A rational design strategy for an extremely deep-blue fluorescent emitter with a small CIE y value for solution processable, high efficiency, organic light-emitting diodes

A rational design strategy is proposed for synthesis of a new deep-blue emitter/dopant (denoted as TPA-3FA) based on triphenylamine (TPA) as the core with the addition of diethylfluorene/acridine analogues to frame a star-shaped material for solution processable high performance OLEDs. The photophysical, thermal, electrochemical, electronic, and hole transporting properties of TPA-3FA are examined. Most importantly, this rational design strategy of introducing diethylfluorene between TPA and acridine imparts high rigidity and non-planarity, which in turn completely suppress intermolecular interactions, and thus yields a strong narrow deep-blue fluorescence with a high quantum yield. Moreover, a solution processed non-doped device with TPA-3FA as an emitter exhibits excellent device performance with a maximum external quantum efficiency (EQE) of 4.43%, CIE (x,y) coordinates of (0.153, 0.045) and good device stability. The device performance was significantly improved with an EQE of 6.11% and CIE (x,y) coordinates of (0.156, 0.049) after doping into a host. The same device when processed in a halogen-free solvent exhibited an impressive EL performance (EQE: 5.72%; CIE (0.157, 0.046)).