Electron transport material for organic electroluminescent device and preparation method thereof

Abstract

The invention belongs to the technical field of organic electroluminescent materials, and provides an electron transport material for an organic electroluminescent device and a preparation method of the electron transport material. The 9-alkyl-9-cyanogen-substituted aryl (or cyanogen-substituted nitrogen-containing heteroaryl) fluorene group with a substituent group enables the molecular structure to be twisted and the intermolecular interaction force to be weakened, cyanogen and pyridine enable the compound to have the electron-withdrawing property, electron transmission is facilitated, compounding of electrons and holes in a light-emitting layer is enhanced, and the light-emitting efficiency is improved. Aryl bridged triazine and pyrimidine six-membered nitrogen heterocycle are used for further improving the transmission performance of electrons, and as an electron transmission layer material of the organic electroluminescent device, the organic electroluminescent device has the characteristics of low driving voltage, high luminous efficiency and long service life.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescent materials, and relates to an electron transport material for organic electroluminescent devices, specifically an electron transport material and its preparation method, and an organic electroluminescent device. Background Technology

[0002] OLEDs have garnered widespread attention due to their potential applications in displays and lighting. Materials used in OLEDs include luminescent materials, auxiliary materials, and electrode materials. Auxiliary materials primarily include carrier transport materials, carrier injection materials, and carrier blocking materials. Carrier transport materials consist of hole transport materials and electron transport materials.

[0003] Electron transport materials are primarily responsible for transporting electrons, transferring electron carriers from the metal cathode and injecting them into the light-emitting layer. The performance of electron transport materials has a significant impact on the efficiency of OLED devices. Electron transport materials that can significantly improve the efficiency of OLED devices typically have the following characteristics: (1) The electrochemical reduction of the material is reversible, because the electron conduction process in organic thin films is a series of redox processes; (2) The HOMO and LUMO energy levels of the material are suitable, minimizing the electron injection barrier, resulting in a low turn-on and operating voltage, and preferably also possessing hole blocking capability; (3) The material has a high electron mobility, ensuring that electrons can recombine in the light-emitting layer, thereby increasing the exciton generation rate; (4) The material has a high glass transition temperature (Tg) and thermal decomposition stability, thus avoiding the impact of Joule heating generated during device operation on device lifetime and efficiency; (5) The material should exhibit an amorphous thin film morphology, thereby avoiding light scattering or decay caused by crystals.

[0004] Triazine derivatives, due to the electron-deficient nature of the triazine ring, are excellent electron acceptors. Compounds containing triazine groups can effectively improve the electron transport properties of molecules. Furthermore, the triazine group can significantly enhance the thermodynamic and morphological stability of molecules. Therefore, electron-deficient triazine derivatives have attracted considerable attention and are frequently used as electron transport groups.

[0005] Currently, the performance of high-efficiency and stable OLEDs, especially blue light devices, still needs to be improved. The key issue is how to improve the performance of electron transport materials. Summary of the Invention

[0006] This invention provides a compound that can be used as an electron transport layer material, and the device thereof has low driving voltage, high luminous efficiency and long service life.

[0007] It should be noted that the present application twists the molecular structure by the 9-alkyl-9-cyanogen-substituted aryl (or cyanogen-substituted nitrogen-containing heteroaryl) fluorene group, weakens the intermolecular interaction force, and the cyanogen and pyridine make the compound have electron-withdrawing properties, which is beneficial to electron transport, enhances the recombination of electrons and holes in the light-emitting layer, and the aryl-bridged triazine, pyrimidine six-membered nitrogen heterocycle further improves the electron transport performance, so as to realize the characteristics of low driving voltage, high luminous efficiency and long service life as the electron transport layer material of the organic electroluminescent device.

[0008] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0009] The first technical purpose of the present application is to provide an electron transport material, the structure general formula of the electron transport material is chemical formula I:

[0010]

[0011] In chemical formula I:

[0012] R is independently selected from methyl, ethyl, isopropyl;

[0013] Ar1, Ar2 is independently selected from the following groups:

[0014]

[0015] Among them, R1 is methyl, and m is an integer of 0, 1 or 2;

[0016] Ar3 is independently selected from hydrogen, phenyl, biphenyl, naphthyl, phenyl naphthyl, cyano-substituted phenyl, cyano-substituted biphenyl, pyridyl, phenyl pyridyl, methyl-substituted pyridyl, methyl-substituted phenyl pyridyl;

[0017] Ar4 is independently selected from the following groups:

[0018]

[0019] L is independently selected from phenyl, biphenyl, terphenyl;

[0020] Z1-Z3 independently represent C or N, and at least two of them are N.

[0021] Further, three of Z1-Z3 are N.

[0022] Further, chemical formula I is selected from chemical formula A-chemical formula E:

[0023]

[0024] Further, chemical formula I is selected from chemical formula-a~chemical formula-o:

[0025]

[0026] Further, the compound has the following structure, but is not limited to:

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036] A second technical object of the present application is to provide a preparation method of the above-mentioned electron transport material. The electron transport material of the present application can be prepared by a synthesis method known to those skilled in the art. Alternatively, the following reaction scheme is preferably used for the preparation, and the specific synthesis route is as follows:

[0037]

[0038] In the above formula, Ar1-Ar4, R, L, Z1-Z3 are defined as in the above Chemical Formula I, and Hal1 is independently selected from chlorine, bromine or iodine.

[0039] In particular, for the complex raw material which has not been disclosed, the classical Suzuki coupling reaction and lithiation reaction are used for the synthesis and applied to the present application.

