Light-emitting auxiliary material, preparation method thereof and laminated organic electroluminescent device

Abstract

The invention belongs to the field of organic electroluminescence, and provides a light-emitting auxiliary material, a preparation method thereof and a laminated organic electroluminescence device. The invention provides a light-emitting auxiliary material. The structure of the light-emitting auxiliary material is shown in the specification. The light-emitting auxiliary material disclosed by the invention has excellent thermal stability, and is applied to a laminated device, so that the device has low driving voltage, excellent light-emitting efficiency and long service life.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescence, specifically relating to a light-emitting auxiliary material, its preparation method, and a stacked organic electroluminescent device. Background Technology

[0002] OLED materials are categorized into luminescent materials, hole transport materials, and electron transport materials. Hole transport materials typically have low highest occupied molecular orbitals (HOMOs). Excitons generated in the luminescent layer diffuse to the hole transport layer interface or side of the hole transport layer, ultimately leading to luminescence at the interface of the luminescent layer or charge imbalance within the luminescent layer. This results in luminescence at the hole transport layer interface, reducing the color purity and efficiency of organic light-emitting devices (OLEDs) and shortening their lifetime. Introducing a light-emitting auxiliary layer between the luminescent and hole transport layers reduces the potential barrier between the two layers, improving hole utilization and thus enhancing OLED luminous efficiency, stability, and lifetime. Currently, there are limited materials suitable for light-emitting auxiliary layers. Most of these materials employ fluorene ring structures, which possess both high hole mobility and high energy to prevent recombination excitons from diffusing into the transport layer, improving overall device efficiency. Simultaneously, a suitable HOMO value lowers the hole transport barrier from the transport layer to the luminescent layer, reducing the device driving voltage and improving lifetime.

[0003] Furthermore, to achieve high current efficiency, researchers have designed a method of stacking two or more light-emitting units, known as a stacked OLED. Stacked devices primarily connect two or more light-emitting units together through a connecting layer. Compared to traditional OLEDs, it boasts higher luminous efficiency, which can increase exponentially with the number of light-emitting units. Moreover, when tested at the same current density, stacked OLEDs exhibit the same degradation characteristics as traditional OLEDs. However, due to the higher initial brightness of stacked OLEDs, their lifespan, when converted to the same initial brightness, will be longer than that of traditional OLEDs.

[0004] However, a stable and efficient light-emitting auxiliary material has not yet been fully developed for use in stacked devices. How to develop a new light-emitting auxiliary material to improve the lifetime and luminous efficiency of stacked devices while reducing the driving voltage has always been a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a light-emitting auxiliary material, a method for preparing the same, and a multilayer organic electroluminescent device. The light-emitting auxiliary material provided by this invention has excellent thermal stability. When applied to multilayer devices, it enables the devices to have low driving voltage while possessing excellent luminous efficiency and long service life.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first technical objective of this invention is to provide a luminescent auxiliary material, the general structural formula of which is chemical formula I: ; 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.

[0008] Furthermore, any one of the hydrogen atoms in the chemical formula I can be independently replaced by deuterium.

[0009] Further preferably, R is selected from methyl, which is partially or completely substituted or unsubstituted by deuterium; ethyl, which is partially or completely substituted or unsubstituted by deuterium; propyl, which is partially or completely substituted or unsubstituted by deuterium; isopropyl, which is partially or completely substituted or unsubstituted by deuterium; and tert-butyl, which is partially or completely substituted or unsubstituted by deuterium.

[0010] Further preferred, chemical formula I has the following structures from chemical formula I-A to chemical formula I-F: .

[0011] In the above technical solution, the luminescent auxiliary material is any one of the following structures, but is not limited to: .

[0012] The luminescent auxiliary material of the present invention can be prepared by methods known to those skilled in the art. Alternatively, the following reaction process is preferred for preparation.

[0013] In the above formula, R, R1-R4, n1-n4, X, and Ar are as defined in the above chemical formula I, and Hal is independently selected from chlorine, bromine, and iodine.

[0014] In contrast to the complex raw materials that are not publicly available, the invention will employ the classic Buchwald–Hartwig coupling reaction, lithiation reaction and / or dehydration reaction to synthesize the materials and apply them to this invention.

