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

摘要

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/cm2 to 29.2 cd/A at 100 mA/cm2. 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 (Förster-type) energy transfer between excited molecules.