Efficient white emission from the mixing of yellow emission from the Re-complexes, (4,4′-dimethyl-2,2′-bipyridine)Re(CO)3Cl (Dmbpy-Re), and blue emission from the N,N′-di-1-naphthyl-N, N′-diphenylbenzidine (NPB) is reported. NPB is used as the hole-transporting layer. 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline is used as the exciton-blocking as well as electron-transporting layer. Dmbpy-Re is doped into the host material (4,4′-N-N′-dicarbazole)biphenyl (CBP). The chromaticity of the white emission can be tuned by adjusting the thickness of Dmbpy-Re:CBP layer or the concentration of Dmbpy-Re in CBP. The maximum luminance, efficiency, and Commission Internationale De L’Eclairage coordinates at 9 V of the devices with 20-nm-thick and 30-nm-thick Dmbpy-Re:CBP layer at a fixed Dmbpy-Re doping concentration of 2 wt % in CBP are 1332 cd/m2, 2.9 cd/A, and (0.30,0.37), and 2410 cd/m2, 5.1 cd/A, and (0.36,0.43), respectively. The turn-on voltage of these devices is ∼4 V. © 2003 American Institute of Physics.