[0015] Specifically, the preparation method of the luminescent auxiliary material is as follows: Step 1: At -78℃, THF and raw material B (1.2 eq) were added to the reaction flask, nitrogen was replaced 3 times, and the mixture was stirred for 10-30 min. Then, n-butyllithium (1.2 eq) was slowly added to the reaction flask and the reaction was allowed to proceed for 2 h. THF containing raw material A was then added to the reaction flask and stirred until homogeneous. The refrigeration was stopped, and the mixture was heated to room temperature and the reaction was allowed to continue for 2-16 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, water and dichloromethane were added for extraction, and the mixture was separated. The organic phases were combined and concentrated. Intermediate 1 was obtained by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V=1:2-1:5).

[0016] Step 2: Add intermediate 1 (1.0 eq) and a mixture of toluene (3.0-8.0 eq) and THF (3.0-8.0 eq) to a reaction flask, stir until dissolved at room temperature, then add methanesulfonic acid (3.0-8.0 eq) to the reaction flask and continue the reaction for 5-60 min. Detect the reaction using thin-layer chromatography. After the reaction is complete, extract with water and dichloromethane, separate the liquid and liquid phases, combine the organic phases and concentrate. Purify intermediate 2 using a mixed solution of dichloromethane and petroleum ether (V:V=1:3-1:8) by column chromatography.

[0017] Step 3: In a reaction flask, intermediate 2 (1.0 eq), starting material C (1.0-1.3 eq), sodium tert-butoxide or potassium tert-butoxide (2.0-4.0 eq), and toluene were added. Under nitrogen protection, tris(dibenzylacetone)dipalladium (0.01-0.03 eq) and tri-tert-butylphosphine (0.02-0.15 eq) were added, and the mixture was heated to 110-120℃ and stirred for 1-10 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, water and dichloromethane were added for extraction, and the mixture was separated. The organic phases were combined and concentrated. Intermediate 3 was obtained by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V=1:3-1:8).

[0018] Step 4: In a reaction flask, intermediate 3 (1.0-1.3 eq), starting material D (1.0 eq), sodium tert-butoxide or potassium tert-butoxide (2.0-4.0 eq), and toluene were added. Under nitrogen protection, tris(dibenzylacetone)dipalladium (0.01-0.03 eq) and tri-tert-butylphosphine (0.02-0.15 eq) were added, and the mixture was heated to 100-120℃ and stirred for 1-15 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, water and dichloromethane were added for extraction, and the mixture was separated. The organic phases were combined and concentrated. The solution of dichloromethane and petroleum ether (V:V=1:3-1:10) was purified by column chromatography to obtain chemical formula I.

[0019] As can be seen from the above technical solution, the present invention has the following beneficial effects: This invention provides a light-emitting auxiliary material. The core structure of this compound is a 9-alkyl-9-naphthylfluorenyl group linked to a triarylamine group, wherein the triarylamine group contains a 9,9-dimethylfluorenyl group, a dibenzofuran group, or a dibenzothiophene group. As a light-emitting auxiliary layer material, it exhibits excellent thermal stability and, when applied to multilayer devices, can effectively improve the luminous efficiency and lifespan of the device.

[0020] The substitution of the 9-position of fluorene with methyl and naphthyl groups creates strong steric hindrance, forcing the naphthyl ring and fluorene ring core to align nearly perpendicularly. This suppresses close intermolecular packing, effectively preventing concentration quenching or excitoassociation formation in the solid state (thin film state), thus maintaining high luminescence efficiency. It also improves the morphological stability of the thin film; non-planar structures are less prone to crystallization, resulting in uniform and stable amorphous films, which helps extend the device's lifespan. Further linking a triarylamine to the 4-position of the fluorene ring reduces the steric hindrance from the 9-position substituent on the triarylamine arm's rotation, allowing for some conformational freedom and facilitating the search for optimal hole transport transition paths in the thin film. Furthermore, the triarylamine group is a classic and efficient hole transport unit; its electron-rich nature facilitates the acceptance of holes from the anode (or hole injection layer) and their transport via intermolecular hopping mechanisms. Additionally, introducing 9,9-dimethylfluorene, dibenzofuran, or dibenzothiophene groups onto the nitrogen atom of the triarylamine can modulate device performance. Attached Figure Description

[0021] 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.

[0022] Figure 1 The above is the proton NMR spectrum of compound 1 provided in Example 1 of this invention. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention discloses a light-emitting auxiliary material, its preparation method, and a stacked organic electroluminescent device.

[0025] 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.

[0026] The features and performance of the present invention will be further described in detail below with reference to specific embodiments.

