Design and Development of Novel 2-D Oligomers for Electroactive Device Application

Abstract

Four novel two-dimensional conjugated poly(p-phenylenevinylene) (PPV)-based molecules have been synthesized, characterized, and evaluated for use in light-emitting diodes (LEDs). These novel molecules all contain a tetra-substituted central phenyl ring, but the length, chemical structure, and placement of the arms is varied in order to tailor their hole and electron transport properties. The materials are all solution-processible, maintain conjugation through the arms and central core, and exhibit evidence of two- and possibly three-dimensional charge delocalization. The first molecule contains four phenylenevinylene arms with solubilizing octyloxy-substituted units. Two of the molecules have two phenylenevinylene arms and two oxadiazole arms that are placed ortho or para with respect to each other. The fourth molecule contains four cyano-phenylenevinylene arms with solubilizing octyloxy groups at the ends of each arm. As a class these molecules all have large Stokes shifts in films, although the propensity for π−π stacking varies between the molecules. The oxadiazole-containing molecules show promise for applications in single-layer LEDs.