An organic electroluminescent material and an organic electroluminescent device

Abstract

This invention provides an organic electroluminescent material and an organic electroluminescent device. The organic electroluminescent material has the structure shown in Formula I. This invention uses 9,9-dimethylfluorene as the parent core, linked to an aromatic amine group. One of the aromatic amine side chains contains a 1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene derivative, and the other aromatic amine side chain is either aryl or heteroaryl. Simultaneously, alkyl, aryl, or heteroaryl substitutions are performed on both sides of the 9,9-dimethylfluorene parent core, resulting in a compound of Formula I with a low refractive index. Using the low-refractive-index compound of Formula I as a light-emitting auxiliary material can narrow the emission spectrum, enhance the luminous intensity of light at specific wavelengths, reduce light loss, improve device luminous efficiency, and simultaneously ensure a low driving voltage and a long device lifetime.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescent materials technology, specifically relating to an organic electroluminescent material and an organic electroluminescent device. Background Technology

[0002] Organic electroluminescence is a physical process in which organic functional materials directly convert electrical energy into light energy under the influence of an electric field. Organic light-emitting diodes (OLEDs), with their superior properties such as self-emission, high contrast, wide viewing angle, and fast response, have achieved large-scale applications in smartphone displays, flat panel displays, high-definition televisions, and solid-state lighting, becoming a core technology in the optoelectronic display and lighting fields. A typical OLED device uses an anode and cathode as electrode structures, with multiple organic functional layers sandwiched between them, forming the basic photoelectric conversion unit. To further optimize the luminous efficiency and lifespan of the device, the industry currently commonly introduces a light-emitting auxiliary layer between the hole transport layer and the light-emitting layer, constructing a multi-level hole transport recombination structure to improve the internal carrier transport and recombination characteristics of the device.

[0003] The core functions of the light-emitting auxiliary layer are twofold: First, it promotes the smooth injection and efficient transport of holes generated at the anode to the light-emitting layer, effectively reducing the energy level barrier at the interface between the hole transport layer and the light-emitting layer, thereby reducing the device driving voltage and improving hole utilization efficiency. Second, it effectively blocks electrons injected from the cathode, confining them within the light-emitting layer and ensuring a balanced distribution of charge carriers within it. Through these mechanisms, this structure enables the simultaneous improvement of OLED device luminous efficiency and operational stability, extending the device's actual lifespan.

[0004] Currently, there is a shortage of organic functional materials suitable for preparing light-emitting auxiliary layers and that can significantly improve the overall optoelectronic performance of devices. Existing materials are insufficient to meet industry demands in synergistically improving the efficiency and lifetime of OLED devices. The final performance of OLED devices is influenced by a combination of factors, including device structure design, material refractive index, HOMO / LUMO energy levels, triplet energy, vacuum evaporation film morphology, carrier mobility, carrier balance, evaporation process temperature, and testing environment conditions. Therefore, performance optimization of organic functional materials often requires extensive experimental screening and precise modification of molecular structures to achieve ideal application levels. Currently, materials R&D companies primarily improve the overall performance of OLED devices by controlling key material performance indicators.

[0005] Given the current industry situation of insufficient supply of high-efficiency organic materials for light-emitting auxiliary layers, and the development trend of downstream panel manufacturers continuously increasing the requirements for material performance, the development of new organic functional materials with both high stability and high luminous efficiency has become a key research topic that urgently needs to be tackled in the OLED field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an organic electroluminescent material and an organic electroluminescent device. The present invention uses 9,9-dimethylfluorene as a core linked to an aromatic amine group. One of the aromatic amine side chains contains a 1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene derivative, and the other side chain is either aryl or heteroaryl. Simultaneously, alkyl, aryl, or heteroaryl substitutions are performed on both sides of the 9,9-dimethylfluorene core, resulting in a compound of formula I with a low refractive index. Using the low-refractive-index compound of formula I as a light-emitting auxiliary material, applied as the thicker layer in a double-layer light-emitting auxiliary material, allows light emitted from within the device to pass through the low-refractive-index film of formula I. The organic electroluminescent device prepared by combining this low-refractive-index film with the high-refractive-index light-emitting auxiliary material can better concentrate light, emitting specific wavelengths of light emitted from the device. This narrows the emission spectrum, enhances the luminous intensity of specific wavelengths, reduces light loss, and improves the device's luminous efficiency, while ensuring a low driving voltage and a long device lifespan.

[0007] To achieve this objective, the present invention adopts the following technical solution: On one hand, the present invention provides an organic electroluminescent material having the structure shown in Formula I: R1 and R2 are independently selected from substituted or unsubstituted C1-C15 alkyl, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C6-C30 heteroaryl, and their heteroatoms are one or more of O, S, N, Si, Ge or P. n is the maximum allowable substitution from 1 to the ring, specifically selected from 1, 2, 3, 4; m is the maximum allowable substitution on the ring from 0, specifically selected from 0, 1, 2, 3, 4; R3 is selected from hydrogen, substituted or unsubstituted C1-C15 alkyl, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C6-C30 heteroaryl, and its heteroatom is one or more of O, S, N, Si, Ge or P. Ar is selected from the following substituent groups; The symbol indicates the position of the group connection. For groups whose substitution positions are not shown, the substitution positions are any substituted positions. In Formula I, hydrogen is either completely substituted with deuterium, partially substituted with deuterium, or completely unsubstituted with deuterium.

[0008] Furthermore, R1 and R2 are independently selected from hydrogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C6-C15 aryl, substituted or unsubstituted C6-C15 heteroaryl, and their heteroatoms are one or more of O, S, N, Si or Ge. R3 is selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C6-C15 aryl, substituted or unsubstituted C6-C15 heteroaryl, and its heteroatom is one or more of O, S, N, Si or Ge.

[0009] Furthermore, the organic electroluminescent material has any one of the structures of formula I-1 to formula I-4: Where m is the maximum allowable substitution from 1 to the ring, specifically selected from 1, 2, 3, 4; R3 is selected from substituted or unsubstituted methyl, substituted or unsubstituted ethyl, substituted or unsubstituted tert-butyl, substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted dibenzothiopheneyl, and substituted or unsubstituted 9,9-dimethylfluorenyl.

