High-efficiency green electrophosphorescent organic light-emitting diodes with a simple device structure

In this study, we demonstrate electrophosphorescent organic light-emitting diodes (PHOLEDs) with a simple structure and high efficiency, utilizing fac-tris(2-phenylpyridine)iridium(III) (Ir(ppy)3) as a green phosphorescent emitter. The device structure (ITO/TAPC/TAPC:Ir(ppy)3/TPBi:Ir(ppy)3/TPBi /LiF/Al) was fabricated by the hole transporting layer of 1,1-bis((di-4-tolylamino)phenyl)cyclohexane (TAPC; T1 = 2.87 eV) and the electron transporting layer of 2,2,2-(1,3,5-benzenetriyl)tris[1-phenyl-1H-benzimidazole] (TPBI; T1 = 2.74 eV) to assemble a double emitting zone without common host materials. The emitting region with a TAPC/TPBI bilayer interface was able to provide an effective energy transference of Ir(ppy)3 (T1 = 2.4 eV). Thus, the green PHOLED exhibited high current efficiency (70 cd/A at 100 cd/m 2 ) and low roll-off in these devices.