Disubstituted seven-membered spiro derivative, electron transport layer comprising same, and organic electroluminescent element

Abstract

The application provides a double-substituted seven-membered spiro derivative, an electron transport layer containing the same and an organic electroluminescent element, the double-substituted seven-membered spiro derivative has the structure shown in the following formula (I). The double-substituted seven-membered spiro derivative provided in the application takes a rigid structure as a mother nucleus, introduces a substituted or unsubstituted nitrogen-containing heteroaryl group, and further improves the electron transport capacity of the compound. The double-substituted seven-membered spiro derivative can be used as an electron transport material of an organic electroluminescent element, can effectively reduce the working voltage of the organic electroluminescent element, and improves the luminous efficiency.

Description

Technical Field

[0001] This invention relates to the field of organic electroluminescent materials technology, and more specifically, to a double-substituted seven-membered spirocyclic derivative, an electron transport layer comprising the derivative, and an organic electroluminescent element. Background Technology

[0002] Organic light-emitting diodes (OLEDs) have significant research value and promising application prospects in fields such as information display materials and organic optoelectronic materials. With the development of multimedia information technology, the performance requirements for flat panel display devices are becoming increasingly stringent. Currently, the main display technologies include plasma display devices, field emission display devices, and organic light-emitting diodes (OLEDs). Among them, OLEDs possess a series of advantages such as self-illumination, low-voltage DC drive, thinness and energy saving, all-solid-state technology, wide viewing angle, and rich colors. Compared with liquid crystal displays (LCDs), OLEDs do not require a backlight, have a wider viewing angle, lower power consumption, and a response speed 1000 times faster than LCDs. Therefore, OLEDs have a broader application prospect.

[0003] Since the first report of high-efficiency organic light-emitting diodes (OLEDs), many researchers have dedicated themselves to improving device efficiency and stability. Currently, commonly used electron transport materials include metal complexes, nitrogen-containing heterocyclic compounds, perfluorinated compounds, organosilicon compounds, and organoboron compounds. Among these, nitrogen-containing heterocyclic compounds are the most studied structures, with a wide variety. However, in the material combinations used to fabricate devices, they all exhibit some defects, failing to reduce operating voltage while improving device efficiency, and even reducing device lifetime. Therefore, it is still necessary to continue developing new structures to optimize the material combinations of devices and improve their overall performance. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a double-substituted seven-membered spirocyclic derivative, an electron transport layer comprising the derivative, and an organic electroluminescent element, in order to solve the problem that in the prior art, nitrogen-containing heterocyclic compounds in the material composition for device fabrication cannot reduce the operating voltage while improving device efficiency, resulting in reduced luminous efficiency.

[0005] To achieve the above objectives, according to one aspect of the present invention, a bisubstituted seven-membered spirocyclic derivative is provided, having the structure shown in formula (I):

[0006]

[0007] Ar1 and Ar2 are each independently represented as a substituted or unsubstituted C6-C18 aryl group or a substituted or unsubstituted C3-C18 heteroaryl group, and at least one of Ar1 and Ar2 is a substituted or unsubstituted nitrogen-containing heteroaryl group.

[0008] L1 and L2 are each independently represented as single bonds, C6-C18 aryl groups.

[0009] According to another aspect of the invention, an electron transport layer is also provided, which comprises any of the bisubstituted seven-membered spirocyclic derivatives provided in the first aspect described above.

[0010] According to a third aspect of the present invention, an organic electroluminescent element is also provided, comprising the electron transport layer provided in the second aspect above.

[0011] By applying the technical solution provided in this application, the bisubstituted seven-membered spirocyclic derivatives, with a rigid structure as the parent core, introduce substituted or unsubstituted nitrogen-containing heteroaryl groups on both sides, further improving the electron transport capability of the compound. These bisubstituted seven-membered spirocyclic derivatives can be used as electron transport materials for organic electroluminescent devices, effectively reducing the operating voltage of organic electroluminescent devices and improving luminous efficiency. Attached Figure Description

[0012] Figure 1 A schematic diagram of the structure of the organic electroluminescent element provided in Device Embodiment 1 according to the present invention is shown;

[0013] The above figures include the following reference numerals:

[0014] 1. Substrate layer; 2. Hole injection layer; 3. Hole transport layer; 4. Light emission layer; 5. Electron transport layer; 6. Cathode layer. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] The present invention will be described in detail below through embodiments.