[0027] Example 1

[0028] Step 1: At -78°C, THF and raw material B-1 (1.2 eq, CAS No.: 1233365-09-7) were added to the reaction flask. Nitrogen gas was replaced three times, and the mixture was stirred for 30 min. Then, n-butyllithium (1.2 eq) was slowly added to the reaction flask, and the reaction was allowed to proceed for 2 h. THF containing raw material A-1 (1.0 eq, CAS No.: 66-99-9) was added to the reaction flask, and the mixture was stirred until homogeneous. The refrigeration was stopped, and the mixture was heated to room temperature and the reaction was allowed to continue for 14 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, water and dichloromethane were added for extraction, and the mixture was separated. The organic phases were combined and concentrated. Intermediate 1 (yield: 71.4%) was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V=1:2).

[0029] Step 2: Intermediate 1 (1.0 eq) and a mixture of toluene (6.0 eq) and THF (6.0 eq) were added to a reaction flask and stirred at room temperature until dissolved. Then, methanesulfonic acid (6.0 eq) was added to the reaction flask and the reaction was continued for 60 min. The reaction was detected by thin-layer chromatography. After the reaction was completed, water and dichloromethane were added for extraction, and the organic phases were separated and concentrated. Intermediate 2 (yield: 78.6%) was obtained by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V=1:4).

[0030] Step 3: Intermediate 2 (1.0 eq), starting material C-1 (1.2 eq, CAS No.: 92-67-1), sodium tert-butoxide (2.0 eq), and toluene were added to a reaction flask. Under nitrogen protection, tris(dibenzylacetone)dipalladium (0.01 eq) and tri-tert-butylphosphine (0.04 eq) were added, and the mixture was heated to 110 °C and stirred for 2 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, water and dichloromethane were added for extraction, and the mixture was separated. The organic phases were combined and concentrated. Intermediate 3 (yield: 79.7%) was obtained by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V=1:5).

[0031] Step 4: Intermediate 3 (1.0 eq), starting material D-1 (1.0 eq, CAS No.: 382602-31-5), sodium tert-butoxide (4.0 eq), and toluene were added to a reaction flask. Tris(dibenzylacetone)dipalladium (0.03 eq) and tritert-butylphosphine (0.06 eq) were added under nitrogen protection. The mixture was heated to 120 °C and stirred for 12 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, water and dichloromethane were added for extraction, and the organic phases were combined and concentrated. Compound 1 was purified by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V=1:5) (yield: 84.6%).

[0032] The obtained compound 1 was analyzed, and the results are as follows: HPLC purity: >99.8%.

[0033] Mass spectrometry test: Waters XEVO TQD mass spectrometer with ESI source.

[0034] Test value MS(ESI, m / Z): [M+H] + =665.46.

[0035] Elemental analysis: The test values ​​are: C, 91.82; H, 6.02; N, 2.21.

[0036] Nuclear magnetic resonance hydrogen spectrum: as shown Figure 1 As shown in (Compound 1).

[0037] In addition, it should be noted that other compounds of the present invention can be obtained by referring to the preparation methods of the examples listed above, so they will not be listed one by one here.

[0038] Device Example 1: Fabrication of a Red Organic Light Emitting Device Anode: ITO anode: An ITO (Indium Tin Oxide)-Ag-ITO (Indium Tin Oxide) glass substrate with a coating thickness of 150nm is cleaned twice in distilled water, ultrasonically washed for 30 minutes, then repeatedly cleaned twice with distilled water, ultrasonically washed for 10 minutes. After washing, it is baked in a vacuum oven at 220℃ for 2 hours. After baking, it is cooled before use. Using this substrate as the anode, the device deposition process is carried out using a vapor deposition machine, and other functional layers are sequentially deposited on it.

[0039] First hole injection layer: On the anode layer after the above washing, HT-1 and P-1 with a thickness of 10 nm are deposited using a vacuum evaporation device. The mass ratio of HT-1 to P-1 is 97:3 as the first hole injection layer.

[0040] First hole transport layer: On the first hole injection layer mentioned above, a 22nm thick HT-1 is then deposited as the first hole transport layer.

[0041] First luminescent auxiliary layer: Subsequently, a compound 1 with a thickness of 5 nm is deposited on the aforementioned first hole transport layer as the first luminescent auxiliary layer.

