温度和共混浓度对激基复合物与电致激基复合物共存体系的磁效率调控  

Regulating magneto-efficiency in coexistence systems of exciplex and electroplex by changing ambient temperature or blending ratio

作　　者：吴雨廷 朱洪强[2] 赵茜 刘俊宏 彭腾 汪波 熊祖洪[1] Yuting Wu;Hongqiang Zhu;Xi Zhao;Junhong Liu;Teng Peng;Bo Wang&Zuhong Xiong(School of Physical Science and Technology,Southwest University,Chongqing 400715,China;College of Physics and Electronic Engineering,Chongqing Normal University,Chongqing 401331,China)

机构地区：[1]西南大学物理科学与技术学院,重庆400715 [2]重庆师范大学物理与电子工程学院,重庆401331

出　　处：《科学通报》2024年第4期596-605,共10页Chinese Science Bulletin

基　　金：重庆市教委科学技术研究项目(KJQN202200569);国家自然科学基金(12104076,11874305);重庆自然科学基金(CSTB2023NSCQ-MSX0207)资助。

摘　　要：激基复合物(exciplex)和电致激基复合物(electroplex)经常同时产生于体异质结的有机发光二极管(organic light emitting diodes,OLEDs),有报道称利用这两种发射态共存的器件实现了高效率发光.器件高效率的物理机制与共存体系中自旋对态(spin-pair states)的微观过程有关,相关微观过程还有待深入研究.本文以特征的有机磁场效应(organic magnetic field effects)作为主要探测工具,通过改变器件的工作温度和给体与受体的共混比例来研究这种双发射态共存体系中自旋对态的演变过程.实验结果表明:降低发光器件的环境温度不仅会减弱从高能激基复合物到低能电致激基复合物的Dexter能量传递过程,而且因器件偏压增高还会引起电致激基复合物电荷转移(charge-transfer,CT)态的场致解离,使其数量较少,导致其CT态的反向系间窜越(reverse intersystem crossing,RISC)过程减弱.另外,增加发光层中给体的浓度会引起电荷注入更不平衡,增强过剩的空穴载流子与电致激基复合物的解离反应,这也会减弱电致激基复合物CT态的RISC过程.因此,温度降低或给体含量增多,器件的磁效率(magneto-efficiency,Mη)从原来受RISC过程主导的负磁效应转化为受系间窜越(intersystem crossing,ISC)过程主导的正磁效应.本工作有利于深入理解激基复合物和电致激基复合物共存体系中自旋对态的物理微观机制.As the third-generation organic light emitting diodes (OLEDs), exciplex-based OLEDs with reverse intersystem crossing(RISC) processes between charge-transfer (CT) states have potential applications for lighting and flat-panel display.Recently, researchers have been committed to improving the luminous efficiency of dual-emission OLEDs with exciplexand electroplex, but the microscopic physical processes of this dual-emission system have not been well investigated. Inthis article, the fingerprint organic magnetic field effects (OMFEs) are used as the main detection tools to study the spinmixing processes of spin-pair states in the coexistence systems of exciplex and electroplex. Because the intensity of eachspin-related microscopic process depends on the external magnetic field (B), alteration in applied B will lead to variation incurrent (I) and electroluminescence (EL) of the device. The change in I intensity caused under constant voltage (V) isreferred to as magneto-conductance (MC), while the changes in EL intensity caused under constant V and I are known asmagneto-electroluminescence (MEL) and magneto-efficiency (Mη), respectively. Furthermore, MEL is the sum of MC andMη due to the linear relationship between EL and the product of external quantum efficiency (η) and I, i.e., EL∝Iη.Previous studies have suggested that because the low-energy electroplexes are formed in exciplex-based devices where di-[4-(N,N-ditoly-amino)-pheny]cyclohexane (TAPC) and 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) serveas donors and acceptors, respectively, the Dexter energy transfer (DET) process from the exciplex to electroplex enhancesthe CT-RISC process of electroplex states, resulting in the smaller value of MEL trace than that of MC trace. Thus, there isa negative value in Mη under higher bias I. It is well known that the radiation of excited states is closely related to thevarious evolution channels of spin-pair states in the device, and the variation in ambient temperature (T) or blending ratiocan also regu

关 键 词：有机发光二极管 磁效率 反向系间窜越 激基复合物 电致激基复合物 

分 类 号：TN383.1[电子电信—物理电子学]