[0040] The specific preparation method is as follows:

[0041] The step 1 specifically includes the following process:

[0042] In a reaction bottle, raw material A (1.0 eq) and raw material B (1.1-1.2 eq) are added, and then a mixed solution of toluene, ethanol, and water (V:V:V = 3:1:1) is added. After being aerated three times, tetrakis(triphenylphosphine)palladium (0.01-0.03 eq) and potassium carbonate (2.0-4.0 eq) are added under nitrogen protection. The reaction is heated to 40-80°C and refluxed for 1-8 h. The reaction is detected by thin layer chromatography. After the reaction is completed, the temperature is slightly lowered, and diatomite is used for filtration to remove salt and catalyst. After the filtrate is cooled to room temperature, it is washed with water three times, and the organic phase is retained. Then, the aqueous phase is extracted with dichloromethane. After the organic phases are combined, they are concentrated, and then purified by column chromatography using petroleum ether or a mixed solution of dichloromethane and petroleum ether (V:V = 1:6-1:10) to obtain intermediate 1.

[0043] Note: In this reaction step, raw material B has three halogens. On the one hand, the characteristics of the Suzuki coupling reaction are utilized, i.e., the reactivity I > Br > Cl. On the other hand, by controlling the reaction conditions, the reaction site is controlled to achieve the preparation of the intermediate with the target structure. The reaction is purified by column chromatography or silica gel funnel to remove byproducts to obtain the target compound. For reaction mechanism, please refer to: Transition Metal Organic Chemistry (6th edition), Robert. H. Crabtree, Publisher: East China University of Technology Press, Publication Time: 2017-09-00, ISBN: 978-7-5628-5111-0, page 388; and Organic Chemistry and Optoelectronic Material Experiment Course, Chen Runfeng, Publisher: Southeast University Press, Publication Time: 2019-11-00, ISBN: 9787564184230, page 174.

[0044] Step 2 specifically includes the following process:

[0045] At -78°C, intermediate 1 (1.2 eq) is dissolved in a tetrahydrofuran solution, aerated three times, and stirred for 10 minutes. N-butyllithium (1.2 eq) is slowly added to the reaction bottle, and the reaction is carried out for 2 h. Raw material C (1.0 eq) is dissolved in tetrahydrofuran, and the solution of raw material C is slowly added dropwise to the reaction bottle. After stirring uniformly, the refrigeration is stopped, and the temperature is raised to room temperature for continued reaction for 2-14 h. The reaction is detected by thin layer chromatography. After the reaction is completed, it is washed with water three times, and the organic phase is retained. Then, the aqueous phase is extracted with dichloromethane. After the organic phases are combined, they are concentrated, and then purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:2-1:5) to obtain intermediate 2.

[0046] Step 3 specifically includes the following process:

[0047] The intermediate 2 (1.0 eq) is dissolved in a mixture of toluene (5.0 eq) and THF (5.0 eq) and stirred at room temperature until dissolved, then methyl sulfonic acid (5.0 eq) is added to the intermediate 2 solution, and the reaction is allowed to proceed for 5-60 min; the reaction is monitored by thin layer chromatography, after the reaction is completed, water is added and stirred, extracted, separated, and the aqueous phase is extracted with dichloromethane, and the combined organic phases are concentrated, and the product is purified by column chromatography using a mixture of dichloromethane and petroleum ether (V:V = 1:4-1:8).

[0048] Step 4 specifically includes the following process:

[0049] The intermediate 3 (1.0 eq), the raw material D (1.0-2.0 eq), and potassium acetate (2.0-3.0 eq) are added to a reaction bottle, then 1,4-dioxane is added, and the bottle is purged three times, then tris(dibenzylideneacetone)dipalladium (0.02-0.15 eq) and X-Phos (0.1-0.2 eq) are added under nitrogen protection, the temperature is raised to 110-120°C, and the reaction is refluxed for 3-18 h; the reaction is monitored by thin layer chromatography, after the reaction is completed, the temperature is slightly lowered, and the salt and catalyst are removed by filtering with celite, the filtrate is cooled to room temperature, washed with water three times, the organic phase is retained, and then the aqueous phase is extracted with dichloromethane; the combined organic phases are concentrated, and the product is purified by column chromatography using a mixture of dichloromethane and petroleum ether (V:V = 1:4-1:10).

[0050] Step 5 specifically includes the following process:

[0051] The intermediate 4 (1.0 eq) and the raw material E (1.0-1.3 eq) are added to a reaction bottle, then a mixture of toluene, ethanol, and water (V:V:V = 3:1:1) is added, and the bottle is purged three times, then tetrakis(triphenylphosphine)palladium (0.01-0.03 eq) and potassium carbonate (2.0-4.0 eq) or palladium acetate (0.03-0.06 eq), X-Phos (0.1-0.02 eq), and cesium carbonate (2.0-4.0 eq) are added under nitrogen protection, the temperature is raised to 80-120°C, and the reaction is refluxed for 4-20 h; the reaction is monitored by thin layer chromatography, after the reaction is completed, the temperature is slightly lowered, and the salt and catalyst are removed by filtering with celite, the filtrate is cooled to room temperature, washed with water three times, the organic phase is retained, and then the aqueous phase is extracted with dichloromethane; the combined organic phases are concentrated, and the product is purified by column chromatography using a mixture of dichloromethane and petroleum ether (V:V = 1:6-1:18).

[0052] Furthermore, the application also claims the use of the above-mentioned electron transport material in the preparation of an organic electroluminescent device.

[0053] Specifically, the organic electroluminescent device comprises a first electrode, a second electrode, and one or more organic layers disposed between the first electrode and the second electrode; and the organic layers comprise at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting auxiliary layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer; and the electron transport layer comprises the electron transport material.

[0054] In addition, the organic electroluminescent device can be used in an organic electroluminescent device.

[0055] The organic electroluminescent device includes, but is not limited to, a flat panel display, a computer monitor, a medical monitor, a television, a billboard, a lamp for interior or exterior lighting and / or signaling, a heads-up display, a fully or partially transparent display, a flexible display, a laser printer, a telephone, a cell phone, a tablet, a photo album, a personal digital assistant (PDA), a wearable device, a notebook computer, a digital camera, a camcorder, a viewfinder, a micro display, a three-dimensional display, a virtual reality or augmented reality display, a vehicle, a video wall comprising multiple displays tiled together, a theater or venue screen, a phototherapy device, and a sign.

