To evaluate the electroluminescence (EL) performance of these emitters, OLEDs employing different doing concertation emitters (2, 5, 8 and 11 wt%, the data for 5 and 8 wt% can be found in the Figure and Table ) The EQE decreased to 3.7% at a luminance of 1000 cd m -2 for the device with DMACBP; however, for the device with DMACPyBP, the EQE1000 was 7.5%. A plausible explanation for this difference in efficiency roll-off behavior is due to the faster kRISC and shorter td in DMACPyBP and DMACPyBPN, thus leading to smaller triplet exciton populations at high current densities in the devices with these two emitters. The DMACPyBP-based OLED showed remarkably low efficiency roll-off, especially compared to other DMAC-containing orange-red TADF OLEDs (Figure ). Increasing the doping concentration to 11 wt% does not lead to further improvement in performance and the EL spectra red-shifted progressively (Figure ). At 11 wt% doping, the OLEDs emit in the range of 600-640 nm and showed EQEmax of 5.5-15.9% (Table ).