N-type Host Derived from Phenyl-Triazine Moiety for Low Driving Voltage in Blue Phosphorescent Organic Light-Emitting Diodes

For commercialization of blue phosphorescent OLED, it is desirable to satisfy low driving voltage, high efficiency, and long device lifetime at the same time. In this work, we developed a new phenyl-triazine type based PTHN-2 host with oxasiline functional group by applying a novel molecular design strategy that modulates intermolecular distance and electron mobility. The PTNH-2 host was compared with PTNH-1 host with tetrapheny lsilane functional group instead of oxasiline functional group. The fabricated blue phosphorescent OLEDs with PTNH-2 as the N type host showed the driving voltage of 4.1 V and the external quantum efficiency of 22.0% relative to driving voltage of 4.5 V and external quantum efficiency of 18.3% collected from PTNH-1 based blue phosphorescent OLED. Additionally, the device lifetime of the blue phosphorescent OLEDs was extended by more than 100% by replacing PTNH-1 host with PTNH-2 host. The driving voltage, quantum efficiency, device lifetime, and power efficiency of the blue phosphorescent OLEDs were dramatically improved by employing the PTNH-2 host.