红荧烯掺杂体系中激子反应的竞争行为  

The competitive behavior of exciton reactions in Rubrene doped system

作　　者：刘冬玉 向杰[1] 陈颖冰[1] 臧克宽[1] 邓军权 胡叶倩 熊祖洪[1] LIU DongYu XIANG Jie CHEN YingBing ZANG KeKuan DENG JunQuan HU YeQian XIONG ZuHong(School of Physical Science and Technology, Southwest University, Chongqing 400715, China)

机构地区：[1]西南大学物理科学与技术学院,重庆400715

出　　处：《中国科学：物理学、力学、天文学》2017年第2期81-88,共8页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(编号:11374242);重庆市研宄生科研创新项目(编号:CYS16049)资助

摘　　要：为研究红荧烯(5,6,11,12-Tetraphenylnaphthacene,Rubrene)掺杂体系中激子的反应过程,向主体材料Rubrene中掺入了1%的客体材料DBP(Tetraphenyldibenzoperiflanthene),制备了掺杂型Rubrene的有机发光器件.实验发现,其电致发光磁效应(Magneto-Electroluminescence,MEL)在室温下呈现出复杂的新特征线型:在外加磁场处于0–27mT范围内MEL随磁场的增加先小幅度上升,在27–200mT随磁场的增加迅速下降,最后200–500mT范围内再次上升.通过分析可知器件内存在3种激子反应过程:单重态-三重态激子淬灭(Singlet-Triplet Annihilation,STA)、三重态激子湮灭(Triplet-Triplet Annihilation,TTA)和单重态激子分裂(Singlet Fission,STT).可通过改变注入电流的大小调节三者的竞争:大注入电流时,器件主要是STA反应和TTA反应;注入电流逐渐减小的过程中,激子反应从以TTA为主逐渐过渡到以STT为主.同时也可通过改变掺杂层的厚度和掺杂层在器件结构中的位置,对这几种反应之间的竞争过程产生重要影响:掺杂层厚度越薄,STT越强,而STA和TTA越弱;掺杂位置越靠近阴极,STA和TTA越强,而STT越弱.这些实验发现不仅可加深对有机发光二级管中激子间相互作用的理解,也为进一步优化器件发光性能提供参考.In this work,organic light-emitting diodes（OLEDs） have been fabricated with 1 percent of tetraphenyldibenzoperiflanthene（DBP） doped into 5,6,11,12-tetraphenylnaphthacene（Rubrene） as active layer,which had excellent properties such as strong electroluminescence,high stability and low threshold voltage.The magneto-eletroluminescence（MEL） curves of this devices have been measured under various injection currents at room temperature.The MEL curves exhibit a complicated line shape：the MEL increases sharply with a tiny amplitude first with increasing magnetic field from 0 mT to 27 mT and then decreases rapidly with a large amplitude until at about 200 mT followed by a slow increase in the high field,and this type of shape shows substantially changes during different currents.The non-monotonic increase and decrease of the MEL suggested that there are abundant exciton reacitons inside the devices,such as singlet-triplet annihilation（STA）,triplet-triplet annihilation（TTA,or triplet fusion） and singlet fission（STT）.These three reactions could be tuned by changing the injection current.The STA and TTA play the mainly role when the injection current is large enough in the devices,and the exciton reaction gradually changes from TTA to STT when the injection current decreases.Furthermore,The MEL curves have also been measured by altering the thickness and location of the doped layer in the devices.Result shows that the STT increases as the thickness of doped layer decreases while the STA and TTA becomes more dominant when the location of doping layer is more closer to the cathode.In conclusion,this study gives insight into the microscopic evolutions of the interactions between singlet and triplet excitons and provides a feasible pathway to control the competition among STA,TTA and STT in OLEDs.

关 键 词：电致发光磁效应 单重态-三重态激子淬灭 三重态激子湮灭 单重态激子分裂 

分 类 号：TN204[电子电信—物理电子学]