A thermally activated delayed fluorescence conjugated polymer and its synthesis method and application

Abstract

The present invention discloses a thermally activated delayed fluorescent conjugated polymer and its synthesis method and application, relating to the technical field of fluorescent conjugated polymers. The polymer is copolymerized by a TADF light-emitting unit having a donor-acceptor-dendritic (D-A-D') structure and a conjugated main chain (Host). The synthesis method includes Buchwald-Hardwig reaction, bromination reaction and Yamamoto polymerization. The obtained polymer is used to prepare non-doped OLEDs devices, showing excellent electroluminescent properties. The thermally activated delayed fluorescent conjugated polymer of the present invention significantly improves the electroluminescent performance and stability of OLEDs through its unique D-A-D' structure. The solubility and film-forming properties are optimized, and the applicability of electronic displays and lighting equipment is enhanced by precisely controlling the luminescent color and charge transfer performance. These improvements meet the market demand for high-performance, low-cost OLEDs and show excellent industrial application potential.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescent conjugated polymers, and in particular to a thermally activated delayed fluorescent conjugated polymer and a synthesis method and application thereof. Background Art

[0002] Since its birth, organic light-emitting diode (OLEDs) technology has been an important development in the field of modern display and lighting. OLEDs use the electroluminescence principle of organic materials to provide higher contrast, wider viewing angle and lower energy consumption, and are widely used in various electronic devices. In particular, the development of thermally activated delayed fluorescence (TADF) materials has greatly promoted the progress of OLED technology. TADF materials use their unique reverse intersystem crossing (RISC) mechanism to theoretically achieve 100% internal quantum efficiency (IQE). This performance is significantly better than traditional fluorescent and phosphorescent materials without relying on precious metals. In addition, solution processing technology has shown great advantages in flexible processing, large-area production and solid-state lighting due to its simple process and low cost. It is one of the key technologies to promote the commercialization of OLEDs.

[0003] Although current OLED technology has achieved certain successes in commercial applications, existing solution-processed OLED materials still have some significant technical bottlenecks. First, although certain dendritic side-chain conjugated polymers used in traditional solution processing methods have improved the solubility and film-forming properties of the materials, their electroluminescence efficiency and stability in non-doped OLEDs have not yet reached the ideal level. In addition, these materials often experience excessive intermolecular aggregation during the preparation process, leading to concentration quenching, which seriously limits their application in high-performance OLEDs. Although the introduction of dendritic side-chain conjugated polymers can theoretically alleviate this problem, in reality, how to precisely control the spatial arrangement and interaction of these macromolecular structures, and how to optimize their optoelectronic properties through chemical modification, remains a huge challenge.

[0004] Faced with these challenges, it is necessary to develop new polymer materials that maintain good solubility and film-forming properties while significantly improving the electroluminescent performance and device stability of undoped OLEDs. This invention aims to address the problems of poor electroluminescent performance and insufficient device stability of polymer materials in undoped OLEDs. These technical challenges not only limit the further commercialization of OLED technology but also hinder the development of a new generation of high-performance electronic displays and lighting devices. Therefore, the development of a new dendritic side-chain conjugated polymer with excellent photophysical properties is crucial for advancing OLED technology. Summary of the Invention

[0005] In order to achieve the above-mentioned purpose of the invention and address the above-mentioned technical problems, the present invention provides a thermally activated delayed fluorescence conjugated polymer, wherein the polymer is copolymerized with a donor-acceptor-dendritic (DA-D') structure as a TADF (thermally activated delayed fluorescence) luminescent unit and a conjugated main chain (Host), and the polymer structure is shown in the general formula (1):

[0006]

[0007] Among them, Host is the main unit for regulating photophysical properties, x=0.05-1, Dendrite is the branch-like structure unit, n>5.

