Tuning of the electronic and optical properties of 4,4′-bis(1-phenyl-phenanthro[9,10-d]imidazol-2-yl)biphenyl via cyano substitution in un-conjugated phenyl

A new phenanthroimidazole-based material named 4,4'-bis(1-(4-cyano-phenyl)-1H-phenanthro[9,10-d] imidazol-2-yl) biphenyl (CN-BPPI) was prepared by simple one-pot chemical reaction. Its structure and its photophysical, electrochemical and mobility properties were carefully studied. CN-BPPI exhibited similar absorption and emission spectra to BPPI, while the thermal stability and photoluminescence quantum yield were enhanced. More balanced carrier mobility was realized in CN-BPPI due to the substitution of cyano, which was proved by cyclic voltammetry (CV) and single-carriers measurements. The electroluminescence (EL) properties of a blue emitting CN-BPPI device were researched and the EL performances were much better than those for BPPI.