Novel Electroluminescent PPV Copolymers Containing Si-phenyl and Difluorovinylene Units

Abstract

New electroluminescent copolymers with fluoro groups in vinylene units, poly(2-(3′-dimethyloctylsilylphenyl)-p-phenylenevinylene-co-p-phenylenedifluorovinylene)s (SiPhPPVPDFVs), have been synthesized by the Gilch polymerization. The fluoro groups were introduced onto the vinylene units to increase electron affinity of the copolymers. The HOMO energy levels of the copolymers were between 5.30–5.35 eV. The EL spectra of devices with the configuration of ITO/PEDOT:PSS/polymer/Al showed maximum peaks between 526–560 nm. By adjusting the feed ratios of PPDFV in SiPhPPVPDFVs, the CIE coordinates moved from yellow to green. The luminescence efficiencies of the copolymers at room temperature ranged from 0.35–2.03 cd/A. SiPhPPVPDFV3 showed the maximum brightness of 4451 cd/m2 and the highest luminescence efficiency of 2.03 cd/A. Introduction of up to 30% of PPDFV in the copolymers with m-SiPhPPV enhanced the device performance to result in high current density, brightness and efficiency due to increased electron injection ability caused by the presence of fluoro groups in the vinylene units.