[0010] In this invention, the hydrogen atoms in the defined groups can be independently substituted with or not substituted with deuterium; In one embodiment of the invention, the term "substituted or unsubstituted C6-C" is used. 30 "Aryl", "Substituted and Unsubstituted C6-C" 18 "Heteroaryl", "substituted or unsubstituted C6-C" 15 Alkyl, substituted or unsubstituted C6-C 30 "Heteroaryl", "substituted and unsubstituted C6-C" 18 "Aryl", "substituted or unsubstituted C1-C6 alkyl", "substituted or unsubstituted C6-C6 alkyl" 15 "Aryl", "substituted or unsubstituted C6-C" 15 The number of carbon atoms in "heteroaryl" refers to the number of carbon atoms constituting the unsubstituted aryl or unsubstituted alkyl group, or the total number of heteroatoms and carbon atoms constituting the heteroaryl group, without considering the number of carbon atoms in the substituents.

[0011] The term "substitution" means substitution by one, two or more substituents selected from the following: hydrogen, deuterium, halogen, cyano, trifluoromethyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methylbutyl, 1-ethylbutyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, 1-methylhexyl, phenyl, naphthyl, anthracene, phenanthrene, thiophene, furanyl, pyrrole, benzothiophene, benzofuranyl, pyridyl, indolyl, cyclopentyl, cyclohexyl, adamantane, or substitution by two or more substituents linked together from the substituents shown above.

[0012] Preferably, the organic electroluminescent material is any one of the following compounds, but not limited to: .

[0013] Synthetic route The series of palladium-catalyzed coupling reactions in this invention utilize the activity differences of halogens I>Br>Cl, and control the reaction sites by controlling the reaction conditions. The reactions are purified by column chromatography or silica gel funnel to remove byproducts and obtain the target compound.

[0014] For raw materials that are not publicly available, those skilled in the art can synthesize them using classic Suzuki coupling reactions, Buchwald–Hartwig coupling reactions, butyllithium reactions, and apply them to this invention.

[0015] The following are common knowledge references: Organometallic Chemistry (6th Edition), Robert H. Crabtree, published by East China University of Science and Technology Press, Shanghai, September 00, 2017, ISBN: 978-7-5628-5111-0, page 388.

[0016] Organic Chemistry and Optoelectronic Materials Experiment Tutorial, Chen Runfeng, Publisher: Southeast University Press, Publication Date: 2019-11-00, ISBN: 9787564184230, Page 174.

[0017] Synthesis route of Formula I: The synthesis method can be carried out by referring to one or more of the following steps: Hal1, Hal2, and Hal3 are each independently selected from fluorine, chlorine, bromine, or iodine; the remaining restrictions are the same as those defined in general formula I. Step 1: Under nitrogen protection, raw material A (1.0 eq) was dissolved in THF, and CH3MgBr (1.2-1.5 eq) was added at -10℃. The mixture was then heated to room temperature and reacted for 12-24 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, 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 DCM. The organic phases were combined and dried with anhydrous magnesium sulfate. The solvent was removed using a rotary evaporator and the mixture was dissolved in petroleum ether / ethanol for recrystallization. The mixture was filtered, and the filter cake was washed multiple times with petroleum ether and dried in a 60℃ oven for 5 h to obtain intermediate 1.

[0018] Step 2: Under nitrogen protection, intermediate 1 (1.0 eq) was dissolved in DCM, and triethylsilane (2.0-2.5 eq) and methanesulfonic acid (2.0-2.5 eq) were added. The reaction was carried out at room temperature for 12-24 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, water was added and the mixture was washed three times. The organic phase was retained, and the aqueous phase was extracted with DCM. The organic phases were combined and dried with anhydrous magnesium sulfate. The solvent was removed by rotary evaporator and the mixture was dissolved in petroleum ether / ethanol for recrystallization. The mixture was filtered, and the filter cake was washed several times with petroleum ether and dried in an oven at 60 °C for 5 h to obtain intermediate 2.

[0019] Step 3: Under nitrogen protection, intermediate 2 (1.0 eq) was dissolved in THF. NaH (3.0-3.5 eq) and CH3I (3.0-3.5 eq) were added at -10℃. After reacting for 1 h, the temperature was raised to room temperature and the reaction was continued for 6-8 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, the solution was filtered with diatomaceous earth to remove salt and catalyst. The filtrate was cooled to room temperature and washed three times with water, retaining the organic phase. The aqueous phase was then extracted with DCM. The organic phases were combined and dried with anhydrous magnesium sulfate. The solvent was removed using a rotary evaporator and dissolved in petroleum ether / ethanol for recrystallization. The solution was filtered, and the filter cake was washed multiple times with petroleum ether and dried in a 60℃ oven for 5 h to obtain intermediate 3.

[0020] Step 4: Under nitrogen protection, raw material B (1.0 eq) and raw material C (1.0 eq) were added to a mixed solution of toluene, ethanol and water. Pd(OAc)2 (0.01-0.02 eq), X-Phos (0.02-0.05 eq) and Cs2CO3 (2.0-2.3 eq) were added to the solution. The temperature was raised to 80-100℃ and the reaction was carried out for 8-12 h. The solution was then cooled to room temperature, and the reaction was detected by thin-layer chromatography. After the reaction was completed, H2O was added. After the solid precipitated completely, the solution was filtered, and the filter cake was dried. The obtained solid was dissolved in toluene by heating and passed through a silica gel funnel while hot. A mixed solution of methanol and dichloromethane was used as the developing solvent. The filtrate was used to remove the solvent using a rotary evaporator. The obtained solid was dried to obtain intermediate 4.

[0021] Step 5: Under nitrogen protection, intermediates 4 (1 eq) and 3 (1.3-1.4 eq) were dissolved in toluene solution, and sodium tert-butoxide (2.00-3.00 eq), tris(dibenzylacetone)dipalladium (0.01-0.03 eq), and tri-tert-butylphosphine (0.05-0.10 eq) were added. The mixture was stirred until homogeneous, heated to 90-110℃, and refluxed for 4-6 h. 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 ethyl acetate. The organic phases were combined, dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was then dissolved in petroleum ether / ethanol, recrystallized, filtered, and the filter cake was washed multiple times with petroleum ether and dried in a 60℃ oven for 5 h to obtain intermediate 5.

