红荧烯掺入多种激基复合物器件的微观过程  

Microscopic processes of Rubrene-doped devices with various exciplexes as hosts

作　　者：马彩虹 汤仙童 许静 叶晟楠 朱洪强[2] 王影 屈芬兰 熊祖洪[1] Caihong Ma;Xiantong Tang;Jing Xu;Shengnan Ye;Hongqiang Zhu;Ying Wang;Fenlan Qu;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》2021年第1期63-72,共10页Chinese Science Bulletin

基　　金：国家自然科学基金(11874305,11374242);重庆市教委科技项目(KJQN201800510);重庆市自然科学基金(CSTC2019JCYJ-MSXM0953)资助。

摘　　要：红荧烯(5,6,11,12-tetraphenylnaphthacene,Rubrene)是一种典型的发射橙黄光的荧光客体材料,因具有丰富的微观过程而被广泛运用于主客体掺杂器件中,但将其掺杂在具有延迟荧光特性的激基复合物主体中的研究还较少.本文把2%的Rubrene掺杂到具有不同三重态激子能量的四种激基复合物主体里,以指纹式的有机电致发光磁响应(magneto-electroluminescence,MEL)曲线作为探测工具,研究了此类掺杂体系的能量传输和光发射机制.实验发现,当主体激基复合物的三重态激子(EX_(3))能量低于Rubrene客体的第二级三重态激子(T_(2,Rub))能量时,器件的MEL曲线表现为主体极化子对间的系间窜越(intersystem crossing,ISC)过程;否则,器件MEL低磁场部分的线型来源于Rubrene激子的高能级反向系间窜越(high-level reverse intersystem crossing,HL-RISC;T_(2,Rub)→S_(1,Rub))过程;MEL高磁场部分的线型在大电流密度下由Rubrene三重态激子间的聚合反应(T_(1,Rub)+T_(1,Rub)→S_(1,Rub)+S0,Rub)引起,在小电流密度下由单重态激子的分裂(S_(1,Rub)+S0,Rub→T_(1,Rub)+T_(1,Rub))过程决定.此外,温度和电流密度会通过调控Rubrene三重态激子(T_(1,Rub)和T_(2,Rub))的寿命和数量来影响上述微观过程的强弱程度.这是由于主体与客体的单、三重态激子的能级差会调控主客体间的能量转移,进而通过调节客体Rubrene分子上三重态激子的数量和寿命来影响三重态激子的利用率,最终影响器件的发光强度.本文工作既可加深基于Rubrene发光器件微观机制的认识,也可为增强其发光效率提供理论参考.Recently,exciplex-based organic light-emitting diodes(OLEDs)have become hot topics in organic optoelectronics in terms of improving luminescent efficiency by controlling the energy transfer of excitons.This is because the formation of an exciplex can result in a small energy level difference,ΔEST between singlet and triplet exciplex states,and with the assistance of external thermal energy,nonradiative triplet exciplex states can transform into radiative singlet ones through the so-called reverse intersystem crossing(RISC)process.Moreover,this RISC process will enhance the luminescence of OLEDs based on host–guest systems through energy transfer from exciplexes to dopants.The energy-transfer capability of OLEDs will affect the number of polaron pairs and exciplexes in host–guest systems.Indeed,it is important to find an effective probing technique for simply studying these microscopic processes.Many literature reports have demonstrated that organic magneto-electroluminescence(MEL)traces could be used for exploring and understanding the formation of and interactions between polaron pairs,excitons,and/or exciplexes.This is because MELs exhibit sensitive fingerprint responses to intersystem crossing(ISC),high-level reverse intersystem crossing(HL-RISC),singlet exciton fission(SF),and triplet exciton fusion(TF).In this study,four different OLEDs with various exciplex hosts have been fabricated,and their MEL curves have been measured at different currents and temperatures.Four exciplexes with different triplet exciton energies were used as host materials,and Rubrene was used as a fluorescent dopant.To study the exciton energy transfer and luminescence mechanism in such doping systems,we fully analyzed the emission spectra of the host materials,absorption spectrum of the guest material,and triplet exciton energy of the host and guest materials.The experimental results show that when the combined energy of the exciplex’s triplet excitons(EX3)is lower than that of the second-order triplet excitons(T_(2,Rub))of the

关 键 词：红荧烯 电致发光磁响应 激基复合物 能量转移 高能级反向系间窜越 

分 类 号：TN383.1[电子电信—物理电子学]