50 0 nm a turn on voltage of 2 5v and a highest luminance of 26000 cd m 2 were achieved by the resultant device a transparent conductive ito coated glass substrate was cleaned ultrasonically with boiling scour water and di water then the substrate was dried under infra red lamp the ito film coated on glass substrate acts as anode layer sheet resistance of the ito film was 100 u03c9 square and the thickness of it was 60 0 nm the cleaned and dried ito coated substrate was put in the vacuum of 2 u00d7 10 u2212 3 pa then a hole transporting layer was vapor deposited on the ito layer the hole transporting layer was an organic quantum well structure consisting of alternating mtdata rubrene layer films with the period number of 10 here the deposition rate of rubrene was 0 1 nm s and the thickness of each rubrene film was about 2 0 nm the deposition rate of mtdata was 0 2 nm s and the thickness of each mtdata film was about 5 0 nm a npb film was further vapor deposited on the hole transporting layer as transitional layer the deposition rate was about 0 2 nm s and its thickness was 5 0 nm an alq 3 film was subsequently vapor deposited on the npb transitional layer as electron transporting layer and electroluminescent emission layer here the deposition rate of alq 3 was 0 2 nm s and its layer thickness.