[0018] As analyzed in the background section of this application, existing nitrogen-containing compounds, commonly used as electron transport materials in device fabrication compositions, cannot reduce the operating voltage while improving device efficiency, leading to a decrease in luminous efficiency. To address this issue, this application provides a bisubstituted seven-membered spirocyclic derivative, an electron transport material, and an organic electroluminescent element.

[0019] In a typical embodiment of this application, a disubstituted seven-membered spirocyclic derivative is provided, which has the structure shown in formula (I):

[0020]

[0021] Ar1 and Ar2 are each independently represented as a substituted or unsubstituted C6-C18 aryl group or a substituted or unsubstituted C3-C18 heteroaryl group, and at least one of Ar1 and Ar2 is a substituted or unsubstituted nitrogen-containing heteroaryl group.

[0022] L1 and L2 are each independently represented as single bonds, C6-C18 aryl groups.

[0023] By applying the technical solution provided in this application, the bisubstituted seven-membered spirocyclic derivatives, with a rigid structure as the parent core, introduce substituted or unsubstituted nitrogen-containing heteroaryl groups on both sides, further improving the electron transport capability of the compound. These bisubstituted seven-membered spirocyclic derivatives can be used as electron transport materials for organic electroluminescent devices, effectively reducing the operating voltage of organic electroluminescent devices and improving luminous efficiency.

[0024] In some embodiments of this application, the disubstituted seven-membered spirocyclic derivative has the structure shown in formula (A), formula (B), or formula (C):

[0025]

[0026] In some embodiments of this application, when at least one of Ar1 and Ar2 is selected from the following groups, it has better electron transport capability and can reduce the operating voltage and improve luminous efficiency when used as an electron transport material.

[0027]

[0028] Z1, Z2 and Z are each independently selected from H, CN, halogen, substituted or unsubstituted C1-C4 straight-chain alkyl, substituted or unsubstituted C3-C4 branched alkyl, substituted or unsubstituted C6-C18 aryl, substituted or unsubstituted C6-C18 heteroaryl.

[0029] In some embodiments of this application, L1 and L2 are each independently represented as a single bond or a phenyl group. The bisubstituted seven-membered spirocyclic derivative with the structure of formula (I) has superior electron transport capabilities as an electron transport material.

[0030] In some embodiments of this application, when the disubstituted seven-membered spirocyclic derivative is selected from at least one of the following compounds, it has superior electron transport capability. When used as an electron transport material in organic electroluminescent elements, it can improve luminous efficiency while reducing the operating voltage of the organic electroluminescent elements.

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] In another typical embodiment of this application, an electron transport layer is also provided, which includes any of the bisubstituted seven-membered spirocyclic derivatives provided in the first typical embodiment described above.

[0055] In some embodiments of this application, the mass content of the disubstituted seven-membered spirocyclic derivative in the electron transport layer is 30-70%.

[0056] In some embodiments of this application, the mass content of the disubstituted seven-membered spirocyclic derivative in the electron transport layer is 45-55%. In a third typical embodiment of this application, an organic electroluminescent element is also provided, which includes the electron transport layer provided in the second embodiment described above.

[0057] In some embodiments of this application, the organic electroluminescent element further includes an anode layer, a hole injection layer, a hole transport layer, a light-emitting layer, an electron injection layer, and a cathode layer, wherein the anode layer, the hole injection layer, the hole transport layer, the light-emitting layer, the electron transport layer, the electron injection layer, and the cathode layer are stacked sequentially.

[0058] The organic electroluminescent element provided in this application uses the above-mentioned double-substituted seven-membered spirocyclic derivative as an electron transport material to prepare the electron transport layer. Since the double-substituted seven-membered spirocyclic derivative has a rigid structure as the core and introduces substituted or unsubstituted nitrogen-containing heteroaryl groups on both sides, the electron transport capability of the electron transport layer is further improved, which can improve the luminous efficiency while operating at organic voltage.

