Synthesis and Light-Emitting Properties of a Novel p-Conjugated Poly[di(p-phenyleneethynylene)-alt-p-phenylenecyanovinylene)] Containing n-Octyloxy Side Branches

Abstract

A novel -conjugated poly[di(p-phenyleneethynylene)-alt-(p-phenylenecyanovinylene)] having n-octyloxy side chains (PPE-C8PPE-PPV) was prepared by polymerization of the monomer DEDB with BCN. Chemical structure of the polymer obtained was confirmed by 1H NMR, FTIR, and EA. PPE-C8PPE-PPV had a molecular weight enough to fabricate the electroluminescent (EL) device, and showed a good organosolubility, excellent thermal stability, and film-forming property. In UV absorption and PL spectra in film it showed a maximum at 430 and 543 nm, respectively, which appeared 5 and 41 nm longer wavelengths than that of the solution, respectively. HOMO, LUMO energy levels and band gap were determined to be -5.70, -3.29, and 2.41 eV, respectively. Two EL devices with low-work function cathodes were fabricated with the structures of ITO/PEDOT/PPE-C8PPE-PPV/cathodes (LiF/Al and Mg:Ag/Ag). The both devices exhibited a bright green light emission at 545 nm and the maximum luminescence of 197 cd/cm2 (LiF/Al) and 158 cd/cm2 (Mg:Ag/Ag).