A novel bipolar D–π–A type phenanthroimidazole/carbazole hybrid material for high efficiency nondoped deep-blue organic light-emitting diodes with NTSC CIE y and low efficiency roll-off

Tremendous efforts have been devoted to developing efficient deep-blue organic light-emitting diodes (OLEDs), but deep-blue OLEDs with high external quantum efficiency (EQE) and CIE y < 0.10 (Commission Internationale de L’éclairage (CIE)), especially matching the National Television System Committee (NTSC) standard blue CIE ( x , y ) coordinates of (0.14, 0.08), are still limited. Herein, we report the synthesis, photophysical properties, thermostability and electrochemical characterization of two phenanthroimidazole/carbazole-based compounds (CBPMCN and CPBPMCN). Single X-ray crystal data of CPBPMCN indicate that it adopts a severely twisted structure, resulting in a low degree of intermolecular π–π stacking, which is appropriate to be employed as a nondoped deep-blue emitter. Nondoped devices based on CPBPMCN exhibited deep-blue electroluminescence (EL) with CIE coordinates of (0.15, 0.08), which is extremely close to the NTSC standard blue. Meanwhile, the devices showed impressively high EQE max up to 5.80% with relatively small efficiency roll-off.