The electrical and the optical properties of polymer light-emitting devices (PLEDs) fabricated utilizing a graphene hole injection layer (HIL) were investigated to clarify the hole injection enhancement caused by the insertion of the graphene HIL. The graphene was synthesized by using chemical vapor deposition, and the PLEDs with a graphene HIL were fabricated by using spin-casting method. The average transmittance for the graphene film with a thickness of 10 nm was approximately 90%, and the surface of the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer deposited on a graphene layer was smoother than that of the PEDOT: PSS deposited on an indium-tin-oxide layer. While the hole current of the PLEDs with a graphene HIL larger than that of the PLEDs without a graphene layer because of the high conductivity of the graphene film, the luminance efficiency was lower due to the leakage of holes that had not recombined with electrons. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3604779] All rights reserved.