基于咔唑和3,3′-二甲基二苯醚共聚物主链的红光热活化延迟荧光聚合物的合成与表征
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摘要
采用咔唑和3,3'-二甲基二苯醚共聚物作为主链,通过Suzuki聚合方法,设计合成了系列红光热活化延迟荧光(TADF)聚合物PCzDMPE-R03～PCzDMPE-R10.和基于芴和3,3'-二甲基二苯醚共聚物主链的红光TADF聚合物相比,芴到咔唑的改变,能够有效地增加主链的最高占据分子轨道(HOMO)能级,进而降低空穴注入势垒.因此,PCzDMPE-R07获得了最优的非掺杂器件性能,启亮电压从原来的9.8 V降低到5.2 V,最大电流效率和外量子效率分别为3.35 cd/A和2.03%.在此基础上,将其分散在mCP中制备了掺杂器件,电流效率和外量子效率进一步提升到7.36 cd/A和3.77%.
A series of red-emitting thermally activated delayed fluorescence(TADF) polymers based on poly(2,7-carbazole-co-3,3′-dimethyldiphenyl ether)(PCzDMPE) main chains, including PCzDMPE-R03,PCzDMPE-R05, PCzDMPE-R07, and PCzDMPE-R10, have been designed and synthesized via Suzuki polycondensation. The thermally stable polymers possessed glass transition temperatures above 90 °C and decomposition temperatures above 410 °C, which is beneficial to the devices of long-term services. As the content of red TADF unit increased, the maximum emission was gradually red-shifted from 577 nm(PCzDMPE-R03) to584 nm(PCzDMPE-R010), while the film photoluminescence quantum yield(PLQY) dropped correspondingly from 0.47 to 0.21 according to the energy gap law. Meanwhile, they all exhibited an obviously delayed fluorescence with the lifetime of 145 – 161 μs, accompanied by a prompt fluorescence of 4.5 – 6.5 ns. For instance, the temperature-dependent transient photoluminescence spectra measured for PCzDMPE-R07 sample displayed an enhanced delayed fluorescence upon the temperature rise from 150 K to 300 K, indicative of its TADF nature. More importantly, compared with earlier reports of red TADF polymers based on poly(fluorene-co-3,3′-dimethyl diphenyl ether), fluorene being replaced by carbazole in the present work could increase the highest occupied molecular orbital(HOMO) level and thus favor the hole injection. As a consequence, the turn-on voltage of PCzDMPE-R07 nondoped device was significantly reduced from 9.8 V to 5.2 V. PCzDMPE-R07 also outperformed the other candidates in terms of a maximum current efficiency of 3.35 cd/A and a maximum external quantum efficiency(EQE) of 2.03%. For performance optimization, a doped device was then fabricated by dispersing 20 wt% of PCzDMPE-R07 into the 1,3-bis(9 H-carbazol-9-yl)benzene(mCP) matrix as an emitting layer. The corresponding current efficiency and EQE were further improved to 7.36 cd/A and 3.77%, respectively.To sum up, the copolymer containing carbazole and 3,3′-dimethyldiphenyl ether provides a favorable backbone framework for the design and synthesis of TADF polymers that possesses high efficiency and low driving voltage simultaneously.
