A series of heteroleptic cyclometalated Ir(III) complexes for organic light-emitting diodes (OLEDs) application have been investigated theoretically to explore their electronic structures and spectroscopic properties. The geometries, the electronic structures, the lowest-lying singlet absorptions and triplet emissions of Ir(dfppy)2(tpip), Ir(tfmppy)2(tpip), and theoretically designed models of Ir(ppy)2(tpip) were investigated with the density functional theory (DFT)-based approaches, where ppy = 2-phenylpyridine, dfppy = 4,6-difluorophenylpyridine, tfmppy = 4-trifluoromethylphenylpyridine, and tpip = tetraphenylimidodiphosphinate. Their structures in the ground and their excited states have been optimized at the DFT/Becke 3-parameter Lee Yang Parr (B3LYP)/Los Alamos National Laboratory 2-double-z (LANL2DZ) and time-dependent DFT/B3LYP/LANL2DZ levels, and the lowest absorptions and emissions were evaluated at B3LYP and M062X level of theory, respectively. Furthermore, the energy transfer mechanism together with the advantage of low efficiency roll-off for these complexes also can be analyzed here. Copyright © 2013 John Wiley & Sons, Ltd.