D-A-A-Type Emitter Featuring Benzo[c][1,2,5]thiadiazole and Polar CN Bond as Tandem Acceptor for High-Performance Near-Infrared Organic Light-Emitting Diodes

Though urgently required, high performance near-infrared (NIR) emitters are still rare given the challenge of obtaining high photoluminance quantum efficiency (PLQY) at the same time ensuring NIR emission. The major issue lies in the design strategy for which strong electron donating/withdrawing moieties with high PLQY should be integrated with a scrumptious way. Herein, a novel donor-acceptor-acceptor (D-A-A) type NIR emitter comprising highly polar cyano group (CN) together with rigid benzo[c][1,2,5]thiadiazole as tandem acceptor and 4,4-dimethyltriphenylamine as donor is successfully designed. This constructing strategy not only allows the D/A maintain their intrinsic electron-donating/withdrawing characteristics, but also retains high PLQY. In merits of these features, excellent external quantum efficiency (EQE) of 3.8% with peak emission at 692 nm for 15% doped device is achieved. Encouragingly, impressive EQE of 3.1% with the peak emission at 708 nm is also successfully achieved without doping technique. It is believed that these efficiencies are the best or among the best comparing to those of the reported NIR organic light-emitting diodes with similar electroluminescence peak. Notably, efficiency roll-offs of both doped and nondoped device are also quite flat.