[0022] Step 6: Under nitrogen protection, intermediate 5 (1.0 eq) and raw material D (1.0-1.5 eq) were added to a mixed solution of toluene, ethanol and water. Pd(OAc)2 (0.01-0.02 eq), X-Phos (0.02-0.05 eq) and Cs2CO3 (2.0-2.3 eq) were added to the solution. The mixture was heated to 80-100℃ and reacted for 8-12 h. After cooling to room temperature, the reaction was detected by thin-layer chromatography. After the reaction was completed, H2O was added. After the solid precipitated completely, the mixture was filtered, the filter cake was dried, and the resulting solid was dissolved in toluene by heating. The solution was then passed through a silica gel funnel with a methanol and dichloromethane mixture as the developing solvent. The filtrate was used to remove the solvent using a rotary evaporator, and the resulting solid was dried to obtain intermediate 6.

[0023] Step 7: Under nitrogen protection, intermediate 6 (1.0 eq) and raw material E (1.0-1.5 eq) were added to a mixed solution of toluene, ethanol and water. Pd(OAc)2 (0.01-0.02 eq), X-Phos (0.02-0.05 eq) and Cs2CO3 (2.0-2.3 eq) were added to the solution. The mixture was heated to 80-100℃ and reacted for 8-12 h. After cooling to room temperature, the reaction was detected by thin-layer chromatography. After the reaction was completed, H2O was added. After the solid precipitated completely, the mixture was filtered, the filter cake was dried, and the resulting solid was dissolved in toluene by heating. While hot, the solid was passed through a silica gel funnel using a mixed solution of methanol and dichloromethane as the developing solvent. The filtrate was used to remove the solvent using a rotary evaporator, and the resulting solid was dried to obtain intermediate 7.

[0024] Step 8: Under nitrogen protection, intermediates 4 (1 eq) and 3 (1.3-1.4 eq) were dissolved in toluene solution, and sodium tert-butoxide (2.00 eq), tris(dibenzylacetone)dipalladium (0.01 eq), and tri-tert-butylphosphine (0.05 eq) were added. The mixture was stirred until homogeneous, heated to 90-110 °C, and refluxed for 4-6 h. 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 ethyl acetate. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was then dissolved in petroleum ether / ethanol, recrystallized, filtered, and the filter cake was washed multiple times with petroleum ether and dried in a 60 °C oven for 5 h to obtain compound formula 1.

[0025] On the other hand, the present invention provides an organic electroluminescent device, the organic electroluminescent device comprising an anode, a cathode and an organic layer disposed between the anode and the cathode, the organic layer comprising a light-emitting auxiliary layer, the light-emitting auxiliary layer comprising the organic electroluminescent material as described above.

[0026] Preferably, the organic electroluminescent device further includes at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer. The structure of the organic light-emitting element is not limited to this, and may include fewer or more organic layers.

[0027] The compound of Formula I prepared in this invention is used as a light-emitting auxiliary layer material.

[0028] Preferably, the light-emitting auxiliary layer comprises multiple light-emitting auxiliary layers.

[0029] Preferably, the organic layer includes a hole transport layer and a light-emitting auxiliary layer. The light-emitting auxiliary layer includes a first light-emitting auxiliary layer and a second light-emitting auxiliary layer. The first light-emitting auxiliary layer includes the organic electroluminescent material as described above, and the first light-emitting auxiliary layer is located between the hole transport layer and the second light-emitting auxiliary layer.

[0030] The second luminescent auxiliary layer is selected from compounds having the chemical formula II structure in application document 202610297970.5: ; R is selected from C1-C6 alkyl groups that are partially or completely substituted with deuterium or are unsubstituted. R1-R4 are independently selected from hydrogen and deuterium; n1 and n4 are independently selected from 0, 1, 2, 3, 4, 5, 6, and 7; n2 is independently selected from 0, 1, 2, 3, and 4; n3 is independently selected from 0, 1, 2, and 3; X is independently selected from CR5R6, O, S, wherein R5 and R6 are independently selected from methyl, ethyl, propyl, isopropyl, tert-butyl, and methyl, which are partially or completely substituted or unsubstituted by deuterium; ethyl, propyl, isopropyl, isopropyl, and tert-butyl, which are partially or completely substituted or unsubstituted by deuterium. Ar is independently selected from one of the following structures that are partially or completely substituted by deuterium or are unsubstituted: ; Indicates the linking site of a functional group.

[0031] More preferably, the second light-emitting auxiliary layer has a specific structure of one or more of the following compounds; .

[0032] Regarding the compound represented by Formula I, in the manufacture of organic light-emitting elements, an organic layer is formed using vacuum evaporation or solution coating. Solution coating methods include spin coating, dip coating, blade coating, inkjet printing, screen printing, spray coating, and roll coating, but are not limited to these.

[0033] Depending on the materials used, the organic light-emitting element of the present invention is classified into top-emitting type, bottom-emitting type, or bidirectional-emitting type.

[0034] The devices of this invention are used in organic electroluminescent devices, including but not limited to flat panel displays, computer monitors, medical monitors, televisions, billboards, lamps for internal or external lighting and / or signals, head-up displays, fully transparent 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, 3D displays, virtual reality or augmented reality displays, vehicles, video walls including multiple displays tiled together, theater or stadium screens, phototherapy devices, and signs.

[0035] As the anode material, a material with a high work function is selected to facilitate the injection of holes into the organic layer. Specific examples of anode materials that can be used in this invention include vanadium, chromium, copper, zinc, gold or their alloys; metal oxides such as zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); combinations of metals and oxides such as ZnO:Al or SnO2:Sb; and conductive polymers such as polypyrrole and polyaniline.

[0036] The hole injection layer is selected as a p-doped hole injection layer, which means a hole injection layer doped with p-doped agents. P-doped agents are materials that can impart p-type semiconductor characteristics. P-type semiconductor characteristics refer to the characteristics of injecting or transporting holes at the HOMO energy level, that is, the characteristics of materials with high hole conductivity.

[0037] Hole transport material is a material capable of receiving holes from the anode or hole injection layer and transporting the holes to the light-emitting layer, and the hole transport material is a material with high hole mobility. The hole transport material is selected from aryl amine derivatives, conductive polymers, and block copolymers that simultaneously contain conjugated and non-conjugated parts.

[0038] An auxiliary light-emitting layer (multilayer hole transport layer) is added between the hole transport layer and the light-emitting layer. The auxiliary light-emitting layer primarily assists the hole transport layer and is therefore sometimes referred to as a second hole transport layer. This layer allows holes transferred from the anode to smoothly move to the light-emitting layer and blocks electrons transferred from the cathode, confining them within the light-emitting layer. This reduces the potential barrier between the hole transport layer and the light-emitting layer, lowers the driving voltage of the organic light-emitting device, and further increases hole utilization, thereby improving the device's luminous efficiency and lifetime.