[0042] First light-emitting layer: After the above-mentioned first light-emitting auxiliary layer material is evaporated, the first light-emitting layer of the OLED light-emitting device is fabricated. Its structure includes using Host-1 as the main material and Dopant-1 as the dopant material. The doping ratio of the dopant material is 3% by weight, and the thickness of the light-emitting layer is 30nm.

[0043] First hole blocking layer: After the first light-emitting layer mentioned above, HB-1 with a thickness of 5nm is deposited as the first hole blocking layer.

[0044] First electron transport layer: After the first hole blocking layer mentioned above, ET-1 and Liq with a thickness of 10 nm are vacuum-deposited, with the mass ratio of ET-1 to Liq being 1:1, as the first electron transport layer.

[0045] NCGL layer: On the first electron transport layer mentioned above, an N-type charge generation layer (NCGL) is vacuum-deposited, wherein the mass ratio of NCGL to Yb is 95:5 and the film thickness is 20nm.

[0046] PCGL layer: On the NCGL layer, a co-evaporated layer of HT-1 and P-1 with a thickness of 10nm is vacuum-deposited, with a mass ratio of HT-1 to P-1 of 95:5, as the PCGL layer.

[0047] Second hole transport layer: On the PCGL layer, a 30nm thick HT-1 film is vacuum-deposited as the second hole transport layer.

[0048] Second luminescent auxiliary layer: Compound 1 with a thickness of 5 nm is deposited on the above-mentioned second hole transport layer as the second luminescent auxiliary layer.

[0049] Second light-emitting layer: After the above-mentioned second light-emitting auxiliary layer material is evaporated, the second light-emitting layer of the OLED light-emitting device is fabricated. Its structure includes using Host-1 as the main material and Dopant-1 as the dopant material. The doping ratio of the dopant material is 3% by weight, and the thickness of the light-emitting layer is 30nm.

[0050] Second hole blocking layer: After the above-mentioned second light-emitting layer, a 5nm thick HB-1 is vacuum-deposited as the second hole blocking layer.

[0051] Second electron transport layer: On the above-mentioned second hole blocking layer, ET-1 and Liq with a thickness of 15nm are deposited, with the mass ratio of ET-1 and Liq being 1:1, as the second electron transport layer.

[0052] Second electron injection layer: On the above-mentioned second electron transport layer, a YB film with a thickness of 1 nm is vacuum-deposited as the second electron injection layer.

[0053] Cathode: A 13 nm thick electrode layer of Mg and Ag is vacuum-deposited on the second electron injection layer, with a mass ratio of Mg to Ag of 1:9, as the cathode layer.

[0054] Light extraction layer: A 65nm thick CPL-1 layer is vacuum-deposited on the cathode as the light extraction layer.

[0055] The substrate after vapor deposition is encapsulated. First, the cleaned cover plate is coated with UV adhesive using an adhesive coating equipment. Then, the coated cover plate is moved to the lamination section, and the vapor-deposited substrate is placed on the top of the cover plate. Finally, the substrate and cover plate are laminated under the action of the lamination equipment, and the UV adhesive is cured by light.

[0056] The material compound structure used in the red light multilayer device is shown below: .

[0057] Device Examples 2-160 Referring to the method provided in Device Example 1 above, the corresponding compounds in Table 1 were selected to replace Compound 1, and the light-emitting auxiliary layer was deposited by vapor deposition to prepare the corresponding organic electroluminescent devices, which are respectively referred to as Device Example 2 to Device Example 160.

[0058] Device Comparison Example 1-Device Comparison Example 12 The comparative example provides an organic electroluminescent device. The only difference between this organic electroluminescent device and device example 1 is that the latter uses existing compound a-compound l instead of the light-emitting auxiliary material (compound 1) in device example 1 for vapor deposition. The chemical structural formula of compound a-compound l is as follows: .

[0059] The driving voltage and luminous efficiency of the organic electroluminescent devices obtained in Device Examples 1 to 160 and Comparative Examples 1 to 12 were characterized at a brightness of 6000 nits, and at a current density of 20 mA / cm². 2 The lifespan of the tested devices was determined, and the test results are shown in Table 1 below: Table 1 Device Test Results

[0060] Device Example 161: Fabrication of Green Organic Light Emitting Device Anode: ITO anode: An ITO (Indium Tin Oxide)-Ag-ITO (Indium Tin Oxide) glass substrate with a coating thickness of 150nm is cleaned twice in distilled water, ultrasonically washed for 30 minutes, then repeatedly cleaned twice with distilled water, ultrasonically washed for 10 minutes. After washing, it is baked in a vacuum oven at 220℃ for 2 hours. After baking, it is cooled before use. Using this substrate as the anode, the device deposition process is carried out using a vapor deposition machine, and other functional layers are sequentially deposited on it.

