Efficient blue phosphorescent organic light-emitting diodes by tuning iridium(III) phenylpyridine complexes

We demonstrated efficient blue electrophosphorescence using the Ir(OMeppy)2(acac) [OMeppy = 2-(phenyl)-4-methoxypyridine, acac = acetylacetonate], Ir[(CF3)2ppy]2(acac) [(CF3)2ppy = 2-(3', 5'-bistrifluoromethyl phenyl)-pyridine], Ir[(CF3)2OMeppy]2(acac) [(CF3)2OMeppy = 2-(3',5'-bistrifluoromethyl phenyl)-4-methoxypyridine] based on Ir(ppy)2(acac) (ppy = phenylpyridine). The methoxy group was substituted on the 4-position of pyridyl ring as electron donating group (EDG) and the trifluoromethyl group was substituted on the 3'5'-position of phenyl ring as electron withdrawing group (EWG). The organic light-emitting diodes (OLEDs) with Ir(OMeppy)2(acac), Ir[(CF3)2ppy]2(acac), Ir[(CF3)2OMeppy]2(acac) and Ir(ppy)2(acac) have maximum luminous efficiency of 42.54 cd/A, 13.67 cd/A, 7.06 cd/A and 40.70 cd/A, respectively. Also, their electroluminescent (EL) emission appeared at 533 nm, 475 nm, 471 nm and 522 nm, respectively.