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 organic light-emitting devices, it can be determined that the mobility of charge carriers in Alq, films is 3.4 +/- 0.2 that of DPVBi in the trap-limited regime of device operation. (C) 1997 Published by Elsevier Science S.A.