Low roll-off efficiency green phosphorescent organic light-emitting devices with simple double emissive layer structure

Using an Ir(ppy)(3) metal complex doped in 4,4'4 ''-tris(N-carbazolyl)-triphenylamine hole and bis[2-(2-hydroxyphenyl)-pyridine]beryllium electron transport host materials, simple three layer green phosphorescent organic light-emitting devices comprising double emissive layers have been fabricated. A low driving voltage value of 3.3 V to reach a luminance of 1000 cd/m(2) and maximum current- and power-efficiency values of 58.7 cd/A and 65.1 lm/W, and maximum external quantum efficiency (EQE) value of 18.6% are reported in this device. EQE exceeding 15% over a wide range of current density from 0.03 to 25 mA/cm(2) is noticed. We demonstrate a low roll-off current efficiency value of 12% at a luminance of 10 000 cd/m(2) in a highly efficient simple double emissive layer device, imperative to high brightness applications. (C) 2008 American Institute of Physics.