Highly efficient phosphorescent organic light-emitting diodes using a beryllium metal-chelate complex as electron-transporting host material

摘要

A classical fluorescent metal-chelate complex bis(2-(2-hydroxyphenyl)-pyridine)beryl-lium (Bepp_2) has been used as an efficient electron-transporting host material to construct highly efficient phosphorescent organic light-emitting diodes (PHOLEDs) with an orange-emitting phosphorescent guest bis(7,8-benzoquinolinato) iridium (III) (N,N'-diisopropyl-benzamidine) ((bzq)_2lr(dipba)). Due to the well-matched energy levels of Bepp_2 with the corresponding hole-/electron- transporting (HT/ET) materials and the high-efficiency and complete energy transfer of this host-guest system, the Bepp2-based PHOLEDs exhibit rather low driving voltage (2.8 V) and high peak EL efficiencies of over 70 cd A~(-1) for luminous efficiency, 55 lm W~(-1) for power efficiency, and 23% for external quantum efficiency, a performance significantly better than that using CBP as the host.