Enhanced reliability by diamond-like carbon in single-layer organic light emitting diodes

Diamond-like carbon (DLC) layers with thickness of 1.5 nm were incorporated, by pulsed laser deposition technique, in organic light emitting diodes (OLEDs), which consisted of a single light-emitting layer of polystyrene (PS) as the host material, but co-doped with N,N´-diphenyl-N,N´-bis(3-methylphenyl)-1,1´-biphenyl-4,4´-diamine (TPD) and Tris-(8-hydroxyquinoline)-Aluminium (Alq₃). For unstable ITO/doped-PS/Al OLEDs, which easily failed with poor light emission when the doped-PS layer used was too thin, the insertion of DLC in the ITO/doped-PS/DLC/Al structure restored the device operation to maximum operating voltage and hence full brightness.