Crystalline Carbazole Based Organic Room-Temperature Phosphorescent Materials

Abstract

Since the demonstration of organic room temperature phosphorescence (ORTP) from carbazole in 2008, using carbazole unit to construct ORTP materials has become a feasible approach to developing a series of diverse, high-performance, widely applicable and highly representative ORTP material system. This review paper firstly summarizes three strategies for improving phosphorescence performance of ORTP materials, namely H-aggregation, heavy-atom effect and donor-acceptor structure. Then, the recent progress of crystalline carbazole-based ORTP materials is systematically introduced. Based on these three strategies, triplet relaxation is suppressed, spin-orbital coupling is enhanced, singlet-triplet energy gaps are reduced, and intermolecular charge transfer interactions are strengthened. As a result, the triplet excited states are stabilized, and intersystem crossing is accelerated to facilitate phosphorescence, and thereby realizing long-lifetime high-efficiency crystalline carbazole-based ORTP materials. Their applications in the fields of anti-counterfeiting, information security and bioimaging are briefly discussed.