Phenanthroimidazole derivatives as emitters for non-doped deep-blue organic light emitting devices

A series of phenanthroimidazole derivatives with N-1 and C-2 position modification have been synthesized, characterized and applied as non-doped emitters in organic light-emitting devices (OLEDs). The compounds show high fluorescence quantum yields high up to 87.51% in solid powder state as well as good thermal and film-forming properties. Crystal structures of 2N-PI, 1N-BPI and 2N-API were determined by X-ray crystallography. Correlations between optoelectronic properties, energy levels and molecular structures of the materials were investigated. It was found that the fluorescence properties of the materials were related to the dihedral angles and moiety replacement position. N-1-imidazole modification (e.g.: 2N-API) favours deep-blue emission, although with a relatively lower quantum yield, it shows comparable device efficiency towards the C-2-imidazole derivative (e.g.: 2N-BPI).