Halide and steric effects on Ir(III) carbene phosphors for blue organic light-emitting diodes

We reported Ir(III) complexes featuring a dicarbene pincer chelate, a bidentate carbene cyclometalate (with either N -benzyl or N -mesityl appendage) and a halide (X − = Cl − , Br − and I − ), for probing the structure-property relationship. They exhibit blue emission with the peak max spanning 465–480 nm in toluene at RT. Particularly, [Ir(DP)(MC5H)Cl] and [Ir(DP)(MS1)Cl] showed the best performance among these Ir(III) emitters due to the high MLCT and LC components and relatively diminished XLCT contribution. This is evidenced by high photoluminescent quantum yield (PLQY) of 60% and 73% and fast radiative rate constant ( k r = 6.7 × 10 6 and 2.0 × 10 6 s −1 ). Phosphorescent organic light-emitting diode (PhOLED) devices based on 20 wt% of [Ir(DP)(MC5H)Cl] and [Ir(DP)(MS1)Cl] exhibited the maximum external quantum efficiency (EQE max ) of 26.1% and 22.0% with peak max at 506 and 468 nm, respectively. Additionally, hyper-OLED featuring sensitizer [Ir(DP)(MS1)Cl] and terminal emitter v-DABNA afforded narrowband blue emission with EQE max of 26.9% and the International Commission on Illumination (CIE) coordinates of (0.129, 0.157).