超小磁场下Rubrene电致发光磁效应的演化  

Magneto-electroluminescence responses in Rubrene-based organic light-emitting diode at ultrasmall magnetic fields

作　　者：陈颖冰[1] 向杰[1] 刘冬玉 胡叶倩 熊祖洪[1] CHEN YingBing XIANG Jie LIU DongYu 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：技术科学》2017年第1期39-45,共7页Scientia Sinica(Technologica)

基　　金：国家自然科学基金(批准号:11374242)资助项目

摘　　要：制备了基于5,6,11,12-tetraphenylnaphthacene(Rubrene)的有机发光二极管,并测量器件在不同偏压与工作温度下电致发光的磁场效应(magneto-electroluminescence,MEL).实验发现:在室温下,MEL曲线在零磁场附近几毫特斯拉范围内为W线型;而当温度降低到75 K左右,该W线型消失,MEL却呈现出一种新的精细结构,即M型的超小场效应,这种演化过程在以前的文献中未见报道.分析表明:室温下MEL的W线型是极化子对(polaron pair,PP)的超精细相互作用和外磁场引起的塞曼作用对载流子自旋共同调控的结果;低温下MEL的M线型与三重态-三重态激子湮灭(triplet-triplet annihilation,TTA)过程相关,可以用零场劈裂与塞曼作用对三重态激子对(triplet pair state,(TT)i)演化过程的共同调控来解释.该发现不仅丰富了有机半导体中的磁现象,而且加深了对有机发光器件中激发态间自旋相互作用的认识.In this work, the organic light-emitting diodes based on Rubrene have been fabricated to investigate the effects at ultrasmall magnetic fields. The magneto-electroluminescences （MELs） of the devices have been measured at different temperatures and at various bias voltages. We find that the MEL responses at ultrasmall fields show two opposite sign reversals at different temperatures： （i） a sign reversal （W-shaped） in a few millitesla range around zero-field at room temperature, and （ii） a peculiar M-shaped sign reversal by applying a ultrasmall magnetic field （[BI〈2 MT） under low temperatures, which has not been reported in the literatures. We conjecture that the the former is strongly dependent on hyperfine interaction and Zeeman splitting of triplet polaron pairs, and the latter is originated from the interplay of zero-field splitting and Zeeman splitting on triplet pair states which generated from triplet-triplet annihilation. The MEL responses of devices examined under different bias voltages give further experimental evidences supporting our hypothesis. This study gives new insights into magnetic phenomena in organic optoelectronic devices and provides a deeper fundamental understanding of the spin dynamics of the injected carriers.

关 键 词：红荧烯 超小磁场 电致发光磁效应 塞曼作用 零场劈裂 

分 类 号：TN383.1[电子电信—物理电子学]