[0039] The luminescent material in the luminescent 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. The material with high quantum efficiency for fluorescence or phosphorescence is selected.

[0040] The light-emitting layer comprises a host material and a dopant material, with a mass ratio of host material to dopant material of 90-99.5:0.5-10.

[0041] The main materials are aromatic fused-ring derivatives or heterocyclic compounds. Specifically, aromatic fused-ring derivatives include anthracene derivatives, pyrene derivatives, naphthalene derivatives, pentane derivatives, phenanthrene compounds, or fluoranthene compounds, while heterocyclic compounds include carbazole derivatives, dibenzofuran derivatives, or pyrimidine derivatives.

[0042] The dopant materials of this invention include fluorescent doping and phosphorescent doping, specifically selected from aromatic amine derivatives, styrylamine compounds, boron complexes, fluoranthene compounds, or metal complexes.

[0043] The electron transport layer can promote electron transport. The electron transport material is a material that can effectively receive electrons from the cathode and transport them to the light-emitting layer. Specifically, it is selected from materials with high electron mobility. The electron transport layer includes an electron buffer layer, a hole blocking layer, and an electron transport layer.

[0044] The electron injection layer facilitates electron injection and has the ability to transport electrons, preventing excitons generated in the light-emitting layer from migrating to the hole injection layer. Materials for the electron injection layer include, but are not limited to, oxazoles, oxadiazoles, triazoles, imidazoles, perylenetetracarboxylic acids, fluorenemethane, anthrones 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.

[0045] The cathode is selected from materials with a small work function to facilitate electron injection into an organic material layer with a thickness between 0.5 and 5 nm. Specifically, the 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 structures.

[0046] Apart from Formula I included in the light-emitting auxiliary layer disclosed in this invention, there are no special restrictions on the materials of other layers in OLED devices. 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.

[0047] Compared with the prior art, the present invention has the following beneficial effects: The compound of the present invention uses 9,9-dimethylfluorene as the parent core, which is linked to an aromatic amino group. One of the aromatic amino side chains contains a 1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene derivative, and the other aromatic amino side chain is an aryl or heteroaryl group. At the same time, alkyl, aryl or heteroaryl substitutions are performed on both sides of the parent core 9,9-dimethylfluorene, and the resulting compound of formula I has a low refractive index.

[0048] The low-refractive-index compound of Formula I of this invention is used as a light-emitting auxiliary material in the thicker layer of a double-layer light-emitting auxiliary material. This allows the light emitted from the device to pass through the low-refractive-index film of Formula I. The organic electroluminescent device prepared by combining the low-refractive-index film of Formula I with the high-refractive-index light-emitting auxiliary material can better concentrate the light, emit specific wavelengths of light emitted from the device, narrow the emission spectrum, enhance the luminous intensity of specific wavelengths of light, reduce light loss, improve the luminous efficiency of the device, and at the same time ensure a low driving voltage and a long device life. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0050] Figure 1 The image shows the 1H NMR spectrum of compound 48.

[0051] Figure 2 The image shows the 1H NMR spectrum of compound 57. Detailed Implementation

[0052] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and related drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0053] Additionally, it should be noted that the values ​​given in the following embodiments are as accurate as possible. However, those skilled in the art will understand that due to unavoidable measurement errors and experimental issues, each number should be understood as an approximation rather than an absolutely accurate value.

[0054] The following are common knowledge references: Organometallic Chemistry (6th Edition), Robert H. Crabtree, published by East China University of Science and Technology Press, Shanghai, September 00, 2017, ISBN: 978-7-5628-5111-0, page 388.

[0055] Organic Chemistry and Optoelectronic Materials Experiment Tutorial, Chen Runfeng, Publisher: Southeast University Press, Publication Date: 2019-11-00, ISBN: 9787564184230, Page 174.

[0056] The features and performance of the present invention will be further described in detail below with reference to specific embodiments.

[0057] Example 1: Synthesis of Compound 48 Since there is no existing technology for the raw material E-48, the following synthetic route was adopted for synthesis: CAS: a-48: 364044-44-0; CAS: b-48: 594-36-5; Under nitrogen protection, raw materials a-48 (1.0 eq) and b-48 (1.0 eq) were added to a mixed solution of toluene, ethanol, and water. Pd(OAc)₂ (0.02 eq), X-Phos (0.05 eq), and Cs₂CO₃ (2.0 eq) were then added. The mixture was heated to 100 °C and reacted for 12 h. After cooling to room temperature, the reaction was detected by thin-layer chromatography. After the reaction was complete, H₂O was added, and the mixture was filtered after the solid precipitated completely. The filter cake was dried, and the resulting solid was dissolved in toluene by heating. While still hot, the solution was passed through a silica gel funnel using a mixed solution of methanol and dichloromethane as the developing solvent. The filtrate was used to remove the solvent using a rotary evaporator, and the resulting solid was dried to obtain raw material E-48. Yield: 42.9%. CAS: A-48: 2425541-05-3; CAS: B-48: 116233-20-6; CAS: C-48: 98-80-6; CAS: D-48: 123324-71-0.

[0058] Step 1: Under nitrogen protection, raw material A-48 (1.0 eq) was dissolved in THF, and CH3MgBr (1.2 eq) was added at -10℃. The mixture was then heated to room temperature and reacted for 12 h. The reaction was detected by thin-layer chromatography. After the reaction was complete, the mixture was filtered through 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 DCM. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was then dissolved in petroleum ether / ethanol and recrystallized. After filtration, the filter cake was washed several times with petroleum ether and dried in a 60℃ oven for 5 h to obtain intermediate 1. Yield: 78.6%.

[0059] Step 2: Under nitrogen protection, intermediate 1 (1.0 eq) was dissolved in DCM, and triethylsilane (2.0 eq) and methanesulfonic acid (2.0 eq) were added. The reaction was carried out at room temperature for 12 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, water was added and the mixture was washed three times, retaining the organic phase. The aqueous phase was then extracted with DCM. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was then dissolved in petroleum ether / ethanol, recrystallized, filtered, and the filter cake was washed several times with petroleum ether and dried in a 60 °C oven for 5 h to obtain intermediate 2. Yield: 88.4%.

