A light-emitting auxiliary material and preparation method thereof and organic electroluminescent device

Abstract

The present invention discloses a luminescence assisting material, a preparation method thereof, and an organic electroluminescent device, belonging to the technical field of organic optoelectronic luminescent materials. The general structural formula of the luminescence assisting material is as shown in the specification: wherein Ar1 and Ar2 are each independently selected from a substituted or unsubstituted C3-C30 cycloalkyl group, a substituted or unsubstituted C6-C30 aryl group, or a substituted or unsubstituted 3-membered - 30-membered heteroaryl group. The present invention can avoid the large structural energy gap that makes it difficult for electrons to jump, can effectively extend the device life, uses a triarylamine material as a luminescence assisting layer to improve the mobility, and the benz[b]naphtho[1,2-d]furan adopted retains the advantage of the high triplet energy level of dibenzofuran, and on this basis, the conjugated plane is increased, the hole transport rate is increased, and the extension of the conjugated plane is avoided, ensuring the relatively high triplet energy level required for the blue light luminescence assisting material.

Description

Technical Field

[0001] The invention belongs to the technical field of organic light-emitting electroluminescent materials, and more specifically relates to a luminescent auxiliary material and a preparation method thereof and an organic electroluminescent device. Background Art

[0002] Organic electroluminescence (OLED) is a type of self-luminous display element, and the display has the advantages of high brightness, high resolution, wide viewing angle, low energy consumption, and high response speed. Generally speaking, organic electroluminescence refers to the phenomenon of converting electrical energy into light energy using organic substances. Organic light-emitting elements that utilize the organic light-emitting phenomenon generally have a structure comprising an anode and a cathode and an organic layer located therebetween. For example, a hole injection layer (HIL), a hole transport layer (HTL), a light-emitting layer, an electron transport layer (ETL), and an electron injection layer (EIL).

[0003] In order to solve the problems of lifespan and efficiency, a luminescent auxiliary layer (multi-layer hole transport layer) is usually added between the hole transport layer and the light-emitting layer. The luminescent auxiliary layer mainly plays the role of assisting the hole transport layer, so it is sometimes also called the second hole transport layer. The luminescent auxiliary layer can enable the holes transferred from the anode to move smoothly to the light-emitting layer, and can block the electrons transferred from the cathode to confine the electrons in the light-emitting layer, reduce the potential barrier between the hole transport layer and the light-emitting layer, reduce the driving voltage of the organic electroluminescent device, and further increase the utilization rate of holes, thereby improving the luminous efficiency and life of the device.

[0004] However, there are few materials that can form a light-emitting auxiliary layer and have excellent device performance. In particular, the lifespan and luminous efficiency of OLEDs have not been significantly improved, so it is particularly important to develop higher-performance organic functional materials to meet the requirements of panel manufacturers.

[0005] Therefore, how to develop a luminescent auxiliary material with high luminous efficiency, long life and improved driving voltage and a preparation method thereof and an organic electroluminescent device is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0006] In view of this, the present invention provides a luminescence auxiliary material and a preparation method thereof, and an organic electroluminescent device.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A luminescence auxiliary material, the general structural formula of the luminescence auxiliary material is shown in Formula I:

[0009]

[0010] Wherein, Ar1 and Ar2 are each independently selected from a substituted or unsubstituted C3-C30 cycloalkyl group, a substituted or unsubstituted C6-C30 aryl group, or a substituted or unsubstituted 3-30 membered heteroaryl group.

[0011] Furthermore, the above Ar1 and Ar2 are each independently selected from a substituted or unsubstituted C3-C18 cycloalkyl group, a substituted or unsubstituted C6-C18 aryl group, or a substituted or unsubstituted 3-24-membered heteroaryl group.

[0012] Furthermore, the above Ar1 and Ar2 are each independently selected from cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, 3-methylcyclopentyl, 3-methylcyclohexyl, 4-methylcyclohexyl, 2,3-dimethylcyclohexyl, 3,4,5-trimethylcyclohexyl, 4-tert-butylcyclohexyl, cycloheptyl, cyclooctyl, 2,3-dimethylcyclopentyl, bicyclo[3.1.1]heptyl or adamantyl.

[0013] Furthermore, the above-mentioned Ar1 and Ar2 are each independently selected from phenyl, biphenyl, terphenyl, naphthyl, binaphthyl, phenylnaphthyl, naphthylphenyl, phenylterphenyl, fluorenyl, dimethylfluorenyl, diphenylfluorenyl, benzofluorenyl, dibenzofluorenyl, phenanthrenyl, phenylphenanthrenyl, anthracenyl, indenyl, triphenylene, pyrene, perylenyl, chrysene, naphthacene, fluoranthenyl, spirobifluorenyl, azulenyl, methylphenyl, ethylphenyl, methoxyphenyl or cyanophenyl.

