Harnessing Triplet Excited States by Fluorescent Dopant Utilizing Codoped Phosphorescent Dopant in Exciplex Host for Efficient Fluorescent Organic Light Emitting Diodes

The singlet fraction of excitons on a conventional fluorescent emitter is increased by reverse intersystem crossing of exciplexes and the sensitization effect of phosphorescent materials. Consequently, a red fluorescent organic light‐emitting diode (OLED) with an external quantum efficiency (EQE) of 23.7% is realized and an EQE of nearly 30% may be expected if all singlet excitons in the fluorescent emitter decay radiatively.