluminescence peak position of the doped device based on VDMP-PhCz is 392nm.

[0089] Figure 2b It is the J-V-L curve diagram of the doped OLEDs device prepared by using the near-ultraviolet organic semiconductor material containing pyrazine in Example 1. It can be seen from the figure that the doped device based on VDMP-PhCz has good maximum brightness and low turn-on voltage in the near-ultraviolet light region, which are 2064cd / m 2 , 3.2V.

[0090] Figure 2c It is the curve diagram of the efficiency of the doped OLEDs device prepared by using the near-ultraviolet organic semiconductor material containing pyrazine in Example 1 changing with brightness. It can be seen from the figure that the doped device based on VDMP-PhCz has excellent efficiency and low efficiency roll-off. Its maximum external quantum efficiency is 7.37%; when the brightness is 1000cd / m 2 , the external quantum efficiency is 4.93%. The maximum utilization rate of electro-excited excitons exceeds the limit value of traditional fluorescent materials and reaches 67.7%.

[0091] Example 6: Performance of OLEDs device of near-ultraviolet organic semiconductor material containing pyrazine (VDMP-36PhCz)

[0092] The near-ultraviolet organic semiconductor material VDMP-36PhCz (near-ultraviolet wavelength = 390nm, full width at half maximum is 49nm) prepared by using Example 2 is used as the luminescent material to prepare a doped device, and its device performance is tested and characterized. The results are shown in Figure 3a , Figure 3b and Figure 3c .

[0093] Doped device structure: ITO / HATCN(5nm) / TAPC(40nm) / TcTa(5nm) / mcp(5nm) / EML(20nm) / PPF(5nm) / TmPyPB(30nm) / LiF(1nm) / Al(120nm), where EML is PPF:30wt% VDMP-36PhCz.

[0094] Figure 3a It is the electroluminescence spectrum diagram of the doped OLEDs device prepared by using the near-ultraviolet organic semiconductor material containing pyrazine in Example 2. It can be seen from the figure that the electroluminescence peak position of the doped device based on VDMP-36PhCz is 404nm.

[0095] Figure 3b It is the J-V-L curve diagram of the doped OLEDs device prepared by using the near-ultraviolet organic semiconductor material containing pyrazine in Example 2. It can be seen from the figure that the doped device based on VDMP-36PhCz has good maximum brightness and low turn-on voltage in the near-ultraviolet light region, which are 2295cd / m 2 , 3.2V.

[0096] Figure 3c It is the curve diagram of the efficiency of the doped OLEDs device prepared by using the near-ultraviolet organic semiconductor material containing pyrazine in Example 2 changing with brightness. It can be seen from the figure that the doped device based on VDMP-36PhCz has excellent efficiency and low efficiency roll-off. Its maximum external quantum efficiency is 7.55%; when the brightness is 1000cd / m 2 , the external quantum efficiency is 5.37%. The maximum utilization rate of electro-excited excitons exceeds the limit value of traditional fluorescent materials and reaches 96.3%.

[0097] Example 7: Performance of OLEDs device with deep blue light organic semiconductor material containing pyrazine (VDMP-TPA)

[0098] Using the deep blue light organic semiconductor material VDMP-TPA containing pyrazine (deep blue light wavelength = 417nm, full width at half maximum is 54nm) prepared in Example 3 as the luminescent material to prepare a doped device, and testing and characterizing its device performance. The results are shown in Figure 4a , Figure 4b and Figure 4c .

[0099] Doped device structure: ITO / HATCN(5nm) / TAPC(40nm) / TcTa(5nm) / mcp(5nm) / EML(20nm) / PPF(5nm) / TmPyPB(30nm) / LiF(1nm) / Al(120nm), where EML is PPF:30wt% VDMP-TPA.

[0100] Figure 4a It is the electroluminescence spectrum diagram of the doped OLEDs device prepared by using the pyrazine-containing deep blue organic semiconductor material in Example 3. It can be seen from the figure that the electroluminescence peak position of the doped device based on VDMP-TPA is 442 nm.