[0059] Synthesis Examples

[0060] 1. General formula (A)

[0061]

[0062] Synthetic formula (B)

[0063]

[0064] Synthetic general formula (C)

[0065]

[0066] 2. Synthesis of intermediates

[0067] Synthesis of intermediates M3, M5, B10-Cl

[0068]

[0069] Under nitrogen protection, phthalic anhydride (216.3 g, 1.46 mol), p-bromophenylacetic acid (345.4 g, 1.61 mol), and sodium acetate (19.87 g, 0.146 mol) were added to a clean, dry 2 L flask. The mixture was heated to approximately 80 °C to begin dissolving, and continued until completely dissolved. The temperature was then raised to 220 °C. After the reaction was complete, the temperature was lowered to 80 °C, and 1 L of ethanol was slowly added and stirred. After stirring for 1 hour, the mixture was cooled to room temperature and filtered under vacuum. It was then washed with a small amount of ethanol. After drying, intermediate M1320 g was obtained with a purity of 99% and a yield of 66.5%.

[0070] Under nitrogen protection, intermediate M1 (99.7 g, 0.33 mol), red phosphorus (40.8 g, 1.32 mol), and 420 mL of hydroiodic acid were added to a clean, dry 2 L flask, and the mixture was heated to 126 °C and refluxed. After the reaction was complete, the temperature was lowered to approximately 0 °C, and 30% liquid alkali (250 g caustic soda flakes + 500 mL water) was slowly added dropwise, with pH = 14, while controlling the temperature to ≤20 °C. After the addition was complete, the mixture was extracted with 500 mL of ethyl acetate. After extraction, the red phosphorus was removed by filtration using diatomaceous earth as a filter bed. The mixture was allowed to stand and separate into layers. The organic layer was washed once with sodium bisulfite and then once with distilled water. The organic layer was then acidified (40 g HCl + 10 mL water) to pH = 1. The organic and aqueous layers were concentrated together, and the ethyl acetate was concentrated away. The mixture was then cooled to room temperature and filtered. The resulting solid was intermediate M2, which was washed twice with distilled water until neutral. The sample was dried at 80℃ for 12 hours to obtain 72g; purity 92%, yield 35.5%.

[0071] Under nitrogen protection, 72 g of intermediate M2 (73.24 g, 0.24 mol), 260 mL of polyphosphoric acid, and 50 mL of water were added to a clean, dry 1 L flask. The mixture was heated to 120-130 °C and reacted for one day, then the temperature was raised to 140-150 °C and reacted for another day. The system was a yellow, turbid liquid. After the reaction was complete, the temperature was lowered to about 0 °C and slowly poured into 500 mL of ice water while stirring. After quenching, the mixture was extracted with dichloromethane, the organic layer was washed once with water, and concentrated to dryness. After concentration, 150 mL of toluene and 10% activated carbon were added, and the mixture was refluxed for 1 hour and passed through a short silica gel column while hot. The filtrate was concentrated again, and the resulting oily substance was dissolved in glacial acetic acid (57.65 g, 0.96 mol), allowed to stand to crystallize, and filtered to obtain a yellow solid. The solid was dried at 50 °C for 12 hours to obtain intermediate M3 35 g; purity 98%, yield 50.1%.

[0072]

[0073] Under nitrogen protection, 2-bromo-4'-chloro-1,1'-biphenyl (53.51 g, 200 mmol) and THF (400 mL) were added to a dry four-necked reaction flask. The mixture was stirred and cooled to below -80°C. A 2.5 M n-butyllithium THF solution (96 mL) was then added dropwise. After the addition was complete, the mixture was kept at this temperature for 1 hour, and samples were taken for analysis. Once the lithium salt reaction was complete, a THF solution of intermediate M3 was added dropwise below -80°C, maintaining the temperature below -80°C throughout the addition. After the addition was complete, the mixture was kept at this temperature for 1 hour, then allowed to warm naturally before stirring for 2 hours. 120 mL of 3M hydrochloric acid was added below 0 °C and stirred for 1 hour. Ethyl acetate (400 mL) and water (400 mL) were added for extraction. The organic phases were combined and dried using anhydrous magnesium sulfate. The mixture was filtered and the solvent was removed under reduced pressure. The crude product was directly added to trifluoroacetic acid (300 mL), stirred, and then gradually heated to reflux for 2 hours. After the reaction was completed, the solid was directly filtered and washed with ethanol (100 mL) to obtain 60.1 g of intermediate M4, which was a white solid powder with a yield of 65.6% and a purity of 99.12%.

