Durene-decorated CBP derivatives as phosphorescent hosts and exciton-blocking materials for efficient blue OLEDs
作者:Lijun Deng、Xinzeng Wang、Zhengchuan Zhang、Jiuyan Li
DOI:10.1039/c2jm33636g
日期:——
Two novel durene-containing molecules, 1,4-bis-[4-(9-carbazolyl)-phenyl]-durene (CPD) and 1,4-bis-4-[9-(3,6-(di-tert-butyl)carbazoyl)]-phenyl}-durene (t-BuCPD), which are derived from 4,4′-bis(9-carbazolyl)biphenyl (CBP) by inserting durene in its biphenyl core, are designed and synthesized for use as host materials for blue phosphors in organic light-emitting diodes (OLEDs). Inserting durene in biphenyl causes a right-angle torsion between the durene and the adjacent phenyl groups due to the strong steric hindrance effect of the durene group, confining the effective π-conjugation on only one carbazole and one phenyl and increasing the triplet energies of CPD and t-BuCPD to over 3.0 eV. These durene-decorated molecules show higher thermal stabilities than many other CBP derivatives. Blue phosphorescent OLEDs were fabricated using CPD and t-BuCPD as triplet hosts and traditional iridium(III)bis(4,6-(difluorophenyl)pyridinato-N,C2′)picolinate (Firpic) as a dopant and excellent performances were achieved. In particular, peak efficiencies of 26.2 cd A−1 and 14.8 lm W−1 were realized when CPD was used as both a host and exciton-blocking material. This is the first report using durene to tune the triplet energy levels of phosphorescent host materials.
两种新型含杜烯分子,1,4-双-[4-(9-咔唑基)-苯基]-杜烯(CPD)和 1,4-双-4-[9-(3,6-(二叔丁基)咔唑基)]-苯基}-杜烯(t-BuCPD),是由 4、4′- 双(9-咔唑基)联苯 (CBP) 通过在其联苯内核中插入杜烯,设计并合成了用作有机发光二极管 (OLED) 中蓝色荧光粉主材料的 t-BuCPD。由于杜烯基团的强立体阻碍效应,在联苯中插入杜烯会导致杜烯和相邻苯基之间产生直角扭转,从而将有效的π-共轭限制在仅一个咔唑和一个苯基上,并将 CPD 和 t-BuCPD 的三重能提高到 3.0 eV 以上。与许多其他 CBP 衍生物相比,这些经杜烯装饰的分子具有更高的热稳定性。使用 CPD 和 t-BuCPD 作为三重宿主和传统的双(4,6-(二氟苯基)吡啶-N,C2′)吡啶甲酸铱(III)(Firpic)作为掺杂剂,制造出了蓝色磷光 OLED,并实现了优异的性能。特别是当 CPD 同时用作宿主材料和阻挡激子的材料时,峰值效率达到 26.2 cd A-1 和 14.8 lm W-1。这是首次报道使用杜烯来调节磷光宿主材料的三重能级。