Dibenzooxasiline‐Derived n ‐Type Host for High Efficiency and Long‐Lifetime Blue Phosphorescent Organic Light‐Emitting Diodes

Abstract Dibenzooxasiline‐derived compounds, 2,4‐bis(10,10‐diphenyl‐10H‐dibenzo[b,e][1,4]oxasilin‐2‐yl)‐6‐phenyl‐1,3,5‐triazine (mOSiTrz) and 9‐(4,6‐bis(10,10‐diphenyl‐10H‐dibenzo[b,e][1,4]oxasilin‐2‐yl)‐1,3,5‐triazin‐2‐yl)‐9H‐carbazole (mOSiCzTrz), are developed as high‐triplet‐energy n ‐type hosts for blue phosphorescent organic light‐emitting diodes (PhOLEDs). They are used as n ‐type hosts in a mixed host to assist positive‐polaron dispersion in the p–n mixed host to achieve high efficiency and long device lifetime. The dibenzooxasiline‐based n ‐type hosts are mixed with a p ‐type 9‐(3‐(triphenylsilyl)phenyl)‐9H‐3,9′‐bicarbazole host and performed better than n ‐type hosts built on a conventional tetraphenylsilane moiety. The external quantum efficiency of the blue PhOLEDs with the mOSiTrz and mOSiCzTrz hosts is over 20%, and their device lifetimes are extended 1.5‐ and 4‐fold, respectively, relative to the well‐known 2‐phenyl‐4,6‐bis(3‐(triphenylsilyl)phenyl)‐1,3,5‐triazine device due to the enhanced positive‐polaron transport and dispersion abilities of the mOSiTrz and mOSiCzTrz hosts assisted by the dibenzooxasiline group.