Organic light-emitting device (OLED) was fabricated using the novel red phosphorescent heteroleptic tris-cyclometalated iridium complex, bis(2-phenylpyridine)iridium(III)[2(5'-methylphenyl)-4-diphenylquinoline] [Ir(ppy)(2)(dpq-5CH(3))], based on 2-phenylpyridine (ppy) and 2(5'-methylphenyl)-4-diphenylquinoline (dpq-5CH(3)) ligand. Generally, the ppy ligand in heteroleptic iridium complexes plays an important role as "sensitizer" in the efficient energy transfer from the host (CBP; 4.4,N,N'-dicarbazolebiphenyl) to the luminescent ligand (dpq-5CH(3)). We demonstrated that high efficiency through the "sensitizer" can be obtained, when the T(1) of the emitting ligand is close to T(1) of the sensitizing ligand. The device containing Ir(ppy)(2)(dpq-5CH(3)) produced red light emission of 614 nm with maximum luminescence efficiency and power efficiency of 829 cd/A (at 0.09 mA/cm(2)) and 5.79 Im/W (at 0.09 mA/cm(2)), respectively. (C) 2009 Elsevier B.V. All rights reserved.