Diamond-like carbon films as electron-injection layer in organic light emitting diodes

In this letter a thin film of diamond-like carbon (DLC) deposited by pulse laser deposition (PLD) is used as an electron injection layer in organic light emitting diodes. The heterojunction structures of these devices consist of: indium tin oxide (ITO)/conducting polymer/DLC/nickel, or ITO/DLC/P3OT/Pt. Poly(3-octylthiophene) conjugated polymer (P3OT) is used as the emission layer. In all the realized diodes, the current is two orders of magnitude larger than in the conventional ITO/P3OT/aluminum structure, and the driving voltage is drastically reduced. However, the light emission is observed only in the ITO/DLC/P3OT/Pt structure. These results can be interpreted in terms of a highly efficient electron injection from the DLC into the conducting polymer and a DLC/P3OT interface.