Carrier Transport Mechanisms in Organic Light-Emitting Devices with a N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine:tris-(8-hydroxyquinoline) Aluminum Mixed Layer Acting as an Emitting Layer

The current density-voltage (J-V) measurements on organic light-emitting devices (OLEDs) with and without a N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (NPB):tris-(8-hydroxyquinoline) aluminum (Alq3) mixed layer were performed to investigate the carrier transport mechanism. The slopes of the double logarithmic J-V curves for the OLEDs with and without the mixed layer in the space-charge-limited current (SCLC) region were 6.5 and 2, respectively. The dramatic increase in the slope of the double logarithmic J-V curve for the OLEDs with the mixed layer was attributed to the decrease in the mobility difference of the charge carriers at the NPB/Alq3 heterointerface resulting from the minimization of the energy barriers, and the carrier transport behaviors in the SCLC region were significantly affected by the unintentional virtual electrode, serving as a charge carrier reservoir, that formed at the heterointerface.