利用有机发光磁效应研究深蓝色激基复合物的发光机理  

Investigation of electroluminescence mechanism in deep blue exciplex devices by utilizing magneto-electroluminescence

作　　者：胡叶倩 刘冬玉 臧克宽[1] 邓军权 陈颖冰[1] 向杰[1] 熊祖洪[1] 

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4期373-382,共10页Scientia Sinica(Technologica)

基　　金：国家自然科学基金(批准号:11374242)资助项目

摘　　要：2013年Jankus等人在Advanced Materials上报道了NPB与TPBi共混的深蓝色激基复合物的发光机理,根据瞬态光谱的实验结果,他们认为器件中室温下较高的量子效率是由三重态激子的湮灭(TTA)导致的,而不是由热辅助引起的三重态激子T_1向单重态激子S_1的转变结果(即反向系间窜越,RISC).最近的研究表明,有机发光二极管(OLEDs)中的磁效应(magneto-electroluminescence,MEL)可作为研究其发光机理的有效手段,对TTA和RISC都有灵敏的指纹响应.本文制备了结构相同的OLEDs,测量了器件的MEL曲线,发现室温下该器件内部既没有发生TTA,也没有发生RISC过程,仅在低温20K且在大电流工作下才能出现TTA过程,采用更低功函数的阴极、对器件阳极进行臭氧O_3处理、甚至呈量级增大器件的注入电流,以有利于TTA过程的实现,但仍未观察到TTA,器件的磁电导实验结果及其理论模拟表明,该体系内部可能发生了三重态激子与空穴极化子的相互作用T_1(↑↑)+P^+(↓)→S_1(↑↓)+P^+(↑),即TPI(triplet-polaron interaction)过程,本研究对理解NPB与TPBi共混器件的发光机制有较好的参考价值.Recently, the electroluminescence （EL） mechanism in organic-light emitting diodes （OLEDs） based on blends of NPB：TPBi for deep blue light-emission has been reported in Advanced Materials by Jankus et al. in 2013. They have recorded EL and photoluminescence transients and fluorescence decays, demonstrating that the electroluminescence in their devices arises from enhanced exciplex emission via triplet-triplet annihilation （TTA） not the reverse intersystem crossing （RISC）. In recent years, a large number of researches have showed that the magneto-electroluminescence （MEL） could be used as an effective measure to study the EL mechanism in OLEDs. And as a fingerprint tool MEL is sensitive to TTA and RISC. In this paper, we report similar exciplex-based OLEDs and show that no triplet-triplet annihilation and reverse intersystem crossing are observed at room temperature. TTA only occurs at low temperature and high current. We use 03 to treat the anode or replace the cathode with lower work function material, we haven＇t observed TTA at room temperature yet. In order to increase the concentration of triplet excitons to facilitate the generation of TTA, we increase the injection current of the devices by over 1 order of magnitude, but we still haven＇t observed the occurrence of TTA. The magneto-current of the device and its theoretical simulation show that triplet exciton interaction with hole polaron TI（↑↑）＋P＋（↓）→SI（↑↓）＋P＋（↑） may have happened in the system, namely TPI （triplet-polaron interaction） process. This study will provide a reference for understanding the EL mechanism in the NPB：TPBi blending devices with deep blue light-emission.

关 键 词：深蓝色激基复合物 有机磁效应 三重态-三重态激子湮灭 

分 类 号：TN383.1[电子电信—物理电子学]