[0014] Further, the above Ar1 and Ar2 are each independently selected from furanyl, thienyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, isoxazolyl, oxazolyl, oxadiazolyl, triazinyl, tetrazinyl, triazolyl, tetrazolyl, furazanyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, benzofuranyl, benzothiophenyl, isobenzofuranyl, dibenzofuranyl, dibenzothiophenyl, benzimidazole yl, benzothiazolyl, benzisothiazolyl, benzisoxazolyl, benzoxazolyl, isoindolyl, indolyl, benzindolyl, indazolyl, benzothiadiazolyl, quinolyl, isoquinolyl, cinnolinyl, quinazolinyl, benzoquinazolinyl, quinoxalinyl, benzoquinoxalinyl, naphthyridinyl, carbazolyl, benzocarbazolyl, dibenzocarbazolyl, phenoxazinyl, phenothiazinyl, phenanthridinyl, benzodioxolyl or dihydroacridinyl.

[0015] Furthermore, the above-mentioned Ar1 and Ar2 are each independently selected from phenyl, naphthyl, phenanthryl, methylphenyl, ethylphenyl, cyanophenyl, methoxyphenyl, phenylpyridyl, phenylpyrimidyl, biphenyl, terphenyl, phenylnaphthyl, dibenzofuranyl, dibenzothiophenyl, carbazolyl, 9-phenyl-9H-carbazolyl, diphenylfluorenyl, dimethylfluorenyl, cyclopentyl, or cyclohexyl.

[0016] Furthermore, the general structural formula of the above-mentioned luminescence auxiliary material is selected from any one of the following general structural formulas:

[0017]

[0018] Further, the above-mentioned "substituted or unsubstituted" means substituted by one or more substituents selected from the following: deuterium; halogen group; nitrile group; hydroxyl group; carbonyl group; ester group; silyl group; boron group; C1-C30 alkyl group; C3-C30 cycloalkyl group; alkoxy group; C6-C30 aryl group; 3-30 membered heteroaryl group, or substituted by two or more substituents connected to each other among the substituents shown above, or having no substituent;

[0019] In the above substituents, the cycloalkyl group is a monocyclic, polycyclic or spiroalkyl group;

[0020] In the above substituents, aryl is a monocyclic aromatic hydrocarbon group or a polycyclic aromatic ring system, or the above polycyclic ring has two or more rings in which two carbon atoms are common to two adjacent rings, and the above rings are "fused";

[0021] In the above substituents, the heteroaryl group includes a monocyclic aromatic group or a polycyclic aromatic ring system containing at least one heteroatom, wherein the heteroatom is selected from O, S, N, P, B, Si or Se.

[0022] Furthermore, the above-mentioned luminescence auxiliary material is selected from any one of the compounds represented by the following structural formulas:

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034] The present invention also provides a method for preparing a luminescent auxiliary material, comprising the following steps:

[0035] (1) Under N2 protection, reactant AI, reactant BI, palladium catalyst, phosphorus ligand and base are added to a mixed solvent of toluene, ethanol and water, heated, reacted, cooled to room temperature, and H2O is added. After solid precipitation is complete, the mixture is filtered, the filter cake is dried, and the remaining substance is purified by column chromatography. The filtrate is subjected to a rotary evaporator to remove the solvent, and the obtained solid is dried to obtain intermediate CI;

[0036] (2) Under N2 protection, the intermediate CI and the reactant DI are added to a reaction vessel and dissolved in xylene, and then a palladium catalyst, a phosphorus ligand and a base are added. After the addition, the reaction temperature is slowly increased, and the mixture is stirred. The mixture is filtered while hot using diatomaceous earth. After the filtrate is cooled to room temperature, distilled water is added to the filtrate for washing. After separation, the organic phase is retained, and the aqueous phase is extracted with ethyl acetate. Finally, the combined organic layer is dried with magnesium sulfate, and the remaining substance is purified by column chromatography to obtain the compound represented by Formula I;

[0037] Synthesis route:

[0038]

[0039] wherein Hal is selected from Br or I;

[0040] R' is

[0041] Furthermore, the preparation method of the above-mentioned luminescence auxiliary material comprises the following steps:

[0042] (1) Under N2 protection, reactant AI, reactant BI, palladium catalyst and base are added to a mixed solvent of toluene, ethanol and water, the temperature is raised to 80-100°C, the reaction is carried out for 8-12 hours, the mixture is cooled to room temperature, H2O is added, and after solid precipitation is completed, the mixture is filtered, the filter cake is dried, and the remaining substance is purified by column chromatography. The solvent is removed from the filtrate by a rotary evaporator, and the obtained solid is dried to obtain intermediate CI.

