We also explored the potential of TPXZPhCor as an emitter in an afterglow OLED. To the best of our knowledge, there were only three prior reports of afterglow OLEDs. Adachi and co-workers demonstrated the first afterglow OLED wherein they employed a hydrophobic steroid derivative as the host and a deuterated fluorene-based compound as the dopant in the emissive layer (EML). The green OLED only showed an EQEmax of ~1%. The same group proposed another strategy and developed an exciplex-based afterglow OLED by reducing the guest concentration to slow the exciton recombination rate and by increasing the EML thickness to enhance the charge accumulation process. However, the abnormally low guest concentration and thick EML contribute to the significantly reduced device brightness and necessitate a very high driving voltage (pulse voltage = 70 V), resulting in an EQEmax of ~0.8%. Further, the device exhibited a long transient EL decay of more than 10 s. Xie et al. as the anode and cathode, respectively, PEDOT:PSS acts as the hole-transporting layer, TPBi acts as the electron-transporting layer, and LiF acts as the electron-injection layer (Figure ). The afterglow OLED performance is summarized in Table . The optimized device has a turn-on voltage of 4.3 V and a driving voltage at 100 cd m -2 of 5.5 V, which is much lower than previously reported afterglow OLEDs. The Lmax reached 5167 cd m -2 (Figure ) and the EQEmax was 3.3% (Figure ). Compared to the previous reports of afterglow OLEDs, device A has the highest performance (Table ). The EL spectrum (Figure ) of the OLED matches the phosphorescence spectrum of the 15 wt%