Transient electroluminescence in multilayer organic light-emitting diodes:: experiment and theory

We have investigated a multilayer organic light-emitting diode (OLED) with 1,3,5-tris(N,N-bis-(4,5-methoxy-phenyl)-aminophenyl)benzene (TAPB) acting as hole transporting layer (HTL) and tris(8-hydroxy-quinolinolato) aluminium (Alq(3)) as electron transporting layer (ETL). Positive charge carriers in the HTL were detected optically as a function of the applied bias. Furthermore, we investigated the DC-characteristics of current and brightness as well as the onset behaviour of the electroluminescence (EL) as a function of the applied bias. An analytical model is developed to describe the ol,served carrier concentrations as well as the current-voltage characteristics and the transient EL measurements quantitatively. (C) 2001 Elsevier Science B.V. All rights reserved.