[0060] Step 3: Under nitrogen protection, intermediate 2 (1.0 eq) was dissolved in THF. NaH (3.0 eq) and CH3I (3.0 eq) were added at -10°C, and the reaction was allowed to proceed for 1 hour. The mixture was then heated to room temperature and reacted for another 8 hours. The reaction was monitored using thin-layer chromatography. After the reaction was complete, the mixture was filtered through diatomaceous earth to remove salts and catalyst. The filtrate was cooled to room temperature and washed three times with water, retaining the organic phase. The aqueous phase was then extracted with DCM. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was then dissolved in petroleum ether / ethanol and recrystallized. After filtration, the filter cake was washed multiple times with petroleum ether and dried in a 60°C oven for 5 hours to obtain intermediate 3. Yield: 90.3%.

[0061] Step 4: Under nitrogen protection, raw materials B-48 (1.0 eq) and C-48 (1.0 eq) were added to a mixed solution of toluene, ethanol, and water. Pd(OAc)₂ (0.02 eq), X-Phos (0.02 eq), and Cs₂CO₃ (2.0 eq) were then added. The mixture was heated to 100 °C and reacted for 12 h. After cooling to room temperature, the reaction was detected by thin-layer chromatography. After the reaction was complete, H₂O was added. After the solid precipitated completely, the mixture was filtered, and the filter cake was dried. The resulting solid was dissolved in toluene by heating and passed through a silica gel funnel while hot. A mixed solution of methanol and dichloromethane was used as the developing solvent. The filtrate was used to remove the solvent using a rotary evaporator. The resulting solid was dried to obtain intermediate 4. Yield: 85.1%.

[0062] Step 5: Under nitrogen protection, intermediates 4 (1 eq) and 3 (1.3 eq) were dissolved in toluene solution, and sodium tert-butoxide (2.00 eq), tris(dibenzylacetone)dipalladium (0.01 eq), and tri-tert-butylphosphine (0.05 eq) were added. The mixture was stirred until homogeneous, heated to 110 °C, and refluxed for 6 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered through 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 ethyl acetate. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was then dissolved in petroleum ether / ethanol, recrystallized, filtered, and the filter cake was washed several times with petroleum ether and dried in a 60 °C oven for 5 h to obtain intermediate 5. Yield: 82.3%.

[0063] Step 6: Under nitrogen protection, intermediate 5 (1.0 eq) and starting material D-48 (1.0 eq) were added to a mixed solution of toluene, ethanol, and water. Pd(OAc)₂ (0.02 eq), X-Phos (0.05 eq), and Cs₂CO₃ (2.0 eq) were then added. The mixture was heated to 100 °C and reacted for 12 h. After cooling to room temperature, the reaction was detected by thin-layer chromatography. After the reaction was complete, H₂O was added, and the mixture was filtered after the solid precipitated completely. The filter cake was dried, and the resulting solid was dissolved in toluene by heating. While still hot, the solution was passed through a silica gel funnel using a methanol and dichloromethane mixture as the developing solvent. The filtrate was used to remove the solvent using a rotary evaporator, and the resulting solid was dried to obtain intermediate 6. Yield: 84.4%.

[0064] Step 7: Under nitrogen protection, intermediate 6 (1 eq) and starting material E-48 (1.3 eq) were dissolved in toluene solution, and sodium tert-butoxide (2.00 eq), tris(dibenzylacetone)dipalladium (0.01 eq), and tri-tert-butylphosphine (0.05 eq) were added. The mixture was stirred until homogeneous, heated to 110 °C, and refluxed for 6 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered through 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 ethyl acetate. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was then dissolved in petroleum ether / ethanol, recrystallized, filtered, and the filter cake was washed several times with petroleum ether and dried in a 60 °C oven for 5 h to obtain compound 48. Yield: 77.8%.

[0065] Characterization: The proton NMR spectrum of compound 48 is as follows: Figure 1 As shown.

[0066] HPLC purity: >99.8%.

[0067] Test value ((ESI, m / Z): [M+H]+): 825.69; Elemental analysis: Test values: C, 89.99; H, 8.29; N, 1.82.

[0068] Example 2: Synthesis of Compound 311 CAS: A-57: 2425541-05-3; CAS: B-57: 116233-20-6; CAS: C-57: 98-80-6; CAS: D-57: 169126-63-0; CAS: E-57: 27452-14-8.

[0069] Step 1: Under nitrogen protection, raw material A-57 (1.0 eq) was dissolved in THF, and CH3MgBr (1.2 eq) was added at -10℃. The mixture was then heated to room temperature and reacted for 12 h. The reaction was detected by thin-layer chromatography. After the reaction was complete, the mixture was filtered through 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 DCM. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was then dissolved in petroleum ether / ethanol and recrystallized. After filtration, the filter cake was washed multiple times with petroleum ether and dried in a 60℃ oven for 5 h to obtain intermediate 1. Yield: 78.6%.

[0070] Step 2: Under nitrogen protection, intermediate 1 (1.0 eq) was dissolved in DCM, and triethylsilane (2.0 eq) and methanesulfonic acid (2.0 eq) were added. The reaction was carried out at room temperature for 12 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, water was added and the mixture was washed three times, retaining the organic phase. The aqueous phase was then extracted with DCM. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was then dissolved in petroleum ether / ethanol, recrystallized, filtered, and the filter cake was washed several times with petroleum ether and dried in a 60 °C oven for 5 h to obtain intermediate 2. Yield: 88.4%.

[0071] Step 3: Under nitrogen protection, intermediate 2 (1.0 eq) was dissolved in THF. NaH (3.0 eq) and CH3I (3.0 eq) were added at -10°C, and the reaction was allowed to proceed for 1 hour. The mixture was then heated to room temperature and reacted for another 8 hours. The reaction was monitored using thin-layer chromatography. After the reaction was complete, the mixture was filtered through diatomaceous earth to remove salts and catalyst. The filtrate was cooled to room temperature and washed three times with water, retaining the organic phase. The aqueous phase was then extracted with DCM. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was then dissolved in petroleum ether / ethanol and recrystallized. After filtration, the filter cake was washed multiple times with petroleum ether and dried in a 60°C oven for 5 hours to obtain intermediate 3. Yield: 90.3%.

