Furthermore, the exciton utilization efficiency (EUE) of the SP-OLEDs with 4DMAC-TPPQ and 4PXZ- TPPQ is high as 74 and 67%, respectively, indicating that there is significant triplet exciton harvesting in these devices. The EL spectrum of the neat film SP-OLED with 4PXZ-TPPQ mirrors the PL spectrum (λPL = 770 nm). These devices are, to the best of our knowledge, the reddest of those based on emitters containing quinoxaline acceptors (Figure and Table ).