Elastic organic crystals with ultralong phosphorescence for flexible anti-counterfeiting

Ultralong organic phosphorescence (UOP) crystals have attracted increased attention due to the distinct photophysical property of a long-lived lifetime. However, organic crystals are generally brittle, leading to a serious problem for their application in flexible technology. Herein, we report three types of elastic organic crystals (EOCs) with ultralong phosphorescence via introducing halogen atoms (Cl, Br, I) into π-conjugated phosphorescent molecules. Especially, the crystal containing iodine atoms displayed both excellent elasticity (ε = 3.01%) and high phosphorescent efficiency (Φph = 19.1%) owing to the strong halogen bonds. Taking advantage of its highly efficient UOP and excellent elasticity, we successfully used a DCz4I crystal for anti-counterfeiting application. These findings may provide guidance for the development of elastic crystals with afterglow and expand the scope of potential applications on flexible materials.

Kaiwei Huang, Lulu Song, Kun Liu, Anqi Lv, Manjeet Singh, Kang Shen, Jing Shen, Jiamin Wang, Hongchen Wang, Huifang Shi, Huili Ma, Mingxing Gu, Gengzhi Sun, Wei Yao, Zhongfu An, Wei Huang