[0043] (2) Under N2 protection, the intermediate CI and the reactant DI are added to a reaction vessel and dissolved in xylene, and then a palladium catalyst, a phosphorus ligand, and a base are added. After the addition, the reaction temperature is slowly raised to 130-140° C., and the mixture is stirred for 8-12 hours. The mixture is filtered while hot using diatomaceous earth. After the filtrate is cooled to room temperature, distilled water is added to the filtrate for washing. After separation, the organic phase is retained, and the aqueous phase is extracted with ethyl acetate. Finally, the combined organic layer is dried with magnesium sulfate, and the remaining substance is purified by column chromatography to obtain the compound represented by Formula I;

[0044] Further, the palladium catalyst is Pd2(dba)3, Pd(PPh3)4, PdCl2, PdCl2(dppf), Pd(OAc)2, Pd(PPh3)2Cl2 or NiCl2(dppf);

[0045] The phosphine ligand is P(t-Bu)3, X-phos, PET3, PMe3, PPh3, KPPh2 or P(t-Bu)2Cl;

[0046] The above-mentioned base is K2CO3, K3PO4, Na2CO3, CsF, Cs2CO3 or t-BuONa.

[0047] Furthermore, in the above step (1), the molar ratio of reactant AI, reactant BI, palladium catalyst and base is 1.0:(1-1.2):(0.01-0.02):(2.0-2.3).

[0048] Furthermore, in the above step (2), the molar ratio of the intermediate CI, the reactant DI, the palladium catalyst, the phosphorus ligand and the base is 1.0:(1.1-1.3):(0.01-0.05):(0.02-0.15):(2.0-2.4).

[0049] The present invention also provides an organic electroluminescent device, comprising the above-mentioned auxiliary luminescent material or the auxiliary luminescent material prepared by the above-mentioned method.

[0050] Beneficial effects of the present invention:

[0051] By connecting 9-phenyl-9H-carbazole to the naphthalene of benzo[b]naphtho[1,2-d]furan, the introduced phenyl bridging structure can avoid the difficulty of electron hopping caused by excessive structural energy gap. The compound structure is stable and can effectively extend the life of the device.

[0052] Triarylamine has excellent hole transport performance. Usually, the hole transport layer, the luminescent auxiliary layer and the electron blocking layer have triarylamine groups. The present invention uses triarylamine materials as the luminescent auxiliary layer to improve the mobility.

[0053] Further research revealed that not all rings connected to dibenzofuran can achieve the effect of a high triplet energy level. Between similar substances, the position of the ring, the type of ring, and the substituents on the ring will all affect the triplet energy level and mobility, thereby affecting the device performance in its organic electroluminescence.

[0054] Although the compound composed of benzo[b]naphtho[2,3-d]furan has an increased conjugated surface, the triplet energy level has been greatly reduced. Therefore, benzo[b]naphtho[1,2-d]furan is selected as the mother nucleus of the present invention to enable the compound to obtain a higher triplet energy level.

[0055] The benzo[b]naphtho[1,2-d]furan used in the present invention retains the advantage of the high triplet energy level of dibenzofuran, and on this basis increases the conjugated surface, increases the hole transfer rate, improves the efficiency, avoids the extension of the conjugated surface, and ensures the higher triplet energy level required by the blue light emitting auxiliary material. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is the hydrogen nuclear magnetic resonance spectrum of intermediate C-1 in Example 1;

[0057] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of compound 1 in Example 1. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] The present invention conducts a series of palladium-catalyzed coupling reactions, which utilize the difference that the activity of Br is greater than that of Cl, and control the reaction site by controlling the reaction conditions, and purify the reaction by column chromatography or silica gel funnel to remove by-products to obtain the target compound. Reference to the common knowledge is as follows:

[0060] "Transition Metal Organic Chemistry" (Original Sixth Edition), Robert H. Crabtree, Publisher: Shanghai East China University of Science and Technology Press, Publication Date: 2017-09-00, ISBN: 978-7-5628-5111-0, page 388.

[0061] "Organic Chemistry and Optoelectronic Materials Experimental Tutorial", Chen Runfeng, Publisher: Southeast University Press, Publication Date: 2019-11-00, ISBN: 9787564184230, Page 174.

[0062] Example 1: Synthesis of Compound 1

[0063]

[0064] CAS: Reactant B-1: 2639159-54-7

[0065] Under N2 protection, reactant A-1 (50 mmol), reactant B-1 (60 mmol), tetrakis(triphenylphosphine)palladium (0.5 mmol) and potassium carbonate (110 mmol) were added to a mixed solvent of toluene, ethanol and water (150 mL: 50 mL: 50 mL), respectively, and the temperature was raised to 95°C, reacted for 10 hours, cooled to room temperature, and H2O was added. After the solid was precipitated, it was filtered, the filter cake was dried, and the remaining substance was purified by column chromatography. The filtrate was used to remove the solvent by a rotary evaporator, and the obtained solid was dried to obtain intermediate C-1. (17.54 g, yield: 71%, test value MS (ESI, m / Z): [M+H] + =494.26).