A series of red-emitting thermally activated delayed fluorescence(TADF) polymers based on poly(2,7-carbazole-co-3,3′-dimethyldiphenyl ether)(PCzDMPE) main chains, including PCzDMPE-R03,PCzDMPE-R05, PCzDMPE-R07, and PCzDMPE-R10, have been designed and synthesized via Suzuki polycondensation. The thermally stable polymers possessed glass transition temperatures above 90 °C and decomposition temperatures above 410 °C, which is beneficial to the devices of long-term services. As the content of red TADF unit increased, the maximum emission was gradually red-shifted from 577 nm(PCzDMPE-R03) to584 nm(PCzDMPE-R010), while the film photoluminescence quantum yield(PLQY) dropped correspondingly from 0.47 to 0.21 according to the energy gap law. Meanwhile, they all exhibited an obviously delayed fluorescence with the lifetime of 145 – 161 μs, accompanied by a prompt fluorescence of 4.5 – 6.5 ns. For instance, the temperature-dependent transient photoluminescence spectra measured for PCzDMPE-R07 sample displayed an enhanced delayed fluorescence upon the temperature rise from 150 K to 300 K, indicative of its TADF nature. More importantly, compared with earlier reports of red TADF polymers based on poly(fluorene-co-3,3′-dimethyl diphenyl ether), fluorene being replaced by carbazole in the present work could increase the highest occupied molecular orbital(HOMO) level and thus favor the hole injection. As a consequence, the turn-on voltage of PCzDMPE-R07 nondoped device was significantly reduced from 9.8 V to 5.2 V. PCzDMPE-R07 also outperformed the other candidates in terms of a maximum current efficiency of 3.35 cd/A and a maximum external quantum efficiency(EQE) of 2.03%. For performance optimization, a doped device was then fabricated by dispersing 20 wt% of PCzDMPE-R07 into the 1,3-bis(9 H-carbazol-9-yl)benzene(mCP) matrix as an emitting layer. The corresponding current efficiency and EQE were further improved to 7.36 cd/A and 3.77%, respectively.To sum up, the copolymer containing carbazole and 3,3′-dimethyldiphenyl ether provides a favorable backbone framework for the design and synthesis of TADF polymers that possesses high efficiency and low driving voltage simultaneously.
引文
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3 Kaji H,Suzuki H,Fukushima T,Shizu K,Suzuki K,Kubo S,Komino T,Oiwa H,Suzuki F,Wakamiya A,Murata Y,Adachi C.Nat Commun,2015,6:8476
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5 Nikolaenko A E,Cass M,Bourcet F,Mohamad D,Roberts M.Adv Mater,2015,27:7236-7240
6 Lee S Y,Yasuda T,Komiyama H,Lee J,Adachi C.Adv Mater,2016,28:4019-4024
7 Shao S Y,Hu J,Wan g X D,Wang L X,Jing X B,Wang F S.J Am Chem Soc,2017,139:17739-17742
8 Xie G H,Luo J J,Huang M L,Chen T H,Wu K L,Gong S L,Yang C L.Adv Mater,2017,29:1604223
9 Shao Shiyang(邵世洋),Ding Junqiao(丁军桥),Wang Lixiang(王利祥).Acta Polymerica Sinica(高分子学报),2018,(2):198-216
10 Shao S Y,Ding J Q,Ye T L,Xie Z Y,Wang LX,Jing X B,Wang F S.Adv Mater,2011,23:3570-3574
11 Wang Y J,Zhu Y H,Xie G H,Zhan H M,Yang C L,Cheng Y X.J Mater Chem C,2017,5:10715-10720
12 Ren Z J,Nobuyasu R S,Dias F B,Monkman A P,Yan S K,Bryce M R.Macromolecules,2016,49:5452-5460
13 Zeng X,Luo J J,Zhou T,Chen T H,Zhou X,Wu K L,Zou Y,Xie G H,Shao L G,Yang C L.Macromolecules,2018,51:1598-1604
14 Yang Y,Zhao L,Wang S M,Ding J Q,Wang L X.Macromolecules,2018,51:9933-9942
15 Dijken A V,Bastiaansen J J A M,Kiggen N M M,Langeveld B M W,Rothe C,Monkman A,Bach I,St?ssel P,Brunner K.J Am Chem Soc,2004,126:7718-7727
16 Garbay G,Muccioli L,Hanifa A,Hadziioannou G,Brochon C,Cloutet E.Polymer,2017,119:274-284
17 Zhang Q S,Kuwabara H,Potscavage W J Jr,Huang S,Hatae Y,Shibata T,Adachi C.J Am Chem Soc,2014,136:18070-18081
18 Caspar Jonathan V,Kober E M,Sullivan B P,Meyer T J.J Am Chem Soc,1982,104:632-634
19 Tao Y,Yuan K,Chen T,Xu P,Li H H,Chen R F,Zheng C,Zhang L,Huang W.Adv Mater,2014,26:7931-7958
20 Li J,Nakagawa T,MacDonald J,Zhang Q,Nomura H,Miyazaki H,Adachi C.Adv Mater,2013,25:3319-3323