利用发光磁效应研究同分异构体mCBP和CBP作为给体的激基复合物器件的微观过程  

Investigations of microscopic mechanisms in exciplex-based devices with isomers of mCBP and CBP as donors via magneto-electroluminescence

作　　者：宁亚茹 赵茜 汤仙童 陈敬 吴凤娇 贾伟尧 陈晓莉 熊祖洪 Ning Ya-Ru;Zhao Xi;Tang Xian-Tong;Chen Jing;Wu Feng-Jiao;Jia Wei-Yao;Chen Xiao-Li;Xiong Zu-Hong(Chongqing Key Laboratory of Micro&Nano Structure Optoelectronics,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,微纳结构光电子学重庆市重点实验室,重庆400715

出　　处：《物理学报》2022年第8期283-294,共12页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11874305,11374242)资助的课题~~。

摘　　要：本文把同分异构体3,3’-Di(9H-carbazol-9-yl)biphenyl (m CBP)和4,4’-Bis(carbazol-9-yl)biphenyl (CBP)作为给体, PO-T2T作为受体,以质量比1∶1制备了两种激基复合物器件,并在不同温度和偏压下测量了器件的发光磁效应(magneto-electroluminescence, MEL).发现室温下m CBP为给体的器件,其MEL的低磁场部分表现出反向系间窜越(reverse intersystem crossing, RISC)过程,降温时该RISC转变为系间窜越(intersystem crossing, ISC)过程;而CBP为给体的器件则表现出ISC过程,且降温时ISC过程先减弱后增强.室温下两种器件MEL的高磁场部分都体现为三重态激子与电荷的猝灭,但在20 K下CBP为给体的器件还出现了三重态-三重态激子湮灭.两种完全相反的低磁场线型与m CBP和CBP不同的结构导致三重态激子能量的高低有关.低温下微观过程的改变是因为低温不利于RISC过程、ISC过程和能量损失等演化通道.此外,当m CBP:PO-T2T质量比从1∶4到1∶1再到4∶1时,器件中的RISC过程越来越强,这是由于器件更趋平衡有利于RISC过程的结果.当以两种激基复合物为主体掺入TBRb荧光客体材料,在m CBP:PO-T2T为主体的器件中得到了更高的外量子效率.本工作为制备高效率激基复合物发光器件提供了实验和理论参考.The mCBP and CBP are two kinds of isomers containing carbazole groups and often used as the device hosts for fluorescence and phosphorescence emission. However, there are little studies on the microscopic mechanisms of exciplex-type devices based on mCBP or CBP. In this paper, the isomers of mCBP and CBP are used as donors and the PO-T2T is selected as an acceptor. The two kinds of exciplex-based devices are fabricated according to a mass ratio of 1∶1, which are respectively referred to as device 1(Dev. 1) and device 2(Dev. 2). Their magneto-electroluminescence(MEL) curves are measured at different working temperatures and various injection currents. It is found that the low field effects of the MEL curves from Dev. 1 are dominated by the B-mediated reverse intersystem crossing(RISC) process at room temperature, and as the operational temperature decreases, the MEL line-shapes change gradually from RISC to the intersystem crossing(ISC)process. Conversely, the low field effects of the MEL curves of Dev. 2 are governed by the B-mediated ISC process at room temperature, and the ISC process first weakens then strengthens with temperature decreasing.The high field effects of the MEL curves of Dev. 1 and Dev. 2 are both dominated by the B-mediated tripletcharge annihilation(TQA) process at room temperature, but those of Dev. 2 at 20 K present the B-mediated triplet-triplet annihilation(TTA) process. The completely opposite low-field line-shapes of MEL traces from Dev. 1 and Dev. 2 can be attributed to their different structures of mCBP and CBP, which lead to the higher and lower triplet state exciton energy, respectively. The higher triplet exciton energy of the mCBP donor causes the triplet exciplex energy to be confined effectively, which promotes the RISC process(EX_(1) ← EX_(3)) in Dev.1.Contrarily, the lower triplet exciton energy of the CBP donor causes the triplet exciplex to experience an energy loss process(EX_(3) → T_(1), CBP), resulting in the suppressed RISC process in Dev. 2. Consequently, the overla

关 键 词：激基复合物 电致发光磁效应 三重态能量 反向系间窜越 

分 类 号：TB30[一般工业技术—材料科学与工程] TN383.1[电子电信—物理电子学]