Enhanced efficiency and reduced roll-off in nondoped phosphorescent organic light-emitting devices with triplet multiple quantum well structures

Highly efficient nondoped phosphorescent organic light-emitting devices (NPOLEDs) with triplet multiple quantum well structures are fabricated by using 4,4'-N,N'-dicarbazole-biphenyl and an iridium(III) complex as the potential barrier layer and the potential well layer/light-emitting layer, respectively. Remarkably, such NPOLED with an optimized device configuration achieves reduced current efficiency roll-off, which slightly decreases from its peak value of 31.5 cd/A at 19.8 mA/cm(2) to 29.2 cd/A at 100 mA/cm(2). We attribute this improvement to the efficient triplet exciton confinement effect and the suppression of triplet-triplet annihilation which occurs via single-step long range (Forster-type) energy transfer between excited molecules. (C) 2010 American Institute of Physics. [doi:10.1063/1.3483131]