One approach to improving device performance by reducing bimolecular annihilation processes in blue phosphorescent OLEDs is to increase the steric bulk of the ligands to reduce intermolecular interactions between adjacent phosphorescent complexes. A recent example is mer-Ir(pmp_Bn)3 (Figure ), which contains N-benzyl groups. This structural change resulted in much improved device performance (EQEmax = 24%, Lmax = 6400 cd/m 2 ) compared to the N-Me analogue [mer-Ir(pmp)3, EQEmax = 14.4%)] while retaining deep-blue emission with CIE of (0.151, 0.086). The lifetime of the devices containing mer-Ir(pmp_Bn)3 was 400 min (LT50@500 cd/m 2 ), an excellent result for a device showing such deep-blue emission. A similar effect is seen in fac-Ir(tpz)3 (Figure ), which contains N-tolyl groups. The sky-blue OLEDs showed excellent brightness (Lmax = 29 000 cd/m 2 ) and minimal efficiency roll-off (EQEmax = 18%, EQE1000 = 16%), although the device lifetime was not investigated.