Phenanthroimidazole substituted imidazo[1,2-a]pyridine derivatives for deep-blue electroluminescence with CIEy ∼ 0.08

Abstract

Blue emitting materials with balanced charge carrying capacity are crucial for effective OLED. Phenanthroimidazole based deep blue materials are developed with a donor–acceptor configuration to optimize charge balance in OLEDs. In this work, three new dipolar materials based on the phenanthroimidazole-imidazopyridine conjugated system were synthesized and characterized. The position and number of phenanthroimidazole substituents are changed to study structure property relationships. All derivatives carried superb thermal stability and high photoluminescence quantum yield. Dyesin which phenanthroimidazole chromophore linked at thepara-position of C2 phenyl ring showed the red-shifted emission band. The positive solvatochromism was observed with the increase of solvent polarity, associated with the intramolecular charge transfer at excited state. The electrochemical measurement revealed that the fluorophores have low-lying LUMO energy levels. Further, doped devices were fabricated with these emitters to estimate the EL performances. Among all the emitters, the doped device fabricated with a dye containing phenanthroimidazole chromophore at para-position of C2 phenyl showed superior electroluminescence performance with CIE coordinates (0.16, 0.08).