A spacer effect on electroluminescent characteristics of white organic light-emitting diodes.

The authors have demonstrated efficient and color-stable white organic light-emitting diodes (WOLEDs) by using three emitters, 4"-(2,2-diphenylvinyl)-1-[4-(N,N-diphenylamino)-styryl]-terphenyl (PVAS-tPh), fac tris(2-phenypyridine) irdium(III) (Ir(ppy)3), and Bis(5-benzoyl-2-phenylpyridinato-C,N)iridium(III) (acetylacetonate) (Bzppy)2Ir(III)acac). In this WOLEDs, 4,4'-N, N'-dicarbazole-biphenyl (CBP) were used as a spacer among three emitting layers. CBP between red and green emitting layers prevented the Commission Internationale de L'Eclairage (CIE(x,y)) coordinates change of white emission. As a result, WOLEDs showed a minimal change of deltaCIE(x,y) < (0.01,0.02) for the brightness change form 100 to 20 000 cd/m2.