Facile synthetic route to a novel electroluminescent polymer-poly(p-phenylenevinylene) containing a fully conjugated aromatic oxadiazole side chain

Herein we report a facile synthetic route to a new conjugated polymer, poly {2-[5'-(2 "-octyloxy)phenyl)-1',3',4'-oxadiazole-2'-yl]-1,4-phenylenevinyle ne)}(OPO-PPV), in which a in which a high-electron-affinity aromatic oxadia zole moiety is attached on the PPV backbone as side chain. It is demonstrat ed that OPO-PPV is a new polymeric material with balanced charge injection for the application as emissive material in single-layer light-emitting dio des (LEDs). The present synthesis of OPO-PPV reveals a promising approach t o balance the charge injection between electrons and holes into electrolumi nescent layers in polymer LEDs by controlling the intrinsic properties of l ight-emitting materials. The NMR (C-13 and H-1) spectra of OPO-PPV demonstr ate a well-defined structure in the polymer. The polymer exhibits good ther mal stability (stable up to 368 degrees C in nitrogen) and high glass-trans ition temperature (170 degrees C). Both the absorption and photoluminescenc e spectra of the polymer have been studied. Cyclic voltammetry (CV) has bee n employed to estimate the highest occupied and lowest unoccupied molecular orbital energy levels of OPO-PPV. A comparison of the electrochemical char acteristics with that of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenev inylene] (MEH-PPV) is also discussed. A single-layer LED device ITO/OPO-PPV /Al is successfully fabricated. The device emits visible yellow-orange ligh t above the bias voltage of 4.0 V under ambient conditions.