[0008] Preferably, the Host unit includes the following structure:

[0009]

[0010] Preferably, the DA unit comprises the following structure:

[0011]

[0012] Preferably, the dendrite unit comprises the following structure:

[0013]

[0014] The present invention also provides a method for synthesizing a thermally activated delayed fluorescence conjugated polymer, comprising the following steps:

[0015] S1: The DA monomer and the dendritic structure monomer provided above are subjected to a Buchwald-Hardwig reaction to obtain a donor-acceptor-dendritic (DA-D') TADF structure monomer;

[0016] S2: brominating the TADF structural monomer obtained in step S1 with nitrobutyl succinimide (NBS) to obtain a bilaterally brominated dendritic TADF monomer;

[0017] S3 bromination of the bilateral monomer with alkyl chain solubilization by bromosuccinimide (NBS) to obtain the bilaterally brominated terminal brominated monomer shown above;

[0018] S4: mixing the bilaterally brominated dendritic TADF monomer and the bilaterally brominated terminal brominated monomer, performing Yamamoto polymerization, and then capping with bromobenzene, and extracting with a Soxhlet extractor to obtain a conjugated polymer.

[0019] Preferably, the catalyst used in step S1 is palladium acetate, Xphos, and potassium phosphate, and the molar ratio of the DA monomer, the dendritic structure monomer, palladium acetate, Xphos, and potassium phosphate is 1:1.1:0.06:0.1:3.

[0020] Preferably, in step S4, the molar ratio of the bilaterally brominated dendritic TADF monomer to the bilaterally brominated terminal brominated monomer is 0.1:0.9.

[0021] Preferably, the catalyst used in step S4 is 2,2-bipyridine, Ni(COD)2, and cyclooctadiene in a molar ratio of 2:2:4, and the bilaterally brominated dendritic TADF monomer, the bilaterally brominated terminal brominated monomer, 2,2-bipyridine, Ni(COD)2, and cyclooctadiene in a molar ratio of 0.1:0.9:2:2:4.

[0022] Preferably, in step S4, the polymerization time is 72 hours; and the extraction time is 48 hours.

[0023] The present invention also provides a thermally activated delayed fluorescence conjugated polymer for use in preparing non-doped OLEDs devices, wherein the conjugated polymer is the above-mentioned conjugated polymer.

[0024] The technical solution provided by the present invention brings beneficial effects:

[0025] Improved electroluminescent performance: The polymer material of this invention utilizes a unique donor-acceptor-dendritic (DA-D') structure, which effectively utilizes the thermally activated delayed fluorescence (TADF) mechanism to significantly enhance the material's internal quantum efficiency. Compared to existing technologies, the photophysical properties of this polymer are fundamentally improved, particularly in terms of electroluminescent efficiency and luminescence stability. This improvement not only increases the luminous efficiency of OLEDs but also enhances the overall performance of the device, maintaining stable light output over extended periods of use.

[0026] Optimized solubility and film-forming properties: Through a carefully designed dendritic side chain structure, the polymers of this invention exhibit excellent solubility and film-forming properties. This structural design enables the polymer to exhibit good rheological properties and film-forming ability during solution processing, greatly facilitating the production of OLEDs and improving process controllability and reproducibility.

[0027] Manipulating luminescence color and charge transport properties: This invention enables precise tuning of the polymer's luminescence color and photophysical properties by selecting different donor-acceptor (DA) structures and their dendritic generations. Furthermore, the charge transport properties of the resulting polymers are optimized by selecting different conjugated backbone structures, further enhancing the overall performance of OLEDs, particularly in terms of charge balance and energy conversion efficiency.

[0028] Improving the applicability and practicality of devices: The comprehensive performance optimization of the polymer obtained by the present invention enables the final non-doped OLEDs device to have higher electroluminescent performance and better stability. This makes this polymer material widely applicable to various practical electronic displays and lighting equipment, meeting the market demand for high-performance, low-cost OLEDs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The room temperature fluorescence emission spectra of the products of Examples 1, 2, and 3 of the present invention in dilute toluene solutions;

[0030] Figure 2 The fluorescence emission spectra of the undoped thin films of the products of Examples 1, 2, and 3 of the present invention are as follows;

[0031] Figure 3 Transient decay spectra of the products of Examples 1, 2, and 3 under vacuum;

[0032] Figure 4 This is the temperature-dependent transient attenuation spectrum of the product of Example 1 under vacuum;

[0033] Figure 5 Steady-state spectra of the product of Example 1 under vacuum and air;

[0034] Figure 6 The current density-voltage-brightness curves of Examples 1, 2, and 3 in solution-processed non-doped OLED devices;

