High Efficiency Hybrid White Organic Light-emitting Diodes Based on Exciplex Host
In organic light-emitting diodes(OLEDs),the balance of carriers in the light-emitting layer and the broadening of the exciton distribution region are crucial for improving device efficiency.In this study,low-efficiency roll-off blue light-emitting devices based on thermally activated delayed fluorescence(TADF)materials DMAC-DPS and TDBA-SAF were fabricated by using exciplex host material SiCzCz∶SiTrzCz2.With the same host material,three-emitting-layer structure was constructed by introducing red phosphorescent emitter RD071 and green phospho-rescent emitter Ir(ppy)2(acac),realizing a high color rendering index.The exciplex host material SiCzCz∶SiTrzCz2 not only broadens the exciton distribution region and improves the charge balance,but also constructs a cascaded ex-citon energy transfer route by aligning the triplet energies of TADF/phosphorescent emitter materials.Subsequently,the white OLEDs(WOLEDs)effectively improve the exciton utilization and reduce the efficiency roll-off.By optimiz-ing the device structure,WOLEDs achieved the highest external quantum efficiency,current efficiency and power efficiency of 23.0%,45.9 cd·A-1 and 33.9 lm·W-1,respectively.Also,the device has a high color rendering index of 87,good color stability and low efficiency roll-off.This study provides a new design scheme for hybrid white light-emitting devices with high color rendering index and low efficiency roll-off.
organic light-emitting diodesthermally activated delayed fluorescenceexciplexcharge balanceex-citon transfer