Transient electroluminescence of single and multilayer organic light emitting devices

The transient current and electroluminescence response induced by a positive step voltage, excitation in both single layer NPB and bi-layer NPB-Alq(3) devices were analyzed in detail. The transport of hole and electron in single NPB layer and bi-layer NPB-Alq(3) devices was investigated, respectively. The hole mobility was measured to be (1-3) x 10(-4) cm(2) V-1 s(-1) in NPB, while the electron mobility in the NPB-Alq3 device was measured to be (4-8) x 10(-6) cm(2) V-1 s(-1). The charge transport delay time in each layer of the bi-layer structure was resolved from the transient current characteristics for voltage pulse amplitude near the turn-on voltage of the device. Such unique measurements applied to the organic bi-layer structures revealed the dynamics of the charge carriers, particularly in terms of the field-dependent mobility. (C) 2001 Elsevier Science B.V. All rights reserved.