[0035] Figure 7 The current efficiency-brightness-power efficiency curves of Examples 1, 2, and 3 in solution-processed non-doped OLED devices are shown;

[0036] Figure 8 The external quantum efficiency-brightness curves of Examples 1, 2, and 3 in solution-processed non-doped OLED devices are shown. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the embodiments. Of course, the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] Example 1

[0039] (1) Synthesis of dendritic TADF monomer DMAC-BP-tBu3Cz:

[0040]

[0041] 3,6-Bis(3,6-di-tert-butylcarbazole)carbazole (722.03 mg, 1 mmol), (4-bromophenyl)(4-(9,9-dimethylacridin-10(9H)-yl)phenyl)methanone (506.13 mg, 1.1 mmol), Pd(OAc)2 (13.47 mg, 6% mmol), Xphos (47.67 mg, 10% mmol), and t-BuONa (288.30 mg, 3 mmol) were placed in a 250 ml two-necked flask. 60 ml of anhydrous toluene was injected with a syringe. The reaction was heated to 110°C under a nitrogen atmosphere for 24 h. After completion of the reaction, the product was cooled to room temperature and extracted with dichloromethane and saturated brine. The product was dried over anhydrous magnesium sulfate and separated by column chromatography using a 1:5 ratio of dichloromethane to petroleum ether as the eluent to obtain 952.88 mg of a yellow-green solid in an 86% yield.

[0042] (2) Synthesis of dendritic TADF monomer Br-DMAC-BP-tBu3Cz:

[0043]

[0044] The product obtained in step (1) (664.86 mg, 0.6 mmol) was dissolved in 20 ml of anhydrous dichloromethane in a 250 ml two-necked flask. A solution of NBS (391.63 mg, 2.2 mmol) in anhydrous dichloromethane (40 ml) was slowly added dropwise under an ice bath in the dark. The mixture was stirred overnight, and the reaction was terminated by adding water. The product was extracted with dichloromethane and saturated brine, dried over anhydrous magnesium sulfate, and separated by column chromatography using a dichloromethane:petroleum ether ratio of 1:3 as the eluent to obtain 757.46 mg of a yellow solid, with a yield of 99%.

[0045] (3) Synthesis of N-methylhexadecane-3,6-dibromocarbazole:

[0046]

[0047] N-Methylhexadecylcarbazole (810.66 mg, 2 mmol) was dissolved in 40 ml of anhydrous dichloromethane in a 250 ml two-necked flask. A solution of NBS (391.63 mg, 2.2 mmol) in anhydrous dichloromethane (40 ml) was slowly added dropwise under an ice bath in the dark. The mixture was stirred overnight and terminated with water. The product was extracted with dichloromethane and saturated brine, dried over anhydrous magnesium sulfate, and separated by column chromatography using a 1:2 ratio of dichloromethane to petroleum ether as the eluent to afford 1120.36 mg of a white solid in a 99% yield.

[0048] (4) Synthesis of target polymer PDB3Cz:

[0049]

[0050] The product obtained in step (2) (126.73 mg, 0.1 mmol), the product obtained in step (3) (507.12 mg, 0.9 mmol), and 2,2-bipyridine (300.00 mg, 1.92 mmol) were placed in a 100 ml two-necked flask and evacuated three times under nitrogen. Ni(COD)2 (500.69 mg, 1.82 mmol) was then added to the flask and evacuated again. 1,5-cyclooctadiene (0.5 ml) and THF (50 ml) were added via syringe. The temperature was raised to 85°C under a nitrogen atmosphere and the reaction was continued for 72 h. Bromobenzene (0.5 ml) was added via syringe for end-capping. After the reaction was completed and cooled to room temperature, the product was extracted with dichloromethane and saturated brine, concentrated by spin drying, and precipitated in cold methanol. The product was extracted with methanol using a Soxhlet extractor for 48 h and dried to obtain the target polymer. The obtained polymer had Mw = 11313 and PDI = 1.70.

