Excimer emission of Ir complex for solution processed single emitting layer white OLEDs

摘要

The application of emissive intermolecular states of non-planar Iridium (III) phosphors in white emitting phosphorescent electroluminescent devices is almost unexplored. Here, I investigate the competing mechanisms of energy transfer and charge trapping as function of temperature in devices whose active layer contains an Ir (III) complex with a rigid cyclometallated ligand structure blended in a polyfluorene host. Keeping a low doping ratio it is possible to boost the formation of the low-energy beta phase in the polymer matrix as well as generate the intermolecular emissive state in the Ir compound so as to enable white emission with CIE coordinates (0.32, 0.23) and external quantum efficiency of 2.32 +/- 0.11% at 25 mAcm(-2) in a single-layer device structure. This device performance is higher than those previously reported for fully solution-processed devices based on intermolecular excited states.