An organic electroluminescent device

Abstract

The application belongs to the technical field of organic electroluminescent materials, and particularly relates to an organic electroluminescent device, which synchronously greatly improves the luminous efficiency and service life of the organic electroluminescent device through deuterium modification of the structure of a compound and optimization of the collocation between a sensitizer and a guest. In terms of efficiency, the guest and the sensitizer have similarity due to structural homology, can form a uniform film, and lay a stable foundation for energy transfer; the guest and the sensitizer adjust the energy level difference through structural difference, realize efficient carrier capture and directional transfer, thereby inhibiting non-radiative transition, reducing exciton energy dissipation, significantly improving the fluorescent quantum yield, and guaranteeing efficient light emission. In terms of life, the high bond energy of the C-D bond effectively inhibits molecular cleavage, reduces material loss from the root, and the moderate deuteration of the sensitizer can further optimize the transmission stability inside the device, thereby greatly prolonging the long-term service life of the device.

Description

Technical Field

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

[0002] Currently, the global display and lighting industry is accelerating its iterative upgrade towards high performance, low energy consumption, and flexibility, with consumer electronics, automotive displays, and high-end lighting demanding increasingly higher device performance. Under this trend, organic light-emitting diodes (OLEDs), with their unique advantages such as self-illumination, high contrast, wide viewing angle, fast response, and flexible fabrication, have surpassed traditional display technologies to become the core development direction in this field, with market penetration increasing year by year.

[0003] As the "heart" of OLED devices, luminescent materials directly determine key performance indicators such as photoelectric conversion efficiency, color performance, lifespan, and stability. Technological breakthroughs and optimizations in luminescent materials are not only crucial for enhancing the competitiveness of OLED products but also a key driving force for the high-quality upgrading of the entire OLED industry. Looking back at the evolution of OLED technology, from the early limitations of traditional fluorescent materials with a quantum efficiency below 25%, to the cost and environmental issues associated with phosphorescent materials due to heavy metals, the industry has consistently explored luminescent technology solutions that balance high efficiency, high color purity, high stability, and low cost.

[0004] Against this backdrop, TADF sensitization (also known as "superfluorescence") technology, through the synergistic design of "sensitizer-terminal emitter," has achieved nearly 100% of the theoretical internal quantum efficiency of fluorescent OLEDs while perfectly preserving the advantages of traditional fluorescent materials in color purity and stability, making it a core technological path for realizing high-end OLED devices. Deuteration modification, as a precise molecular engineering method, effectively reduces non-radiative energy loss and improves the thermal stability and excited-state lifetime of materials by replacing hydrogen atoms at key molecular sites with deuterium atoms. It is crucial for optimizing the energy transfer efficiency of TADF sensitization systems and suppressing efficiency roll-off, gradually becoming an indispensable core supporting technology in the research and development of high-end OLED materials, laying a solid foundation for breakthroughs in OLED technology towards higher performance. Summary of the Invention

[0005] To address the problems existing in the background art, the present invention provides an organic electroluminescent device.

[0006] The technical solution of the present invention is as follows: An organic electroluminescent device includes a light-emitting layer having a host and a guest, the light-emitting layer further including a sensitizer, the structure of the sensitizer and the guest being shown in general formula 1 below: ; A is selected from the following structure: ; B is selected from the following structure: ; When A is selected from A-1, A-2, or A-3, the structure represented by general formula 1 is used as the object; when A is selected from A-4, A-5, or A-6, the structure represented by general formula 1 is used as the sensitizer.

[0007] As a preferred embodiment of the present invention, when A in the guest is A-1, A in the sensitizer is A-4; when A in the guest is A-2, A in the sensitizer is A-5; and when A in the guest is A-3, A in the sensitizer is A-6.

[0008] As a preferred embodiment of the present invention, the specific structure of general formula 1 is as follows: .

[0009] As a preferred embodiment of the present invention, the mass content of the host in the light-emitting layer is 50%, and the mass content of the sensitizer and the guest is 50%.

[0010] As a preferred embodiment of the present invention, the mass ratio of the host, sensitizer, and guest is 50:48:2.

[0011] As a preferred embodiment of the present invention, the device comprises, from bottom to top, an anode, a hole injection layer, a hole transport layer, an electron blocking layer, the light-emitting layer, the hole blocking layer, the electron transport layer, the electron injection layer, and a cathode.

[0012] The present invention also provides a display device including the above-described organic electroluminescent device.