[0056] According to the technical solutions described above, compared with the prior art, the present application has the following beneficial effects:

[0057] The compound effectively exhibits the characteristics of a blue electron transport material, and the service life and efficiency of the organic electroluminescent device prepared therefrom are significantly improved.

[0058] Specifically, (1) a 9-alkyl-9-cyanophenyl (cyano-substituted nitrogen-containing heteroaryl) fluorene group is introduced, wherein the SP 3 Hybridization maintains the spatial configuration of the compound, the cyano-substituted aryl (cyano-substituted nitrogen-containing heteroaryl) bridging group at the 9-position of the fluorene reduces the symmetry of the molecule, twists the molecular structure, weakens the intermolecular interaction, effectively increases the service life of the device, and in addition, the cyano group and the pyridine make the compound have electron-withdrawing properties, which is beneficial to electron transport, enhances the recombination of electrons and holes in the light-emitting layer, and thus improves the light-emitting efficiency of the device.

[0059] (2) The introduction of a bridged L group (phenylene, biphenylene, terphenylene) can reduce the occurrence of large planes in the molecule, weaken the intermolecular interaction, and prolong the service life of the device; it can also act as a buffer, extend the system, enhance the electron mobility, and make the migration rate faster, thereby reducing the voltage and improving the light-emitting efficiency.

[0060] (3) The connection of triazine, pyrimidine six-membered nitrogen heterocycle to improve the mobility of organic molecules, the N atom has good electron transport performance, can lower the ability of molecular LUMO level, is conducive to matching with high work function electrode, enhances the conductivity of the material, especially 1,3,5-triazine has high electron affinity, electrochemical stability and easy modification of structure and other advantages. BRIEF DESCRIPTION OF DRAWINGS

[0061] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the provided drawings.

[0062] Figure 1 is the nuclear magnetic resonance hydrogen spectrum of compound 1-intermediate 1 provided by the embodiment 1 of the present application.

[0063] Figure 2 is the nuclear magnetic resonance hydrogen spectrum of compound 1 provided by the embodiment 1 of the present application. DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0065] The present application discloses a preparation method of an electron transport material.

[0066] In addition, it should be noted that the numerical values given in the following embodiments are as accurate as possible, but those skilled in the art understand that due to unavoidable measurement errors and experimental operation problems, each number should be understood as an approximate number, not an absolutely accurate number.

[0067] B-1 and B-81 are the same substance and are prior art, CAS No.: 59273-30-2; C-1, D-62, C-81, D-202 are the same substance and are prior art, CAS No.: 73183-34-3; C-62 and C-202 are the same substance and are prior art, CAS No.: 59211-64-2.

[0068] Embodiment 1

[0069]

[0070] Dissolve the starting material A-1 (1.2 eq, CAS No.: 1805001-22-2) in a tetrahydrofuran solution at -78°C, exchange the air three times, stir for 10 minutes, slowly add n-butyllithium (1.2 eq) to the reaction bottle, react for 2 h, dissolve the starting material B-1 (1.0 eq, CAS No.: 59273-30-2) in tetrahydrofuran, and then slowly drop the solution of the starting material B-1 into the reaction bottle, stir uniformly, stop the refrigeration, and continue to react at room temperature for 8 h; detect the reaction by thin layer chromatography, after the reaction is completed, wash with water three times, reserve the organic phase, and then extract the aqueous phase with dichloromethane; after the organic phases are combined, concentrate, purify by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:2) to obtain the intermediate 1 (yield: 73.4%).

[0071] Dissolve the intermediate 1 (1.0 eq) in a mixture of toluene (5.0 eq) and THF (5.0 eq), stir at room temperature until dissolution, then add methyl sulfonic acid (5.0 eq) to the intermediate 1 solution, and react for 20 min; detect the reaction by thin layer chromatography, after the reaction is completed, add water to stir, extract, separate, extract the aqueous phase with dichloromethane, concentrate the combined organic phases, purify by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:5) to obtain the intermediate 2 (yield: 86.8%).

[0072] Add the intermediate 2 (1.0 eq), the starting material C-1 (1.5 eq, CAS No.: 73183-34-3), and potassium acetate (2.0 eq) to a reaction bottle, then add 1,4-dioxane, exchange the air three times, add tris(dibenzylideneacetone)dipalladium (0.02 eq) and X-Phos (0.1 eq) under nitrogen protection, heat to 120°C, and reflux for 10 h; detect the reaction by thin layer chromatography, after the reaction is completed, slightly reduce the temperature, filter using diatomite to remove the salt and catalyst, cool the filtrate to room temperature, wash with water three times, reserve the organic phase, and then extract the aqueous phase with dichloromethane; after the organic phases are combined, concentrate, purify by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:6) to obtain the intermediate 3 (yield: 74.4%).

[0073] In a reaction flask, intermediate 3 (1.0 eq) and starting material D-1 (1.1 eq, CAS No: 1606981-69-4) were taken followed by a mixture of toluene, ethanol, water (V:V:V = 3:1:1), purged with nitrogen three times, followed by the addition of tetrakis(triphenylphosphine)palladium (0.03 eq) and potassium carbonate (3.0 eq) under nitrogen atmosphere, heated to 95 °C and refluxed for 14 h; the reaction was monitored by thin layer chromatography, after completion of the reaction, the temperature was lowered, filtered using celite to remove salts and catalyst, the filtrate was cooled to room temperature, washed with water three times, the organic layer was retained, followed by the extraction of aqueous layer with dichloromethane; the organic layers were combined and concentrated, purified by column chromatography using a mixture of dichloromethane and petroleum ether (V:V = 1:8) to obtain compound 1 (yield: 80.3%).

[0074] The compound 1 obtained was analyzed and the results are as follows:

[0075] HPLC purity: >99.8%.

