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Modulation of Thermally Activated Delayed Fluorescence in Waterborne Polyurethanes via Charge‐Transfer Effect
Author(s) -
Li Zongren,
Wang Tao,
Xu Dong,
Zuo Jie,
Li Xinyu,
Li Zhiwei,
Xu Fei,
Zhang Xingyuan
Publication year - 2019
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201900423
Subject(s) - intersystem crossing , nanosecond , microsecond , fluorescence , photochemistry , singlet state , materials science , triplet state , charge (physics) , optoelectronics , chemistry , atomic physics , excited state , physics , optics , laser , quantum mechanics
Here, we designed several waterborne polyurethanes (WPUs) with efficient thermally activated delayed fluorescence (TADF) via serving charge‐transfer (CT) states as a mediate bridge between singlet and triplet states to boost reverse intersystem crossing (RISC). By tuning substituents of diphenyl sulfone (DS), we found that O,O′‐ and S,S′‐substituted DS covalently incorporated in WPUs solely show typical fluorescence emission with lifetimes in the nanosecond range. Interestingly, TADF appears by replacing the substituent with the nitrogen atom, of which lifetimes are up to ≈10 microseconds and ≈1 millisecond in air and vacuum, respectively, even though the energy gap between singlet and triplet states (Δ E ST ) is still large for generating TADF. To explain this phenomenon, an energy level mode based on CT states and an 3 (n‐π*) receiver state was proposed. By the rational modulation of CT states, it is possible to tune the Δ E ST to render TADF‐based materials suitable for versatile applications.