5 years ago

Enhancing Fluorescence of Naphthalimide Derivatives by Suppressing the Intersystem Crossing

Enhancing Fluorescence of Naphthalimide Derivatives by Suppressing the Intersystem Crossing
Zengqi Xie, Jiadong Zhou, Muddasir Hanif, Yuwei Xu, Yuguang Ma, Wenqiang Zhang, Dehua Hu, Shitong Zhang
The control over intersystem crossing (ISC) during an excited state of an organic molecule is critical to realize high-efficiency fluorescent materials. We report newly designed naphthalimide (NMI) based emitters (Ph-NMI and TPA-NMI), in which the photoluminescence (PL) efficiency increased by suppressing the intersystem crossing (ISC). The experimental and theoretical analysis revealed that the enlarged energy gap between the lowest singlet state (S1) and lowest triplet state (T1), and the mismatched electronic configuration of these two states can effectively suppress the ISC process in Ph-NMI and TPA-NMI as compared to the original H-NMI. Moreover, the electronic configuration of S1-state changed to the π–π* transition in Ph-NMI and TPA-NMI (n-π* tansition in H-NMI), resulting in large radiation transition rate constant (Kr). Therefore, Ph-NMI and TPA-NMI exhibit significantly improved PL efficiencies when compared with H-NMI. The optimized OLEDs using TPA-NMI as yellow emitting layers in doped device showed high performance with a maximum external quantum efficiency of 5.96%, which is the best device performance ever achieved based on the naphthalimide derivatives.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b07513

DOI: 10.1021/acs.jpcc.7b07513

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