[0076] Mass spectrometry: Mass spectrometer of Waters XEVO TQD type, using ESI source.

[0077] Test value ((ESI, m / Z): [M+H]+): 665.33.

[0078] Elemental analysis:

[0079] Calculated: C, 86.72; H, 4.85; N, 8.43;

[0080] Test value: C, 86.34; H, 5.11; N, 8.66.

[0081] Nuclear magnetic resonance hydrogen spectrum: as shown in Figure 1 (Intermediate 1 of compound 1), as shown in Figure 2 (compound 1).

[0082] Example 2

[0083]

[0084] In a reaction flask, raw material A-62 (1.0 eq, CAS No.: 663954-31-2) and raw material B-62 (1.1 eq, CAS No.: 31928-44-6) were added, followed by a mixed solution of toluene, ethanol, and water (V:V:V = 3:1:1), and then the reaction flask was purged with nitrogen three times. Then, tetrakis(triphenylphosphine)palladium (0.01 eq) and potassium carbonate (3.0 eq) were added under nitrogen protection, and the reaction was heated to 55°C and refluxed for 1.5 h. After the reaction was completed, the temperature was slightly lowered, and the salt and catalyst were removed by filtration using diatomite. After the filtrate was cooled to room temperature, it was washed with water three times, and the organic phase was retained. Then, the aqueous phase was extracted with dichloromethane. After the organic phases were combined, they were concentrated, and the intermediate 1 was purified by column chromatography using petroleum ether (yield: 73.4%).

[0085] At -78°C, the intermediate 1 (1.2 eq) was dissolved in a tetrahydrofuran solution, and then the reaction flask was purged with nitrogen three times. After stirring for 10 min, n-butyllithium (1.2 eq) was slowly added to the reaction flask, and the reaction was performed for 2 h. Then, raw material C-62 (1.0 eq, CAS No.: 59211-64-2) was dissolved in tetrahydrofuran, and the solution of raw material C-62 was slowly added dropwise to the reaction flask. After stirring, the cooling was stopped, and the reaction was continued at room temperature for 10 h. After the reaction was completed, the reaction was detected by thin layer chromatography, and then the organic phase was retained after being washed with water three times. Then, the aqueous phase was extracted with dichloromethane. After the organic phases were combined, they were concentrated, and the intermediate 2 was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:2) (yield: 70.2%).

[0086] The intermediate 2 (1.0 eq) was dissolved in a mixed solution of toluene (5.0 eq) and THF (5.0 eq) and stirred at room temperature until dissolution. Then, methyl sulfonic acid (5.0 eq) was added to the intermediate 2 solution, and the reaction was performed for 30 min. After the reaction was completed, the reaction was detected by thin layer chromatography, and then the organic phase was retained after being extracted, separated, and extracted with dichloromethane. After the organic phases were combined, they were concentrated, and the intermediate 3 was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:6) (yield: 81.0%).

[0087] In a reaction flask, intermediate 3 (1.0 eq), starting material D-62 (1.5 eq, CAS No: 73183-34-3) and potassium acetate (2.0 eq) were added, followed by 1,4-dioxane, purged with nitrogen gas for three times, tris(dibenzylideneacetone)dipalladium (0.02 eq) and X-Phos (0.1 eq) were added under nitrogen atmosphere, heated to 120 °C and refluxed for 13 h; the reaction was monitored by TLC, after completion of the reaction, the temperature was lowered, filtered using celite to remove salts and catalyst, the filtrate was cooled to room temperature, washed with water thrice, the organic layer was retained, followed by extraction of aqueous layer with dichloromethane; the organic layers were combined and concentrated, purified by column chromatography using a mixture of dichloromethane and petroleum ether (V:V = 1:7) to obtain intermediate 4 (yield: 71.1%).

[0088] In a reaction flask, intermediate 4 (1.0 eq) and starting material E-62 (1.1 eq, CAS No: 2351180-02-2) were added, followed by a mixture of toluene, ethanol, water (V:V:V = 3:1:1), purged with nitrogen gas for three times, tetrakis(triphenylphosphine)palladium (0.03 eq) and potassium carbonate (3.0 eq) were added under nitrogen atmosphere, heated to 95 °C and refluxed for 17 h; the reaction was monitored by TLC, after completion of the reaction, the temperature was lowered, filtered using celite to remove salts and catalyst, the filtrate was cooled to room temperature, washed with water thrice, the organic layer was retained, followed by extraction of aqueous layer with dichloromethane; the organic layers were combined and concentrated, purified by column chromatography using a mixture of dichloromethane and petroleum ether (V:V = 1:8) to obtain compound 62 (yield: 79.9%).

[0089] The compound 62 obtained was analyzed and the results are as follows:

[0090] HPLC purity: >99.7%.

[0091] Mass spectrometry test: Waters XEVO TQD mass spectrometer, ESI source.

[0092] Test value ((ESI, m / Z): [M+H]+): 969.46.

[0093] Elemental analysis:

[0094] Calculated: C, 89.23; H, 4.99; N, 5.78;

[0095] Test value: C, 88.84; H, 5.23; N, 6.03.

[0096] Example 3

[0097]

[0098] Dissolve the starting material A-81 (1.2 eq, CAS No.: 2356110-42-2) in tetrahydrofuran solution at -78°C, replace the air 3 times, stir for 10 minutes, slowly add n-butyllithium (1.2 eq) to the reaction bottle, react for 2 h, dissolve the starting material B-81 (1.0 eq, CAS No.: 59273-30-2) in tetrahydrofuran, and then slowly drop the solution of the starting material B-81 into the reaction bottle, stir uniformly, stop the refrigeration, and continue to react at room temperature for 9 h; detect the reaction by thin layer chromatography, after the reaction is completed, wash with water for 3 times, reserve the organic phase, then extract the aqueous phase with dichloromethane; after the organic phases are combined, concentrate, purify by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:3) to obtain the intermediate 1 (yield: 72.1%).

