Characterization of Blue-Light-Emitting Organic Electroluminescent Devices

The electrical and optical characteristics of blue-light-emitting organic electroluminescent devices have been studied by varying their layer structure. Four-organic-layer structures consisting of anode/hole injection layer/hole transport layer/emission layer/electron transport layer/cathode were analyzed, where DPVBi
(or 1,4-bis(2, 2-diphenylvinyl)biphenyl) was used as the blue-light emission layer. Device characteristics were observed to be systematically dependent on the thicknesses of both the emission and electron transport layers, which in this experiment was Alq(3) [tris(8-hydroxy-quinoline)aluminum]. By analyzing the charge injection and charge transport processes in these OLEDs, it can be determined that the mobility of charge carriers in Alq(3) films is
3.4+/-0.2 that of DPVBi in the trap-limited regime of device operation.