[0074] In a 1000 mL reaction flask, intermediate M4 (59.51 g, 130 mmol), pinacol diborate (39.61 g, 156 mmol), and toluene (550 mL) were added. The mixture was stirred under nitrogen for 15 minutes, then potassium acetate (38.28 g, 390 mmol), tris(dibenzylindeneacetone)palladium (2.41 g), and X-Phos (2.47 g) were added. The mixture was heated to reflux for 6 hours. After the reaction was complete, the mixture was filtered by silica gel short column chromatography, eluted with hot toluene, and the organic phase was removed. The mixture was then hot-particled with ethanol and dried to obtain 55.79 g of intermediate M5 as an off-white solid, with a yield of 85% and a purity of 99.43%.

[0075]

[0076] In a 500 mL reaction flask, the following ingredients were added: starting material (CAS: 1931136-94-5) (9.98 g, 31.5 mmol), 4-chloro-1-phenylboronic acid (4.9 g, 31.5 mmol), potassium carbonate (10.9 g, 78.8 mmol), tetra-(triphenylphosphine)palladium (0.7 g), toluene (150 mL), ethanol (30 mL), and water (40 mL). The mixture was heated under reflux for 3 hours under nitrogen protection. After the reaction was complete, the mixture was cooled to room temperature and extracted with toluene and water. The extract was filtered through an organic-coated silica gel filter, and the solvent was removed by vacuum evaporation of the filtrate to obtain a crude product. The crude product was slurried with a hexane / ethanol mixture to obtain 8.04 g of intermediate B10-Cl, which was an off-white solid powder with a yield of 80% and a purity of 99.50%.

[0077] 3. Synthesis of the target compound

[0078] 3.1 Synthesis of Compound A5

[0079]

[0080] In a 500 mL reaction flask, intermediate M5 (16.66 g, 33 mmol), 4-chloro-2,6-diphenylpyridine (7.97 g, 30 mmol), potassium carbonate (12.44 g, 90 mmol), toluene (150 mL), ethanol (45 mL), and water (45 mL) were added. The mixture was stirred under nitrogen for 15 min, then palladium acetate (0.067 g) and X-Phos (0.286 g) were added, and the mixture was heated under reflux for 5 hours. After the reaction was completed, extraction was performed, and the organic phase was filtered by silica gel short column chromatography. The solvent was removed from the filtrate under vacuum to obtain the crude product. The crude product was recrystallized from toluene / ethanol and filtered to obtain 11.89 g of intermediate M6-A5 as a white solid powder, with a yield of 65.1% and a purity of 99.85%.

[0081]

[0082] In a 1000 mL reaction flask, intermediate M6-A5 (42.57 g, 70 mmol), pinacol diborate (21.33 g, 84 mmol), and toluene (300 mL) were added. The mixture was stirred under nitrogen for 15 minutes, followed by the addition of potassium acetate (20.61 g, 210 mmol), tris(dibenzyl indeneacetone)dipalladium (1.30 g), and X-Phos (1.33 g). The mixture was then heated to reflux for 3 hours. After the reaction was complete, the mixture was filtered by silica gel short column chromatography, eluted with hot toluene, and the organic phase was removed. Hot slurrying with ethanol yielded 42.12 g of intermediate M7-A5 as a white solid, with a yield of 86% and a purity of 99.23%.

