Fig. 2. (a) Absorption and (b) PL spectra of Ir-OO, Ir-ON, Ir-NN, Ir-OB and Ir-BB in degassed CH₂Cl₂ (inset: luminescence photographs of iridium complexes). (c) EL spectra and (d) CIE coordinates and (e) the efficiency versus current density relationship for devices of all complexes.