[0099] Dissolve the intermediate 1 (1.0 eq) in a mixture of toluene (5.0 eq) and THF (5.0 eq), stir at room temperature until dissolution, then add methyl sulfonic acid (5.0 eq) to the solution of the intermediate 1, react for 25 min; detect the reaction by thin layer chromatography, after the reaction is completed, add water to stir, extract, separate, then extract the aqueous phase with dichloromethane, after the organic phases are combined, concentrate, purify by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:6) to obtain the intermediate 2 (yield: 84.9%).

[0100] Add the intermediate 2 (1.0 eq), the starting material C-81 (1.5 eq, CAS No.: 73183-34-3) and potassium acetate (2.0 eq) to the reaction bottle, then add 1,4-dioxane, replace the air 3 times, add tris(dibenzylideneacetone)dipalladium (0.02 eq) and X-Phos (0.1 eq) under the protection of nitrogen, heat to 120°C and reflux for 11 h; detect the reaction by thin layer chromatography, after the reaction is completed, slightly reduce the temperature, filter using diatomite to remove the salt and catalyst, after the filtrate is cooled to room temperature, wash with water for 3 times, reserve the organic phase, then extract the aqueous phase with dichloromethane; after the organic phases are combined, concentrate, purify by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:7) to obtain the intermediate 3 (yield: 72.5%).

[0101] Intermediate 3 (1.0 eq) and starting material D-81 (1.1 eq, CAS No.: 864377-31-1) were added to a reaction flask, followed by a mixed solution of toluene, ethanol, and water (V:V:V = 3:1:1). The mixture was purged three times, and tetrakis(triphenylphosphine)palladium (0.03 eq) and potassium carbonate (3.0 eq) were added under nitrogen protection. The mixture was heated to 95 °C and refluxed for 15 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered with diatomaceous earth to remove salts and catalysts. The filtrate was cooled to room temperature and washed three times with water, retaining the organic phase. The aqueous phase was then extracted with dichloromethane. The organic phases were combined and concentrated. Compound 81 (yield: 81.7%) was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:9).

[0102] The obtained compound 81 was analyzed, and the results are as follows:

[0103] HPLC purity: >99.8%.

[0104] Mass spectrometry test: Waters XEVO TQD mass spectrometer with ESI source.

[0105] Test value ((ESI, m / Z): [M+H]+): 665.27.

[0106] Elemental analysis:

[0107] The calculated values ​​are: C, 86.72; H, 4.85; N, 8.43.

[0108] The test values ​​are: C, 86.33; H, 5.10; N, 8.69.

[0109] Example 4

[0110]

[0111] In a reaction flask, raw material A-202 (1.0 eq, CAS No.: 1408000-96-3) and raw material B-202 (1.1 eq, CAS No.: 148836-41-3) were added, followed by a mixed solution of toluene, ethanol, and water (V:V:V = 3:1:1). The mixture was purged three times, and tetrakis(triphenylphosphine)palladium (0.01 eq) and potassium carbonate (3.0 eq) were added under nitrogen protection. The mixture was heated to 55°C and refluxed for 2 hours. The reaction was detected by thin-layer chromatography. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered with diatomaceous earth to remove salts and catalysts. The filtrate was cooled to room temperature, washed three times with water, and the organic phase was retained. The aqueous phase was then extracted with dichloromethane. The organic phases were combined and concentrated. The intermediate 1 was purified by column chromatography using petroleum ether (yield: 70.1%).

[0112] Intermediate 1 (1.2 eq) was dissolved in THF at -78°C, and the reaction bottle was purged three times with nitrogen. After stirring for 10 min, n-butyllithium (1.2 eq) was slowly added to the reaction bottle. The reaction was allowed to proceed for 2 h. The starting material C-202 (1.0 eq, CAS No.: 59211-64-2) was dissolved in THF, and the solution of the starting material C-202 was slowly added dropwise to the reaction bottle. After stirring, the cooling was stopped, and the reaction was allowed to proceed at room temperature for 12 h. The reaction was monitored by TLC. After the reaction was completed, the reaction mixture was washed with water three times, and the organic phase was retained. The aqueous phase was then extracted with dichloromethane. The combined organic phase was concentrated, and the product was purified by column chromatography using a mixture of dichloromethane and petroleum ether (V:V = 1:3) to obtain intermediate 2 (yield: 68.7%).

[0113] Intermediate 2 (1.0 eq) was dissolved in a mixture of toluene (5.0 eq) and THF (5.0 eq) and stirred at room temperature until dissolution. Methyl sulfonic acid (5.0 eq) was then added to the solution of intermediate 2, and the reaction was allowed to proceed for 40 min. The reaction was monitored by TLC. After the reaction was completed, water was added and stirred, and the mixture was extracted and separated. The aqueous phase was then extracted with dichloromethane. The combined organic phase was concentrated, and the product was purified by column chromatography using a mixture of dichloromethane and petroleum ether (V:V = 1:6) to obtain intermediate 3 (yield: 80.1%).

[0114] Intermediate 3 (1.0 eq), starting material D-202 (1.5 eq, CAS No.: 73183-34-3), and potassium acetate (2.0 eq) were added to a reaction bottle, followed by the addition of 1,4-dioxane. The reaction bottle was purged three times with nitrogen. Tris(dibenzylideneacetone)dipalladium (0.02 eq) and X-Phos (0.1 eq) were added under nitrogen protection, and the reaction was allowed to proceed at 120°C while refluxing for 13 h. The reaction was monitored by TLC. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered using celite to remove the salt and catalyst. The filtrate was cooled to room temperature, and the mixture was washed with water three times. The organic phase was retained, and the aqueous phase was then extracted with dichloromethane. The combined organic phase was concentrated, and the product was purified by column chromatography using a mixture of dichloromethane and petroleum ether (V:V = 1:8) to obtain intermediate 4 (yield: 70.6%).

