Dendritic sensitizer and electroluminescent device thereof

Abstract

The invention relates to a dendritic sensitizer and an electroluminescent device thereof, and belongs to the field of organic luminescent materials. The technical problem that the efficiency and the color purity of an existing organic light-emitting device are difficult to synergistically improve is solved. According to the invention, a dendritic compound with a broadband system and a high reverse intersystem crossing rate is used as a sensitizer, a dendritic donor unit is used as a branch, a cyanophenyl unit is used as an acceptor central core, a relatively small single triplet state energy level difference is achieved, a thermal activation delayed fluorescence effect can be generated, triplet state excitons can cross to a singlet state in a reverse intersystem manner, and the quantum efficiency is improved. And then energy is transferred to a luminescent dye with a narrow band characteristic through # imgabs0 # energy transfer, so that the organic electroluminescent device based on the dendritic sensitizer provided by the invention can realize synergistic improvement of external quantum efficiency and color purity.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic light-emitting materials, and particularly relates to a dendritic sensitizer and an electroluminescent device thereof. Background Art

[0002] Organic light-emitting devices (OLEDs) have the characteristics of being lightweight, low in energy consumption, rich in colors, wide in viewing angle, and capable of fabricating flexible and wearable devices, etc., and play a crucial role in the display field. OLEDs are usually composed of an indium tin oxide (ITO) anode, a hole injection layer (HIL), a hole transport layer (HTL), a light-emitting layer (EL), a hole blocking layer (HBL), an electron transport layer (ETL), an electron injection layer (EIL), and a cathode. According to needs, 1-2 organic layers can be omitted. By combining holes (Hole) and electrons (Electron) injected from the positive electrode and the negative electrode on the organic thin film to form excitons (Exciton), the excitons radiatively transition back to the ground state to achieve device luminescence.

[0003] According to the luminescence mechanism, luminescent materials can be mainly divided into three categories: fluorescent materials, phosphorescent materials, and thermally activated delayed fluorescence (TADF) materials. Among them, fluorescent materials have the advantages of high fluorescence quantum efficiency and high color purity. However, they can only utilize singlet excitons that account for 25% of all excitons, and the remaining 75% of triplet excitons are inactivated by non-radiative transitions. Therefore, the limit value of the internal quantum efficiency in the device is 25%. Due to the spin-orbit coupling effect of heavy metal atoms, phosphorescent materials can utilize triplet excitons, thereby achieving an internal quantum efficiency of 100%. However, their disadvantage is that expensive heavy metals (such as iridium and platinum, etc.) need to be used. TADF materials can utilize the fast reverse intersystem crossing (RISC) process to convert triplet excitons into singlet excitons and emit light, breaking the theoretical limit of 25% of the internal quantum efficiency of traditional fluorescent materials, and being able to obtain an internal quantum efficiency of 100% in the device without using precious metals. However, their emission peaks are often relatively wide (70-100nm), resulting in low color purity.

[0004] Currently, developing OLEDs based on the idea of "thermally activated sensitized luminescence", that is, selecting dyes with narrow spectral bands (high color purity) and high fluorescence quantum efficiency as the light-emitting units, and TADF molecules with wide bandgaps and high reverse intersystem crossing rates as sensitizers, and using the energy transfer from the TADF sensitizer to the dye to transfer excitons to the dye for luminescence, can achieve the synergistic improvement of the exciton utilization rate and fluorescence quantum efficiency and the improvement of color purity, and is an important way to develop organic electroluminescent devices with both high device efficiency and high color purity. However, due to the lack of solution-processable sensitizers, this method is mainly applied to OLED devices in the vacuum evaporation process.

[0005] Therefore, how to develop a solution-processable TADF sensitizer suitable for thermally activated delayed fluorescence OLEDs through reasonable chemical structure design has become one of the urgent problems to be solved by many forward-looking researchers in the field. Summary of the Invention

[0006] The present invention aims to solve the technical problem that it is difficult to synergistically improve the utilization rate of triplet excitons and color purity in the prior art, and provides a dendritic sensitizer and an electroluminescent device thereof. The dendritic sensitizer of the present invention has both a wide bandgap, a TADF effect, and a high reverse intersystem crossing rate.

