Blue-Green Light Emitting Poly(phenylenevinylene) Derivatives as Candidates for Polymer LEDs: Synthesis and Characterization

Alkoxy substituted derivatives of poly- and oligo-[(m-phenylenevinylene)-alt-(p-phenylenevinylene)] were synthesized via the Wittig (P1, OPV1, OPV2) and the Wittig-Horner (P2, OPV3, OPV4) condensation routes. The polymers were characterized by 13 C NMR, 1 H NMR, FT-IR spectroscopy and GPC. 1 H NMR was a convenient tool to distinguish between the cis and trans double bonds in the compounds. Poly [(4-decycloxy-1,3-phenylenevinylene)-alt-(1,4-phenylene)] (P1) contained cis and trans double bonds in significant amounts, the vinylene configuration of poly [(4-decycloxy-1,3-phenylenevinylene)-alt-(2,5-dipentyloxy-1,4-phenylenevinylene)] (P2) was nearly exclusively trans. Model compounds (OPV1-4) were also synthesized to support the structural and optical characterization. UV-vis absorption, photoluminescence (PL) and cyclic voltammetry measurements have been performed to investigate the influence of the positions and the number of substituents on electronic levels. The polymers exhibited an intensive solid-state emission in the blue-green (P1) and the green (P2) region of the spectrum. Light emitting diodes have been fabricated consisting of ITO, PEDOT:PSS, P2 and Ca/A1. They exhibited high luminance of 100 cd.m -2 at 5.9 V and low onset voltages (4.3 V) for the electroluminescence (EL).