White-electrophosphorescence devices based on rhenium complexes

Efficient white emission from the mixing of yellow emission from the Re-complexes, (4,4'-dimethyl-2,2'-bipyridine)Re(CO)(3)Cl (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/m(2), 2.9 cd/A, and (0.30,0.37), and 2410 cd/m(2), 5.1 cd/A, and (0.36,0.43), respectively. The turn-on voltage of these devices is similar to4 V. (C) 2003 American Institute of Physics.