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Time-Dependent Afterglow Color in a Single-Component Organic Molecular Crystal |
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| Authors: | Jian-Xin Wang Ye-Guang Fang Chun-Xiang Li Li-Ya Niu Wei-Hai Fang Ganglong Cui Qing-Zheng Yang |
| Affiliation: | 1. Institution Key Laboratory of Radiopharmaceuticals, College of Chemistry, Beijing Normal University, Beijing, 100875 P. R. China These authors contributed equally to this work.;2. Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875 P. R. China These authors contributed equally to this work.;3. Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875 P. R. China;4. Institution Key Laboratory of Radiopharmaceuticals, College of Chemistry, Beijing Normal University, Beijing, 100875 P. R. China |
| Abstract: | An organic crystal of 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (pCBP) exhibits time-dependent afterglow color from blue to orange over 1 s. Both experimental and computational data confirm that the color evolution results from well-separated, long-persistent thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) with different but comparable decay rates. TADF is enabled by a small S1–T1 energy gap of 0.7 kcal mol−1. The good separation of TADF and RTP is due to a 11.8 kcal mol−1 difference in the S0 energies of the S1 and T1 structures, indicating that apart from the excited-state properties, tuning the ground state is also important for luminescence properties. This afterglow color evolution of pCBP allows its applications in anticounterfeiting and data encryption with high security levels. |
| Keywords: | Datenverschlüsselung Anhaltende RTP Phosphoreszenz Thermisch aktivierte verzögerte Fluoreszenz |