Tunable crystal packing for enhanced electroluminescent properties based on novel thiazole derivatives with different connecting positions of carbazole

Two novel deep-blue fluorescent compounds, namely, 2-(4-(9-phenyl-9H- carbazol-3-yl)phenyl)benzo [d]thiazole (BCzBTZ) and 2-(4'-(9H-carbazol-9-yl)-[1.1'- biphenyl]-4-yl)benzo [d]thiazole (CzBBTZ) were designed, synthesized and characterized. It is particularly intriguing to compare their crystal packing of BCzBTZ and CzBBTZ, both of them construct with the same heterocyclic units and linker. Their crystal packing can be effectively regulated by changing the connecting position of carbazole. Their thermal stabilities, optical and electrochemical properties were studied systematically and exhibited ideal performance for electroluminescent emitters. The device based on BCzBTZ as emitter shows deep-blue emission with the CIE (x, y) of (0.15, 0.08), which is close to the blue standard (0.14, 0.08) of National Television System Committee (NTSC). The maximal external quantum efficiency is 1.4% and current efficiency is 1.39 cd/A with low efficiency roll-off.