[0051] Example 2

[0052] (1) Synthesis of dendritic TADF monomer DMAC-BP-tBuCz:

[0053]

[0054] 3,6-Di-tert-butylcarbazole (279.19 mg, 1 mmol), (4-bromophenyl)(4-(9,9-dimethylacridin-10(9H)-yl)phenyl)methanone (506.13 mg, 1.1 mmol), Pd(OAc)2 (13.47 mg, 6% mmol), Xphos (47.67 mg, 10% mmol), and t-BuONa (288.30 mg, 3 mmol) were placed in a 250 ml two-necked flask. 60 ml of anhydrous toluene was injected with a syringe. The reaction was heated to 110°C under a nitrogen atmosphere for 24 h. After completion of the reaction, the mixture was cooled to room temperature and extracted with dichloromethane and saturated brine. The mixture was dried over anhydrous magnesium sulfate and dried by spin drying. The mixture was then separated by column chromatography using a 1:5 ratio of dichloromethane to petroleum ether eluent to afford 593.54 mg of a yellow-green solid in an 89% yield.

[0055] (2) Synthesis of dendritic TADF monomer Br-DMAC-BP-tBuCz:

[0056]

[0057] The product obtained in step (1) (398.92 mg, 0.6 mmol) was dissolved in 20 ml of anhydrous dichloromethane in a 250 ml two-necked flask. A solution of NBS (391.63 mg, 2.2 mmol) in anhydrous dichloromethane (40 ml) was slowly added dropwise under an ice bath in the dark. The mixture was stirred overnight, and the reaction was terminated by adding water. The product was extracted with dichloromethane and saturated brine, dried over anhydrous magnesium sulfate, and separated by column chromatography using a dichloromethane:petroleum ether ratio of 1:3 as the eluent to obtain 488.37 mg of a yellow solid with a yield of 99%.

[0058] (3) Synthesis of N-methylhexadecane-3,6-dibromocarbazole: Same as Example 1

[0059] (4) Synthesis of target polymer PDBCz:

[0060]

[0061] The product obtained in step (2) (82.22 mg, 0.1 mmol), the product obtained in step (3) (507.12 mg, 0.9 mmol), and 2,2-bipyridine (300.00 mg, 1.92 mmol) were placed in a 100 ml two-necked flask and evacuated three times under nitrogen. Ni(COD)2 (500.69 mg, 1.82 mmol) was then added to the flask and evacuated again. 1,5-cyclooctadiene (0.5 ml) and THF (50 ml) were added via syringe. The temperature was raised to 85°C under a nitrogen atmosphere for reaction for 72 h. Bromobenzene (0.5 ml) was added via syringe for end-capping. After the reaction was completed and cooled to room temperature, the mixture was extracted with dichloromethane and saturated brine, concentrated by spin drying, and precipitated in cold methanol. The mixture was extracted with methanol using a Soxhlet extractor for 48 h and dried to obtain the target polymer. The obtained polymer had Mw = 16359 and PDI = 6.33.

[0062] Example 3

[0063] (1) Synthesis of dendritic TADF monomer DMAC-BP-tBu7Cz:

[0064]

[0065] 3,6-Bis(3,6-bis(3,6-di-tert-butylcarbazole)carbazolyl)carbazole (1660.99 mg, 1 mmol), (4-bromophenyl)(4-(9,9-dimethylacridin-10(9H)-yl)phenyl)methanone (506.13 mg, 1.1 mmol), Pd(OAc)2 (13.47 mg, 6% mmol), Xphos (47.67 mg, 10% mmol), and t-BuONa (288.30 mg, 3 mmol) were placed in a 250 ml two-necked flask. 60 ml of anhydrous toluene was injected with a syringe. The reaction was heated to 110°C under a nitrogen atmosphere for 24 h. After completion of the reaction, the product was cooled to room temperature and extracted with dichloromethane and saturated brine. The product was dried over anhydrous magnesium sulfate and separated by column chromatography using a 1:5 ratio of dichloromethane to petroleum ether eluent to afford 1514.74 mg of a yellow-green solid in a 76% yield.

[0066] (2) Synthesis of dendritic TADF monomer Br-DMAC-BP-tBu7Cz:

[0067]

[0068] The product obtained in step (1) (1195.85 mg, 0.6 mmol) was dissolved in 20 ml of anhydrous dichloromethane in a 250 ml two-necked flask. A solution of NBS (391.63 mg, 2.2 mmol) in anhydrous dichloromethane (40 ml) was slowly added dropwise under an ice bath in the dark. The mixture was stirred overnight, and the reaction was terminated by adding water. The product was extracted with dichloromethane and saturated brine, dried over anhydrous magnesium sulfate, and separated by column chromatography using a dichloromethane:petroleum ether ratio of 1:3 as the eluent to obtain 1276.45 mg of a yellow solid with a yield of 99%.