[0066] The H NMR spectrum of intermediate C-1 is as follows Figure 1 As shown:

[0067] Under N2 protection, intermediate C-1 (35 mmol) and reactant D-1 (38.5 mmol) were added to the reaction vessel and dissolved in xylene (200 mL), and then Pd(OAc)2 (0.7 mmol), X-Phos (1.4 mmol), and t-BuONa (77 mmol) were added; after the addition, the reaction temperature was slowly raised to 135°C, and the mixture was stirred for 10 hours; diatomaceous earth was used for hot suction filtration, and after the filtrate was cooled to room temperature, distilled water was then added to the filtrate for washing, and the organic phase was retained after separation, and the aqueous phase was extracted with ethyl acetate; the combined organic layer was then dried with magnesium sulfate, and the remaining substance was purified by column chromatography to obtain compound 1. (21.27 g, yield: 78%, test value MS (ESI, m / Z): [M+H] + =779.17).

[0068] The H NMR spectrum of compound 1 is as follows Figure 2 As shown:

[0069] Characterization:

[0070] HPLC purity: >99.8%.

[0071] Elemental Analysis:

[0072] Theoretical value: C, 89.43; H, 4.92; N, 3.60; O, 2.05

[0073] Test values: C, 89.26; H, 5.01; N, 3.68; O, 2.10

[0074] Example 2: Synthesis of Compound 127

[0075]

[0076] Under N2 protection, reactant A-127 (50 mmol), reactant B-127 (60 mmol), tetrakis(triphenylphosphine)palladium (0.5 mmol) and potassium carbonate (110 mmol) were added to a mixed solvent of toluene, ethanol and water (150 mL: 50 mL: 50 mL), respectively, and the temperature was raised to 95°C, reacted for 10 hours, cooled to room temperature, and H2O was added. After the solid was precipitated, it was filtered, the filter cake was dried, and the remaining substance was purified by column chromatography. The filtrate was used to remove the solvent by a rotary evaporator, and the obtained solid was dried to obtain intermediate C-127. (18.53 g, yield: 75%, test value MS (ESI, m / Z): [M+H] + =494.32).

[0077] Under N2 protection, intermediate C-127 (35 mmol) and reactant D-127 (38.5 mmol) were added to the reaction vessel and dissolved in xylene (200 mL), and then Pd(OAc)2 (0.7 mmol), X-Phos (1.4 mmol), and t-BuONa (77 mmol) were added; after the addition, the reaction temperature was slowly raised to 135°C, and the mixture was stirred for 10 hours; diatomaceous earth was used for hot suction filtration, and after the filtrate was cooled to room temperature, distilled water was then added to the filtrate for washing, and the organic phase was retained after separation, and the aqueous phase was extracted with ethyl acetate; the combined organic layer was then dried with magnesium sulfate, and the remaining substance was purified by column chromatography to obtain compound 127. (23.51 g, yield: 82%, test value MS (ESI, m / Z): [M+H] + =819.28).

[0078] Characterization:

[0079] HPLC purity: >99.8%.

[0080] Elemental Analysis:

[0081] Theoretical value: C, 89.46; H, 5.26; N, 3.42; O, 1.95

[0082] Test values: C, 89.23; H, 5.33; N, 3.48; O, 1.98

[0083] Example 3: Synthesis of Compound 171

[0084]

[0085] Under N2 protection, reactant A-171 (50 mmol), reactant B-171 (60 mmol), tetrakis(triphenylphosphine)palladium (0.5 mmol) and potassium carbonate (110 mmol) were added to a mixed solvent of toluene, ethanol and water (150 mL: 50 mL: 50 mL), respectively, and the temperature was raised to 95°C, reacted for 10 hours, cooled to room temperature, and H2O was added. After the solid was precipitated, it was filtered, the filter cake was dried, and the remaining substance was purified by column chromatography. The filtrate was used to remove the solvent by a rotary evaporator, and the obtained solid was dried to obtain intermediate C-171. (18.28 g, yield: 74%, test value MS (ESI, m / Z): [M+H] + =494.28).