[0115] In a reaction flask, intermediate 4 (1.0 eq) and starting material E-202 (1.1 eq, CAS No: 1433982-54-7) were added, followed by a mixture of toluene, ethanol, and water (V:V:V = 3:1:1), and the reaction flask was purged with nitrogen three times. Then, tetrakis(triphenylphosphine)palladium (0.03 eq) and potassium carbonate (3.0 eq) were added under nitrogen protection, and the reaction was heated to 95°C and refluxed for 18 h. After the reaction was completed, the temperature was slightly lowered, and the reaction mixture was filtered using celite to remove the salt and catalyst. After the filtrate was cooled to room temperature, it was washed with water three times, and the organic phase was retained. Then, the aqueous phase was extracted with dichloromethane. After the organic phases were combined, they were concentrated, and the resulting compound 202 was purified by column chromatography using a mixture of dichloromethane and petroleum ether (V:V = 1:10) as the eluent (yield: 77.8%).

[0116] The obtained compound 202 was analyzed, and the results are as follows:

[0117] HPLC purity: >99.7%.

[0118] Mass spectrometry: Waters XEVO TQD, ESI source.

[0119] Test value ((ESI, m / Z): [M+H]+): 894.42.

[0120] Elemental analysis:

[0121] Calculated: C, 87.32; H, 4.85; N, 7.83;

[0122] Test value: C, 86.92; H, 5.08; N, 8.08.

[0123] Examples 5-108

[0124] The synthesis of the following compounds was completed according to the synthesis methods of Examples 1-4, and the mass spectrometry was tested using a Waters XEVO TQD mass spectrometer with an accuracy of 0.1 Da and an ESI source. The mass spectrometry test values are shown in Table 1 below.

[0125] Table 1 Mass spectrometry test values of Examples 5-108

[0126]

[0127]

[0128]

[0129] In addition, it should be noted that other compounds of the present application can be obtained according to the synthesis methods listed above, and therefore, they will not be listed one by one here.

[0130] Another objective of this application is to provide an organic electroluminescent device, including a first electrode, a second electrode, and at least one organic layer disposed between the first electrode and the second electrode.

[0131] The organic material layer of the organic electroluminescent device disclosed in this invention can be a single-layer structure, or it can be formed as a multilayer structure with one or more organic material layers. For example, the organic electroluminescent device disclosed in this invention can have a structure including a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting auxiliary layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a hole blocking layer as organic material layers. However, the structure of the organic light-emitting device is not limited to this, and it can include fewer or more organic material layers.

[0132] The organic electroluminescent devices described in this application can be used in organic electroluminescent devices, including but not limited to flat panel displays, computer monitors, a medical monitor, a television set, billboards, a lamp for internal or external lighting and / or signaling, head-up displays, fully transparent or partially transparent displays, flexible displays, a laser printer, a telephone, a mobile phone, tablets, a photo album, a personal digital assistant (PDA), a wearable device, a laptop computer, a digital camera, a camcorder, a viewfinder, a microdisplay, a 3D display, a virtual reality or augmented reality display, vehicles, video walls including multiple displays tiled together, theater or stadium screens, phototherapy devices, and signs.

[0133] The following detailed description, in conjunction with specific embodiments, illustrates an organic electroluminescent composition and an organic electroluminescent device provided by the present invention.

[0134] Device Example 1: Fabrication of Organic Electroluminescent Devices

[0135] The structure of the fabricated OLED device is: ITO anode / HIL / HTL / Prime / EML / HBL / ETL / EIL / cathode / CPL.

[0136] (1) ITO anode: The coating thickness is... The ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrate was cleaned twice with distilled water, ultrasonically washed for 30 minutes, then repeatedly cleaned twice with distilled water, ultrasonically washed for 10 minutes. After washing, it was ultrasonically washed sequentially with methanol, acetone, and isopropanol (5 minutes each time), dried, and then transferred to a plasma cleaner for 5 minutes. Finally, it was sent to an evaporation machine, where other functional layers were sequentially deposited on the substrate as the anode.

[0137] (2) HIL (hole injection layer): with HT and P-dopant, whose chemical formulas are shown below, were vacuum evaporated at a rate of 97:3. The thickness of the HT and P-dopant was 10 nm.

[0138] (3) HTL (Hole Transport Layer): HT was vacuum evaporated at a rate of 120 nm on the hole injection layer as a hole transport layer.

[0139] (4) Prime (Light Emitting Auxiliary Layer): Prime was vacuum evaporated at a rate of 5 nm on the hole transport layer as a light emitting auxiliary layer.

[0140] (5) EML (Light Emitting Layer): Then, Host and Dopant, whose chemical formulas are shown below, were vacuum evaporated at a rate of 98:2 on the light emitting auxiliary layer as a light emitting layer. The thickness of the Host and Dopant was 25 nm.

[0141] (6) HBL (Hole Blocking Layer): A hole blocking layer HB was vacuum evaporated at a rate of 5 nm.

[0142] (7) ETL (Electron Transport Layer): Compound 1 and Liq were vacuum evaporated at a rate of 50:50 as an electron transport layer. The thickness of the Compound 1 and Liq was 30 nm.

[0143] (8) EIL (Electron Injection Layer): Yb was evaporated at a rate of 1.0 nm to form an electron injection layer.

[0144] (9) Cathode: Magnesium and silver were evaporated at a rate of 1:9 to obtain an OLED device.

[0145] (10) CPL (Light Extraction Layer): CPL was vacuum evaporated at a rate of 65 nm on the cathode as a light extraction layer.

[0146] (11) The substrate on which the evaporation was completed was then encapsulated. First, the cleaned cover plate was coated with UV glue using a coating device, and then the coated cover plate was moved to the pressing section, the substrate on which the evaporation was completed was placed on the end of the cover plate, and finally the substrate and the cover plate were attached under the action of the attaching device, and the UV glue was cured by light at the same time.​​​​​​​​

[0147]

[0148] According to the method provided in the above device embodiment 1, the corresponding compounds in Table 2 are respectively selected to replace compound 1 to perform evaporation of the electron transport layer, and the corresponding organic electroluminescent devices are prepared and are respectively recorded as device embodiments 2-108.

