Benzothiazole derivatives with varied substituents: Synthesis, aggregated luminescence properties, and application in single-component WLEDs

White light emitting diodes (WLEDs) and its related lighting technology can effectively reduce electricity consumption. In this work, six benzothiazole derivatives (BTZ1-BTZ6) have been synthesized by introducing different substituents. In particular, the emission of excimers is dominant in the aggregated photoluminescence of compounds BTZ1-BTZ3 and their luminescence colors are completely different from their single-molecule states. The results of ultraviolet absorption, fluorescence emission and DFT calculation confirm that the solid emission of BTZ1-BTZ3 is derived from excimers. Single crystal analysis reveal that the C[sbnd]H⋅⋅⋅π interaction between molecules is a key contributor to the formation of excimers, and the different luminous efficiency of excimers directly affects the luminescence colors of these compounds in aggregated state. Finally, eight LED devices were fabricated by doping different contents of BTZ1-BTZ3 into UV-LED chips. Among them, device 4, which was prepared by doping 10 % content of BTZ2 into the substrate materials, is a WLED device. Its CIE coordinates are (0.31, 0.35) and its CRI is as high as 80. BTZ2 is one of the simplest molecular structures in single-component WLEDs reported at present. These findings demonstrate that the aggregated luminescence characteristics can be effectively controlled by fine-tuning molecular substituents, which provides new insights into the design and manufacture of single-component WLEDs.