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, C²) (3-benzoyl-camphor) (ppy)pt(bcam) phosphorescent layer acting as the emitting layer. A maximum power efficiency η_p of 6.62lm/W and current efficiency of 14.78cd/A at 745cd/m² are obtained from the device. The roll-off percentage of η_p of the pure phosphorescent phosphor layer device is reduced to 5% at a current density of 20mA/cm², 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.