[0083]

[0084] In a 500 mL reaction flask, intermediate M7-A5 (23.09 g, 33 mmol), 4-chloro-2,6-diphenylpyridine (7.97 g, 30 mmol), potassium carbonate (12.44 g, 90 mmol), toluene (200 mL), ethanol (45 mL), and water (45 mL) were added. The mixture was stirred under nitrogen for 15 min, then palladium acetate (0.067 g) and X-Phos (0.286 g) were added, and the mixture was heated under reflux for 6 hours. After the reaction was completed, extraction was performed, and the organic phase was filtered by silica gel short column chromatography. The solvent was removed from the filtrate under vacuum to obtain the crude product. The crude product was recrystallized from toluene / ethanol and filtered to obtain 14.89 g of compound A5 as a white solid powder, with a yield of 61.8% and a purity of 99.69%. After one sublimation, the purity was 99.88%.

[0085] Product MS[M+H] +:803; 1 H NMR (400MHz, CDCl3): δ8.27-8.22(m,8H),8.05-8.00(d,4H),7.99(d,1H),7.84(dd,1H),7.74(dd,1H),7.53-7 .45(m,10H),7.45-7.26(m,9H),7.23-7.15(m,2H),7.09-7.03(m,1H),6.86-6.84(dd,1H),3.04-2.90(m,4H).

[0086] 3.2 Synthesis of other compound A

[0087] Referring to the preparation method of compound A5, intermediate M5 was used as the starting material, and different raw materials Ar1-X and Ar2-X, or Ar1-L1-X and Ar2-X, or Ar1-X and Ar2-L2-X (X = Br or Cl), and using appropriate bases, palladium catalysts and solvent systems (selected from: potassium carbonate\palladium acetate\Xphos\toluene\ethanol\water, potassium carbonate\tris(dibenzylindeneacetone)dipalladium\Xphos\toluene\ethanol\water, potassium carbonate\tetra(triphenylphosphine)palladium\toluene\ethanol\water, potassium carbonate\di(triphenylphosphine)dichloride(II)\toluene\ethanol\water, potassium acetate\tris(dibenzylindeneacetone)dipalladium\Xphos\toluene, etc.) to catalyze the reaction, compounds A38, A65, A92, A118, A142, B9, B38, B71, B116, B132, C28, C67, C100, C120, and C146 were synthesized, as detailed in Table 1.

[0088] Table 1

[0089]

[0090]

[0091]

[0092]

[0093] Product B116: 1H NMR (400MHz, CDCl3): δ8.45-8.36(m,4H),8.02-7.95(m,2H),7.90-7.83(m,2H),7.83-7.76(m ,2H),7.69(d,1H),7.58-7.53(m,2H),7.55-7.49(m,2H),7.53-7.45(m,7H),7.41-7.26(m,4H) ,7.23-7.15(m,2H),7.06(dd,1H),6.95-6.89(m,2H),6.86(dd,1H),6.19-6.12(m,2H),6.15-6 .08(m,1H),6.01(ddt,1H),5.15(tq,1H),4.68(tq,1H),3.04-2.95(m,1H),2.98-2.90(m,4H).

[0094] 4. Fabrication of Organic Electroluminescent Element

[0095] The above-mentioned organic compounds of the present invention are particularly suitable for electron transport layers in OLED devices, as described below in conjunction with the appendix. Figure 1 The device structure is described, and specific embodiments are used to illustrate in detail the application effect of the organic compounds of the present invention as electron transport layers in OLED devices.

[0096] The structural formulas of the organic materials used are as follows:

[0097]

[0098] An organic electroluminescent element using the double-substituted seven-membered spirocyclic derivative of the present invention as an electron transport layer may include a glass and transparent conductive layer (ITO) substrate layer 1, a hole injection layer 2, a hole transport layer 3, an emitting layer 4, an electron transport layer 5, and a cathode layer 6.

[0099] Device Example 1

[0100] like Figure 1 As shown, the electroluminescent element (OLED device) provided in this embodiment includes a substrate layer 1, a hole injection layer 2, a hole transport layer 3, a light-emitting layer 4, an electron transport layer 5, and a cathode layer 6 stacked sequentially. The specific fabrication method is as follows:

[0101] The specific steps for manufacturing OLED devices using a Sunic SP1710 evaporation deposition machine are as follows:

[0102] (1) Cleaning substrate 1: The glass substrate (Corning glass 40mm*40mm*0.7mm) plated with ITO (indium tin oxide) with a thickness of 135nm was ultrasonically washed with isopropanol and pure water for 5 minutes respectively, and then cleaned with ultraviolet ozone to obtain the cleaned substrate 1.