[0101] Figure 4b It is the J-V-L curve diagram of the doped OLEDs device prepared by using the pyrazine-containing deep blue organic semiconductor material in Example 3. It can be seen from the figure that the doped device based on VDMP-TPA has good maximum brightness and low turn-on voltage in the near ultraviolet region, which are 10810 cd / m 2 , 2.8 V.

[0102] Figure 4c It is the curve diagram of the efficiency of the doped OLEDs device prepared by using the pyrazine-containing deep blue organic semiconductor material in Example 3 changing with brightness. It can be seen from the figure that the doped device based on VDMP-TPA has excellent efficiency and low efficiency roll-off. Its maximum external quantum efficiency is 9.03%; when the brightness is 1000 cd / m 2 , the external quantum efficiency is 7.04%. The maximum utilization rate of electro-excited excitons exceeds the limit value of traditional fluorescent materials and reaches 57.4%.

[0103] Example 8: Performance of the sensitizing host OLEDs device of the pyrazine-containing near ultraviolet organic semiconductor material (VDMP-PhCz) as the green light MR-TADF material BN2

[0104] Using the pyrazine-containing near ultraviolet organic semiconductor material VDMP-PhCz prepared in Example 1 as the sensitizing host and the green light MR-TADF material BN2 as the guest, a doped device was prepared, and its device performance was tested and characterized. The results are shown in Figure 5a , Figure 5b and Figure 5c .

[0105] Doped device structure: ITO / HATCN(5nm) / TAPC(50nm) / TcTa(15nm) / mcp(10nm) / EML(20nm) / PPF(10nm) / TmPyPB(30nm) / LiF(1nm) / Al(120nm), where EML is VDMP-PhCz:3wt%BN2.

[0106] Figure 5a It is the electroluminescence spectrum diagram of the doped OLEDs device prepared by using the near-ultraviolet organic semiconductor material containing pyrazine in Example 1 as the sensitizing host of the green-light MR-TADF material BN2. As can be seen from the figure, there is only the emission peak of the BN2 guest molecule, the main peak is at 546 nm, and the full width at half maximum is 41 nm, which is a narrow emission characteristic with a multiple resonance effect. The emission of the sensitizing host VDMP-PhCz is not observed, indicating that the energy transfer between the host and the guest is very sufficient.

[0107] Figure 5b It is the J-V-L curve diagram of the doped OLEDs device prepared by using the near-ultraviolet organic semiconductor material containing pyrazine in Example 1 as the sensitizing host of the green-light MR-TADF material BN2. As can be seen from the figure, the doped device has excellent maximum brightness and low turn-on voltage in the green-light region, which are 16880 cd / m 2 , 3.0 V respectively.

[0108] Figure 5c It is the curve diagram of the efficiency of the doped OLEDs device prepared by using the near-ultraviolet organic semiconductor material containing pyrazine in Example 1 as the sensitizing host of the green-light MR-TADF material BN2 changing with brightness. As can be seen from the figure, the doped device has very high efficiency and the efficiency roll-off is inhibited to a certain extent. Its maximum external quantum efficiency is 34.93%; when the brightness is 100 cd / m 2 , the external quantum efficiency still remains at 24.99%.

[0109] Example 9: Performance of OLEDs device with near-ultraviolet organic semiconductor material containing pyrazine (VDMP-36PhCz) as the sensitizing host of yellow-light MR-TADF material BN3

[0110] Using the near-ultraviolet organic semiconductor material VDMP-36PhCz prepared in Example 2 as the sensitizing host and the yellow-light MR-TADF material BN3 as the guest, a doped device was prepared, and its device performance was tested and characterized. The results are shown in Figure 6a , Figure 6b and Figure 6c .

[0111] Doped device structure: ITO / HATCN(5nm) / TAPC(50nm) / TcTa(15nm) / mcp(10nm) / EML(20nm) / PPF(10nm) / TmPyPB(30nm) / LiF(1nm) / Al(120nm), where EML is VDMP-36PhCz:3wt%BN3.

