2 research outputs found
Up to 100% Formation Ratio of Doublet Exciton in Deep-Red Organic Light-Emitting Diodes Based on Neutral π‑Radical
In a neutral π-radical-based
organic light-emitting diode (OLED), although the emission comes from
the doublet excitons and their transition to the ground state is spin-allowed,
the upper limit of internal quantum efficiency (IQE) is not clear,
50% or 100%? In this work, the deep-red OLEDs based on a neutral π-radical
were fabricated. Up to 100% doublet exciton formation ratio was obtained
through rational designing device structure and host–guest
doping system. This indicates the IQE of neutral π-radical-based
OLEDs will reach 100% if the nonradiative pathways of radicals can
be suppressed. The maximum external quantum efficiency of the optimized
device is as high as 4.3%, which is among the highest values of deep-red/near-infrared
OLEDs with nonphosphorescent materials as emitters. Our results also
indicate that using partially reduced radical mixture as emitter may
be a way to solve aggregation-caused quenching in radical-based OLEDs