High-efficiency and color-stable white organic light-emitting devices based on sky blue electrofluorescence and orange electrophosphorescence

Highly efficient and color-stable two-wavelength white organic light-emitting devices (WOLEDs) combining an orange phosphor [Ir(Cz-CF3)] and a sky blue fluorescent dye BUBD-1 are fabricated where the host singlet is resonant with the fluorophore singlet state and the host triplet is resonant with the phosphor triplet level. A thin layer of 1,3,5-tris[N-(phenyl)benzimidazole]benzene between the phosphorescent and the fluorescent regions confines both singlet and triplet excitons efficiently and,suppress Dexter transfer of the phosphor excitons to the nonradiative triplet state of BUBD-1. The best device reaches peak efficiencies of 19.3 cd/A and 11.1 lm/W which are superior to common two-color all-fluorescent or all-phosphor WOLEDs. (c) 2008 American Institute of Physics.