[0013] The beneficial effects of this invention are as follows: This invention significantly improves the luminous efficiency and lifespan of organic electroluminescent devices by precisely deuterating the TADF structure and optimizing the combination of sensitizer and guest. In terms of efficiency, the guest and sensitizer, due to their structural homology, can form a uniform thin film, laying a stable foundation for energy transfer. The differences in their structures adjust the energy level difference, enabling efficient carrier capture and directional transport, thereby suppressing nonradiative transitions, reducing exciton energy dissipation, significantly improving fluorescence quantum yield, and ensuring high-efficiency luminescence. Regarding lifespan, deuterated guest exhibits higher chemical stability, reducing luminescence decay caused by molecular degradation; the high bond energy of the CD bond effectively inhibits molecular fragmentation, reducing material loss at its source. Furthermore, appropriate deuteration of the sensitizer further optimizes the internal transport stability of the device, thus significantly extending its long-term operating life. Detailed Implementation

[0014] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0015] Preparation Examples

[0016] Example 1: Preparation of Compound 1 ; Synthesis of 1-3: Under nitrogen atmosphere, 1-1 (2.0 g, 10 mmol) and 1-2 (4.1 g, 22 mmol) were dissolved in dimethyl sulfoxide (DMSO) (100 mL) in a 250 mL three-necked flask. Potassium carbonate (5.5 g, 40 mmol) was then added to the reaction mixture, and the mixture was heated and stirred at 100 °C for 4 hours. After cooling, the reaction mixture was poured into water, and the aqueous layer was extracted with ethyl acetate. The mixed organic matter was washed with water and brine, and the organic phase was collected and dried over anhydrous sodium sulfate. After filtration, the organic phase was evaporated using a rotary evaporator to remove organic reagents. Recrystallization from the organic phase with methanol yielded 1-3 (3.8 g, 71%), with a molecular weight determined by mass spectrometry of 535.59 (theoretical value: 535.72). Synthesis of 1-4: Under nitrogen atmosphere, 1-3 (13.4 g, 25 mmol), palladium trifluoroacetate (Pd(TFA)2) (0.8 g, 2.5 mmol), silver acetate (AgOAc) (16.7 g, 100 mmol), potassium carbonate (3.5 g, 25 mmol), and pivoxilic acid (PivOH) (50 mL) were added to a 500 mL three-necked flask. The mixture was stirred at 130 °C for 24 hours. After the reaction was complete, the reaction mixture was cooled to room temperature, and dichloromethane and water were added for separation. The organic phase was collected, and the filtrate was concentrated using a rotary evaporator. The concentrated crude product was purified by column chromatography to obtain 1-4 (6.0 g, 45%). The molecular weight determined by mass spectrometry was 531.80 (theoretical value: 531.69). Synthesis of 1-6: Under a nitrogen atmosphere, 1-5 (16.3 g, 60 mmol), cuprous cyanide (CuCN) (12 g, 134 mmol), and N-methyl-2-pyrrolidone (NMP) (80 ml) were added to a 2 L three-necked flask, and the mixture was stirred at 150 °C for 5 hours. 100 ml of dichloromethane was added to the reaction mixture, the mixture was filtered through diatomaceous earth, and the filtrate was concentrated using an evaporator. After purification and concentration by silica gel chromatography, 1-6 (6.2 g, 63%) was obtained. The molecular weight determined by mass spectrometry was 164.29 (theoretical value: 164.11). Synthesis of 1-8: Under a nitrogen atmosphere, 1-6 (2.0 g, 12 mmol), potassium carbonate (3.3 g, 24 mmol), palladium acetate (0.1 g, 0.6 mmol), tricyclohexylphosphine (P(Cy)3) (0.5 g, 1.8 mmol), 1-7 (4.9 mL, 30 mmol), 2-ethylhexanoic acid (7.8 mL, 5 mmol), and xylene (50 mL) were added to a 500 mL three-necked flask and stirred at 100 °C for 5 hours. 100 mL of dichloromethane was added to the reaction solution and passed through diatomaceous earth. The dichloromethane in the resulting solution was removed, and the precipitated solid was filtered. The solid was purified by silica gel column chromatography to obtain 1-8 (1.3 g, 34%), with a molecular weight determined by mass spectrometry of 326.23 (theoretical value: 326.37). Synthesis of 1-10: Under a nitrogen atmosphere, 1-8 (3.3 g, 10 mmol), 1-9 (2.4 g, 10 mmol), cesium carbonate (Cs₂CO₃) (8.2 g, 25 mmol), and N,N-dimethylformamide (DMF) (50 mL) were added to a 250 mL two-necked flask. The reaction was carried out overnight at 120 °C under nitrogen protection. Heating was stopped, and after cooling to room temperature, 150 mL of water was added and stirred for 10 min. A large amount of white solid precipitated out. The solid was filtered, and the filter cake was washed with ethanol for 2 h. After cooling, the solid was filtered again to obtain 1-10 (4.0 g, 73%). The molecular weight determined by mass spectrometry was 549.53 (theoretical value: 549.67). Synthesis of Compound 1: Under a nitrogen atmosphere, 1-10 (5.5 g, 10 mmol), 1-4 (5.3 g, 10 mmol), cesium carbonate (Cs₂CO₃) (8.2 g, 25 mmol), and N,N-dimethylformamide (DMF) (50 mL) were added to a 250 mL two-necked flask. The reaction was carried out overnight at 120 °C under nitrogen protection. Heating was stopped, and after cooling to room temperature, 150 mL of water was added and stirred for 10 min. A large amount of white solid precipitated. The solid was filtered, and the filter cake was washed with ethanol for 2 h. After cooling, the solid was filtered again to obtain Compound 1 (8.1 g, 76%). The molecular weight determined by mass spectrometry was 1061.22 (theoretical value: 1061.36).