[0086] Under N2 protection, intermediate C-171 (35 mmol) and reactant D-171 (38.5 mmol) were added to the reaction vessel and dissolved in xylene (200 mL), and then Pd(OAc)2 (0.7 mmol), X-Phos (1.4 mmol), and t-BuONa (77 mmol) were added; after the addition, the reaction temperature was slowly raised to 135°C, and the mixture was stirred for 10 hours; diatomaceous earth was used for hot suction filtration, and after the filtrate was cooled to room temperature, distilled water was then added to the filtrate for washing, and the organic phase was retained after separation, and the aqueous phase was extracted with ethyl acetate; the combined organic layer was then dried with magnesium sulfate, and the remaining substance was purified by column chromatography to obtain compound 171. (24.78 g, yield: 85%, test value MS (ESI, m / Z): [M+H] + =833.22).

[0087] Characterization:

[0088] HPLC purity: >99.8%.

[0089] Elemental Analysis:

[0090] Theoretical values: C, 87.96; H, 4.84; N, 3.36; O, 3.84

[0091] Test values: C, 87.80; H, 4.91; N, 3.40; O, 3.92

[0092] Example 4-55

[0093] The following compounds were synthesized by referring to the synthesis methods of Examples 1 to 3. Their molecular formulas and mass spectra are shown in Table 1 below.

[0094] Table 1 Molecular formula and mass spectrum

[0095]

[0096]

[0097] In addition, it should be noted that other compounds of the present invention can be obtained by referring to the synthesis methods of the embodiments listed in Examples 1-3, so they are not listed one by one here.

[0098] The organic electroluminescent device has a structure including one or more 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, an electron injection layer, and a capping layer as organic layers. The structure of the organic light-emitting element is not limited thereto and includes fewer or more organic layers.

[0099] The compound shown in formula I prepared by the present invention is used as a light-emitting auxiliary layer material.

[0100] When manufacturing an organic light-emitting element, the compound represented by Formula I is subjected to vacuum evaporation or solution coating to form an organic layer, wherein the solution coating method refers to spin coating, dip coating, blade coating, inkjet printing, screen printing, spraying, roller coating, etc., but is not limited thereto.

[0101] The organic light emitting element of the present invention may be a top emission type, a bottom emission type or a bi-directional emission type depending on the materials used.

[0102] The devices of the present invention are used in organic light-emitting devices, including but not limited to flat panel displays, computer monitors, medical monitors, televisions, billboards, lights for interior or exterior lighting and / or signaling, heads-up displays, fully or partially transparent displays, flexible displays, laser printers, telephones, mobile phones, tablets, photo albums, personal digital assistants (PDAs), wearable devices, laptops, digital cameras, camcorders, viewfinders, microdisplays, three-dimensional displays, virtual reality or augmented reality displays, vehicles, video walls including multiple displays tiled together, theater or venue screens, light therapy devices and signs.

[0103] As the anode material, in order to allow holes to be smoothly injected into the organic layer, a material with a large work function is selected. Specific examples of the anode material that can be used in the present invention include vanadium, chromium, copper, zinc, gold or their alloys; metal oxides such as zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO); combinations of metals and oxides such as ZnO:Al or SnO2:Sb; conductive polymers such as polypyrrole and polyaniline.

[0104] The hole injection layer is selected from a p-doped hole injection layer, which means a hole injection layer doped with a p-dopant. The p-dopant is a material that can impart p-type semiconductor characteristics. The p-type semiconductor characteristics mean the characteristics of injecting holes or transporting holes at the HOMO energy level, that is, the characteristics of a material with high hole conductivity.

[0105] The hole transport material is a material that can receive holes from the anode or the hole injection layer and transport the holes to the light-emitting layer, and has a high hole mobility. The hole transport material is selected from aromatic amine derivatives, conductive polymers, and block copolymers having both conjugated and non-conjugated parts.

[0106] A luminescent auxiliary layer (multi-layer hole transport layer) is added between the hole transport layer and the light-emitting layer. The luminescent auxiliary layer mainly assists the hole transport layer, so it is sometimes also called the second hole transport layer. The luminescent auxiliary layer enables the holes transferred from the anode to move smoothly to the light-emitting layer, and can block the electrons transferred from the cathode to confine the electrons in the light-emitting layer, reduce the potential barrier between the hole transport layer and the light-emitting layer, reduce the driving voltage of the organic electroluminescent device, and further increase the utilization rate of holes, thereby improving the luminous efficiency and life of the device.

[0107] The light-emitting material of the light-emitting layer is a material that can receive holes and electrons from the hole transport layer and the electron transport layer, respectively, and combine them to emit light in the visible light region. A material with high quantum efficiency for fluorescence or phosphorescence is selected.

[0108] The light-emitting layer includes a host material and a dopant material.

[0109] The mass ratio of the main material to the doping material is 90-99.5:0.5-10.

