Controlling Ion Distribution for High-Performance Organic Light-Emitting Diodes Based on Sublimable Cationic Iridium(III) Complexes

Sublimable charged iridium­(III) complexes
are becoming an attractive family of new phosphors and making their
way into vacuum-evaporated-deposited organic light-emitting diodes,
while it remains challenging to achieve high device performance. Here,
we demonstrate a substantial mitigation of exciton quenching not
only by reducing the dopant concentration, but also by controlling
the ion distribution in the emissive material layers. We, therefore,
achieved green luminescence with high brightness, superior efficiencies,
and low driving voltages. Following this strategy, we further developed
another six sublimable charged iridium­(III) complexes and attained
blue-green, yellow, and red-emitting devices with record-high performance.
This study represents an important advance in the construction of
bright electroluminescence from ionic transition metal complexes and
shows their great promise in various optoelectronic applications.