Li Wei, Li Jiuyan, Liu Di, Li Deli, Zhang Dan
State Key Laboratory of Fine Chemicals , College of Chemical Engineering , Dalian University of Technology , 2 Linggong Road , Dalian 116024 , P. R. China . Email:
College of Chemistry , Dalian University of Technology , P. R. China.
Chem Sci. 2016 Nov 1;7(11):6706-6714. doi: 10.1039/c6sc01797e. Epub 2016 Jul 19.
By using pyridine and diphenylphosphine oxide (DPPO) as dual n-type units, two novel bipolar hosts, namely (5-(3,5-di(9-carbazol-9-yl)phenyl)pyridin-3-yl)diphenylphosphine oxide (-PyPOmCP), and (6-(3,5-di(9-carbazol-9-yl)phenyl)pyridin-3-yl)diphenylphosphine oxide (-PyPOmCP) are developed for blue and green phosphorescent organic light-emitting diodes (PhOLEDs). Direct linking of the dual n-type units not only pulls the LUMOs down, but also keeps the HOMO levels shallow, and leads to high triplet energies (2.78-2.86 eV) and small singlet-triplet energy differences (0.23-0.35 eV). Blue and green PhOLEDs are fabricated using FIrpic and Ir(ppy) as dopants in the hosts. A low turn-on voltage of 2.6 V is achieved for the green PhOLEDs. The -PyPOmCP hosted blue PhOLED achieves a high current efficiency of 55.6 cd A (corresponding to a maximum external quantum efficiency of 25.3% and a power efficiency of 43.6 lm W). The -PyPOmCP hosted green PhOLED exhibits an efficiency of 98.2 cd A (28.2% and 102.8 lm W). These data are among the best values for blue and green PhOLEDs reported so far. These "dual n-type units" hosts show much better performance than their DPPO-free analogue, clearly proving that the direct linking of DPPO and pyridine as dual n-type units is an effective molecular design strategy for host materials for use in high-performance PhOLEDs.
通过使用吡啶和二苯基氧化膦（DPPO）作为双n型单元，开发了两种新型双极主体，即（5-(3,5-二(9-咔唑-9-基)苯基)吡啶-3-基）二苯基氧化膦（-PyPOmCP）和（6-(3,5-二(9-咔唑-9-基)苯基)吡啶-3-基）二苯基氧化膦（-PyPOmCP），用于蓝色和绿色磷光有机发光二极管（PhOLEDs）。双n型单元的直接连接不仅降低了最低未占分子轨道（LUMOs），还使最高已占分子轨道（HOMO）能级变浅，并导致高三重态能量（2.78 - 2.86电子伏特）和小的单重态-三重态能量差（0.23 - 0.35电子伏特）。以FIrpic和Ir(ppy)作为主体中的掺杂剂制备了蓝色和绿色PhOLEDs。绿色PhOLEDs实现了2.6伏的低开启电压。以-PyPOmCP为主体的蓝色PhOLED实现了55.6坎德拉每安培的高电流效率（对应最大外量子效率为25.3%，功率效率为43.6流明每瓦）。以-PyPOmCP为主体的绿色PhOLED表现出98.2坎德拉每安培的效率（28.2%和102.8流明每瓦）。这些数据是迄今为止报道的蓝色和绿色PhOLEDs中的最佳值之一。这些“双n型单元”主体表现出比其不含DPPO的类似物更好的性能，清楚地证明了DPPO和吡啶作为双n型单元的直接连接是用于高性能PhOLEDs的主体材料的有效分子设计策略。
