Exciplex emission and Auger process assistant green organic electrophosphorescence devices with very low doped level of iridium complex

We demonstrate efficient and simple structure phosphorescence organic light-emitting diodes, in which 4, 4', 4-tris[3-methyl-pheny(phenyl)-amino]triphenyl-amine (m-MTDATA) and 4,7-diphenyl-1, 10-phenanthroline (Bphen) are used as hole transport and electron transport layers, respectively, accompanied by 3 wt% fac-tris(2-phenylpyridine) iridium doped in 1,3,5-tris(N-phenylbenzimidazol-2-yl)-benzene (Ir:TPBi) as the emitting layer. As a result, a 29 lm W-1 peak power efficiency and 2.2V turn-on voltage are achieved, respectively. The achievement of excellent electroluminescence (EL) properties was attributed to the contribution of exciplex formation at the interface of m-MTDATA/Ir : TPBi and the Auger-type two-step process of charge carrier injection. The competition between the interfacial exciplex and Ir-complex emissions in the EL processes was also discussed.