LiF分子的极化对有机发光二极管磁效应的影响

The influence of polarization in LiF molecules on the magnetic field effects in OLEDs

在常规的有机发光二极管的发光层中掺入lithium fluoride(LiF),可以有效调控器件在不同温度下的电流与电致发光的磁场效应.与未掺杂的参考器件相比,LiF掺杂器件的磁场效应的线型与幅度都发生了明显的改变.在室温下,当外加磁场强度达到几百毫特斯拉时,常规器件的磁场效应随磁场增加缓慢增大并趋于饱和,而掺杂器件的磁场效应随磁场增加几乎呈直线增加,且表现出了不饱和的高场效应.此外,随LiF掺杂浓度的增大,电流与发光的高场效应的幅度均表现出先增加后降低的变化趋势.掺杂器件与未掺杂器件磁场效应的差异,可以归结为LiF颗粒在器件内电场中发生介电极化的结果.发光层中的激子与LiF颗粒表面的极化电荷发生反应,导致了器件特殊的磁场效应.

Doping lithium fluoride （LiF） in the fluorescent layer of conventional organic light-emitting diode is able to effectively tune the magnetic field effects （MFEs） on the current and electroluminescence. As compared with the undoped device, the line-shape and amplitude of MFEs in LiF-doped device showed apparent variation. At room temperature, when the applied external magnetic field reached several hundreds mili-Tesla, the MFEs in conventional device slowly increased and tended to be saturated. However, the MFEs in doped device almost linearly increased with the increasing field, displaying the abnormal and unsaturated high-field effects. Additionally, the amplitudes of high-field effects in current and fluorescence all went up firstly and down later when increasing the doping concentration of LiF. The differences between the MFEs in doped and undoped devices can be attributed to the dielectric polarization of LiF particles in the device＇s internal electric field. The reaction between the excitons in fluorescent layer and polarization charges on the surface of LiF particles resulted in the special MFEs in doped device.