[0007] To solve the above technical problems, the technical solution of the present invention is specifically as follows:

[0008] A dendritic sensitizer, the structure of which is shown in formula (Ⅰ):

[0009]

[0010] is a dendritic electron donor;

[0011] m is 0 or 1, and n is 1, 2 or 3;

[0012] X is selected from one or more of -C(R1R2)-, -Si(R1R2)-, -N(R1)-, -O-, -S-, -SO-, -SO2-, -B(R1)-, -P(R1)-, and -PO(R1)-;

[0013] R1 and R2 are each independently selected from H, halogen, -CF3, -CN, substituted or unsubstituted C1-C 20 alkyl, substituted or unsubstituted C3-C 20 cycloalkyl, substituted or unsubstituted C6-C 20 aryl, and substituted or unsubstituted C2-C 20 heteroaryl;

[0014] R is selected from H, halogen, -CF3, -CN, -NO2, substituted or unsubstituted C1-C 20 alkyl, substituted or unsubstituted C1-C 20 alkoxy, substituted or unsubstituted C3-C 20 cycloalkyl, substituted or unsubstituted C5-C 20 heterocycloalkyl, substituted or unsubstituted C6-C 20 aryl, and substituted or unsubstituted C2-C 20 heteroaryl;

[0015] R' is selected from halogen, -CF3, -CN, -NO2, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C1-C 20 alkoxy, substituted or unsubstituted C3-C 20 cycloalkyl, substituted or unsubstituted C5-C 20 heterocycloalkyl, substituted or unsubstituted C6-C 20 aryl, and substituted or unsubstituted C2-C 20 one or more of heteroaryl;

[0016] p is 1, 2 or 3;

[0017] In the above technical solution, preferably, the is selected from any one or more of those shown in Formula (D1-1) to Formula (D5-2):

[0018]

[0019]

[0020] In the above technical solution, preferably, the dendritic sensitizer has any one of the structures shown in Formula S-1 to 17:

[0021]

[0022]

[0023] The present invention also provides an organic electroluminescent device, including a sensitizer; the sensitizer includes the dendritic compound described in any one of the above technical solutions.

[0024] The present invention does not particularly limit the structure of the organic electroluminescent device, and a conventional organic electroluminescent device well-known to those skilled in the art can be used. Those skilled in the art can select and adjust according to application situations, quality requirements and product requirements. For example, the organic electroluminescent device of the present invention includes an anode, a cathode, and an organic thin film layer located between the anode and the cathode; the organic thin film layer includes the dendritic sensitizer described in the present invention. Further, the organic thin film layer containing the dendritic sensitizer can be a light-emitting layer or an organic thin film layer adjacent to the light-emitting layer. The structure of the organic electroluminescent device of the present invention preferably specifically includes: a substrate; an anode disposed on the substrate; an organic thin film layer disposed on the anode; and a cathode disposed on the organic thin film layer.

[0025] The thickness of the substrate is preferably 0.3 to 0.7 mm, more preferably 0.4 to 0.6 mm; the present invention has no special limitation on the selection of the substrate, and a conventional substrate for an organic electroluminescent device well-known to those skilled in the art can be used. Those skilled in the art can select and adjust according to the application situation, quality requirements, and product requirements. In the present invention, the substrate is preferably glass or plastic.

[0026] According to the present invention, the anode is preferably a material that is easy for hole injection, more preferably a conductive metal or a conductive metal oxide, and still more preferably indium tin oxide (ITO).

[0027] The organic thin film layer can be one layer or multiple layers, and at least one layer is a light-emitting layer; in the present invention, the organic thin film layer preferably includes a light-emitting layer; the light-emitting layer includes the dendritic sensitizer shown in the above formulas S1-17.

[0028] The cathode is preferably a metal, including but not limited to calcium, magnesium, barium, aluminum, and silver, and preferably aluminum.

[0029] In order to improve the performance and efficiency of the device, the organic thin film layer between the anode and the light-emitting layer preferably further includes one or more of a hole injection layer, a hole transport layer, and an electron blocking layer. The organic thin film layer between the light-emitting layer and the cathode preferably further includes one or more of a hole blocking layer, an electron injection layer, and an electron transport layer. The present invention has no particular limitation on the materials and thicknesses of the hole injection layer, the hole transport layer, the electron blocking layer, the organic electroluminescent layer, the hole blocking layer, the electron injection layer, and the electron transport layer, and can be selected and adjusted according to the materials and thicknesses well-known to those skilled in the art. The present invention has no particular limitation on the preparation processes of the electrodes, the hole injection layer, the hole transport layer, the electron blocking layer, the organic electroluminescent layer, the hole blocking layer, the electron injection layer, and the electron transport layer, and preferably uses solution spin coating, solution blade coating, inkjet printing, offset printing, and stereolithography processes for preparation.

