High efficiency and low roll-off blue phosphorescent organic light-emitting devices using mixed host architecture

We report high efficiency and low roll-off for blue electrophosphorescent organic light emitting devices based on a mixed host layer architecture. The devices were fabricated using a mixed layer of di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane, a hole transport material, and 2,8-bis(diphenylphosphoryl)dibenzothiophene, an electron transport material, as the host layer doped with the blue phosphor iridium (III) bis[(4,6-difluorophenyl)-pyridinato-N,C-2']picolinate. Using a mixed layer as the host allowed us to achieve high power efficiency (59 lm/W at 100 cd/m(2)), low turn-on voltage (2.7 V for >10 cd/m(2)), and low roll-off in these devices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3464969]