The geometry structures, electronic structures, absorption, and phosphorescence properties of five heteroleptic cyclometalated osmium(II) complexes have been theoretically investigated. The lowest absorption of these complexes are located at 442, 441, 445, 439, and 446 nm, respectively, and the HOMO -> LUMO or HOMO -> LUMO + 1 is the predominant transitions. The lowest energy emissions of these complexes are localized at 620, 615, 616, 609 and 638 nm, respectively. Ionization potential (IP) and electron affinity (EA) have been calculated to evaluate the injection abilities of holes and electrons into these complexes. The reorganization energies indicate complex 5 has the best electron injection ability and electron-transporting performance. (C) 2013 Elsevier B.V. All rights reserved.