This paper studies color tuning in efficient electrophosphorescent organic light-emitting diodes using heteroleptic iridium complexes, bis(2-phenylquinoline)(2-phenylpyridine)iridium(111) [Ir(pq)(2)(ppy)], and bis(2-phenylpyridine)(2-phenylquinoline)iridium(III) [Ir(ppy)(2)(pq)]. After tuning the emission color by adjusting the number of each ligand, observation revealed the emission peaks at 512 and 600 nm, which arise from ppy and pq ligand, respectively. At a luminance of 1000 cd/m(2), the experiment maintained good current efficiency: 11.5 and 13.5 cd/A for Ir(pq)(2)(ppy) and Ir(ppy)(2)(pq). respectively. (C) 2011 Published by Elsevier B.V.