Synthesis and Properties of Oxygen-Linked N-Phenylcarbazole Dendrimers

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• 作者：Chung-Chieh Lee ; Man-kit Leung ; Pei-Yu Lee ; Tien-Lung Chiu ; Jiun-Haw Lee ; Chun Liu ; Pi-Tai Chou
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：January 24, 2012
• 年：2012
• 卷：45
• 期：2
• 页码：751-765
• 全文大小：775K
• 年卷期：v.45,no.2(January 24, 2012)
• ISSN：1520-5835

文摘

A series of novel oxygen-linked N-phenylcarbazole (NPC) dendritic wedges (3鈥?b>5) and triphenylamine-centered dendrimers (CBD-G0 to -G2) have been synthesized and extensively studied. The aryl鈥搊xygen鈥揳ryl (Ar鈥揙鈥揂r) linkages were established on 3,6-positions of carbazole and 4-position of N-phenyl group. UV鈥搗is spectra revealed that the Ar鈥揙鈥揂r linkage would break down the 蟺 conjugation and make NPC units manifest their individual absorption moiety. Both steady-state luminescence and fluorescence decay dynamics at room temperature and 77 K in tetrahydrofuran suggested that the transfer of energy from the carbazole wedges to the triphenylamine (TPA) core operates in CBD-G1, so that the luminescence mainly arises from the core unit. The quenching of the emission from carbazole wedges by the TPA core becomes less effective as the generation develops into CBD-G2. The oxidation potential of the NPC derivatives clearly revealed the mesomeric electron-donating effect of the oxygen atom and inductive electron-withdrawing effect of the carbazole unit. The potential gradient could be established on those triphenylamine-centered dendrimers (CBD-G1 and CBD-G2), such that the outer layer is electron-poor and the inner layer is electron-rich. It is remarkable that the HOMO level of the NPC dendrimers is as high as 鈭?.17 eV and triplet energy level is kept above 2.85 eV. These levels of HOMO and triplet energy, together with good thermal stability and compatibility of solution processing, make NPC dendrimers ideal host materials for blue triplet emitters. Using CBD-G2 as the host material, the FIrpic-doped solution-processed light-emitting diodes were fabricated, and maximum luminous efficiency could be achieved at a record high of 24.7 cd/A at 484 cd/m².