[0110] The host material includes an aromatic fused ring derivative or a heterocyclic compound. Specifically, as the aromatic fused ring derivative, there are anthracene derivatives, pyrene derivatives, naphthalene derivatives, pentacene derivatives, phenanthrene compounds or fluoranthene compounds, and as the heterocyclic compound, there are carbazole derivatives, dibenzofuran derivatives or pyrimidine derivatives.

[0111] The dopant material of the present invention includes fluorescent doping and phosphorescent doping, and is selected from aromatic amine derivatives, styrylamine compounds, boron complexes, fluoranthene compounds or metal complexes.

[0112] The electron transport layer can promote electron transport. The electron transport material is a material that advantageously receives electrons from the cathode and transports the electrons to the light-emitting layer. A material with high electron mobility is selected. The electron transport layer includes an electron buffer layer, a hole blocking layer, and an electron transport layer.

[0113] The electron injection layer can promote electron injection. It has the ability to transport electrons and prevent the excitons generated in the light-emitting layer from migrating to the hole injection layer. The materials of the electron injection layer include oxazole, oxadiazole, triazole, imidazole, perylene tetracarboxylic acid, fluorenyl methane, anthrone and their derivatives, magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin, ytterbium or their alloys, metal complexes or nitrogen-containing 5-membered ring derivatives, but are not limited thereto.

[0114] The cathode material is selected to have a small work function so that electrons can be smoothly injected into the organic material layer, and the layer thickness of the layer is between 0.5 and 5 nm. In order to easily inject electrons into the organic layer, the cathode material is selected to have a small work function. Specific examples of cathode materials include magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin and lead or their alloys: LiF / Al or LiO2 / Al, Mg / Ag multilayer structure material.

[0115] Except for the light-emitting auxiliary layer disclosed in the present invention containing Formula I, there is no special restriction on the materials of other layers in the OLED device. Existing hole injection materials, hole transport materials, hole transport auxiliary materials, dopant materials, hole blocking layer materials, electron transport layer materials and electron injection materials can be used.

[0116] The organic electroluminescent composition and the organic electroluminescent device provided by the present invention are described in detail below with reference to specific embodiments.

[0117] [Application Example 1] Preparation of organic electroluminescent devices:

[0118] a. ITO anode: Wash the ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrate with a coating thickness of 150nm in distilled water twice, ultrasonically wash for 30 minutes, and then repeatedly wash it with distilled water twice, ultrasonically wash for 10 minutes. After washing, bake it in a vacuum oven at 220℃ for 2 hours. After baking, cool it down and it can be used. Use this substrate as the anode, use an evaporation machine to perform the evaporation device process, and evaporate other functional layers on it in sequence.

[0119] b. HIL (hole injection layer): The hole injection layer materials HT and P-dopant are vacuum evaporated at a deposition rate of 97:3, and the thickness is 10 nm;

[0120] c. HTL (hole transport layer): At a deposition rate of 100%, 120 nm of HT was vacuum-deposited on the hole injection layer as a hole transport layer.

[0121] d. Prime (luminous auxiliary layer): The evaporation rate is 10 nm, and the compound of the present invention is vacuum-evaporated on the hole transport layer as a light-emitting auxiliary layer;

[0122] e. EML (light-emitting layer): Then on the above-mentioned light-emitting auxiliary layer, The host material (Host) and dopant material (Dopant) with a thickness of 25nm are vacuum-deposited as the light-emitting layer. The chemical formulas of Host and Dopant are shown below. The evaporation rate ratio of Host to Dopant is 97:3.

[0123] f. HB (hole blocking layer): The hole blocking layer with a thickness of 5.0 nm was vacuum deposited at a deposition rate of .

[0124] g. ETL (Electron Transport Layer): ET and Liq were vacuum-deposited at a deposition rate of 35 nm as an electron transport layer, where the deposition rate ratio of ET to Liq was 50:50.

[0125] h. EIL (electron injection layer): The evaporation rate is 1.0 nm, and a Yb film layer is evaporated to form an electron injection layer.

[0126] i. Cathode: The evaporation rate ratio is 1:9, and magnesium and silver are evaporated at 18nm, and the evaporation rate ratio is 1:9 to obtain an OLED device.

[0127] j. Light extraction layer: At a deposition rate of , CPL with a thickness of 70 nm was vacuum-deposited on the cathode as a light extraction layer.

[0128] k. Package the substrate after evaporation. First, use the glue coating equipment to coat the cleaned cover with UV glue, then move the coated cover to the pressing section, place the evaporation-deposited substrate on the upper end of the cover, and finally bond the substrate and cover with the bonding equipment, and complete the light curing of the UV glue.

[0129] Device structure:

[0130] ITO / Ag / ITO / HT:P-dopant (10nm, 2%) / HT (120nm) / prime (compound of the present invention) (10nm) / Host:Dopant (25nm, 3%) / HB (5nm) / ET:Liq (35nm, 50%) / Yb (1nm) / Mg:Ag (18nm, 1:9) / CPL (70nm).

