We demonstrate efficient red electrophosphorescence using bis[2-(5-methoxyphenyl)-4-phenylquinolinato-N C(2)] iridium(III)(acetylacetonate) [Ir(dpq-5OCH(3))(2)(acac)], bis[2-(5-methylphenyl)-4-phenylquinolinato-N, C(2)] iridium(III)(acetylacetonate)[Ir(dpq-5CH(3))(2)(acac)] and bis[2-(5-fluorophenyl)-4-phenylquinotinato-N,C(2)] iridium(III) (acetylacetonate) [Ir(dpq-5F)(2)(acac)] in compared with bis[2,4-diphenylquinolinato-N,C(2)] iridium (III)(acetylacetonate) [Ir(dpq)(2)(acac)]. The -CH(3), -OCH(3) and -F group substituted on the 5'-position of phenyl ring strongly affected the energy level of molecule. The organic light-emitting diodes (OLEDs) with Ir(dpq-50CH(3))(2)(acac), Ir(dpq-5CH(3))(2)(acac), Ir(dpq-5F)(2)(acac) and Ir(dpq)(2)(acac) have a maximum luminous efficiency of 8.20 cd/A, 10.20 cd/A, 15.80 cd/A and 11.60 cd/A, respectively. Also, their electroluminescent emission appeared at 605, 617, 610 and 617 nm, respectively. (C) 2008 Elsevier B.V. All rights reserved.