The effect of multilayer quantum well structure on the characteristics of OLEDs

Organic light-emitting diodes (OLEDs) with multilayer quantum well (MQW) structure were fabricated, which consisted of alternate organic materials 2-(4-biphenylyl)-5(4-tert-butyl-phenyl)-1,3,4-oxadiazole (PBD) and tris(8-hydroxyquinoline) aluminum (Alq3). PBD is used as potential barrier layer, Alq3 used as potential well layer and emitting layer. Compared with double-layer structure, the luminescent characteristics of the devices with MQW structure were investigated. MQW structures conduce to energy transfer between wells and barriers, which is attributed to good overlap and the decrease of the distance between layers. The MQW structures make electrons and holes distribute in different wells and then increase the number of the formation of excitons to further enhance their recombination efficiency. Hence, such device achieves the maximum brightness and efficiency of 3630 cd/m2 and 3.28 cd/A, respectively.