摘要
热活化延迟荧光(TADF)器件中,三线态激子可以吸收环境热量通过反向系间窜越(RISC)转化为单线态激子从而发出延迟荧光,可望实现100%的内量子效率.为揭示TADF器件中电致发光的微观机制,本文选取4CzTPN-Ph,2CzPN,PIC-TRZ2三种不同带隙的高效TADF材料制成有机发光器件,测量并分析器件的电致发光磁效应(MEL).研究发现,尽管这几种TADF器件具有增强发光的RISC过程,但它们的MEL曲线却表现出与不具有RISC过程的普通荧光器件相似的线型,这是由于外加磁场只影响极化子对间的超精细相互作用,而并不影响激子间的系间窜越与RISC过程.但是,这些TADF器件的磁效应幅度却会随注入电流的增加而变强,表现出与普通荧光器件相反的结果,电流对三线态激子的形成速率kt和单线态激子的形成速率ks的相对影响(kt/ks)被用来解释了这一反常结果.
In device with the activation of delayed fluorescence （TADF）, triplet excitons can be activated by the environment and then converted into singlet excitons through reverse intersystem crossing （RISC）, leading to delayed fluorescence and internal quantum efficiency of 100%. To further reveal the underlying mechanism of electroluminescence based on TADF devices, this paper selected three types of high efficient TADF materials, 4CzTPN-Ph, 2CzPN, and PIC-TRZ2 to fabricate organic light emitting devices. Our results show that, although the TADF devices have RISC process, their magneto-electroluminescence （MEL） curves exhibited similar line-shapes with those in the ordinary devices. This is due mainly to the facts that magnetic field can only affect the intersystem crossing （ISC） and Reverse ISC of polaron pairs rather than exciton in the these devices. At the same time, we found that the magnitudes of magnetic field effects in TADF devices increase with increasing the injection current, which is contrary to those from ordinary exciton-based devices. The relative change between the triplet polaron to triplet exciton rate kt and the singlet Polaron to singlet excitons rate ks is used to interpret these abnormal experimental results.
出处
《中国科学：物理学、力学、天文学》
CSCD
北大核心
2016年第8期52-59,共8页
Scientia Sinica Physica,Mechanica & Astronomica
基金
国家自然科学基金(编号:11374242)
中央高校基本科研业务费专项资金(编号:XDJK2015C149)资助项目
关键词
热活化延迟荧光
电致发光
反向系间窜越
磁效应
thermally activated delayed fluorescence, electroluminescence, reverse inter-system crossing, magnetic field effects
