Reduced efficiency roll-off in phosphorescent organic light emitting diodes at ultrahigh current densities by suppression of triplet-polaron quenching

High-performance phosphorescent organic light emitting devices with reduced efficiency roll-off at ultrahigh current densities were realized. The devices were Ir(ppy)(3)-based phosphorescent organic light emitting diodes that employed 1,3-bis[2-(2,2(')-bipyridine-6-yl)-1,3,4-oxadiazo-5-yl]benzene as a high mobility electron transfer layer. The device's brightness was enhanced while the efficiency roll-off was reduced. The device exhibits high current efficiency (21 cd/A) at high brightness (80 000 cd/m(2)), with a maximum luminescence of 136 000 cd/m(2) at over 1 A/m(2) (with an efficiency of 13 cd/A). This reduction in efficiency roll-off is attributed to the suppression of the triplet-polaron quenching rate through balancing the charge carrier ratio in the device. (C) 2008 American Institute of Physics.