| abstract |
An OLED includes a wide gap inert host material doped with two dopants. One of the dopants is an emissive phosphorescent material that can transport either electrons or holes. The other dopant is a charge carrying material that can transport whichever of the electrons and holes that is not transported by the phosphorescent dopant. The materials are selected so that the lowest triplet energy level of the host material and the lowest triplet energy level of the charge carrying dopant material are each at a higher energy level than the lowest triplet state energy level of the phosphorescent dopant material. The device is capable, in particular, of efficiently emitting light in the blue region of the visible spectrum. |