The luminance efficiency as a function of the applied voltage for the blue organic light-emitting devices (OLEDs) with a 4,4'-Bis(carbazol-9-yl)biphenyl (CBP)/4,4'-Bis(2,2'-diphenyl-ethen-1-yl)biphenyl (DPVBi) double emitting layer (DEML) was more stable than that of the OLEDs with a DPVBi emitting layer (EML), a CBP EML, or a DPVBi/CBP DEML, regardless of the variation of the applied voltage. The electroluminescence spectra showed that the dominant peak in the OLEDs with a CBP/DPVBi DEML was shifted to higher energy in comparison to that with a DPVBi EML, a CBP EML, or DPVBi/CBP DEML, indicative of the enhancement of the blue color purity.