Electrical and optical properties of blue organic light-emitting devices (OLEDs) with doped or undoped emitting layers (EMLs) consisting of a heterostructure layer or a single layer were investigated. The driving voltage of the OLEDs with an undoped heterostructure multiple EML was lower than those of both OLEDs with a single EML and a doped heterostructure multiple EML The electroluminescence spectra of the OLEDs with an undoped and a doped heterostructure EMLs showed dominant peaks related to two heterostructure layers. (C) 2009 Elsevier B.V. All rights reserved.