基于Alq3的有机发光二极管的磁电导效应

Magnetoconductance in Alq_3 -based organic light-emitting diodes

制备了结构为ITO/CuPc/NPB/Alq3/LiF/Al的有机发光二极管,并在300,260,220和180K四个温度测量了器件在恒压偏置下注入电流的磁场效应(磁电导效应).在注入电流从双极电流过渡到单极电流的过程中,随电流减小,器件的磁电导呈现先上升后下降的变化趋势.当温度降低,磁电导的值下降.但在任何测量条件下,器件的磁电导始终为正,没有出现如文献报道的磁电导从正到负的变化.实验结果表明,有机发光二极管中正负磁电导现象的产生,并非仅取决于注入电流是单极电流还是双极电流,它还与有机材料、器件结构等密切相关.利用受磁场调控的"电子-空穴对"机理与"双极化子"模型,分别解释了器件双极电流和单极电流的正磁电导效应.

Organic light-emitting diode （ OLED ） with structure of ITO /CuPc /NPB /Alq3 /LiF /Al was fabricated,and the magnetic field effect on the injection current （magnetoconductance or MC effect） at 300 K,260 K,220 K,and 180 K were measured at constant voltage bias. During the transition of injection current from bipolar current to unipolar current,the MC of the device increased firstly and fell with the decreasing current. The MC became smaller at the lower temperatures. However,under all measurement conditions,the values of the MC were always positive. The inversion of MC from positive to negative as reported in literatures was not observed. The experimental results demonstrate that the ± MC effects in OLED not only depend on the unipolar or bipolar current. It is also related with the organic materials and device structure. Using the magnetic field modulated electron-hole pair mechanism and bipolaron model,the positive MC effects in bipolar and unipolar injection current are interpreted,respectively.