Non-radiative decay mechanisms in blue phosphorescent iridium(III) complexes

By using phosphorescent emitters, organic light emitting displays can be up to four times more efficient than those of fluorescent materials. Full colour displays based on phosphorescent materials have not been achieved thus far due to the poor efficiency of blue phosphorescent emitters. We show that there is a correlation between non-radiative decay of phosphorescence and vibrational coupling for related blue emissive materials containing similar iridium(III) complex chromophores. The materials had solution photoluminescence quantum yields (PLQYs) of up to 55% at room temperature with Commission Internationale de l’Eclairage co-ordinates of (0.155, 0.16). Stronger vibrational coupling was found to lead to an increased non-radiative decay rate and decreased PLQY. The activation energy for non-radiative decay was found to depend on the environment with the non-radiative decay rate being decreased when the emissive materials were placed in a solid host.