[0030] The present invention has no special limitation on the preparation method of the organic electroluminescent device, and can be carried out according to the following method: forming an anode on the substrate; forming one or more organic thin film layers on the anode, including a light-emitting layer; and forming a cathode on the organic thin film layer. The light-emitting layer includes the dendritic sensitizer shown in the formulas S1-17.

[0031] The present invention can correspond the structures and materials of the organic electroluminescent device in the above preparation method, as well as the corresponding preferred principles, to the corresponding materials and structures, and the corresponding preferred principles in the foregoing organic electroluminescent device, and will not be elaborated herein one by one.

[0032] First, an anode is formed on a substrate. There are no special restrictions on the formation method of the anode in the present invention, and it can be formed according to methods well-known to those skilled in the art. There are no special restrictions on the formation methods of the light-emitting layer and the organic thin-film layers below and above the light-emitting layer, and they can be formed on the anode by solution spin coating, inkjet printing, offset printing, or stereolithography. After the organic light-emitting layer is formed, a hole-blocking layer and an electron injection / transport layer can be formed on its surface by vacuum evaporation or spin coating. After the organic thin-film layer is formed, a cathode is prepared on its surface. There are no special restrictions on the formation method of the cathode in the present invention, and it is preferably a method well-known to those skilled in the art, including but not limited to vacuum deposition.

[0033] The beneficial effects of the present invention are as follows:

[0034] The dendritic sensitizer provided by the present invention is shown in formula (I). Compared with the prior art, the present invention uses a dendritic sensitizer with a dendritic donor unit as the branch and a benzonitrile unit as the acceptor central core, having a small singlet-triplet energy level difference (ΔE ST ), capable of generating the TADF effect, and the triplet excitons can reverse intersystem crossing to the singlet state, and then transfer the energy to the light-emitting dye with narrow spectral band characteristics through energy transfer. Therefore, the organic electroluminescent device based on the dendritic sensitizer provided by the present invention can achieve a synergistic improvement in external quantum efficiency and color purity. Specific Embodiments

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0036] All reagents used in the following examples are commercially available.

[0037] Example 1

[0038] Synthesis route of S-1:

[0039]

[0040] Under argon atmosphere, 3-methyl-2,6-difluorobenzonitrile (0.15 g, 1.00 mmol), secondary tert-butyl carbazole (1.60 g, 2.20 mmol) and cesium carbonate (1.30 g, 4.00 mmol) were successively added into a 100 mL reaction flask. Subsequently, 40 mL of anhydrous N,N-dimethylformamide was added, and the temperature was raised to 140 °C. The mixture was refluxed and stirred for 24 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, poured into 300 mL of water, and a white precipitate was formed. The precipitate was filtered and dried. The obtained crude product was purified by column chromatography to obtain S-1 (1.00 g of white solid, yield 64.0%).

[0041] Elemental analysis of its structure (C 112 H 113 N7): Theoretical values: C, 86.39; H, 7.31; N, 6.30; Measured values: C, 86.38; H, 7.32; N, 6.31.

[0042] MALDI-TOF-MS: Theoretical value 1555.9; Experimental value 1554.8.

[0043] Example 2

[0044] Synthetic route of S-3:

[0045]

[0046] Under argon atmosphere, 4-methyl-2,6-difluorobenzonitrile (0.15 g, 1.00 mmol), secondary tert-butyl carbazole (1.60 g, 2.20 mmol) and cesium carbonate (1.30 g, 4.00 mmol) were successively added into a 100 mL reaction flask. 40 mL of anhydrous N,N-dimethylformamide was added, and the temperature was raised to 140 °C. The mixture was refluxed and stirred for 24 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, poured into 300 mL of water, and a white precipitate was formed. The precipitate was filtered and dried. The obtained crude product was purified by column chromatography to obtain S-3 (0.50 g of white solid, yield 32.0%).

[0047] Elemental analysis of its structure (C 112 H 113 N7): Theoretical values: C, 86.39; H, 7.31; N, 6.30; Measured values: C, 86.36; H, 7.35; N, 6.28.

[0048] MALDI-TOF-MS: Theoretical value 1555.9; Experimental value 1554.7.

