Tandem red PhOLEDs based on exciplex-forming co-host

Exciplex forming cohosts have been widely adopted in phosphorescent organic light-emitting diodes (PHOLEDs), achieving high efficiency with low roll-off and low driving voltage. We employed a new exciplex forming cohost composed of TAPC and CN-T2T as charge-transporting and emitting materials. The tandem red-emitting PhOLEDs using the exciplex forming cohost achieved a maximum external quantum efficiency (EQE) of 40.6 % and power efficiency of 38.9 lm W−1 with low operating voltages and low efficiency roll-offs.