A triphenylamine substituted quinacridone derivative for solution processed organic light emitting diodes

We report on a novel quinacridone derivative design, namely, 2,9-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-5,12-bis(2-ethylhexyl)-5,12-dihydroquinolino[2,3-b]acridine-7,14-dione (TPA-QA-TPA) for possible use as a solution processable emissive layer in organic light emitting diodes (OLEDs). TPA-QA-TPA contains branched alkyl chains for enhanced solubility and methoxytriphenylamine moieties (TPA) as end capping groups. The end capping groups not only extend the molecular conjugation leading to a red shifted emission, but have a propeller shaped conformation. The propeller design hinders the intermolecular π-π stacking, hindering aggregation and hence suppressing concentration quenching of the fluorophores in the solid state. The new molecular design shows good thermal stability, with a decomposition temperature of 390 °C and a melting temperature of 295 °C. The absorption and emission maxima for TPA-QA-TPA compound are 552 and 622 nm respectively. Using TPA-QA-TPA as a dopant in tris(8-hydroxyquinolinato)aluminum (Alq₃), organic light emitting diodes were realized in a simple device structure.