An OLED comprises an anode, a hole source, an emissive region, an electron
source and a cathode, wherein the materials for the electron source and
the hole source are chosen such that the electrical conductivity of these
charge carrier sources is greater than the electrical conductivity of the
emissive region. In particular, the electrical conductivity of the source
layers is between 10.sup.-8 to 10.sup.2 S/cm. Furthermore, one or both of
the hole source and the electron source are made substantially of one or
more inorganic materials. The emissive region can have one or more layers
of organic material. The materials for the emissive region are
insulators. The cathode can be made of a metal such as Mg:Ag and Al, and
the anode is made of ITO or the like. The electrical conductivity of the
cathode and the anode is significantly higher than 10.sup.2 S/cm.