Electron mobility in tris(8-hydroxy-quinoline)aluminum thin films determined via transient electroluminescence from single- and multilayer organic light-emitting diodes

被引:210
作者
Barth, S
Müller, P
Riel, H
Seidler, PF
Riess, W
Vestweber, H
Bässler, H
机构
[1] IBM Corp, Zurich Res Lab, Res, CH-8803 Ruschlikon, Switzerland
[2] Cov Organ Semicond GmbH, D-65926 Frankfurt, Germany
[3] Univ Marburg, Ctr Mat Sci, D-35032 Marburg, Germany
[4] Univ Marburg, Inst Phys Nucl & Macromol Chem, D-35032 Marburg, Germany
关键词
D O I
10.1063/1.1330766
中图分类号
O59 [应用物理学];
学科分类号
摘要
Transient electroluminescence (EL) from single- and multilayer organic light-emitting diodes (OLEDs) was investigated by driving the devices with short, rectangular voltage pulses. The single-layer devices consist of indium-tin oxide (ITO)/tris(8-hydroxy-quinoline)aluminum (Alq(3))/magnesium (Mg):silver (Ag), whereas the structure of the multilayer OLEDs are ITO/copper phthalocyanine (CuPc)/N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine (NPB)/Alq(3)/Mg:Ag. Apparent model-dependent values of the electron mobility (mu (e)) in Alq(3) have been calculated from the onset of EL for both device structures upon invoking different internal electric field distributions. For the single-layer OLEDs, transient experiments with different dc bias voltages indicated that the EL delay time is determined by the accumulation of charge carriers inside the device rather than by transport of the latter. This interpretation is supported by the observation of delayed EL after the voltage pulse is turned off. In the multilayer OLED the EL onset-dependent on the electric field-is governed by accumulated charges (holes) at the internal organic-organic interface (NPB/Alq(3)) or is transport limited. Time-of-flight measurements on 150-nm-thin Alq(3) layers yield weak field-dependent mu (e) values of the order of 1x10(-5) cm(2)/Vs at electrical fields between 3.9x10(5) and 1.3x10(6) V/cm. (C) 2001 American Institute of Physics.
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页码:3711 / 3719
页数:9
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