Ir(ppy)3调控Rubrene激子分裂和发光过程的微观机制研究  

Study of the microscopic mechanism of Ir(ppy)3 regulating exciton splitting and luminescence process in Rubrene

作　　者：屈芬兰 汤仙童 朱洪强 许静 段谋正 赵茜 熊祖洪[1] Fenian QU;Xiantong TANG;Hongqiang ZHU;Jing XU;Mouzheng DUAN;Xi ZHAO;Zuhong XIONG(School of Physical Science and Technology,Southwest University,Chongqing 400715,China;School of Agriculture and Biotechnology,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 [2]西南大学农学与生物科技学院,重庆400715

出　　处：《中国科学：信息科学》2020年第1期151-162,共12页Scientia Sinica(Informationis)

基　　金：国家自然科学基金(批准号:11874305)资助项目。

摘　　要：为探究红荧烯(Rubrene)内部的单重态激子分裂(S1+S0→T1+T1,STT)和发光过程的微观机制,本文选用具有强自旋轨道耦合(spin-orbit coupling,SOC)且发射绿光的磷光材料Ir(ppy)3,以不同比例混入到发射橙光的Rubrene薄膜中制备了一系列发光器件,并在不同温度和电流下测量了器件的电致发光磁效应(magneto-electroluminescence,MEL)和电流–发光(I-B)曲线.实验发现:室温下不同混入比例的发光器件,其MEL线型均表现为磁场调制的STT指纹式特征曲线,但MEL幅值随混入比例的增加却表现出先增加后减小的特性,而其发光强度则表现为单调增加的特点,这与常规Rubrene掺杂器件(如mCP:y%Rubrene)随浓度增大其STT增强但发光减弱的结果不同.通过对Ir(ppy)3的单、三重态激子能级和发射谱以及Rubrene吸收谱的分析可知,器件中除了Rubrene分子间距会影响STT过程的强弱外,还包括由Ir(ppy)3强的SOC导致的激子间的系间穿越(intersystem crossing,ISC)和Ir(ppy)3的T1激子与Rubrene的S1激子间的能量传递(energy transfer,ET)过程,这3种微观机制的共同作用导致了器件MEL和发光的复杂变化,且电流密度的大小和器件工作温度的高低对它们还有较好的调控作用.显然,本研究有助于深入理解基于红荧烯光电器件的微观过程及其演化机制.To explore the microscopic mechanism of singlet exciton splitting(S1+S0→T1+T1,STT)and luminescence in Rubrene,a phosphorescent material Ir(ppy)3 with strong spin-orbit coupling(SOC)and green emission was selected and mixed into Rubrene thin films with different proportions to fabricate a series of luminescent devices.By measuring the magneto-electroluminescence(MEL)and current-luminescence(I-B)curves of the devices under different temperatures and currents,we found that the MEL profiles of light-emitting devices with different mixing ratios at room temperature show an STT fingerprint characteristic curve of magnetic field modulation.MEL amplitude first increases and then decreases with increased mixing ratio,whereas luminescence intensity increases monotonously.This is different from conventional Rubrene doped devices(such as mCP:y%Rubrene)which show STT increases with increasing concentration but with decreasing luminescence.By analyzing the singlet and triplet energy levels and emission spectra of Ir(ppy)3 and absorption spectra of Rubrene,it can be seen that aside from Rubrene’s molecular space’s influence on the STT process,intersystem crossing(ISC)caused by the strong SOC of Ir(ppy)3 and energy transfer processes between the T1 exciton of Ir(ppy)3 and the S1 exciton of Rubrene are also included in the devices.The combined action of these three micro-mechanisms leads complex MEL and luminescence changes in the device,and the device’s current density and working temperature also have a good regulatory effect on them.Obviously,this study helps with understanding of the microscopic process and its evolution mechanism based on Rubrene optoelectronic devices.

关 键 词：红荧烯 单线态激子分裂 自旋轨道耦合 能量转移 发光的磁效应 

分 类 号：TN383.1[电子电信—物理电子学] TB383.2[一般工业技术—材料科学与工程]