[0131]

[0132] Application Example 2-55

[0133] The organic electroluminescent devices of Application Examples 2-55 were prepared according to the preparation method of the organic electroluminescent device of Application Example 1, except that the compound 1 in Application Example 1 was replaced by corresponding compounds to form a light-emitting auxiliary layer.

[0134] Comparative Example 1

[0135] An organic electroluminescent device was prepared according to the method for preparing an organic electroluminescent device in Application Example 1, except that the compound 1 in Application Example 1 was replaced by a comparative compound 1, wherein the structural formula of the comparative compound 1 is as follows:

[0136] Comparative Example 2

[0137] An organic electroluminescent device was prepared according to the method for preparing an organic electroluminescent device in Application Example 1, except that the compound 1 in Application Example 1 was replaced by a comparative compound 2, wherein the structural formula of the comparative compound 2 is as follows:

[0138] Comparative Example 3

[0139] An organic electroluminescent device was prepared according to the method for preparing an organic electroluminescent device in Application Example 1, except that the compound 1 in Application Example 1 was replaced by a comparative compound 3, wherein the structural formula of the comparative compound 3 is as follows:

[0140] Comparative Example 4

[0141] An organic electroluminescent device was prepared according to the method for preparing an organic electroluminescent device in Application Example 1, except that the compound 1 in Application Example 1 was replaced by a comparative compound 4, wherein the structural formula of the comparative compound 4 is as follows:

[0142] Comparative Example 5

[0143] An organic electroluminescent device was prepared according to the method for preparing an organic electroluminescent device in Application Example 1, except that the compound 1 in Application Example 1 was replaced by a comparative compound 5, wherein the structural formula of the comparative compound 5 is as follows:

[0144] Comparative Example 6

[0145] An organic electroluminescent device was prepared according to the method for preparing an organic electroluminescent device in Application Example 1, except that the compound 1 in Application Example 1 was replaced by a comparative compound 6, wherein the structural formula of the comparative compound 6 is as follows:

[0146] Comparative Example 7

[0147] An organic electroluminescent device was prepared according to the method for preparing an organic electroluminescent device in Application Example 1, except that the compound 1 in Application Example 1 was replaced by a comparative compound 7, wherein the structural formula of the comparative compound 7 is as follows:

[0148] Comparative Example 8

[0149] An organic electroluminescent device was prepared according to the method for preparing an organic electroluminescent device in Application Example 1, except that the compound 1 in Application Example 1 was replaced by a comparative compound 8, wherein the structural formula of the comparative compound 8 is as follows:

[0150]

[0151] The driving voltage, luminous efficiency, BI value and life of the organic electroluminescent devices obtained from the device application examples 1-55 and the device comparative examples 1-8 were characterized at a brightness of 1000 (nits). The test results are shown in Table 2 below:

[0152] Table 2 Luminous characteristics test results (brightness value is 1000nits)

[0153]

[0154]

[0155]

[0156]

[0157] Those skilled in the art will know that the energy level of the light-emitting auxiliary layer matches the light-emitting layer and the hole transport layer. Different target values ​​need to be adjusted for different light-emitting layers. There are large differences for light-emitting layers of different colors. Even for the same blue light, there are significant differences for different host and dopant materials.

[0158] Blue light organic electroluminescent devices are affected by the microcavity effect, and the luminous efficiency is greatly affected by the chromaticity. Therefore, the BI value is introduced as the basis for the efficiency of blue light emitting materials, BI = luminous efficiency / CIEy. In this field, the short life and low efficiency of blue light devices have always been one of the problems that technicians in this field need to solve urgently.

[0159] It can be seen from Table 2 that, compared with the existing organic electroluminescent devices provided by comparative examples 1 to 8, the organic electroluminescent device application examples 1 to 55 prepared using the blue light luminescent auxiliary materials provided by the embodiments of the present invention show the technical effect of improving the driving voltage and life while exhibiting an ultra-long device life.

[0160] Among them, compared with the compound 21 provided in the embodiment of the present invention and the comparative compound 3; the compound 97 of the present invention and the comparative compound 4, the present invention adopts benzo[b]naphtho[1,2-d]furan, and the comparative compound is benzo[b]naphtho[2,3-d]furan.

[0161]

[0162]

[0163] After DFT (Density functional theory) calculations, using the gaussian16 software package, B3lyp functional and 6-31g* basis set, the ground state configuration of the structure was optimized, and the triplet energy of the ground state configuration was calculated using time-dependent density functional theory (TDDFT). Compared with the triplet energy level of compound 4, which is 2.2557eV, and the triplet energy level of compound 97, which is 2.2943eV, the compound composed of benzo[b]naphtho[2,3-d]furan has a significantly decreased triplet energy level, although the conjugated surface increases.

