磁场对有机电致发光的影响

制备了常规有机发光二极管ITO/NPD/Alq₃/LiF/Al，测量了该器件发光的磁场效应.发现尽管在1T范围内的磁场对发光层Alq₃的光致发光没有影响，但磁场作用下器件的电致发光(MEL)却呈现出明显的磁效应，且MEL与器件的偏压有很强的依赖关系：在小偏压时，随着磁场的增加MEL是单调递增，且在大小约为40kA/m的磁场下达到饱和，之后即使磁场增大到约1T 的情况下也没有变化；但当偏压变大时，MEL则呈现先增加，在40kA/m处达到峰值后却又减弱，而且偏压越大该MEL的减弱则越明显.对所观察到的实验结果进行了定形解释，即三线态激子相互淬灭产生单线态激子和三线态激子与器件中的非平衡载流子相互作用是此效应的物理机理. 关键词： 有机发光 磁场效应 激子淬灭

Magnetic field effects on organic electroluminescence

A conventional organic light emitting diode, which has a structure of ITO/NPD/Alq_3/LiF/Al, was fabricated and the magnetic field effects(MFEs) on its electroluminescence(EL) were measured. We found that the MFEs of the organic EL is strongly dependent on the applied bias on the device while the photoluminescence from the Alq_3 film within the device is independent of the magnetic field. At low bias, the MFEs first rapidly increase with the magnetic field and then saturate at about 40kA/m, however at high bias the MFEs will decrease after this saturation, and the larger the bias, the stronger the decrease. The mutual annihilation of triplet-triplet pairs producing excited singlet excitons and the interaction between triplet excitons and excess carriers of Alq_3 anion or cation are the physical mechanisms of the phenomena observed in this study.