[0112] Figure 6a It is the electroluminescence spectrum diagram of the doped OLEDs device prepared by using the near-ultraviolet organic semiconductor material containing pyrazine in Example 2 as the sensitizing host of the yellow-light MR-TADF material BN3. As can be seen from the figure, there is only the emission peak of the BN3 guest molecule, the main peak is at 568 nm, and the full width at half maximum is 39 nm, which is a narrow emission characteristic with multiple resonance effects. The emission of the sensitizing host VDMP-36PhCz is not observed, indicating that the energy transfer between the host and the guest is very sufficient.

[0113] Figure 6b It is the J-V-L curve diagram of the doped OLEDs device prepared by using the near-ultraviolet organic semiconductor material containing pyrazine in Example 2 as the sensitizing host of the yellow-light MR-TADF material BN3. As can be seen from the figure, this doped device has excellent maximum brightness and low turn-on voltage in the yellow-light region, which are 27370 cd / m 2 , 3.4 V respectively.

[0114] Figure 6c It is the curve diagram of the efficiency of the doped OLEDs device prepared by using the near-ultraviolet organic semiconductor material containing pyrazine in Example 2 as the sensitizing host of the yellow-light MR-TADF material BN3 changing with brightness. As can be seen from the figure, this doped device has very high efficiency and the efficiency roll-off is inhibited to a certain extent. Its maximum external quantum efficiency is 32.64%; when the brightness is 100 cd / m 2 , the external quantum efficiency still remains at 23.14%.

[0115] Example 10: Performance of OLEDs device with the deep blue light organic semiconductor material containing pyrazine (VDMP-TPA) as the sensitizing host of the yellow-light MR-TADF material BN3

[0116] Using the deep blue light organic semiconductor material VDMP-TPA containing pyrazine prepared in Example 3 as the sensitizing host and the yellow-light MR-TADF material BN3 as the guest, a doped device was prepared, and its device performance was tested and characterized. The results are shown in Figure 7a , Figure 7b and Figure 7c .

[0117] Doped device structure: ITO / HATCN(5nm) / TAPC(50nm) / TcTa(15nm) / mcp(10nm) / EML(20nm) / PPF(10nm) / TmPyPB(30nm) / LiF(1nm) / Al(120nm), where EML is VDMP-TPA: 3wt% BN3.

[0118] Figure 7a It is the electroluminescence spectrum diagram of the doped OLEDs device prepared by using the deep blue organic semiconductor material containing pyrazine in Example 3 as the sensitizing host of the yellow light MR-TADF material BN3. As can be seen from the figure, there is only the emission peak of the BN3 guest molecule, the main peak is at 568 nm, and the full width at half maximum is 38 nm, which is a narrow emission characteristic with a multiple resonance effect. The emission of the sensitizing host VDMP-TPA is not observed, indicating that the energy transfer between the host and the guest is very sufficient.

[0119] Figure 7b It is the J-V-L curve diagram of the doped OLEDs device prepared by using the deep blue organic semiconductor material containing pyrazine in Example 3 as the sensitizing host of the yellow light MR-TADF material BN3. As can be seen from the figure, the doped device has excellent maximum brightness and low turn-on voltage in the yellow light region, which are 36870 cd / m 2 , 3.0 V respectively.

[0120] Figure 7c It is the curve diagram of the efficiency of the doped OLEDs device prepared by using the deep blue organic semiconductor material containing pyrazine in Example 3 as the sensitizing host of the yellow light MR-TADF material BN3 changing with the brightness. As can be seen from the figure, the doped device has very high efficiency and the efficiency roll-off is inhibited to a certain extent. Its maximum external quantum efficiency is 37.16%; when the brightness is 100 cd / m 2 , the external quantum efficiency still remains at 26.91%.

[0121] The above data show that the present invention uses pyrazine as the building block of the material. By connecting a weak electron-donating group to the meta position of pyrazine, near-ultraviolet and deep blue light molecules with "hot exciton" characteristics can be obtained. The doped near-ultraviolet and deep blue light OLEDs devices prepared with such materials as the light-emitting layer have high efficiency and small efficiency roll-off. In addition, the green and yellow light OLEDs devices prepared with such materials as the sensitizing host of the green and yellow light MR-TADF materials have very excellent maximum external quantum efficiency, and the efficiency roll-off is greatly inhibited. Therefore, such organic semiconductor materials have very broad application prospects in the field of organic electroluminescence.