[0149] Device comparative examples 1-21:

[0150] The comparative examples provide an organic electroluminescent device, and the only difference between the preparation method of the organic electroluminescent device and device embodiment 1 is that the organic electroluminescent device is evaporated by using the existing comparative compounds a-u to replace the electron transport layer (compound 1) in the above device embodiment 1. The chemical structural formula of the comparative compounds a-u is as follows:

[0151]

[0152] The driving voltage, BI value and lifetime of the organic electroluminescent devices obtained by the above device embodiments 1-108 and device comparative examples 1-21 are characterized under the brightness of 1000 (nits), and the test results are as follows Table 2:

[0153] Table 2 device test results

[0154]

[0155]

[0156]

[0157]

[0158] As known by those skilled in the art, in a blue light top-emitting device, the luminous efficiency is greatly affected by the chromaticity, therefore, the factor of the influence of the chromaticity on the efficiency is considered, and the luminous efficiency and CIEy ratio are defined as BI value, that is, BI=(cd / A) / CIEy.

[0159] From the data in Table 2, the organic electroluminescent devices prepared by using the electron transport material provided in the present application in device embodiments 1-108 are compared with the devices prepared by using comparative compounds 1-21, and the driving voltage, BI and lifetime are all improved.

[0160]

[0161] The comparative compounds a, b and the compounds 141, 142 are parallel comparative examples, the difference is that in the comparative compounds a, b, the cyano-substituted phenyl and the cyano-substituted biphenyl are connected to the inner benzene ring of the fluorene (substituted at the 4th position), and are ortho- connected with the bridged phenylene, while in the inventive compounds 141, 142, the cyano-substituted phenyl and the cyano-substituted biphenyl are connected to the 9th position of the fluorene, so that the molecular structure is twisted, the intermolecular interaction force is weakened, and the device lifetime is increased compared with the comparative compounds.

[0162]

[0163] The comparative compounds c, d, e and the compounds 22, 148, 29 are parallel comparative examples, the difference is that in the comparative compounds c, d, e, the 9th position of the fluorene is connected with a methyl and a phenyl, while in the inventive compounds 22, 148, 29, the 9th position of the fluorene is connected with a cyano-substituted aryl or a nitrogen-containing heteroaryl (cyano-substituted phenyl, cyano-substituted biphenyl, cyano-substituted pyridyl with a methyl), due to the electron-withdrawing properties of pyridine and cyano, the overall electron transport performance of the compound is stronger, which is more conducive to the recombination of holes and electrons, thereby improving the efficiency of the device and effectively prolonging the service life of the device.

[0164]

[0165] The comparative compounds f, g, i and the compounds 143, 154, 144 are comparative examples, the difference is that in the comparative compounds f, g, i, the triazine is connected with a phenyl bridged 9,9-dimethylfluorenyl, 9,9-diphenylfluorenyl, spirobifluorenyl, while in the inventive compounds 143, 154, 144, the phenyl is bridged with a cyano-substituted aryl or a cyano-substituted nitrogen-containing heteroaryl, the applicant's previous research shows that the performance of 9-alkyl-9-aryl is better than that of 9,9-dimethylfluorenyl and 9,9-diphenylfluorenyl, and from the data in Table 2, it can be seen that the aryl or nitrogen-containing heteroaryl at the 9th position substituted with cyano can effectively improve the efficiency and service life of the device.

[0166]

[0167] The comparative compound m is a compound in the applicant's previous research CN115417861B, which is a comparative example with the compound 153, the difference between the two is that in the inventive compound 153, the 9th position of the fluorene is substituted with a methyl and a cyano-substituted phenyl, while in the comparative compound m, the 9th position of the fluorene is connected with a methyl and a dibenzofuranyl group, the dibenzofuranyl is highly rigid, the evaporation temperature is increased, and the stability is decreased, thereby leading to a shortened service life of the device.

[0168]

[0169] The comparative compound p and the compound 25 are parallel comparative examples, and the difference between them is that the triazine in the comparative compound p is connected with the 9th position of the fluorene after the phenylene, which interrupts the conjugation of this position, and the fluorene itself cannot participate in the conjugated system at the upper end, and the symmetry is better than that of the compound 25, so that the molecule is easy to stack, reducing the service life of the device, while in the compound 25 of the application, the triazine is connected with the phenyl below the fluorene (2nd position) after the phenylene, compared with the conjugation of the comparative compound, the conjugated system of the compound of the application is longer, which is beneficial to electron transport and has faster mobility, so that the voltage is lower.

[0170]

[0171] The comparative compound q is a compound in the patent CN116283909B of the applicant's previous research, and it is a comparative example with the compound 26, and the difference between them is that the L group (naphthalene group) in the compound q is connected with the triazine at one end and the benzene ring at the 9th position of the fluorene at the other end, while the L group (phenylene group) in the compound 26 of the application is connected with the triazine at one end and the benzene ring below the fluorene at the other end, compared with the conjugated surface of the comparative compound (the two benzene rings of the fluorene itself do not participate in the conjugation), the conjugated surface of the compound of the application is different, the energy gap is narrow, which is beneficial to electron transport and has faster mobility, so that the voltage is lower.

[0172]

[0173] The comparative compounds s, t and the compounds 30, 151 are comparative examples, respectively, and the difference between them is that the comparative compounds s, t are connected with the bridged phenylene group with a cyano-substituted spiro[fluorene-9,8'-fluorene[4,5-bcd]furan] group, which has a larger molecular weight and a higher evaporation temperature, which is easy to cause material cracking and affect the service life of the device, while the phenylene group in the compounds 30, 151 of the application is connected with the 9-methyl 9-cyano-substituted phenyl fluorene group, which effectively adjusts the molecular stacking condition and makes the mobility faster.

