An organic light-emitting device including a transparent substrate, a first
electrode layer, a second electrode layer, a hole-transporting layer, and
a electron-transporting layer sandwiched between the first and second
electrode layers, wherein the hole-transporting layer consists of organic
multiple-quantum-well structure. The multiple-quantum-well structure has a
period number of alternating layers formed of a layer of organic material
A with wide energy gap and a layer of organic material B with narrow
energy gap. Organic material A and organic material B are selected such
that the highest occupied molecular orbital (HOMO) levels of organic
material A are lower than those of organic material B and the lowest
unoccupied molecular orbital (LUMO) levels of organic material A are
higher than those of organic material B.