[0049] Example 3

[0050] Synthetic route of S-4:

[0051]

[0052] Under argon, 4-methoxy-2,6-difluorobenzonitrile (0.17 g, 1.00 mmol), secondary tert-butyl carbazole (1.60 g, 2.20 mmol), and cesium carbonate (1.30 g, 4.00 mmol) were successively added to a 100 mL reaction flask. 40 mL of anhydrous N,N-dimethylformamide was added, and the temperature was raised to 140 °C and refluxed with stirring for 24 hours. After the reaction was completed, the temperature was lowered to room temperature. The reaction solution was poured into 300 mL of water to obtain a white precipitate, which was filtered and dried. The obtained crude product was purified by column chromatography to obtain S-4 (0.35 g of white solid, yield 22.0%).

[0053] Elemental analysis of its structure (C 112 H 113 N7O): Theoretical values: C, 85.51; H, 7.24; N, 6.23; O, 1.02; Measured values: C, 85.35; H, 7.20; N, 2.67; O, 1.01.

[0054] MALDI-TOF-MS: Theoretical value 1571.9; Experimental value 1571.0.

[0055] Example 4

[0056] Synthesis route of S-5:

[0057]

[0058] Under argon, 3-trifluoromethyl-2,6-difluorobenzonitrile (0.21 g, 1.00 mmol), secondary tert-butyl carbazole (1.60 g, 2.20 mmol), and cesium carbonate (1.30 g, 4.00 mmol) were successively added to a 100 mL reaction flask. Subsequently, 40 mL of anhydrous N,N-dimethylformamide was added, and the temperature was raised to 140 °C and refluxed with stirring for 24 hours. After the reaction was completed, the temperature was lowered to room temperature. The reaction solution was poured into 300 mL of water to obtain a white precipitate, which was filtered and dried. The crude product was purified by column chromatography to obtain S-5 (0.20 g of white solid, yield 12.0%).

[0059] MALDI-TOF-MS: Theoretical value 1609.9; Experimental value 1610.1.

[0060] Example 5

[0061] Synthesis route of S-6:

[0062]

[0063] Under argon atmosphere, 3-methyl-2,6-difluorobenzonitrile (0.15 g, 1.00 mmol), n-butoxycarbazole dimer (1.73 g, 2.20 mmol) and cesium carbonate (1.30 g, 4.00 mmol) were successively added into a 100 mL reaction flask. Subsequently, 40 mL of anhydrous N,N-dimethylformamide was added, and the temperature was raised to 140 °C, followed by reflux stirring for 24 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, poured into 300 mL of water, and a white precipitate was formed. The precipitate was filtered and dried. The obtained crude product was purified by column chromatography to obtain S-6 (0.80 g of white solid, yield 47.3%).

[0064] Elemental analysis of its structure (C 112 H 113 N7O8): Theoretical values: C, 79.83; H, 6.76; N, 5.82; O, 7.60; Measured values: C, 79.80; H, 6.75; N, 5.82; O, 7.54.

[0065] MALDI-TOF-MS: Theoretical value 1683.9; Experimental value 1683.7.

[0066] Example 6

[0067] Synthetic route of S-7:

[0068]

[0069] Under argon atmosphere, 4-methyl-2,6-difluorobenzonitrile (0.15 g, 1.00 mmol), n-butoxycarbazole dimer (1.73 g, 2.20 mmol) and cesium carbonate (1.30 g, 4.00 mmol) were successively added into a 100 mL reaction flask. Subsequently, 40 mL of anhydrous N,N-dimethylformamide was added, and the temperature was raised to 140 °C, followed by reflux stirring for 24 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, poured into 300 mL of water, and a white precipitate was formed. The precipitate was filtered and dried. The obtained crude product was purified by column chromatography to obtain S-7 (0.92 g of white solid, yield 49.7%).

[0070] Elemental analysis of its structure (C 112 H 113 N7O8): Theoretical values: C, 79.83; H, 6.76; N, 5.82; O, 7.60; Measured values: C, 79.85; H, 6.70; N, 5.72; O, 7.56.

[0071] MALDI-TOF-MS: Theoretical value 1683.9; Experimental value 1683.5.