[0061] First hole injection layer: On the anode layer after the above washing, HT-2 and P-1 with a thickness of 10 nm are deposited using a vacuum evaporation device. The mass ratio of HT-2 to P-1 is 97:3 as the first hole injection layer.

[0062] First hole transport layer: On the first hole injection layer mentioned above, a 22nm thick HT-2 is then deposited as the first hole transport layer.

[0063] First luminescent auxiliary layer: Subsequently, a compound 1 with a thickness of 5 nm is deposited on the aforementioned first hole transport layer as the first luminescent auxiliary layer.

[0064] First light-emitting layer: After the above-mentioned first light-emitting auxiliary layer material is evaporated, the first light-emitting layer of the OLED light-emitting device is fabricated. Its structure includes using (Host-2 and Host-3) as the host material and Dopant-2 as the dopant material, with a total thickness of 30nm. Host-2 and Host-3 are co-evaporated with the dopant material as dual host materials. The ratio of Host-2 to Host-3 is 50%:50%, and the evaporation rate ratio of the host material to Dopant is 90:10.

[0065] First hole blocking layer: After the first light-emitting layer mentioned above, HB-2 with a thickness of 5nm is deposited as the first hole blocking layer.

[0066] First electron transport layer: After the first hole blocking layer mentioned above, ET-2 and Liq with a thickness of 10 nm are vacuum-deposited, with the mass ratio of ET-2 and Liq being 1:1, as the first electron transport layer.

[0067] NCGL layer: On the first electron transport layer mentioned above, an N-type charge generation layer (NCGL) is vacuum-deposited, wherein the mass ratio of NCGL to Yb is 95:5 and the film thickness is 20nm.

[0068] PCGL layer: On the NCGL layer, a co-evaporated layer of HT-2 and P-1 with a thickness of 10 nm is vacuum-deposited, with a mass ratio of HT-2 to P-1 of 95:5, as the PCGL layer.

[0069] Second hole transport layer: On the PCGL layer, a 30nm thick HT-2 film is vacuum-deposited as the second hole transport layer.

[0070] Second luminescent auxiliary layer: Compound 1 with a thickness of 5 nm is deposited on the above-mentioned second hole transport layer as the second luminescent auxiliary layer.

[0071] Second light-emitting layer: After the above-mentioned second light-emitting auxiliary layer material is deposited, the second light-emitting layer of the OLED light-emitting device is fabricated. Its structure includes using (Host-2 and Host-3) as the host material and Dopant-2 as the dopant material, with a total thickness of 30nm. Host-2 and Host-3 are co-evaporated with the dopant material as dual host materials. The mass ratio of Host-2 to Host-3 is 50%:50%, and the evaporation rate ratio of the host material to Dopant is 90:10.

[0072] Second hole blocking layer: After the above-mentioned second light-emitting layer, a 5nm thick HB-2 is vacuum-deposited as a second hole blocking layer.

[0073] Second electron transport layer: On the above-mentioned second hole blocking layer, ET-2 and Liq with a thickness of 15nm are deposited, with the mass ratio of ET-2 and Liq being 1:1, as the second electron transport layer.

[0074] Second electron injection layer: On the above-mentioned second electron transport layer, a YB film with a thickness of 1 nm is vacuum-deposited as the second electron injection layer.

[0075] Cathode: A 13 nm thick electrode layer of Mg and Ag is vacuum-deposited on the second electron injection layer, with a mass ratio of Mg to Ag of 1:9, as the cathode layer.

[0076] Light extraction layer: A 65nm thick CPL-2 layer is vacuum-deposited on the cathode as the light extraction layer; The substrate after vapor deposition is encapsulated. First, the cleaned cover plate is coated with UV adhesive using an adhesive coating equipment. Then, the coated cover plate is moved to the lamination section, and the vapor-deposited substrate is placed on the top of the cover plate. Finally, the substrate and cover plate are laminated under the action of the lamination equipment, and the UV adhesive is cured by light.

[0077] The structure of the material compound used in the green light stacked device is shown below: .

