White organic light-emitting devices (WOLEDs) were fabricated by using a highly blue fluorescent dye of 4,4’-bis(2,2’-diphenyl vinyl)-1,1’-biphenyl (DPVBi) and a red fluorescent dye of 5H-benzo[ij] quinolizin-9-yl) ethenyl]-4H-pyran-4-ylidene] propane-dinitrile (DCM2), together with a green fluorescent dye of 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-(1)-benzopyroyran-o(6,7-8-i,j) quinolizin-11-one (C545T). The multilayer WOLEDs does not involve the doping process. The structure of the device is indium tin oxide (ITO)/4,4’,4”-tris{N,-(3-methylphenyl)-N-phenylamin}triphenylamine (m-MTDATA) (55 nm)/ N,N’-bis-(1-naphthyl)-N,N’-diphenyl-1,1’-biph-enyl-4,4’-diamine (NPB) (10 nm)/ DPVBi (8 nm)/ C545T (x nm)/ DPVBi (5 nm)/ DCM2 (y nm)/ tris- (8-hydroxyquinoline) aluminum (Alq3) (60nm)/ LiF (1 nm)/ Al, where the DPVBi is introduced as a spacer. By changing the thicknesses of dual ultrathin layers of C545T and DCM2, the WOLED is obtained. When x=y=0.05, the Commission Internationale de 1’Eclairage (CIE) coordinates of the device change from (0.262 6, 0.351 4) at 4 V to (0.214 7, 0.269 3) at 12 V that are well in the white region. Its maximum luminance is 41400 cd/m2 at 13 V, and the maximum current efficiency and the maximum power efficiency are 7.95 cd/A at 6 V and 5.37 lm/W at 5 V, respectively.
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