[0072] Example 7

[0073] Synthetic route of S-8:

[0074]

[0075] Under argon atmosphere, 4-methoxy-2,6-difluorobenzonitrile (0.17 g, 1.00 mmol), n-butoxycarbazole dimer (1.73 g, 2.20 mmol) and cesium carbonate (1.30 g, 4.00 mmol) were successively added into a 100 mL reaction flask. Subsequently, 40 mL of anhydrous N,N-dimethylformamide was added, and the temperature was raised to 140 °C, followed by reflux stirring for 24 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, poured into 300 mL of water, and a white precipitate was formed. The precipitate was filtered and dried. The obtained crude product was purified by column chromatography to obtain S-8 (0.52 g of white solid, yield 30.6%).

[0076] Elemental analysis of its structure (C 112 H 113 N7O9): Theoretical values: C, 79.08; H, 6.70; N, 5.76; O, 8.64; Measured values: C, 79.00; H, 6.68; N, 5.72; O, 8.70.

[0077] MALDI-TOF-MS: Theoretical value 1699.9; Experimental value 1700.5.

[0078] Example 8

[0079] Synthetic route of S-9:

[0080]

[0081] Under argon atmosphere, 3-trifluoromethyl-2,6-difluorobenzonitrile (0.21 g, 1.00 mmol), n-butoxycarbazole dimer (1.73 g, 2.20 mmol) and cesium carbonate (1.30 g, 4.00 mmol) were successively added into a 100 mL reaction flask. Subsequently, 40 mL of anhydrous N,N-dimethylformamide was added, and the temperature was raised to 140 °C, followed by reflux stirring for 24 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, poured into 300 mL of water, and a white precipitate was formed. The precipitate was filtered and dried. The obtained crude product was purified by column chromatography to obtain S-9 (0.36 g of white solid, yield 25.9%).

[0082] MALDI-TOF-MS: Theoretical value 1737.8; Experimental value 1738.8.

[0083] See Table 1. Table 1 shows the photophysical properties of the dendritic sensitizers S-2, S-4, S-5, and S-6 prepared in the examples of the present invention.

[0084] Table 1

[0085] Fluorescent material <![CDATA[λ abs (nm)]]> <![CDATA[λ em (nm)]]> <![CDATA[ΔE ST (eV)]]> S-1 297，348 458 0.10 S-3 298，351 444 0.04 S-4 297，348 431 0.04 S-5 296，349 513 0.01

[0086] As shown in Table 1, the emission peak positions of the dendritic sensitizers provided by the present invention are all in the visible light range, and their emission colors can be changed by changing the chemical structures of the dendritic electron donor units or benzonitrile electron acceptor units. On the other hand, the space charge transfer dendritic fluorescent materials provided by the present invention have a very small singlet-triplet energy level difference (0.01 eV to 0.15 eV), and thus exhibit a significant thermally activated delayed fluorescence effect. When applied to organic light-emitting devices, it is beneficial to utilize triplet excitons, and thus has a high luminous efficiency.

[0087] Device Examples

[0088] The process of fabricating a device with the organic light-emitting layer prepared by a solution processing technique is as follows: Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS) is spin-coated on indium tin oxide (ITO) supported on a glass substrate and annealed at 120 °C for 30 minutes. Subsequently, a toluene solution of the dendritic sensitizer of the present invention, dye DABNA-1, and host material Ad-4D2 mixed in a mass ratio of 10:2:88 is spin-coated at a speed of 1500 rpm for 1 minute and annealed at 100 °C for 15 minutes. Then, TSPO1, TmPyPB, and LiF / Al cathode are sequentially deposited under a vacuum of 4×10 -4 Pa to obtain an organic light-emitting device, where TSPO1 and TmPyPB serve as a hole-blocking layer, an electron-transporting layer, and a host material, respectively. The specific device structure is ITO / PEDOT:PSS (40 nm) / EML (40 nm - 60 nm) / TSPO1 (8 nm) / TmPyPB (42 nm) / LiF (1 nm) / Al (100 nm). The structural formulas of DABNA-1, Ad-4D2, TSPO1, and TmPyPB are shown as follows:

[0089]

[0090] Example 9

[0091] Taking the dendritic sensitizer S-1 as the implementation object, the dendritic sensitizer S-1, DABNA-1, and Ad-4D2 are mixed in a mass ratio of 10:2:88 as the organic light-emitting layer. An organic light-emitting device is fabricated with the organic light-emitting layer prepared by a solution processing technique, and the obtained device is tested.

[0092] Referring to Table 2, Table 2 provides the performance parameters of the electroluminescent devices fabricated with the dendritic compound S-1 provided by the present invention as the sensitizer.

