Fig. 5
a Structure of devices with the different dopant in EML: pure CBP layer without dopant, CBP-doped 10 wt% Ir(ppy)3 (G) 5 wt% Ir(MDQ)2(acac) (R) and 15 wt% FIrpic (B). Normalized intensity of transient EL b Ir(MDQ)2(acac), c Ir(ppy)3 depending on the reverse bias (0 V, − 1 V, − 3 V, and − 5 V) after the applied voltage turning off .The voltage pulse width was 1 ms, and the pulse frequency was 100 Hz. A current density of 90 mA cm−2 was chosen to be the voltage pulse height