激子复合区厚度对有机磁效应的影响

在常规型有机发光二极管的基础上, 通过改变发光层tri-(8-hydroxyquinoline) aluminum (III) (Alq₃)厚度, 研究了激子复合区厚度对有机发光二极管磁效应的影响.测量了器件在不同温度及偏压下电致发光及注入电流在外加磁场作用下的变化, 着重研究了低温下的有机磁电导效应和有机磁电致发光效应.实验发现, 低温(50 K)高磁场 (500 mT)下, 器件表现出随Alq₃厚度的减薄, 磁电导值由正到负再到正的非单调变化.利用磁场调控的超精细相互作用、 磁场抑制的三重态激子-电荷反应以及激子在界面的淬灭效应, 对有机磁电导在低温下表现出的现象进行了定性的解释.实验结果表明, 通过改变激子复合区的厚度, 可以实现对激子浓度的有效调节, 进而实现对有机磁电导和磁电致发光效应的调节. 该研究进一步丰富了有机磁效应的实验现象, 同时提供了一种调控有机磁效应的手段.关键词：激子复合区激子浓度有机磁电导有机磁电致发光

The influence of the excition recombination zone on the organic magnetic-field effect

In this work we explore the influence of the exciton recombination zone (RZ) on magnetic-field effect in tris-(8-hydroxyquinolinato) aluminum (Alq₃) based organic light-emitting diodes by changing the thickness of Alq₃. The magneto-electroluminescence and magneto-conductance (MC) in these devices are investigated at various temperatures and bias voltages. It is found that the sign of MC changes from positive to negative, and then back to positive with the reduction of the thickness of Alq₃ at 50 K. The phenomenon observed is ascribed to the change of the exciton density in the exciton RZ. Based on the mechanisms including the hyperfine mixing, the triplet-charge interaction and interfacial dissociation or quenching of excitons, the observed results are explained qualitatively.