Ultrathin diamond-like carbon (DLC) was deposited by pulsed Nd:YAG laserablation of graphite target on the indium tin oxide (ITO) surface that functioned as the buffered anode for single-layer organic light emitting devices (OLEDs). Deposited by 355 nm Nd:YAG laser, DLC films were characterized by the Raman spectroscopy and the bulk resistivity measurement. Insertion of DLC in the hole-transport ITO/DLC/TPD/AI device slightly increased the injection current density and reduced the turn-on voltage. But DLC insertion in the electron-transport ITO/DLC/Alq(3)/Al device greatly decreased the injection current density and increased the turn-on voltage. For the ITO/DLC/(TPD + Alq(3) + PVK)/Al device, that was doped with Alq(3) and TPD, improved performance with a higher current density and brightness were consistently obtained. Possible mechanisms for the DLC effect in these single-layer devices were discussed. (C) 2009 Elsevier B.V. All rights reserved.