Deep-blue phosphorescent iridium complexes with picolinic acid N-oxide as the ancillary ligand for high efficiency organic light-emitting diodes

A new series of highly efficient deep-blue phosphorescent Ir(III) complexes, (F2CH3ppy)2Ir(pic-N-oxide) 6 and (F2CF3CH3ppy)2Ir(pic-N-oxide) 7, based on phenylpyridine (ppy) as the main ligand and picolinic acid N-oxide (pic-N-oxide) as the ancillary ligand, were synthesized for applications in phosphorescent organic light-emitting diodes (PhOLEDs). The photophysical, electrochemical, and electroluminescent (EL) properties of these substances were investigated. The energy levels of these substances were adjusted by the introduction of electron-donating and electron-withdrawing substituents on the ppy ligand. The Ir(III) complexes have high phosphorescent quantum yields as well as high thermal stability. High performance PhOLEDs fabricated using the Ir(III) complexes showed bright deep-blue emissions with the Commission Internationale de L’Eclairage (CIE) coordinates of (0.147, 0.210) at the current density of 0.1 mA/cm2, and high external quantum (23.3%) and current (36.1 cd/A) efficiencies.