[0174] The above only describes the preferred embodiments of the application and is not intended to limit the application. Those skilled in the art can make various modifications and changes to the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. An electron transport material, characterized by, having the structure of Formula I: In Formula I, R is independently selected from methyl, ethyl, isopropyl; Ar1, Ar2 are independently selected from the following groups: wherein R1 is methyl and m is an integer of 0, 1 or 2; Ar3 is independently selected from hydrogen, phenyl, biphenyl, naphthyl, phenyl naphthyl, cyano-substituted phenyl, cyano-substituted biphenyl, pyridyl, phenyl pyridyl, methyl-substituted pyridyl, methyl-substituted phenyl pyridyl; Ar4 is independently selected from the following groups: L is independently selected from phenyl, biphenyl, terphenyl; Z1-Z3 independently represent C or N, and at least two of them are N simultaneously.

2. The electron transport material according to claim 1, characterized in that, Formula I is selected from Formula A-Formula E:

3. The electron transport material according to claim 1, wherein Formula I is selected from Formula-a-Formula-o:

4. The electron transport material according to claim 1, wherein The electron transport material is selected from any one of the compounds shown in the following structural formula:

5. A method of preparing the electron transport material according to claim 1, characterized by, The method specifically comprises the following steps: (1) adding raw material A (1.0 eq) and raw material B (1.1-1.2 eq) into a reaction bottle, then adding a mixed solution of toluene, ethanol and water (V:V:V=3:1:1), replacing the air three times, adding tetrakis(triphenylphosphine)palladium (0.01-0.03 eq) and potassium carbonate (2.0-4.0 eq) under nitrogen protection, heating to 40-80°C and refluxing for 1-8 h; detecting the reaction by thin layer chromatography, after the reaction is completed, slightly reducing the temperature, filtering with diatomite to remove the salt and catalyst, cooling the filtrate to room temperature, washing with water three times, retaining the organic phase, then extracting the aqueous phase with dichloromethane; after the organic phases are combined, concentrating, purifying the intermediate 1 by column chromatography with a mixed solution of petroleum ether or dichloromethane and petroleum ether (V:V=1:6-1:10); (2) dissolving the intermediate 1 (1.2 eq) in a tetrahydrofuran solution at -78°C, replacing the air three times, stirring for 10 min, slowly adding n-butyllithium (1.2 eq) into the reaction bottle, reacting for 2 h, dissolving raw material C (1.0 eq) in tetrahydrofuran, slowly dropping the solution of raw material C into the reaction bottle, stirring uniformly, stopping the refrigeration, warming to room temperature and continuing to react for 2-14 h; detecting the reaction by thin layer chromatography, after the reaction is completed, washing with water three times, retaining the organic phase, then extracting the aqueous phase with dichloromethane; after the organic phases are combined, concentrating, purifying the intermediate 2 by column chromatography with a mixed solution of dichloromethane and petroleum ether (V:V=1:2-1:5); (3) dissolving the intermediate 2 (1.0 eq) in a mixed solution of toluene (5.0 eq) and THF (5.0 eq), stirring at room temperature until dissolution, then adding methyl sulfonic acid (5.0 eq) to the intermediate 2 solution, reacting for 5-60 min; detecting the reaction by thin layer chromatography, after the reaction is completed, stirring with water, extracting, separating, extracting the aqueous phase with dichloromethane, after the organic phases are combined, concentrating, purifying the intermediate 3 by column chromatography with a mixed solution of dichloromethane and petroleum ether (V:V=1:4-1:8); (4) In a reaction flask, add intermediate 3 (1.0 eq), raw material D (1.0-2.0 eq) and potassium acetate (2.0-3.0 eq), then add 1,4-dioxane, replace three times with nitrogen, add tris(dibenzylideneacetone)dipalladium (0.02-0.15 eq) and X-Phos (0.1-0.2 eq) under nitrogen protection, heat to 110-120°C, and reflux for 3-18 h; detect the reaction by thin layer chromatography, after the reaction is completed, slightly reduce the temperature, filter using diatomite to remove the salt and catalyst, cool the filtrate to room temperature, wash with water three times, reserve the organic phase, then extract the aqueous phase with dichloromethane; combine the organic phase, concentrate, purify by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V=1:4-1:10) to obtain intermediate 4; (5) In a reaction flask, add intermediate 4 (1.0 eq) and raw material E (1.0-1.3 eq), then add a mixed solution of toluene, ethanol and water (V:V:V=3:1:1), replace three times with nitrogen, add tetrakis(triphenylphosphine)palladium (0.01-0.03 eq) and potassium carbonate (2.0-4.0 eq) or palladium acetate (0.03-0.06 eq), X-Phos (0.1-0.02 eq) and cesium carbonate (2.0-4.0 eq) under nitrogen protection, heat to 80-120°C, and reflux for 4-20 h; detect the reaction by thin layer chromatography, after the reaction is completed, slightly reduce the temperature, filter using diatomite to remove the salt and catalyst, cool the filtrate to room temperature, wash with water three times, reserve the organic phase, then extract the aqueous phase with dichloromethane; combine the organic phase, concentrate, purify by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V=1:6-1:18) to obtain chemical formula I; The specific synthesis route is as follows: wherein, Hal1 is independently selected from chlorine, bromine or iodine; R, L, Z1-Z3, Ar1-Ar4 have the definitions as described in claim 1.

6. Use of the electron transport material according to claim 1 in the preparation of an organic electroluminescent device.

7. Use according to claim 6, characterized in that, The organic electroluminescent device comprises a first electrode, a second electrode, and one or more organic layers disposed between the first electrode and the second electrode; and The organic layer comprises at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting auxiliary layer, a light-emitting layer, a hole blocking layer, an electron transport layer and an electron injection layer; and The electron transport layer comprises the electron transport material.

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