[0017] Example 2: Preparation of Compound 4 ; Synthesis of 4-3: Under a nitrogen atmosphere, 4-1 (2.8 g, 10 mmol), 4-2 (2.7 g, 22 mmol), Pd(dppf)Cl2 (149 mg, 0.2 mmol), and K2CO3 (8.3 g, 60 mmol) were added to a 250 mL three-necked flask, along with a mixed solution of 51 mL tetrahydrofuran and 17 mL water. The mixture was refluxed for 4 hours. After the reaction was complete, the mixture was allowed to return to room temperature. The organic phase was filtered to obtain the organic phase. The organic phase was dried over anhydrous magnesium sulfate and then distilled under reduced pressure. The resulting solid was recrystallized from toluene to obtain 4-3 (2.2 g, 78%). The molecular weight determined by mass spectrometry was 285.24 (theoretical value: 285.37). Synthesis of 4-4: Under a nitrogen atmosphere, 4-3 (1.4 g, 5 mmol), triphenylphosphine (6.6 g, 25 mmol), and 30 ml of o-dichlorobenzene were added to a 100 ml three-necked flask, stirred and mixed, heated to 180 °C, and reacted for 12 hours. A TLC sample was taken, showing no residue of 4-3, indicating complete reaction. The mixture was allowed to cool naturally to room temperature, filtered, and the filtrate was rotary evaporated under reduced pressure until no fraction remained. The filtrate was then passed through a neutral silica gel column to obtain 4-4 (0.9 g, 75%). Mass spectrometry analysis determined the molecular weight to be 252.21 (theoretical value: 252.36). The synthesis methods for 4-5 and 1-10 are the same, except that 1-9 is replaced by 4-4. The molecular mass determined by mass spectrometry analysis is 558.86 (theoretical value: 558.73). Compound 4 was synthesized using the same method as compound 1, except that 1-10 was replaced with 4-5. The molecular mass determined by mass spectrometry was 1070.26 (theoretical value: 1070.41).

[0018] Example 3: Preparation of Compound 6 ; Synthesis of 6-3: Under a nitrogen atmosphere, 6-1 (7.4 g, 30 mmol), 2-2 (1.2 g, 45 mmol), potassium carbonate (13.5 g, 97.5 mmol), tetrakis(triphenylphosphine)palladium(0) (0.8 g, 0.7 mmol), toluene (54 ml), THF (27 ml), and deionized water (27 ml) were added to a 300 mL three-necked flask and stirred at 80 °C for 4 hours. The organic layer of the reaction solution was extracted with toluene, washed with water and brine, dried with magnesium sulfate, and the solvent was removed by rotary evaporation under reduced pressure. The compound obtained after solvent removal under reduced pressure was purified by silica gel column chromatography to give 6-3 (1.1 g, 15%), with a molecular weight determined by mass spectrometry of 248.51 (theoretical value: 248.34). The synthesis methods for 6-5 and 1-3 are the same, except that 1-2 is replaced by 6-4. The molecular mass determined by mass spectrometry is 543.89 (theoretical value: 543.77). The synthesis methods for 6-6 and 1-4 are the same, except that 1-3 is replaced by 6-5. The molecular mass determined by mass spectrometry analysis is 541.88 (theoretical value: 541.75). The synthesis methods for 6-7 and 1-10 are the same, except that 1-9 is replaced by 6-3. The molecular mass determined by mass spectrometry analysis is 554.84 (theoretical value: 554.70). Compound 6 was synthesized using the same method as compound 1, except that 6-7 replaced 1-10 and 6-6 replaced 1-4. The molecular mass determined by mass spectrometry was 1076.62 (theoretical value: 1076.45).

