Highly Efficient Greenish-Yellow Phosphorescent Organic Light-Emitting Diodes Based on a Novel 2,3-Diphenylimidazo[1,2-a]Pyridine Iridium(III) Complex

A cyclometalated greenish-yellow emitter 2,3-diphenylimidazo[1,2-a]pyridine iridium(III) complex is successfully synthesized and used to fabricate phosphorescent organic light-emitting diodes. The optimized device exhibits a greenish-yellow emission with the peak at 523nm and a strong shoulder at 557 nm, corresponding to Commission Internationale de l'Eclairage coordinates of (0.38, 0.58). The full width at half maximum of the device is 93 nm, which is broader than the fac-tris(2-phenylpyridine)iridium [Ir(ppy)(3)] based reference device of 78 nm. Meanwhile, a maximum current efficiency of 62.6 cd/A (47.5 lm/W) is obtained. This result is higher than a maximum current efficiency of 54.8 cd/A (43 lm/W) of the Ir(ppy)(3) based device. The results indicate that this new iridium complex may have potential applications in fabricating high color rendering index white organic light emitting diodes.