Efficient co-host emission layer has been demonstrated by mixing blue-emitting p-DMDPVBi and hole-transporting NPB in optimal weight ratio (w/w = 80/20). First, efficiency enhancement was observed in the fabrication of blue organic light-emitting diodes (ITO/NPB/p-DMDPVBi:NPB/TPBi/LiF/Al). Then, bright, efficient and stable fluorescent white organic light-emitting diodes were obtained by doping the optimal co-host emissive layer with orange dye (rubrene). The device performance was significantly improved, with a turn-on voltage, maximum luminance and maximum current efficiency of 2.9 V, 18100 cd/m(2) and 10.6 cd/A, respectively. The improvement mechanisms were elucidated using energy level diagrams, photoluminescence spectra, absorption spectra, and electroluminescence spectra. Current results show that forming the co-host emission layer is a promising way to improve device performance, making it applicable for facile fabrication of efficient OLEDs. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.092204jes] All rights reserved.