[0069] (3) Synthesis of N-methylhexadecane-3,6-dibromocarbazole: Same as Example 1

[0070] (4) Synthesis of target polymer PDB7Cz:

[0071]

[0072] The product obtained in step (2) (214.89 mg, 0.1 mmol), the product obtained in step (3) (507.12 mg, 0.9 mmol), and 2,2-bipyridine (300.00 mg, 1.92 mmol) were placed in a 100 ml two-necked flask and evacuated three times under nitrogen. Ni(COD)2 (500.69 mg, 1.82 mmol) was then added to the flask and evacuated again. 1,5-cyclooctadiene (0.5 ml) and THF (50 ml) were added via syringe. The temperature was raised to 85°C under a nitrogen atmosphere and the reaction was continued for 72 h. Bromobenzene (0.5 ml) was added via syringe for end-capping. After the reaction was completed and cooled to room temperature, the product was extracted with dichloromethane and saturated brine, concentrated by spin drying, and precipitated in cold methanol. The product was extracted with methanol using a Soxhlet extractor for 48 h and dried to obtain the target polymer. The obtained polymer had a Mw = 8502 and a PDI = 1.42.

[0073] Table 1 Device performance data of the embodiment

[0074]

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A thermally activated delayed fluorescent conjugated polymer, characterized in that The polymer is copolymerized with a donor-acceptor-dendritic (DA-D') structure as a TADF (thermally activated delayed fluorescence) luminescent unit and a conjugated main chain (Host), and the polymer structure is shown in the general formula (1): General formula (1) Among them, Host is the main unit for regulating photophysical properties, x = 0.05-1, Dendrite is the dendritic structure unit, n>5, The Host unit includes the following structure: The dendrite unit includes the following structure: 。 2. A method for synthesizing a conjugated polymer according to claim 1, characterized in that: The following steps are involved: S1. The DA monomer provided in claim 1 and the dendritic structure monomer are subjected to a Buchwald-Hardwig reaction to obtain a donor-acceptor-dendritic (DA-D') TADF structure monomer; S2: brominating the TADF structural monomer obtained in step S1 with nitrobutane succinimide (NBS) to obtain a bilaterally brominated dendritic TADF monomer; S3 brominates the bilateral monomer with alkyl chain solubilization by bromosuccinimide (NBS) to obtain a bilaterally brominated terminal brominated monomer; S4: mixing the bilaterally brominated dendritic TADF monomer and the bilaterally brominated terminal brominated monomer, performing Yamamoto polymerization, and then capping with bromobenzene, and extracting with a Soxhlet extractor to obtain a conjugated polymer.

3. A method for synthesizing a conjugated polymer according to claim 2, characterized in that: The catalyst used in step S1 is palladium acetate, Xphos, and potassium phosphate, and the molar ratio of the DA monomer, the dendritic structure monomer, palladium acetate, Xphos, and potassium phosphate is 1:1.1:0.06:0.1:

3.

4. A method for synthesizing a conjugated polymer according to claim 2, characterized in that: In the step S4, the molar ratio of the bilaterally brominated dendritic TADF monomer to the bilaterally brominated terminal brominated monomer is 0.1:0.

9.

5. A method for synthesizing a conjugated polymer according to claim 2, characterized in that: The catalyst used in step S4 is 2,2-bipyridine, Ni(COD)2, and cyclooctadiene, and the molar ratio of the bilaterally brominated dendritic TADF monomer, the bilaterally brominated terminal brominated monomer, 2,2-bipyridine, Ni(COD)2, and cyclooctadiene is 0.1:0.9:2:2:

4.

6. A method for synthesizing a conjugated polymer according to claim 2, characterized in that: In step S4, the polymerization time is 72 hours; and the extraction time is 48 hours.

7. A thermally activated delayed fluorescence conjugated polymer is used to prepare a non-doped OLED device, characterized in that: The conjugated polymer is the thermally activated delayed fluorescence conjugated polymer according to claim 1.

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