[0078] Device Examples 162-318 Referring to the method provided in Device Example 161 above, the corresponding compounds in Table 2 were selected to replace compound 1, and the light-emitting auxiliary layer was deposited by vapor deposition to prepare the corresponding organic electroluminescent devices, which are respectively referred to as Device Example 162 to Device Example 318.

[0079] Device Comparison Examples 13-24 The comparative example provides an organic electroluminescent device. The only difference between this organic electroluminescent device and the device of example 161 is that the organic electroluminescent device uses existing compound a-compound l instead of the light-emitting auxiliary material (compound 1) in device example 161 for vapor deposition. The chemical structural formula of compound a-compound l is as follows: .

[0080] The driving voltage and luminous efficiency of the organic electroluminescent devices obtained in Device Examples 161-318 and Comparative Examples 13-24 were characterized at a brightness of 15000 nits, and at a current density of 20 mA / cm². 2 The lifespan of the tested devices was determined, and the test results are shown in Table 2 below: Table 2 Device Test Results

[0081] As can be seen from Tables 1 and 2, both green and red multilayer devices show improved luminous efficiency and lifespan when using the luminescent auxiliary material provided by this invention compared to devices prepared with the comparative compound.

[0082] Compounds c and d, and compounds 28 and 174, are parallel comparative examples. The difference lies in the substituents on the triarylamine in compounds c and d, which are different from those in compounds 28 and 174. In the compounds of this invention, at least one substituent in the 9-methyl-9-naphthylfluorene group attached to the aromatic amine group is 9,9-dimethylfluorene, while in compounds c and d, the corresponding positions are benzene-naphthyl and phenyl, respectively. The two methyl groups at position 9 of the 9,9-dimethylfluorene group force the fluorene ring to twist, forming a rigid "propeller"-like three-dimensional structure, providing extremely strong three-dimensional spatial shielding and inhibiting molecular aggregation. Moreover, the rigid three-dimensional structure greatly improves the glass transition temperature and anti-crystallization ability, forming an extremely stable amorphous film, which helps to extend the lifespan of the device. Dimethylfluorene itself is a wide bandgap, high triplet energy level unit with excellent hole transport capability. Its twisted structure inhibits excessive conjugation with the nitrogen of the triarylamine, helping to maintain the high triplet energy level on the entire triarylamine side, resulting in better luminous efficiency of the device.

[0083] Compounds e and 7 are parallel comparative examples. The difference lies in that in compound e, the triarylamine N is attached to the 2-position of the fluorene group below the 9-methyl-9-naphthylfluorene group, while in compound 7 of this invention, the triarylamine N is attached to the 4-position of the fluorene group below the 9-methyl-9-naphthylfluorene group. Data shows that devices using this attachment configuration exhibit superior performance. The 4-position allows for better electron transfer, and the electron-rich properties (hole supply capability) of the triarylamine can be more efficiently transferred to the entire 9-methyl-9-naphthylfluorene core. This results in a more uniform HOMO energy level distribution, a lower hole injection barrier, and stronger hole migration capability. At the same brightness, the required operating voltage is reduced, leading to lower device power consumption.

[0084] Compound f is a compound in the applicant's prior patent (CN119241373B), and is a parallel comparative example with compound 90 in this invention. The difference is that compound f has an additional phenyl group attached to the fluorene position 2 below the 9-methyl-9-naphthylfluorene group. As can be seen from the data results in Tables 1 and 2 above, when the compound in this application is used as a light-emitting auxiliary layer in a multilayer device, it has better device performance than compound f, with lower driving voltage, higher luminous efficiency, and longer service life.

[0085] Compounds hl and 274, 665, 565, 1, and 2 are parallel comparative examples. The difference lies in the core structure: the core structure used in the comparative compounds is 9,9-diphenylfluorenyl, 9-methyl-9-phenylfluorenyl, and 9,9-dimethylfluorenyl, while the core structure in the corresponding positions of the compounds in this invention is 9-methyl-9-naphthylfluorenyl. The naphthyl ring is a larger bicyclic planar structure. When it is attached to the 9-position of fluorene, it generates stronger steric repulsion with the methyl group at the 9-position and the fluorenyl group itself, forming a larger dihedral angle with the fluorenyl ring core. This extreme three-dimensional distortion and non-planarity make it difficult for molecules to pack tightly and regularly, making it easier to form a uniform, dense, and stable glassy thin film. It has a higher glass transition temperature, and during long-term operation and heat generation of the device, the thin film morphology is less prone to crystallization, phase separation, or defects, effectively improving the device's lifespan. Furthermore, the stronger steric hindrance allows molecules to be further apart in the thin film, suppressing triplet-triplet annihilation.

