Photoluminescence and electroluminescence of a novel green-yellow emitting material–5,6-Bis-[4-(naphthalene-1-yl-phenyl-amino)-phenyl]-pyrazine-2,3-dicarbonitrile

Abstract: A new compound with intramolecular charge transfer (ICT) property—5,6-Bis-[4-(naphthalene-1-yl-phenyl-amino)-phenyl]-pyrazine-2,3-dicarbonitrile(BNPPDC) was synthesized. The new compound was strongly fluorescent in non-polar and moderately polar solvents, as well as in thin solid film. The absorption and emission maxima shifted to longer wavelength with increasing solvent polarity. The fluorescence quantum yield also increased with increasing solvent polarity from non-polar to moderately polar solvents, then decreased with further increase of solvent polarity. This indicates both “positive” and “negative” solvatokinetic effects co-existed. Using this material as hole-transporting emitter and host emitter, we fabricated two electroluminescent (EL) devices with structures of A (ITO/BNPPDC (45nm)/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) (45nm)/Mg:Ag (200nm) and B (ITO/N,N′-diphenyl-N,N′-bis-(3-methylphenyl) (1,1′-diphenyl)4,4′-diamine (TPD) (50nm)/BNPPDC (20nm)/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) (45nm)/Mg:Ag (200nm). The devices showed green-yellow EL emission with good efficiency and high brightness. For example, the device A exhibited a high brightness of 17400cd/m2 at a driving voltage of 11V and a very low turn-on voltage (2.9V), as well as a maximum luminous efficiency 3.61cd/A. The device B showed a similar performance with a high brightness of 12650cd/m2 at a driving voltage of 13V and a maximum luminous efficiency 3.62cd/A. In addition, the EL devices using BNPPDC as a host and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as a dopant (configuration: ITO/TPD (60nm)/BNPPDC:DCJTB (2%) (30nm)/TPBI (35nm)/Mg:Ag (200nm)) showed a good performance with a brightness of 150cd/m2 at 4.5V, a maximum brightness of 12600cd/m2 at 11.5V, and a maximum luminous efficiency of 3.30cd/A. [Copyright &y& Elsevier]