[0122] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, substitutions, modifications, etc. made by those skilled in the art without departing from the spirit and essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A class of pyrazine-containing organic semiconductor materials, characterized in that, The chemical structural formula is as follows: Ar1 and Ar2 are weak electron-donating groups; The weak electron-donating groups of Ar1 and Ar2 are one of the structures of the following structural formulas 1-6:

2. The preparation method of the pyrazine-containing organic semiconductor material according to claim 1, characterized in that, It includes the following steps: (1) When Ar1 and Ar2 are the same, The compound 1 reacts with ammonium acetate to undergo a ring-forming reaction to obtain a dibromo-substituted compound containing pyrazine; the dibromo-substituted compound containing pyrazine is directly subjected to a one-step Suzuki cross-coupling with an arylboronic acid or borate ester to obtain an organic semiconductor material containing pyrazine; (2) When Ar1 and Ar2 are different, The compound 1 reacts with ammonium acetate to undergo a ring-forming reaction to obtain a dibromo-substituted compound containing pyrazine; the dibromo-substituted compound containing pyrazine undergoes a Suzuki cross-coupling with an arylboronic acid or borate ester to obtain an aryl bromide compound, and the aryl bromide compound undergoes a Suzuki cross-coupling with another arylboronic acid or borate ester to obtain an organic semiconductor material containing pyrazine; The structural formula of the compound 1 is Formula I, the structural formula of the dibromo-substituted compound containing pyrazine is Formula II, and the structural formula of the aryl bromide compound is Formula III:

3. The preparation method according to claim 2, characterized in that, The preparation method of the compound 1 in steps (1) and (2) is: using 4-bromopropiophenone and elemental iodine as raw materials, an α-ketone oxidation reaction occurs in a dimethyl sulfoxide solvent to obtain the compound 1; The molar ratio of the 4-bromopropiophenone to the elemental iodine is 5:1 - 5:2; the conditions of the α-ketone oxidation reaction are: heating at 70 - 80 °C for 12 - 24 h.

4. The preparation method according to claim 2, characterized in that, The molar ratio of the compound 1 to ammonium acetate in steps (1) and (2) is 1:2.3 - 1:3; The molar ratio of the dibromo-substituted compound containing pyrazine to the arylboronic acid or borate ester in step (1) is 1:3 - 1:4; The molar ratio of the dibromo-substituted compound containing pyrazine to the arylboronic acid or borate ester in step (2) is 1:1 - 1:2, and the molar ratio of the aryl bromide compound to the arylboronic acid or borate ester is 1:1 - 1:

2.

5. The preparation method according to claim 2, wherein The reaction conditions of the ring-forming reaction in steps (1) and (2) are: using stannous chloride dihydrate as a catalyst, heating and stirring at 80 - 90 °C for 4 - 6 h; the conditions of the Suzuki cross-coupling reaction are: temperature 80 - 90 °C, time 8 - 12 h, the solvent is toluene, ethanol and water, and the catalyst is tetrakis(triphenylphosphine)palladium and potassium carbonate.

6. Application of the organic semiconductor material containing pyrazine described in claim 1 in the preparation of an organic electroluminescent device.

7. The application according to claim 6, characterized in that, The organic semiconductor material containing pyrazine is used as the guest material of the light-emitting layer; the organic electroluminescent device is a doped device.

8. The application according to claim 6, wherein The organic semiconductor material containing pyrazine is used as the host material of the light-emitting layer; the organic electroluminescent device is a doped device.

9. The application according to claim 8, wherein The guest material of the organic electroluminescent device is an MR-TADF material; the MR-TADF material is green light BN2 or yellow light BN3; The structural formula of the green light BN2 is Formula IV; the structural formula of the yellow light BN3 is Formula V;

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