High efficiency yellow fluorescent organic light emitting diodes based on m-MTDATA/BPhen exciplex

High efficient yellow organic light emitting diodes (OLEDs) based on exciplex were reported. The exciplex was formed by 4,4',4''-tris [3-methylphenyl (phenyl) amino]-triphenylamine (m-MTDATA) and 4, 7-diphenyl-1, 10-phenanthroline (BPhen). The resulting yellow OLEDs exhibited an external quantum efficiency of over 7%, which is attributed to the effective energy back transfer from exciplex triplet state to exciplex singlet state. The maximum power efficiency of 25 lm/W was achieved. Doping a yellow phosphor Ir(bt) 2(acac) into m-MTDATA: BPhen blend, a high efficiency device was achieved with a turn-on voltage of 2.1 V, maximum power efficiency and external quantum efficiency of 86.1 lm/W and 20.7%, respectively.