[0019] Example 4: Preparation of Compound 11 ; Synthesis of 11-1: Under a nitrogen atmosphere, 1-9 (2.4 g, 10 mmol), 50 mL of heavy water, and 20 mL of toluene were added to a 250 mL three-necked flask and stirred at 120 °C for 24 h. After cooling the reaction system to room temperature, it was extracted three times with dichloromethane and water. After separation, the organic phase was used to remove the solvent using a rotary evaporator to obtain the crude product. The crude product was purified by column chromatography to obtain 11-1 (2.3 g, 91%), with a molecular weight determined by mass spectrometry of 255.51 (theoretical value: 255.38). The synthesis method of 11-2 is the same as that of 11-1. The difference is that 1-4 is used instead of 1-9. The molecular mass determined by mass spectrometry is 551.95 (theoretical value: 551.81). The synthesis methods of 11-3 and 1-10 are the same, except that 1-9 is replaced by 11-1. The molecular mass determined by mass spectrometry analysis is 561.90 (theoretical value: 561.75). Compound 11 was synthesized using the same method as compound 1, except that 1-10 was replaced by 11-3 and 1-4 was replaced by 11-2. The molecular mass determined by mass spectrometry was 1093.72 (theoretical value: 1093.55).

[0020] Unless otherwise specified, all reagents and instruments used were commercially available products. Some reaction compounds were purchased from a supplier (Zhengzhou Alpha Chemical Co., Ltd.), while others were prepared from commercially available raw materials through simple reactions. Percentages refer to mass percentages, and temperatures are in degrees Celsius (°C). The principles, procedures, routine post-treatments, silica gel column chromatography, and recrystallization purification methods of this type are well-known to synthesizers in this field, and the synthesis process can be fully realized to obtain the target product.

[0021] In addition, it should be noted that other compounds in this application can be obtained by referring to the preparation methods of the examples listed above, so they will not be listed one by one here.

[0022] Device Examples To evaluate the luminescence performance of the compounds described in this invention in organic electroluminescent devices, a series of OLED devices based on multilayer organic thin film structures were designed and constructed, and the specific fabrication process is shown below: The glass plate coated with the ITO transparent conductive layer was ultrasonically treated in a cleaning agent, rinsed in deionized water, ultrasonically degreased in a mixed solvent of acetone and ethanol, baked in a clean environment until all moisture was removed, cleaned with ultraviolet light and ozone, and bombarded with a low-energy cation beam. The treated ITO transparent conductive layer was placed in a vacuum evaporation chamber. After the system reached a high vacuum, a hole injection layer with a thickness of 10 nm was deposited first. This layer used a co-evaporation combination of HT-1 and HI (mass ratio 97:3, w / w), with the two materials placed in different evaporation sources. Precise ratio control was achieved by adjusting the evaporation rate. This doping system aims to improve the energy level matching between the anode and the organic layer and reduce the hole injection barrier. A 15 nm thick HT-1 layer is deposited on top of the hole injection layer as a hole transport layer. The main function of this layer is to efficiently transport holes and suppress electron back injection, maintaining a good charge balance in the device. Subsequently, a 20 nm thick HT-2 layer is deposited as an electron blocking layer to restrict electron penetration to the hole transport layer, thereby effectively improving the exciton binding ability and recombination efficiency in the light-emitting region. A 30nm thick light-emitting layer is deposited on the electron blocking layer using a multi-source co-evaporation process. The host, sensitizer, and guest dopant are placed in independent evaporation sources, and a co-doped composite light-emitting film is formed by controlling their evaporation rates. A 5nm thick HB layer is deposited on the light-emitting layer as a hole blocking layer to prevent holes from escaping into the electron region, while enhancing the electron injection interface. A 30 nm thick electron transport layer was deposited on the hole blocking layer using an ET and LiQ doping system (mass ratio 50:50, w / w). This combination helps to improve the electron transport rate and interface injection efficiency. Depositing 1 nm of Yb on the electron transport layer as an electron injection layer, its excellent insulation and extremely low work function help to form an interfacial dipole, thereby improving the injection efficiency of electrons from the Al cathode to the electron transport layer. A Mg:Ag electrode layer with a thickness of 13 nm is deposited on top of the electron injection layer, wherein the mass ratio of Mg to Ag is 1:9. This layer serves as the cathode layer. The entire organic layer and cathode evaporation process is completed in a continuous vacuum to avoid interface oxidation or contamination, with the deposition rate set to 0.1 nm / s.

