A semitrans parent white organic light-emitting diode (WOLED) is produced based on a blue phosphorescence from iridium(III) [bis(4,6-difuorop henyl)-pyridinato-N,C2] picolinate and an orange phosphorescence from bis(2-(9,9-diethyl-9H-fluoren-2-yl)-1-phenyl-1H-benzoimidazolN,C3) iridium(acetylacetonate). In this work, a hole-transporting layer of N,N0-diphenyl-N,N0-bis(1-naphthylphenyl)-1,1 0-biphenyl-4,4 0-diamine (NPB) and an electron-transporting layer of 3,5,3 00,5 00-tetra-3-pyridyl-[1,1 0;3 0,1 00] terphenyl (B3PyPB) were used. B3PyPB has high electron
mobility and a high triplet energy level. The use of B3PyPB helps to reduce the triplet quenching and also to confine the charge recombination in the emissive region of a single-host two-color WOLED. A bi-layer Ag (10 nm)/MoO3 (2.5 nm)-modified indium tin oxide anode and a cathode of
Al (1.5 nm)/Ag (15 nm)/NPB (50 nm) were employed. The semitransparent WOLEDs thus developed have perfect symmetrical, bi-directional illumination characteristics, and the weak angular dependent EL emission spectra, which are beneficial for application in planar diffused lighting.