[0072] Step 4: Under nitrogen protection, raw materials B-57 (1.0 eq) and C-57 (1.0 eq) were added to a mixed solution of toluene, ethanol, and water. Pd(OAc)₂ (0.02 eq), X-Phos (0.02 eq), and Cs₂CO₃ (2.0 eq) were then added. The mixture was heated to 100 °C and reacted for 12 h. After cooling to room temperature, the reaction was detected by thin-layer chromatography. After the reaction was complete, H₂O was added. After the solid precipitated completely, the mixture was filtered, and the filter cake was dried. The resulting solid was dissolved in toluene by heating and passed through a silica gel funnel while hot. A mixed solution of methanol and dichloromethane was used as the developing solvent. The filtrate was used to remove the solvent using a rotary evaporator. The resulting solid was dried to obtain intermediate 4. Yield: 85.1%.

[0073] Step 5: Under nitrogen protection, intermediates 4 (1 eq) and 3 (1.3 eq) were dissolved in toluene solution, and sodium tert-butoxide (2.00 eq), tris(dibenzylacetone)dipalladium (0.01 eq), and tri-tert-butylphosphine (0.05 eq) were added. The mixture was stirred until homogeneous, heated to 110 °C, and refluxed for 6 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered through 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 ethyl acetate. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was then dissolved in petroleum ether / ethanol, recrystallized, filtered, and the filter cake was washed several times with petroleum ether and dried in a 60 °C oven for 5 h to obtain intermediate 5. Yield: 83.1%.

[0074] Step 6: Under nitrogen protection, intermediate 5 (1.0 eq) and starting material D-57 (1.0 eq) were added to a mixed solution of toluene, ethanol, and water. Pd(OAc)₂ (0.02 eq), X-Phos (0.05 eq), and Cs₂CO₃ (2.0 eq) were then added. The mixture was heated to 100 °C and reacted for 12 h. After cooling to room temperature, the reaction was detected by thin-layer chromatography. After the reaction was complete, H₂O was added, and the solid was filtered after precipitation. The filter cake was dried, and the resulting solid was dissolved in toluene by heating. While still hot, the solution was passed through a silica gel funnel using a methanol and dichloromethane mixture as the developing solvent. The filtrate was used to remove the solvent using a rotary evaporator, and the resulting solid was dried to obtain intermediate 6. Yield: 80.7%.

[0075] Step 7: Under nitrogen protection, intermediate 6 (1 eq) and starting material E-57 (1.3 eq) were dissolved in toluene solution, and sodium tert-butoxide (2.00 eq), tris(dibenzylacetone)dipalladium (0.01 eq), and tri-tert-butylphosphine (0.05 eq) were added. The mixture was stirred until homogeneous, heated to 110 °C, and refluxed for 6 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered through 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 ethyl acetate. The combined organic phases were dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator. The mixture was then dissolved in petroleum ether / ethanol, recrystallized, filtered, and the filter cake was washed several times with petroleum ether and dried in a 60 °C oven for 5 h to obtain compound 48. Yield: 75.5%.

[0076] Characterization: HPLC purity: >99.8%.

[0077] Test value ((ESI, m / Z): [M+H]+): 843.71; Elemental analysis: Test values: C, 89.47; H, 8.85; N, 1.78.

[0078] Additionally, it should be noted that other compounds in this application can be obtained by referring to the synthesis methods listed in the examples above, so they will not be listed one by one here. The mass spectrometer used for mass spectrometry in this application is a Waters XEVO TQD, which is low-precision and uses an ESI source.

[0079] Refractive index test Preparation of monolayer films for optical property evaluation Compound I (see Table 1 for the compounds of this invention) and comparative compound an were respectively deposited on silicon substrates with a film thickness of 40 nm. The refractive index n and extinction coefficient k at a wavelength of 530 nm were measured. The structure of comparative compound an is shown below, and the measurement data are shown in Table 1. Table 1. Test results of refractive index n and extinction coefficient k Under a refractive index test at 530 nm, the refractive index of compound I of the present invention is between 1.60 and 1.69, while that of the comparative compound is between 1.72 and 1.81. Under similar structures, the refractive index is reduced by about 1.74% to 11.6%, and the extinction coefficient k value is almost 0 in each color gamut, which does not affect the luminescence of the light-emitting layer.

[0080] Compound I of this invention uses 9,9-dimethylfluorene as its core, linked to an aromatic amine group. One of the aromatic amine side chains contains a 1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene derivative, and the other side chain is either aryl or heteroaryl. Alkyl, aryl, or heteroaryl substitutions are applied to both sides of the 9,9-dimethylfluorene core. The presence of numerous alkyl structures effectively increases the molecular volume, reducing the number of molecules per unit volume, thus lowering the overall density of the material. According to the Lorentz-Lorentz equation, refractive index is positively correlated with material density. A decrease in intermolecular density further contributes to a decrease in refractive index. Therefore, the resulting compound of formula I has a low refractive index.

[0081] The low-refractive-index compound of Formula I of this invention is used as a light-emitting auxiliary material in the thicker layer of a double-layer light-emitting auxiliary material. This allows the light emitted from the device to pass through the low-refractive-index film of Formula I. The organic electroluminescent device prepared by combining the low-refractive-index film of Formula I with the high-refractive-index light-emitting auxiliary material can better concentrate the light, emit specific wavelengths of light emitted from the device, narrow the emission spectrum, enhance the luminous intensity of specific wavelengths of light, reduce light loss, improve the luminous efficiency of the device, and at the same time ensure a low driving voltage and a long device life.

[0082] The following examples illustrate the application of the low refractive index material of Formula I provided in this application in organic electroluminescent devices.

[0083] Green organic light-emitting diode 1: a. ITO anode: An ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrate with a coating thickness of 14nm / 150nm / 14nm is washed twice in distilled water, ultrasonically cleaned for 30 minutes, then washed twice more in distilled water, ultrasonically cleaned for 10 minutes. After washing, it is transferred to a spin dryer for spin drying, and finally baked in a vacuum oven at 220℃ for 2 hours. After baking, it is cooled down before use. Using this substrate as the anode, the device process is carried out using a vapor deposition machine, and other functional layers are sequentially vapor deposited on it.