[0164] The present invention adopts benzo[b]naphtho[1,2-d]furan, which retains the advantage of high triplet energy level of dibenzofuran, and on this basis increases the conjugated surface, increases the hole transmission rate, improves the efficiency, avoids the extension of the conjugated surface, ensures the high triplet energy level required by the blue light emitting auxiliary material, has the technical effect of improving device efficiency, greatly increasing life span, and extending life span by nearly 130 hours

[0165] Compared with comparative compound 1 and comparative compound 2, compound 1 provided in an embodiment of the present invention has 9-phenyl-9H-carbazole connected to the naphthalene of benzo[b]naphtho[1,2-d]furan, and the introduced phenyl bridging structure can avoid the difficulty of electron hopping caused by excessive structural energy gap. The compound structure is stable and can effectively prolong the device life, which is increased by about 160 hours.

[0166]

[0167] The present invention is further verified by devices, and the device life of the obtained devices is also significantly improved by replacing the benzo[b]naphtho[1,2-d]furan mother core with similar compounds, such as comparative compound 6, which is benzo[b]naphtho[1,2-d]thiophene, comparative compound 7, which is dibenzofuran, and example compounds 53 and 25.

[0168]

[0169] It can be seen that not all the rings connected to dibenzofuran can achieve the effect of high triplet energy level. Among similar substances, the position of the ring, the type of ring, and the substituents on the ring will affect the triplet energy level and mobility, and thus affect the device performance in its organic electroluminescence. Although the structure of the present invention is similar to that of the prior art compound, only the compound conforming to Formula I of the present invention can significantly improve the device life when used as a blue light emitting auxiliary layer.

[0170] The blue light emitting auxiliary material provided by the present invention is based on benzo[b]naphtho[1,2-d]furan, 9-phenyl-9H-carbazole is connected to naphthalene, and the triarylamine group is connected to the benzene ring on the other side. The organic electroluminescent device prepared from the luminescent auxiliary material provided by the embodiment of the present invention exhibits the performance advantages of long life, improved driving voltage, and improved efficiency.

[0171] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A luminescent auxiliary material, characterized in that: The general structural formula of the luminescence auxiliary material is shown in Formula I: in, Ar1 and Ar2 are each independently selected from phenyl, biphenyl, terphenyl, naphthyl, binaphthyl, phenylnaphthyl, naphthylphenyl, phenylterphenyl, fluorenyl, dimethylfluorenyl, diphenylfluorenyl, benzofluorenyl, dibenzofluorenyl, phenanthryl, phenylphenanthryl, triphenylene, pyrene, perylenyl, naphthacene, spirobifluorenyl, methylphenyl, ethylphenyl, methoxyphenyl, cyanophenyl, dibenzofuranyl, dibenzothiophenyl, phenylpyridyl, phenylpyrimidyl, carbazolyl, benzocarbazolyl, dibenzocarbazolyl, and 9-phenyl-9H-carbazolyl.

2. A luminescence auxiliary material according to claim 1, characterized in that: The general structural formula of the luminescence auxiliary material is selected from any one of the following general structural formulas:

3. A luminescence auxiliary material according to claim 1, characterized in that: The luminescence auxiliary material is selected from any one of the compounds represented by the following structural formulas:

4. A method for preparing the luminescence auxiliary material according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Under N2 protection, reactant AI, reactant BI, palladium catalyst and base are added to a mixed solvent of toluene, ethanol and water, heated, reacted, cooled to room temperature, H2O is added, and after solid precipitation is complete, the mixture is filtered, the filter cake is dried, and the remaining substance is purified by column chromatography. The filtrate is used to remove the solvent by a rotary evaporator, and the obtained solid is dried to obtain intermediate CI; (2) Under N2 protection, the intermediate CI and the reactant DI are added to a reaction vessel and dissolved in xylene, and then a palladium catalyst, a phosphorus ligand and a base are added. After the addition, the reaction temperature is slowly increased, and the mixture is stirred. The mixture is filtered while hot using diatomaceous earth. After the filtrate is cooled to room temperature, distilled water is added to the filtrate for washing. After separation, the organic phase is retained, and the aqueous phase is extracted with ethyl acetate. Finally, the combined organic layer is dried with magnesium sulfate, and the remaining substance is purified by column chromatography to obtain the compound represented by Formula I; Synthesis route: wherein Hal is selected from Br or I; R' is 5. An organic electroluminescent device, characterized in that: The invention comprises the luminescence auxiliary material according to any one of claims 1 to 3 or the luminescence auxiliary material prepared by the method according to claim 4.

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