The present invention relates to an organic light emitting device
structure having an organic light emitting device (OLED) over a
substrate, where the OLED has, for example, an anode, a hole transporting
layer (HTL), a first electron transporting layer (ETL) that is doped with
a phosphorescent material, a second electron transporting layer (ETL),
and a cathode. The OLEDs of the present invention are directed, in
particular, to devices that include an emissive layer comprised of an
electron transporting host material having a triplet excited state energy
level that is higher than the emissive triplet excited state energy level
of the phosphorescent dopant material.