We demonstrate a high efficiency organic electrophosphorescent device comprised of a 4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA) hole transport layer and a 4,4′-N,N′-dicarbazole-biphenyl (CBP) host doped with the metallorganic phosphor, fac-tris(2-phenylpyridine)iridium (Ir(ppy)3) as the green light-emitting layer. The device exhibits peak external quantum and power efficiencies of (12.0 ± 0.6)% and (45 ± 2) lm/W, respectively, corresponding to ∼60% internal quantum efficiency. A luminance of 1850 cd/m2 is observed at a current density of 10 mA/cm2. The device operating properties are controlled by electron injection into, and transport by the CBP layer along with hole injection from m-MTDATA directly into the Ir(ppy)3 highest occupied molecular level, leading to direct carrier recombination and exciton formation on the phosphor dopant. Ambipolar conduction properties of the Ir(ppy)3:CBP layer are established by analysis of triplet-triplet annihilation, exciton formation and the luminance-current-voltage characteristics.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Materials Chemistry
- Electrical and Electronic Engineering