[0103] (2) The substrate layer 1 is transferred to the vacuum deposition chamber; the hole transport material HT1 doped with 4% HD is vacuum thermally deposited on the transparent ITO electrode with a thickness of 20 nm (about 10-7 Torr) to form the hole injection layer 2.

[0104] (3) A hole transport layer 3 is formed by vacuum deposition of HT1 with a thickness of 120 nm and HT2 with a thickness of 10 nm on the hole injection layer 2.

[0105] (4) A 25 nm layer of 4% BD-doped BH was vacuum deposited on the hole transport layer 3 as the light-emitting layer 4.

[0106] (5) An electron transport layer 5 with a thickness of 30 nm is formed by vacuum deposition of compound A5 doped with 50% LiQ (lithium 8-hydroxyquinoline) on the light-emitting layer 4;

[0107] (6) A 1 nm thick LiQ (electron injection layer) and a 150 nm thick Al layer are deposited on the electron transport layer 5 to form a cathode layer 6;

[0108] (7) Finally, the device is transferred from the deposition chamber to the glove box and then encapsulated with UV-curable epoxy resin and a glass cover containing a desiccant.

[0109] In the above manufacturing steps, the deposition rates of organic materials and aluminum are maintained at 0.1 nm / s and 0.2 nm / s, respectively.

[0110] The device structure is represented as: ITO (135nm) / HT1:4%HD (20nm) / HT1 (120nm) / HT2 (10nm) / BH:4%BD (25nm) / compound A5:LiQ (5:5,30nm) / LiQ / (1nm) / Al (150nm).

[0111] Device Examples 2 to 16

[0112] The organic light-emitting device was manufactured in the same manner as in Device Example 1, except that the compounds shown in Table 2 below were used instead of compound A5 in Device Example 1.

[0113] Device Comparison Example 1

[0114] The organic light-emitting device was manufactured in the same manner as in Device Example 1, except that compound ETA was used instead of compound A5 in Device Example 1.

[0115] Device Comparison Example 2

[0116] The organic light-emitting device was manufactured in the same manner as in Device Example 1, except that compound ETB was used instead of compound A5 in Device Example 1.

[0117] The brightness, luminous efficiency, and external quantum efficiency (EQE) of the device were measured using a Suzhou Fresenius FS-100GA4 tester, with all measurements performed at room temperature and atmospheric conditions. Furthermore, the device achieved a luminous efficiency of 10 mA / cm². 2 The specific performance data of operating voltage (V), current efficiency (CE), external quantum efficiency (EQE), and color coordinates (CIEx, CIEy) at current density are shown in Table 2.

[0118] Table 2

[0119]

[0120]

[0121] As can be seen from the above description, the above embodiments of the present invention achieve the following technical effects: compared with device comparative examples 1 and 2, the device using the double-substituted seven-membered spirocyclic derivative provided in this application as the electron transport material has a lower voltage and a significantly improved efficiency.

[0122] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A bisubstituted seven-membered spirocyclic derivative, characterized in that, The disubstituted seven-membered spirocyclic derivative is selected from at least one of the following compounds: 。 2. An electron transport layer comprising the bisubstituted seven-membered spirocyclic derivative of claim 1.

3. The electron transport layer according to claim 2, characterized in that, In the electron transport layer, the mass content of the disubstituted seven-membered spirocyclic derivative is 30% to 70%.

4. The electron transport layer according to claim 2, characterized in that, In the electron transport layer, the mass content of the disubstituted seven-membered spirocyclic derivative is 45%~55%.

5. An organic electroluminescent element comprising the electron transport layer as described in any one of claims 2-4.

6. The organic electroluminescent element according to claim 5, characterized in that, The organic electroluminescent element further includes an anode layer, a hole injection layer, a hole transport layer, a light-emitting layer, an electron injection layer, and a cathode layer, wherein the anode layer, the hole injection layer, the hole transport layer, the light-emitting layer, the electron transport layer, the electron injection layer, and the cathode layer are stacked sequentially.

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