[0093] Example 10

[0094] Taking the dendritic sensitizer S-3 as the implementation object, the dendritic sensitizer S-3, DABNA-1 and Ad-4D2 are mixed according to the mass ratio of 10:2:88 as the organic light-emitting layer. The organic light-emitting layer is used to prepare an organic electroluminescent device by a solution processing technology, and the obtained device is tested.

[0095] Referring to Table 2, Table 2 provides the performance parameters of the electroluminescent devices prepared with the dendritic compound S-3 provided by the present invention as the sensitizer.

[0096] Example 11

[0097] Taking the dendritic sensitizer S-4 as the implementation object, the dendritic sensitizer S-4, DABNA-1 and Ad-4D2 are mixed according to the mass ratio of 10:2:88 as the organic light-emitting layer. The organic light-emitting layer is used to prepare an organic electroluminescent device by a solution processing technology, and the obtained device is tested.

[0098] Referring to Table 2, Table 2 provides the performance parameters of the electroluminescent devices prepared with the dendritic compound S-4 provided by the present invention as the sensitizer.

[0099] Example 12

[0100] Taking the dendritic sensitizer S-5 as the implementation object, the dendritic sensitizer S-5, DABNA-1 and Ad-4D2 are mixed according to the mass ratio of 10:2:88 as the organic light-emitting layer. The organic light-emitting layer is used to prepare an organic electroluminescent device by a solution processing technology, and the obtained device is tested.

[0101] Referring to Table 2, Table 2 provides the performance parameters of the electroluminescent devices prepared with the dendritic compound S-5 provided by the present invention as the sensitizer.

[0102] Table 2

[0103]

[0104] As can be seen from Table 2, the devices prepared with the dendritic sensitizers provided by the present invention have a very narrow electroluminescent spectrum, with a full width at half maximum of less than 30 nm, and high color purity; at the same time, the devices prepared with the dendritic sensitizers provided by the present invention all have relatively high device efficiency, and the maximum external quantum efficiency reaches 24.6%, realizing the synergistic improvement of device efficiency and color purity.

[0105] Obviously, the above examples are only for clearly illustrating the examples and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A dendritic sensitizer, characterized in that: Its structure is shown in formula (I): in, It is a dendritic electron donor; m is 0 or 1, n is 1, 2 or 3; X is selected from one or more of -C(R1R2)-, -Si(R1R2)-, -N(R1)-, -O-, -S-, -SO-, -SO2-, -B(R1)-, -P(R1)- and -PO(R1)-; R1 and R2 are independently selected from H, halogen, -CF3, -CN, substituted or unsubstituted C1-C 20 Alkyl, substituted or unsubstituted C3~C 20 Cycloalkyl, substituted or unsubstituted C6~C 20 Aryl and substituted or unsubstituted C2~C 20 One or more of the heteroaryl groups; R is selected from H, halogen, -CF3, -CN, -NO2, substituted or unsubstituted C1~C 20 Alkyl, substituted or unsubstituted C1~C 20 Alkoxy, substituted or unsubstituted C3~C 20 Cycloalkyl, substituted or unsubstituted C5~C 20 Heterocycloalkyl, substituted or unsubstituted C6~C 20 Aryl and substituted or unsubstituted C2~C 20 One or more of the heteroaryl groups; R' is selected from halogen, -CF3, -CN, -NO2, substituted or unsubstituted C1~C 20 Alkyl, substituted or unsubstituted C1~C 20 Alkoxy, substituted or unsubstituted C3~C 20 Cycloalkyl, substituted or unsubstituted C5~C 20 Heterocycloalkyl, substituted or unsubstituted C6~C 20 Aryl and substituted or unsubstituted C2~C 20 One or more of the heteroaryl groups; p is 1, 2 or 3.

2. The dendritic sensitizer according to claim 1, characterized in that Said Any one or more selected from formula (D1-1) to formula (D5-2):

3. The dendritic sensitizer according to claim 1, characterized in that The dendritic sensitizer has any one of the structures shown in Formulas S-1 to S-17:

4. An organic electroluminescent device, comprising an anode, a cathode and an organic thin film layer located between the anode and the cathode; characterized in that: The organic thin film layer comprises the dendritic sensitizer according to any one of claims 1 to 3.

5. The organic electroluminescent device according to claim 4, characterized in that: The organic thin film layer comprises a light-emitting layer; the light-emitting layer comprises the dendritic sensitizer according to any one of claims 1 to 3.

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