Abstract
A highly efficient orange organic electrophosphorescent device was fabricated by using double emission layers of 2,7-Bis(9-carbazoly-l)-9,9- spirobifluorene and 4,4′-Bis-(9-carbazolyl)-biphenyl as hosts and both doping 4 wt% orange emitter, tris(2-phenylquinoline)iridium(III). Efficiency of 29.5 lm/W at 100 cd/m 2 was obtained by adjusting the emission layers thicknesses at 19 nm and 5 nm, respectively.