Intermolecular Electronic Coupling of Organic Units for Efficient Persistent Room-Temperature Phosphorescence

• Published in: Angewandte Chemie International Edition Vol. 55; no. 6; pp. 2181 - 2185
• Main Authors: Yang, Zhiyong, Mao, Zhu, Zhang, Xuepeng, Ou, Depei, Mu, Yingxiao, Zhang, Yi, Zhao, Cunyuan, Liu, Siwei, Chi, Zhenguo, Xu, Jiarui, Wu, Yuan-Chun, Lu, Po-Yen, Lien, Alan, Bryce, Martin R.
• Format: Journal Article
• Language: English
• Published: WEINHEIM Blackwell Publishing Ltd 05.02.2016; Wiley; Wiley Subscription Services, Inc; John Wiley and Sons Inc
• Edition: International ed. in English
• Subjects: Chemistry; Chemistry, Multidisciplinary; Communication; Communications; Coupling (molecular); Crystal structure; Emission; Emissions; intersystem crossing; Organic chemistry; organic materials; Phosphorescence; photochemistry; Physical Sciences; Quantum efficiency; Room temperature; Science & Technology; spin-orbit coupling; Temperature; Temperature effects; STATES; spin-orbit coupling; CONVERSION; MOLECULE; phosphorescence; STIMULI; intersystem crossing; LIGHT-EMITTING-DIODES; DUAL-EMISSION; DELAYED FLUORESCENCE; LUMINESCENCE; photochemistry; LUMINOGENS; organic materials
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201509224

Although persistent room‐temperature phosphorescence (RTP) emission has been observed for a few pure crystalline organic molecules, there is no consistent mechanism and no universal design strategy for organic persistent RTP (pRTP) materials. A new mechanism for pRTP is presented, based on combining the advantages of different excited‐state configurations in coupled intermolecular units, which may be applicable to a wide range of organic molecules. By following this mechanism, we have developed a successful design strategy to obtain bright pRTP by utilizing a heavy halogen atom to further increase the intersystem crossing rate of the coupled units. RTP with a remarkably long lifetime of 0.28 s and a very high quantum efficiency of 5 % was thus obtained under ambient conditions. This strategy represents an important step in the understanding of organic pRTP emission. Persistence pays off: Bright persistent room‐temperature phosphorescence from pure organic molecules was achieved by intermolecular electronic coupling of selected units in crystals. The combined advantages of their different excited‐state configurations (i.e., the nπ* state with a high intersystem crossing rate and the ππ* state with a low radiative rate) results in a hybrid intersystem‐crossing process that leads to efficient persistent room‐temperature phosphorescence.