Nondoped Electrophosphorescent Organic Light-Emitting Diodes Based on Platinum Complexes

An undoped electrophosphorescent organic light-emitting diode is fabricated using a pure platinum(II) (2-phenylpyridinato-N, C-2) (3-benzoyl-camphor) [(ppy)pt(bcam)] phosphorescent layer acting as the emitting layer. A maximum power efficiency eta(p) of 6.62 lm/W and current efficiency of 14.78 cd/A at 745 cd/m(2) are obtained from the device. The roll-off percentage of eta(p) of the pure phosphorescent phosphor layer device is reduced to 5% at a current density of 20 mA/cm(2), which is about 11% for conventional phosphorescent devices. The low roll-off efficiency is attributed to the phosphorescent material, which has the molecular structure of a strong steric hindrance effect.