Enabling efficient and ultralong room-temperature phosphorescence from organic luminogens by locking the molecular conformation in polymer matrix

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-10, Vol.497, p.154949, Article 154949
• Main Authors: Zhang, Huaqing, Wu, Shiying, Liang, Yaohui, Zhang, Zhexian, Wei, Hengshan, Yang, Qingchen, Hu, Pengtao, Liu, Cong, Yang, Zhan, Zheng, Chunxiong, Shi, Guang, Chi, Zhenguo, Xu, Bingjia
• Format: Article
• Language: English
• Subjects: Host–guest doping; Nonradiative decay; Organic afterglow; Polymer matrix; Room-temperature phosphorescence
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.154949

[Display omitted] Gradually enhancing afterglow under ambient conditions is generated by embedding a typical class of organic luminogens with ingeniousness lying in their architectures into melamine-formaldehyde polymer. Due to effective intramolecular motion resistance, the resulting material exhibits one of the most excellent polymer-based organic afterglow with a phosphorescence quantum yield (Φphos.) up to 38.31% and a lifetime (τphos.) up to 2.73 s. •Gradually enhancing afterglow under ambient conditions is generated.•Effective intramolecular motion resistance is achieved by host–guest doping.•The material exhibits one of the most fabulous polymer-based organic afterglow.•Locking intramolecular conformation contributes to suppressing nonradiative decay. Tackling the challenge of developing ultralong organic phosphorescence (UOP) materials with a high phosphorescence quantum yield (Φphos.) and an ultralong phosphorescence lifetime (τphos.) under ambient conditions is urgently needed. Herein, typical organic luminogens with simple chemical structures, namely, triphenylamine (TPA), 9-phenylcarbazole (PCz), and indolo[3,2,1-jk]carbazole (ICz), are doped into a melamine–formaldehyde (MF) polymer matrix with a compact three-dimensional covalent network to prepare UOP materials, respectively. Both experiments and theoretical calculations suggest that restricting intramolecular motions to suppress the nonradiative decay of triplet excitons plays a critical role in achieving ultralong room-temperature phosphorescence from organic molecules in polymer matrices. The luminophore ICz with a planar and rigid chemical structure, constructed by locking the molecular conformation of TPA via carbon–carbon single bonds, exhibits a bright organic afterglow with a Φphos. up to 38.31 % and a τphos. up to 2.73 s in the MF polymer under ambient conditions, representing one of the most excellent polymer-based organic afterglow materials in comprehensive UOP performance. The gradual enhancement in UOP of the resulting luminescent materials has led to their successful use in multi-level anti-counterfeiting. This work provides an effective strategy for developing organic afterglow materials with both high Φphos. and τphos. values.