[0023] In the glove box, the vapor-deposited device is coated with UV adhesive using a coating equipment. The coated cover plate is then 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 using a bonding equipment and cured with UV adhesive.

[0024] The structures of the compounds used in the device are as follows: ; .

[0025] Preparation of Examples 1-12: The organic electroluminescent device was prepared according to the above-described preparation process, wherein Dopant was prepared using compounds 1-12, MH was prepared using compounds 13-24, and HOST:MH:Dopant = 50:48:2 (w / w / w).

[0026] Preparation of Comparative Examples 1-4: The organic electroluminescent device was prepared according to the above-described preparation process, wherein Dopant was prepared using compounds 1-4, MH was prepared using compounds 21-24, and HOST:MH:Dopant = 50:48:2 (w / w / w).

[0027] Preparation of Comparative Examples 5 and 6: The organic electroluminescent device was prepared according to the above-described preparation process, wherein Dopant was prepared using compounds 5 and 6, MH was prepared using compounds 17 and 18, and HOST:MH:Dopant = 50:49:1 (w / w / w).

[0028] Preparation of Comparative Examples 7 and 8: The organic electroluminescent device was prepared according to the above-described preparation process, wherein Dopant was prepared using compounds 5 and 6, MH was prepared using compounds 17 and 18, and HOST:MH:Dopant = 50:47:3 (w / w / w).

[0029] Device evaluation: Current efficiency was tested using an IVL (current-voltage-luminance) testing system (Suzhou Fushida Scientific Instruments Co., Ltd.), at 35 mA / cm². 2 The time required for the brightness to decrease to 95% of the initial brightness at a given current density (LT95) was measured. The lifetime testing system used was the OLED lifetime testing system from Suzhou Fosstar Scientific Instruments Co., Ltd. The results are shown in Table 1 below: ; The data in Table 1 show that the device provided by this invention has higher current efficiency and longer service life compared with the comparative devices. For example, the difference between Examples 1-4 and Comparative Examples 1-4 lies in the different combinations of Dopant and MH, resulting in different device effects. Similarly, the difference between Examples 5 and 6 and Comparative Examples 5-8 lies in the different blending ratios of Dopant and MH, resulting in different device effects.

[0030] Those skilled in the art will readily recognize that many modifications and variations can be made to this invention without departing from its spirit and scope. Therefore, it is contemplated that this invention covers the modifications and variations provided within the scope of the appended claims and their equivalents.

Claims

1. An organic electroluminescent device, comprising a light-emitting layer having a host and a guest, characterized in that, The light-emitting layer further includes a sensitizer, and the structure of the sensitizer and the guest is shown in general formula 1 below: ； A is selected from the following structure: ； B is selected from the following structure: ； When A is selected from A-1, A-2, or A-3, the structure represented by general formula 1 is used as the object; when A is selected from A-4, A-5, or A-6, the structure represented by general formula 1 is used as the sensitizer.

2. The organic electroluminescent device according to claim 1, characterized in that, When A in the object is A-1, A in the sensitizer is A-4; when A in the object is A-2, A in the sensitizer is A-5; when A in the object is A-3, A in the sensitizer is A-6.

3. The organic electroluminescent device according to claim 1, characterized in that, The specific structure of General Formula 1 is as follows: 。 4. The organic electroluminescent device according to claim 1, characterized in that, The luminescent layer contains 50% by mass of the host and 50% by mass of the sensitizer and guest.

5. The organic electroluminescent device according to claim 3, characterized in that, The mass ratio of the subject, sensitizer, and guest is 50:48:

2.

6. The organic electroluminescent device according to claim 1, characterized in that, The device comprises, from bottom to top, an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode.

7. A display device, characterized in that, Includes the organic electroluminescent device according to any one of claims 1 to 6.

Images