High efficiency phosphorescent organic light-emitting devices with a new organic material as the host of the emitting layer

In this paper, we demonstrate a phosphorescent organic light emitting device (PHOLED) with low turn-on voltage by using a n-type organic material as the host of the emitting layer (EML) doped with green emitting complex, fac tris(2-phenylpyridine) iridium Ir(ppy) 3 . This material exhibits high glass transition temperature (over 200 °C) that may help to elongate the operation lifetime. We compare our devices to the classical 4,4'-N,N'-dicarbazole-biphenyl (CBP) based green device. Driving voltage of the CBP and the new-host based OLED is 16 and 11 V with the current density of 100mA/cm 2 , respectively. The lower driving voltage of the new-host based device comes from the lower HOMO value, i.e. 5.7 eV, which is nearly the same as that of NPB. The current efficiency at 10000 cd/m 2 is slightly decreased from 24 to 21 cd/A. However, the power efficiency is increased from 5 to 6 lm/W.