[0086] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A luminescent auxiliary material, characterized in that, The general structural formula of the luminescent auxiliary material is chemical formula I: ； 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.

2. The luminescent auxiliary material according to claim 1, characterized in that, Chemical formula I has the following structures from chemical formula I-A to chemical formula I-F: ； In chemical formula I, any one hydrogen atom is independently replaced by deuterium.

3. The luminescent auxiliary material according to claim 1 or 2, characterized in that, R is selected from methyl (partially or completely substituted with deuterium or unsubstituted), ethyl (partially or completely substituted with deuterium or unsubstituted), propyl (partially or completely substituted with deuterium or unsubstituted), isopropyl (partially or completely substituted with deuterium or unsubstituted), and tert-butyl (partially or completely substituted with deuterium or unsubstituted).

4. The luminescent auxiliary material according to claim 1, characterized in that, The luminescent auxiliary material has the specific structure shown in the following formula: 。 5. A method for preparing the luminescent auxiliary material as described in claim 1, characterized in that, The specific preparation method is as follows: At -78℃, THF and 1.2 eq of raw material B were added to the reaction flask. Nitrogen gas was replaced three times, and the mixture was stirred for 10-30 min. Then, 1.2 eq of n-butyllithium was slowly added to the reaction flask, and the reaction was allowed to proceed for 2 h. THF containing raw material A was then added to the reaction flask, and the mixture was stirred until homogeneous. The refrigeration was stopped, and the mixture was heated to room temperature and the reaction was allowed to continue for 2-16 h. The reaction was detected by thin-layer chromatography. After the reaction was completed, water and dichloromethane were added for extraction, and the mixture was separated. The organic phases were combined and concentrated. Intermediate 1 was obtained by column chromatography using a mixed solution of dichloromethane and petroleum ether with a volume ratio of 1:2-1:

5. Add 1.0 eq of intermediate 1 and a mixture of 3.0-8.0 eq of toluene and 3.0-8.0 eq of THF to a reaction flask, stir until dissolved at room temperature, then add 3.0-8.0 eq of methanesulfonic acid to the reaction flask and continue the reaction for 5-60 min. Detect the reaction using thin-layer chromatography to determine when the reaction is complete. Extract with water and dichloromethane, separate the liquids, combine the organic phases, concentrate, and purify using a mixed solution of dichloromethane and petroleum ether (volume ratio 1:3-1:8) by column chromatography to obtain intermediate 2. Add 1.0 eq intermediate 2, 1.0-1.3 eq starting material C, 2.0-4.0 eq sodium tert-butoxide or potassium tert-butoxide and toluene to a reaction flask. Under nitrogen protection, add 0.01-0.03 eq tris(dibenzylacetone)dipalladium and 0.02-0.15 eq tritert-butylphosphine. Heat to 110-120℃ and stir for 1-10 h. Detect the reaction using thin-layer chromatography. After the reaction is complete, extract with water and dichloromethane, separate the liquids, combine the organic phases, concentrate, and purify using column chromatography with a mixed solution of dichloromethane and petroleum ether at a volume ratio of 1:3-1:8 to obtain intermediate 3. Add 1.0-1.3 eq intermediate 3, 1.0 eq raw material D, 2.0-4.0 eq sodium tert-butoxide or potassium tert-butoxide and toluene to a reaction flask. Under nitrogen protection, add 0.01-0.03 eq tris(dibenzylacetone)dipalladium and 0.02-0.15 eq tritert-butylphosphine. Heat to 100-120℃ and stir for 1-15 h. Detect the reaction using thin-layer chromatography. After the reaction is complete, extract with water and dichloromethane, separate the liquids, combine the organic phases, concentrate, and purify by column chromatography using a mixed solution of dichloromethane and petroleum ether at a volume ratio of 1:3-1:10 to obtain chemical formula I. The corresponding synthetic route is as follows: ； Among them, R, R1-R4, n1-n4, X, and Ar are as defined in the above chemical formula I, and Hal is independently selected from chlorine, bromine, and iodine.

6. A stacked organic electroluminescent device, characterized in that, The stacked organic electroluminescent device includes the light-emitting auxiliary material as described in claim 1.

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