Long Persistent Luminescence Enabled by Dissociation of Triplet Intermediate States in an Organic Guest/Host System
journal contributionposted on 23.04.2020, 14:06 by Leixin Xiao, Zhiwei Wang, Chunfeng Zhang, Xiaoyu Xie, Haibo Ma, Qian Peng, Zhongfu An, Xiaoyong Wang, Zhigang Shuai, Min Xiao
Any type of content formally published in an academic journal, usually following a peer-review process.
Organic guest/host systems with long persistent luminescence benefiting from the formation of a long-lived charge-separated state have recently been demonstrated. However, the photogeneration mechanism of such key charge-separated states remains elusive. Here, we report the identification of intermediate triplet states with mixed local excitation and charge-transfer character that connect the initial photoexcited singlet states and the long-lived charge-separated states. Using time-resolved optical spectroscopy, we observe the intersystem crossing from photoexcited singlet charge-transfer states to triplet intermediate states on a time scale of ∼52 ns. Temperature-dependent measurements reveal that the long-lived triplet intermediate states ensure a relatively high efficiency of diffusion-driven charge separation to form the charge-separated state responsible for LPL emission. The findings in this work provide a rationale for the development of new LPL materials that may also improve our understanding of the mechanism of photon-to-charge conversion in many organic optoelectronic devices.