[0084] b. HIL (hole injection layer): Hole injection layer materials HT-1 and P-dopant were vacuum-deposited at a deposition rate of 1 Å / s, with a deposition rate ratio of HT-1 to P-dopant of 95:5 and a thickness of 10 nm. c. HTL (hole transport layer): 130 nm of HT1 is vacuum-deposited on the hole injection layer at a deposition rate of 1.0 Å / s as a hole transport layer. d. Light-emitting auxiliary layer-1: Compound 48 of Formula I provided in this embodiment of the invention is vacuum-deposited on the hole transport layer at a deposition rate of 1.0 Å / s for 40 nm as light-emitting auxiliary layer-1. e. Light-emitting auxiliary layer-2: A 5 nm prime 2-1 is vacuum-deposited on the light-emitting auxiliary layer-1 at a deposition rate of 1.0 Å / s as the light-emitting auxiliary layer-2; f. EML (Emitting Layer): Then, on the above-mentioned emitting auxiliary layer, a host material (Host-1 and Host-2) and a dopant material (Dopant-G) with a thickness of 40 nm are vacuum-deposited at a deposition rate of 1 Å / s as the emitting layer. Host-1 and Host-2 are co-deposited with the dopant material as dual host materials, with a ratio of 50%:50%. The deposition rate ratio of the host material to the dopant is 90:10.

[0085] g. HBL (hole blocking layer): HB-1 with a thickness of 5.0 nm was vacuum-deposited at a deposition rate of 0.5 Å / s as a hole blocking layer.

[0086] h. ETL (Electron Transport Layer): ET-1 and Liq, with a thickness of 30 nm, were vacuum-deposited at a deposition rate of 1 Å / s as the electron transport layer. The deposition rate ratio of ET-1 to Liq was 50:50.

[0087] i. EIL (Electron Injection Layer): A 1.0 nm Yb film is deposited at a deposition rate of 0.5 Å / s to form an electron injection layer.

[0088] j. Cathode: Magnesium and silver are deposited at a deposition rate of 1 Å / s for 13 nm, with a deposition rate ratio of 1:9, to form the cathode.

[0089] k. Optical extraction layer: CPL-1 with a thickness of 60 nm is vacuum-deposited on the cathode at a deposition rate of 1 Å / s as the optical extraction layer.

[0090] The vapor-deposited substrate is then encapsulated. First, a UV adhesive is applied to the cleaned cover plate using a coating equipment. Then, the coated cover plate is moved to the lamination section, where the vapor-deposited substrate is placed on top of the cover plate. Finally, the substrate and cover plate are laminated together using a bonding equipment, while simultaneously curing the UV adhesive under UV light.

[0091] The structural formulas of the raw materials required for each of the above layers are shown below: .

[0092] Device Examples 2-76 Organic electroluminescent devices of application examples 2-76 were prepared according to the above-described method for preparing organic electroluminescent devices, except that compound 48 in device example 1 was replaced with compounds 1, 4, 5, 7, 10, 11, 14, 18, 20, 23, 33, 41, 45, 51, 57, 58, 60, 61, 65, 66, 70, 78, 81, 84, 90, 96, 100, 107, 113, 120, 127, 131, 137, 145, and 152, respectively. The numbers 158, 166, 177, 181, 190, 197, 212, 221, 233, 239, 245, 251, 260, 265, 275, 282, 285, 291, 302, 306, 323, 331, 342, 350, 355, 362, 367, 375, 381, 388, 392, 397, 401, 408, 410, 415, 421, 428, 431, and 437 form the luminescent auxiliary layer-1.

[0093] Device Examples 76-92 Organic electroluminescent devices of application examples 76-92 were prepared according to the above-described method for preparing organic electroluminescent devices, except that compound prime2-1 in device example 1 was replaced with compounds prime2-15, prime2-63, prime2-112, prime2-157, prime2-222, prime2-524, prime2-695, and prime2-758, respectively, to form a light-emitting auxiliary layer-2.

[0094] Device Comparison Examples 1-14 Organic electroluminescent devices of Comparative Examples 1-14 were prepared according to the preparation method of Organic Electroluminescent Device Application Example 1 above, except that compound 48 in Device Example 1 was replaced with the corresponding comparative compounds (refer to comparative compounds 1-14 in Table 2) to form a light-emitting auxiliary layer.

[0095] The driving voltage, luminous efficiency, and lifetime of the organic electroluminescent devices obtained in Application Example 1 and Comparative Examples 1-14 were characterized at a brightness of 15000 nits. The test results are shown in Table 2 below.

[0096] Table 2. Results of luminous properties test (luminance value 15000 nits) As shown in Table 2, changing the substituents and their positions alters the device performance, improving luminous efficiency and lifetime to varying degrees. The table also shows that, compared to existing organic electroluminescent devices provided in Comparative Examples 1-14, the OLED devices prepared using the luminescent auxiliary materials provided in the embodiments of this invention (Examples 1-76) exhibit a significant advantage in device lifetime, increasing it by 6.81-26.39% compared to the comparative examples. Furthermore, the luminescent auxiliary materials also show some improvement in device driving voltage and luminous efficiency, with driving voltage reduced by 1.87-10.41% and luminous efficiency increased by 2.15-11.92% compared to the comparative examples. In the prior art, comparative compounds d and f are parallel comparative examples to compound 58 of the present invention, and comparative compound e is a parallel comparative example to compound 5 of the present invention. The main difference between them lies in whether there is a substituent on the side of the parent core 9,9-dimethylfluorene besides the one connected to the aromatic amine. The parent core 9,9-dimethylfluorene of the comparative compounds has an aromatic amine side chain on only one side, and no substituent on the other side. The parent core of the present invention has a substituent on the other side of the parent core 9,9-dimethylfluorene. Compared with the comparative compounds, the introduction of substituents on the other side of the parent core of the present invention can make the molecular structure more symmetrical, which can effectively improve the thermal stability and lifespan of the compound. At the same time, the introduction of large-volume substituents on both sides of the parent core 9,9-dimethylfluorene can effectively disrupt the planarity of the molecule and prevent the close packing between molecules. This helps to suppress excessive intermolecular interactions that lead to luminescence quenching. Moreover, this symmetrical molecular structure is sometimes conducive to the formation of ordered molecular packing, which may result in better charge transport ability, thereby improving the high luminescence efficiency of the material under solid film.

