Polymers with High Electron Affinities for Light-Emitting Diodes

Polymers with high electron affinities have been widely used as electron injection/transport layers in polymer light-emitting diodes. Among them, cyano-containing poly(phenylenevinylene)s (CN−PPVs) have been demonstrated to be highly efficient in electron transport. These CN−PPVs are synthesized by a Knoevenagel-type condensation between an aromatic diacetonitrile and a corresponding aromatic dialdehyde. Careful control of reaction conditions is required to avoid side reactions and the polymer molecular weight is usually low. In this paper, we report a CN−PPV synthesized by the Heck coupling reaction. We also report a new pyrazine-containing PPV. Both polymers show good electron injection/transport ability and luminescence properties. Single layer LED devices with the configuration of (ITO/polymer/Al) show external quantum efficiencies up to 0.025%.