While the current density of the organic light-emitting devices (OLEDs) with 5,6,11,12-tetraphenylnaphthacene (rubrene) layers in both the hole transport layer (HTL) and the emitting layer (EML) was lower than those of the OLEDs without a rubrene layer or with a rubrene layer in only a HTL or an EML, the luminance efficiency of the OLEDs with rubrene layers in both the HTL and the EML were significantly enhanced. While the rubrene layer in the HTL acting as a hole trap decreased the hole mobility of the HTL, the rubrene layer in the EML acting as an emitting site increased the luminance.