[0097] Comparative compound b and compound 221 of the present invention are parallel comparative examples. The main difference between the two is whether the aryl substituent and the arylamine substituent are on the same side or on both sides of the parent nucleus 9,9-dimethylfluorene. In the present invention, the aryl substituent is located on the other side of the parent nucleus, while in the comparative compound, the aryl substituent and the arylamine substituent are on the same side of the parent nucleus. The comparative compound has too many substituents on the same side, which leads to excessive intermolecular interactions, resulting in molecular stacking and causing fluorescence quenching, thus reducing the luminescence efficiency of the compound. Comparative compound i and compound 61 of the present invention are parallel comparative examples. The main difference between the two is whether the 1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene attached to the side chain of the aromatic amine contains substituents. The 1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene on the side chain of the aromatic amine in the comparative compound does not contain substituents, while the 1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene in the compound of the present invention contains aryl, heteroaryl, or alkyl substituents. By connecting these groups, the conjugated system can be effectively extended, reducing the π-π stacking effect between molecules and the fluorescence quenching phenomenon caused by excessive molecular aggregation, thereby effectively improving luminescence efficiency and device lifetime.

[0098] Comparative compound m is a parallel comparative example to compound 4 of the present invention, and comparative compound n is a parallel comparative example to compound 20 of the present invention. The main difference between them is the 1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene derivative on the aromatic amine. The compound of the present invention is a 1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene-substituted derivative, while the comparative compound is a 1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene-fused cyclic derivative. As can be clearly seen from the data in Table 2, when the substituent on the aromatic amine is a 1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene-substituted derivative, the device lifetime is significantly improved, and the driving voltage and luminous efficiency are also improved to a certain extent.

[0099] As can be seen from the parallel comparative examples above, Compound I of the present invention uses 9,9-dimethylfluorene as the parent core, linked to an aromatic amine group. One of the aromatic amine side chains contains a 1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene-substituted derivative, and the other aromatic amine side chain is an aryl or heteroaryl group. This effectively extends the conjugated system, reduces the π-π stacking interaction between molecules and the fluorescence quenching phenomenon caused by excessive molecular aggregation, and effectively improves luminous efficiency and device lifetime. The obtained compound also has a low refractive index. As can be seen from the data in Table 2, using the compound of the present invention with a low refractive index as a luminescent auxiliary material, applied to the thicker layer of a bilayer luminescent auxiliary material, results in a green light device with a longer lifetime and better luminous efficiency.

[0100] The applicant declares that the organic electroluminescent materials and organic electroluminescent devices of the present invention are illustrated through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An organic electroluminescent material, characterized in that, The organic electroluminescent material has the structure shown in Formula I: ； R1 and R2 are independently selected from substituted or unsubstituted C1-C15 alkyl, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C6-C30 heteroaryl, and their heteroatoms are one or more of O, S, N, Si, Ge or P. n is the maximum allowable substitution from 1 to the ring; m is the maximum allowable substitution on the ring from 0; R3 is selected from substituted or unsubstituted C1-C15 alkyl, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C6-C30 heteroaryl, and its heteroatom is one or more of O, S, N, Si, Ge or P. Ar is selected from the following substituent groups; ； The symbol indicates the position of the group connection. For groups whose substitution positions are not shown, the substitution positions are any substituted positions. In Formula I, hydrogen is either completely substituted with deuterium, partially substituted with deuterium, or completely unsubstituted with deuterium.

2. The organic electroluminescent material according to claim 1, characterized in that, R1 and R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C6-C15 aryl, substituted or unsubstituted C6-C15 heteroaryl, and their heteroatoms are one or more of O, S, N, Si or Ge. R3 is selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C6-C15 aryl, substituted or unsubstituted C6-C15 heteroaryl, and its heteroatom is one or more of O, S, N, Si or Ge.

3. The organic electroluminescent material according to claim 1, characterized in that, The organic electroluminescent material has any one of the structures of formula I-1 to I-4: ； Where m is the maximum allowable substitution from 1 to the ring; R3 is selected from substituted or unsubstituted methyl, substituted or unsubstituted ethyl, substituted or unsubstituted tert-butyl, substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted dibenzothiopheneyl, and substituted or unsubstituted 9,9-dimethylfluorenyl.

4. The organic electroluminescent material according to any one of claims 1-3, characterized in that, "Substitution" means substitution by one, two or more substituents selected from the following: hydrogen, deuterium, halogen, cyano, trifluoromethyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methylbutyl, 1-ethylbutyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, 1-methylhexyl, phenyl, naphthyl, anthracene, phenanthrene, thiophene, furanyl, pyrrole, benzothiophene, benzofuranyl, pyridyl, indolyl, cyclopentyl, cyclohexyl, adamantane, or substitution by two or more substituents linked together from the substituents listed above.

5. The organic electroluminescent material according to claim 1, characterized in that, The organic electroluminescent material is any one of the following compounds: 。 6. An organic electroluminescent device, characterized in that, The organic electroluminescent device includes an anode, a cathode, and an organic layer disposed between the anode and the cathode. The organic layer includes a light-emitting auxiliary layer, which includes the organic electroluminescent material according to any one of claims 1-5.

7. The organic electroluminescent device according to claim 6, characterized in that, The organic electroluminescent device further includes at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer.

8. An organic electroluminescent device, characterized in that, The organic electroluminescent device includes an anode, a cathode, and an organic layer disposed between the anode and the cathode. The organic layer includes a hole transport layer and a light-emitting auxiliary layer. The light-emitting auxiliary layer includes a first light-emitting auxiliary layer and a second light-emitting auxiliary layer. The first light-emitting auxiliary layer includes the organic electroluminescent material according to any one of claims 1-5. The first light-emitting auxiliary layer is located between the hole transport layer and the second light-emitting auxiliary layer.

9. The organic electroluminescent device according to claim 8, characterized in that, The second light-emitting auxiliary layer comprises a compound having a chemical formula II structure: ； R is selected from C1-C6 alkyl groups that are partially or completely substituted with deuterium or are unsubstituted. R1-R4 are independently selected from hydrogen and deuterium; n1 and n4 are independently selected from 0, 1, 2, 3, 4, 5, 6, and 7; n2 is independently selected from 0, 1, 2, 3, and 4; n3 is independently selected from 0, 1, 2, and 3; X is independently selected from CR5R6, O, S, wherein R5 and R6 are independently selected from methyl, ethyl, propyl, isopropyl, tert-butyl, and methyl, which are partially or completely substituted or unsubstituted by deuterium; ethyl, propyl, isopropyl, isopropyl, and tert-butyl, which are partially or completely substituted or unsubstituted by deuterium. Ar is independently selected from one of the following structures that are partially or completely substituted by deuterium or are unsubstituted: ； Indicates the linking site of a functional group.

10. The organic electroluminescent device according to claim 9, characterized in that, The second light-emitting auxiliary layer includes one or more of the following compounds; 。

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